JSON Class
Properties Methods Events Configuration Settings Errors
The JSON class can be used to parse and write JSON documents.
Syntax
JSON
Remarks
The JSON class offers a fast and simple way to parse and write information in JSON documents.
Parsing JSON
The JSON class parses JSON documents and verifies that they are well-formed. The results are provided through a set of events.
In addition, the document structure may be queried through an XPath mechanism that supports a subset of the XPath and JSONPath specification.
The parser is optimized for read applications, with a very fast engine that builds internal DOM structures with close to zero heap allocations. Additionally, BuildDOM can be set to False which reduces the overhead of creating the DOM and offers a fast forward-only parsing implementation which fires events to provide the parsed data.
When parsing a document events will fire to provide information about the parsed data. After Parse returns the document may be navigated by setting XPath if BuildDOM is True (default). If BuildDOM is False parsed data is only accessible through the events.
The following events will fire during parsing:
If BuildDOM is True (default), XPath may be set after this method returns. XPath may be set to navigate to specific elements within the JSON document. This will be the path to a specified value within the document. Since arrays in JSON only contain values, and no associated object name, an empty name will be used for these values. To reach an array element at position 1, the path must be set to "[1]". In addition, a root element named "json" will be added to each JSON document in the parser.
BuildDOM must be set to True prior to parsing the document for the XPath functionality to be available.
The XPath property accepts both XPath and JSONPath formats. Please see notes below on both formats.
XPath
The path is a series of one or more element accessors separated by '/'. The path can be absolute (starting with '/') or relative to the current XPath location.
The following are possible values for an element accessor:
| 'name' | A particular element name. |
| [i] | The i-th subelement of the current element. |
| .. | the parent of the current element. |
When XPath is set to a valid path the following properties are updated:
- XElement
- XElementType
- XParent
- XText
- XSubTree
- XChildren*
BuildDOM must be set to True prior to parsing the document for the XPath functionality to be available.
Simple JSON document
{
"firstlevel": {
"one": "value",
"two": ["first", "second"],
"three": "value three"
}
}
Example (Setting XPath)
| Document root | JsonControl.XPath = "/" |
| Specific Element | JsonControl.XPath = "/json/firstlevel/one/" |
| i-th Child | JsonControl.XPath = "/json/firstlevel/two/[i]/" |
Note: When using XPath notation the root element is always referred to as "json". As in the above examples this means all paths will begin with "/json".
JSONPath
This property implements a subset of the JSONPath notation. This may be set to point to a specific element in the JSON document.The JSONPath is a series of one or more accessors in either dot-notation
$.store.book[0].titleOr bracket-notation
$['store']['book'][0]['title']
After setting XPath the following properties are populated:
- XChildren
- XElement
- XElementType
- XSubTree
- XText
Given the following JSON document:
{
"store": {
"book": [
{
"category": "reference",
"author": "Nigel Rees",
"title": "Sayings of the Century",
"price": 8.95
},
{
"category": "fiction",
"author": "Evelyn Waugh",
"title": "Sword of Honour",
"price": 12.99
},
{
"category": "fiction",
"author": "Herman Melville",
"title": "Moby Dick",
"isbn": "0-553-21311-3",
"price": 8.99
},
{
"category": "fiction",
"author": "J. R. R. Tolkien",
"title": "The Lord of the Rings",
"isbn": "0-395-19395-8",
"price": 22.99
}
],
"bicycle": {
"color": "red",
"price": 19.95
}
},
}
The following code shows several examples.
Get the first book's author:
json.XPath = "$.store.book[0].author";
Console.WriteLine(json.XText);
//Output
//"Nigel Rees"
Select the first book and inspect the children:
json.XPath = "$.store.book[0]";
Console.WriteLine("Child Count: " + json.XChildren.Count);
Console.WriteLine(json.XChildren[1].Name + ": " + json.XChildren[1].XText);
//Output
//Child Count: 4
//author: "Nigel Rees"
Get the price of the second book:
json.XPath = "$['store']['book'][1]['price']";
Console.WriteLine(json.XText);
//Output
//12.99
Get the second to last book's author:
json.XPath = "$['store']['book'][last() - 1]['author']";
Console.WriteLine(json.XText);
Console.WriteLine(json.XPath); //Note that "last() - 1" is resolved to "3".
//Output
//"Herman Melville"
//$['store']['book'][3]['author']
Display the full subtree at the current path:
json.XPath = "$.store.book[0]";
Console.WriteLine(json.XSubTree);
//Output
// {
// "category": "reference",
// "author": "Nigel Rees",
// "title": "Sayings of the Century",
// "price": 8.95
// }
Input Properties
The class will determine the source of the input based on which properties are set.
The order in which the input properties are checked is as follows:
When a valid source is found the search stops.If parsing multiple documents call Reset between documents to reset the parser.
Writing JSON
The JSON class can also be used to create a JSON document.
The document is written to the selected output property. In addition as the document is written, the JSON event will fire. The Text event parameter contains the part of the document currently being written.
Output Properties
The class will determine the destination of the output based on which properties are set.
The order in which the output properties are checked is as follows:
- OutputFile
- OutputData: The output data is written to this property if no other destination is specified.
Example
Writing a simple JSON document describing a pet:
Json json = new Json();
json.OutputFile = "C:\\temp\\fido.json";
json.StartObject();
json.PutProperty("name", "fido", 2);
json.PutName("previousOwners");
json.StartArray();
json.PutValue("Steve Widgetson", 2);
json.PutValue("Wanda Widgetson", 2);
json.PutValue("Randy Cooper", 2);
json.PutValue("Linda Glover", 2);
json.EndArray();
json.PutProperty("weightUnit", "lbs", 2);
json.PutProperty("weight", "62", 3);
json.EndObject();
json.Flush();
This example results in the following JSON:
{
"name": "fido",
"previousOwners": [
"Steve Widgetson",
"Wanda Widgetson",
"Randy Cooper",
"Linda Glover"
],
"weightUnit": "lbs",
"weight": 62
}
When writing multiple documents call Reset between documents to reset the writer.
Modifying JSON
The JSON class also allows for modifying existing JSON documents. After loading a JSON document with Parse the document may be editted. The class supports inserting new values, renaming or overwriting existing values, and removing values. After editting is complete call Save to output the updated JSON document.
The following methods are applicable when modifying a JSON document:
When Save is called the modified JSON is written to the specified output location.
Output Properties
The class will determine the destination of the output based on which properties are set.
The order in which the output properties are checked is as follows:
- OutputFile
- OutputData: The output data is written to this property if no other destination is specified.
Inserting New Values
To insert new values in a JSON document first load the existing document with Parse. Next set XPath to the sibling or parent of the data to be inserted. Call InsertProperty or InsertValue and pass the ValueType and Position parameters to indicate the type of data being inserted and the position.
The ValueType parameter of the above methods specifies the type of the value. Possible values are:
- 0 (Object)
- 1 (Array)
- 2 (String)
- 3 (Number)
- 4 (Bool)
- 5 (Null)
- 6 (Raw)
The Position parameter of the above methods specifies the position of Value. Possible values are:
- 0 (Before the current element)
- 1 (After the current element)
- 2 (The first child of the current element)
- 3 (The last child of the current element)
For example:
Given the following JSON:
{
"store": {
"books": [
{
"category": "reference",
"author": "Nigel Rees",
"title": "Sayings of the Century",
},
{
"category": "fiction",
"author": "Evelyn Waugh",
"title": "Sword of Honour",
}
]
}
}
Insert a new property "price" for each book:
json.XPath = "/json/store/books/[1]";
json.InsertProperty("price", "8.95", 3, 3); //3 - Number, 3 - Last Child
json.XPath = "/json/store/books/[2]";
json.InsertProperty("price", "12.99", 3, 3); //3 - Number, 3 - Last Child
json.Save();
Produces the JSON:
{
"store": {
"books": [
{
"category": "reference",
"author": "Nigel Rees",
"title": "Sayings of the Century",
"price": 8.95
},
{
"category": "fiction",
"author": "Evelyn Waugh",
"title": "Sword of Honour",
"price": 12.99
}
]
}
}
To add a new book to the array:
json.XPath = "/json/store/books";
json.InsertValue("", 0, 3); //0 - Object, 3 - Last Child
json.XPath = "/json/store/books/[3]";
json.InsertProperty("category", "fiction", 2, 3); //2 - String, 3 - Last Child
json.InsertProperty("author", "Herman Melville", 2, 3); //2 - String, 3 - Last Child
json.InsertProperty("title", "Moby Dick", 2, 3); //2 - String, 3 - Last Child
json.InsertProperty("price", "8.99", 3, 3); //3 - Number, 3 - Last Child
json.Save();
Produces the JSON:
{
"store": {
"books": [
{
"category": "reference",
"author": "Nigel Rees",
"title": "Sayings of the Century",
"price": 8.95
},
{
"category": "fiction",
"author": "Evelyn Waugh",
"title": "Sword of Honour",
"price": 12.99
},
{
"category": "fiction",
"author": "Herman Melville",
"title": "Moby Dick",
"price": 8.99
}
]
}
}
To add a new array property to each book:
json.XPath = "/json/store/books/[1]";
json.InsertProperty("tags", "", 1, 2); //1 - Array, 2 - First Child
json.XPath = "/json/store/books/[1]/tags";
json.InsertValue("quotes", 2, 3); //2 - String, 3 - Last Child
json.InsertValue("british", 2, 3); //2 - String, 3 - Last Child
json.XPath = "/json/store/books/[2]";
json.InsertProperty("tags", "", 1, 2); //1 - Array, 2 - First Child
json.XPath = "/json/store/books/[2]/tags";
json.InsertValue("trilogy", 2, 3); //2 - String, 3 - Last Child
json.InsertValue("war", 2, 3); //2 - String, 3 - Last Child
json.XPath = "/json/store/books/[3]";
json.InsertProperty("tags", "", 1, 2); //1 - Array, 2 - First Child
json.XPath = "/json/store/books/[3]/tags";
json.InsertValue("classic", 2, 3); //2 - String, 3 - Last Child
json.InsertValue("whales", 2, 3); //2 - String, 3 - Last Child
json.Save();
Producse the JSON:
{
"store": {
"books": [
{
"tags": ["quotes", "british"],
"category": "reference",
"author": "Nigel Rees",
"title": "Sayings of the Century",
"price": 8.95
},
{
"tags": ["trilogy", "war"],
"category": "fiction",
"author": "Evelyn Waugh",
"title": "Sword of Honour",
"price": 12.99
},
{
"tags": ["classic", "whales"],
"category": "fiction",
"author": "Herman Melville",
"title": "Moby Dick",
"price": 8.99
}
]
}
}
Removing Values
To remove existing values set XPath and call the Remove method. Continuing with the example above, to remove
the first book:
json.XPath = "/json/store/books/[1]";
json.Remove();
json.Save();
Produces the JSON:
{
"store": {
"books": [
{
"tags": ["trilogy", "war"],
"category": "fiction",
"author": "Evelyn Waugh",
"title": "Sword of Honour",
"price": 12.99
},
{
"tags": ["classic", "whales"],
"category": "fiction",
"author": "Herman Melville",
"title": "Moby Dick",
"price": 8.99
}
]
}
}
To remove the "category" properties from each book:
json.XPath = "/json/store/books/[1]/category";
json.Remove();
json.XPath = "/json/store/books/[2]/category";
json.Remove();
json.Save();
Produces the JSON:
{
"store": {
"books": [
{
"tags": ["trilogy", "war"],
"author": "Evelyn Waugh",
"title": "Sword of Honour",
"price": 12.99
},
{
"tags": ["classic", "whales"],
"author": "Herman Melville",
"title": "Moby Dick",
"price": 8.99
}
]
}
}
Updating Existing Names and Values
The SetName and SetValue methods may be used to modify existing names and values. Continuing with the JSON directly above, to rename "tags" to "meta" and update values within the array and prices:
//Rename "tags" to "meta" for 1st book
json.XPath = "/json/store/books/[1]/tags";
json.SetName("meta");
//Update Price
json.XPath = "/json/store/books/[1]/price";
json.SetValue("13.99", 3); //3 - Number
//Rename "tags" to "meta" for 2nd book
json.XPath = "/json/store/books/[2]/tags";
json.SetName("meta");
//Update tag "whales" to "revenge"
json.XPath = "/json/store/books/[2]/meta/[2]";
json.SetValue("revenge", 2); //2 - String
//Update Price
json.XPath = "/json/store/books/[2]/price";
json.SetValue("9.99", 3); //3 - Number
json.Save();
Produces the JSON:
{
"store": {
"books": [
{
"meta": ["trilogy", "war"],
"author": "Evelyn Waugh",
"title": "Sword of Honour",
"price": 13.99
},
{
"meta": ["classic", "revenge"],
"author": "Herman Melville",
"title": "Moby Dick",
"price": 9.99
}
]
}
}
Property List
The following is the full list of the properties of the class with short descriptions. Click on the links for further details.
| BuildDOM | When True, an internal object model of the JSON document is created. |
| InputData | The JSON data to parse. |
| InputFile | The file to process. |
| OutputData | The output JSON after processing. |
| OutputFile | The path to a local file where the output will be written. |
| Overwrite | Indicates whether or not the class should overwrite files. |
| Validate | When True, the parser checks that the document consists of well-formed XML. |
| XChildCount | The number of records in the XChild arrays. |
| XChildElementType | The ElementType property indicates the data type of the element. |
| XChildName | The Name property provides the name of the element. |
| XChildXText | This property contains the text of the element. |
| XElement | The name of the current element. |
| XElementType | Indicates the data type of the current element. |
| XErrorPath | An XPath to check the server response for errors. |
| XParent | The parent of the current element. |
| XPath | Provides a way to point to a specific element in the response. |
| XSubTree | A snapshot of the current element in the document. |
| XText | The text of the current element. |
Method List
The following is the full list of the methods of the class with short descriptions. Click on the links for further details.
| Config | Sets or retrieves a configuration setting. |
| EndArray | Writes the closing bracket of a JSON array. |
| EndObject | Writes the closing brace of a JSON object. |
| Flush | Flushes the parser's or writer's buffers. |
| HasXPath | Determines whether a specific element exists in the document. |
| InsertProperty | This method inserts the specified name and value at the selected position. |
| InsertValue | This method inserts the specified value at the selected position. |
| Parse | This method parses the specified JSON data. |
| PutName | Writes the name of a property. |
| PutProperty | Write a property and value. |
| PutRaw | Writes a raw JSON fragment. |
| PutValue | Writes a value of a property. |
| Remove | Removes the element or value set in XPath. |
| Reset | Resets the class. |
| Save | Saves the modified JSON document. |
| SetName | Sets a new name for the element specified by XPath. |
| SetValue | Sets a new value for the element specified by XPath. |
| StartArray | Writes the opening bracket of a JSON array. |
| StartObject | Writes the opening brace of a JSON object. |
| TryXPath | Navigates to the specified XPath if it exists. |
Event List
The following is the full list of the events fired by the class with short descriptions. Click on the links for further details.
| Characters | Fired for plain text segments of the input stream. |
| EndDocument | Fires when the end of a JSON document is encountered. |
| EndElement | Fired when an end-element tag is encountered. |
| Error | Information about errors during data delivery. |
| IgnorableWhitespace | Fired when a section of ignorable whitespace is encountered. |
| JSON | Fires with the JSON data being written. |
| StartDocument | Fires when the start of a new JSON document is encountered. |
| StartElement | Fired when a new element is encountered in the document. |
Configuration Settings
The following is a list of configuration settings for the class with short descriptions. Click on the links for further details.
| CacheContent | If true, the original JSON is stored internally in a buffer. |
| ElementXPath | The XPath value for the current element in the document. |
| EscapeForwardSlashes | Whether to escape forward slashes when writing a JSON object. |
| InputFormat | Specifies the input format used in JSON streaming. |
| PrettyPrint | Determines whether output is on one line or "pretty printed". |
| RecordEndDelimiter | The character sequence after the end of a JSON document. |
| RecordStartDelimiter | The character sequence before the start of a JSON document. |
| StringProcessingOptions | Defines options to use when processing string values. |
| XPathNotation | Specifies the expected format when setting XPath. |
| BuildInfo | Information about the product's build. |
| CodePage | The system code page used for Unicode to Multibyte translations. |
| LicenseInfo | Information about the current license. |
| UseInternalSecurityAPI | Tells the class whether or not to use the system security libraries or an internal implementation. |
BuildDOM Property (JSON Class)
When True, an internal object model of the JSON document is created.
Syntax
bool GetBuildDOM();
int SetBuildDOM(bool bBuildDOM);
Default Value
true
Remarks
Set this property to True when you need to browse the current document through XPath.
Data Type
Boolean
InputData Property (JSON Class)
The JSON data to parse.
Syntax
QString GetInputData();
int SetInputData(QString qsInputData);
Default Value
""
Remarks
This property specifies the JSON to be processed. Set this property before calling Parse.
This may be set to a complete JSON document, or partial data. When setting partial data call Parse after each chunk of data is set. For instance:
//Parse the following in chunks: { "data": 1}
json.InputData = "{ \"data\""
json.Parse();
json.InputData = ": 1}"
json.Parse();
Input Properties
The class will determine the source of the input based on which properties are set.
The order in which the input properties are checked is as follows:
- InputFile
- InputData
Data Type
String
InputFile Property (JSON Class)
The file to process.
Syntax
QString GetInputFile();
int SetInputFile(QString qsInputFile);
Default Value
""
Remarks
This property specifies the file to be processed. Set this property to the full or relative path to the file which will be processed.
After setting this property call Parse to parse the document.
Input Properties
The class will determine the source of the input based on which properties are set.
The order in which the input properties are checked is as follows:
- InputFile
- InputData
Data Type
String
OutputData Property (JSON Class)
The output JSON after processing.
Syntax
QString GetOutputData();
int SetOutputData(QString qsOutputData);
Default Value
""
Remarks
This property contains the resultant JSON after processing.
Output Properties
The class will determine the destination of the output based on which properties are set.
The order in which the output properties are checked is as follows:
- OutputFile
- OutputData: The output data is written to this property if no other destination is specified.
Data Type
String
OutputFile Property (JSON Class)
The path to a local file where the output will be written.
Syntax
QString GetOutputFile();
int SetOutputFile(QString qsOutputFile);
Default Value
""
Remarks
This property specifies the file to which the output will be written. This may be set to an absolute or relative path.
Output Properties
The class will determine the destination of the output based on which properties are set.
The order in which the output properties are checked is as follows:
- OutputFile
- OutputData: The output data is written to this property if no other destination is specified.
Data Type
String
Overwrite Property (JSON Class)
Indicates whether or not the class should overwrite files.
Syntax
bool GetOverwrite();
int SetOverwrite(bool bOverwrite);
Default Value
false
Remarks
This property indicates whether or not the class will overwrite OutputFile. If Overwrite is False, an error will be thrown whenever OutputFile exists before an operation. The default value is False.
Data Type
Boolean
Validate Property (JSON Class)
When True, the parser checks that the document consists of well-formed XML.
Syntax
bool GetValidate();
int SetValidate(bool bValidate);
Default Value
true
Remarks
You can set Validate to False when you want to ignore XML format rules (e.g. while parsing HTML files).
Data Type
Boolean
XChildCount Property (JSON Class)
The number of records in the XChild arrays.
Syntax
int GetXChildCount();
int SetXChildCount(int iXChildCount);
Default Value
0
Remarks
This property controls the size of the following arrays:
The array indices start at 0 and end at XChildCount - 1.
This property is not available at design time.
Data Type
Integer
XChildElementType Property (JSON Class)
The ElementType property indicates the data type of the element.
Syntax
int GetXChildElementType(int iXChildIndex);
Possible Values
ET_OBJECT(0),
ET_ARRAY(1),
ET_STRING(2),
ET_NUMBER(3),
ET_BOOL(4),
ET_NULL(5)
Default Value
0
Remarks
The XChildElementType property indicates the data type of the element.
Possible values are:
- 0 (Object)
- 1 (Array)
- 2 (String)
- 3 (Number)
- 4 (Bool)
- 5 (Null)
- 6 (Raw)
The XChildIndex parameter specifies the index of the item in the array. The size of the array is controlled by the XChildCount property.
This property is read-only and not available at design time.
Data Type
Integer
XChildName Property (JSON Class)
The Name property provides the name of the element.
Syntax
QString GetXChildName(int iXChildIndex);
Default Value
""
Remarks
The XChildName property provides the name of the element. For elements within an array, the XChildName property will be empty.
The XChildIndex parameter specifies the index of the item in the array. The size of the array is controlled by the XChildCount property.
This property is read-only and not available at design time.
Data Type
String
XChildXText Property (JSON Class)
This property contains the text of the element.
Syntax
QString GetXChildXText(int iXChildIndex);
Default Value
""
Remarks
This property contains the text of the element.
The XChildIndex parameter specifies the index of the item in the array. The size of the array is controlled by the XChildCount property.
This property is read-only and not available at design time.
Data Type
String
XElement Property (JSON Class)
The name of the current element.
Syntax
QString GetXElement();
int SetXElement(QString qsXElement);
Default Value
""
Remarks
This property contains the name of the current element. The current element is specified via the XPath property.
Data Type
String
XElementType Property (JSON Class)
Indicates the data type of the current element.
Syntax
int GetXElementType();
Possible Values
ET_OBJECT(0),
ET_ARRAY(1),
ET_STRING(2),
ET_NUMBER(3),
ET_BOOL(4),
ET_NULL(5)
Default Value
0
Remarks
This property specifies the data type of the current element. After setting XPath this property is populated. Possible values are:
- 0 (Object)
- 1 (Array)
- 2 (String)
- 3 (Number)
- 4 (Bool)
- 5 (Null)
- 6 (Raw)
Note: This property is not applicable when parsing a document and BuildDOM is False.
This property is read-only.
Data Type
Integer
XErrorPath Property (JSON Class)
An XPath to check the server response for errors.
Syntax
QString GetXErrorPath();
int SetXErrorPath(QString qsXErrorPath);
Default Value
""
Remarks
This property contains an XPath to check the server response for errors. If the XPath exists, an exception will be thrown containing the value of the element at the path.
Data Type
String
XParent Property (JSON Class)
The parent of the current element.
Syntax
QString GetXParent();
Default Value
""
Remarks
This property contains the parent of the current element. The current element is specified via the XPath property.
This property is read-only.
Data Type
String
XPath Property (JSON Class)
Provides a way to point to a specific element in the response.
Syntax
QString GetXPath();
int SetXPath(QString qsXPath);
Default Value
""
Remarks
XPath may be set to navigate to specific elements within the JSON document. This will be the path to a specified value within the document. Since arrays in JSON only contain values, and no associated object name, an empty name will be used for these values. To reach an array element at position 1, the path must be set to "[1]". In addition, a root element named "json" will be added to each JSON document in the parser.
BuildDOM must be set to True prior to parsing the document for the XPath functionality to be available.
The XPath property accepts both XPath and JSONPath formats. Please see notes below on both formats.
XPath
The path is a series of one or more element accessors separated by '/'. The path can be absolute (starting with '/') or relative to the current XPath location.
The following are possible values for an element accessor:
| 'name' | A particular element name. |
| [i] | The i-th subelement of the current element. |
| .. | the parent of the current element. |
When XPath is set to a valid path the following properties are updated:
- XElement
- XElementType
- XParent
- XText
- XSubTree
- XChildren*
BuildDOM must be set to True prior to parsing the document for the XPath functionality to be available.
Simple JSON document
{
"firstlevel": {
"one": "value",
"two": ["first", "second"],
"three": "value three"
}
}
Example (Setting XPath)
| Document root | JsonControl.XPath = "/" |
| Specific Element | JsonControl.XPath = "/json/firstlevel/one/" |
| i-th Child | JsonControl.XPath = "/json/firstlevel/two/[i]/" |
Note: When using XPath notation the root element is always referred to as "json". As in the above examples this means all paths will begin with "/json".
JSONPath
This property implements a subset of the JSONPath notation. This may be set to point to a specific element in the JSON document.The JSONPath is a series of one or more accessors in either dot-notation
$.store.book[0].titleOr bracket-notation
$['store']['book'][0]['title']
After setting XPath the following properties are populated:
- XChildren
- XElement
- XElementType
- XSubTree
- XText
Given the following JSON document:
{
"store": {
"book": [
{
"category": "reference",
"author": "Nigel Rees",
"title": "Sayings of the Century",
"price": 8.95
},
{
"category": "fiction",
"author": "Evelyn Waugh",
"title": "Sword of Honour",
"price": 12.99
},
{
"category": "fiction",
"author": "Herman Melville",
"title": "Moby Dick",
"isbn": "0-553-21311-3",
"price": 8.99
},
{
"category": "fiction",
"author": "J. R. R. Tolkien",
"title": "The Lord of the Rings",
"isbn": "0-395-19395-8",
"price": 22.99
}
],
"bicycle": {
"color": "red",
"price": 19.95
}
},
}
The following code shows several examples.
Get the first book's author:
json.XPath = "$.store.book[0].author";
Console.WriteLine(json.XText);
//Output
//"Nigel Rees"
Select the first book and inspect the children:
json.XPath = "$.store.book[0]";
Console.WriteLine("Child Count: " + json.XChildren.Count);
Console.WriteLine(json.XChildren[1].Name + ": " + json.XChildren[1].XText);
//Output
//Child Count: 4
//author: "Nigel Rees"
Get the price of the second book:
json.XPath = "$['store']['book'][1]['price']";
Console.WriteLine(json.XText);
//Output
//12.99
Get the second to last book's author:
json.XPath = "$['store']['book'][last() - 1]['author']";
Console.WriteLine(json.XText);
Console.WriteLine(json.XPath); //Note that "last() - 1" is resolved to "3".
//Output
//"Herman Melville"
//$['store']['book'][3]['author']
Display the full subtree at the current path:
json.XPath = "$.store.book[0]";
Console.WriteLine(json.XSubTree);
//Output
// {
// "category": "reference",
// "author": "Nigel Rees",
// "title": "Sayings of the Century",
// "price": 8.95
// }
Data Type
String
XSubTree Property (JSON Class)
A snapshot of the current element in the document.
Syntax
QString GetXSubTree();
Default Value
""
Remarks
The current element is specified via this property. In order for this property to work you must have the CacheContent set to true.
This property is read-only.
Data Type
String
XText Property (JSON Class)
The text of the current element.
Syntax
QString GetXText();
int SetXText(QString qsXText);
Default Value
""
Remarks
This property contains the text of the current element. The current element is specified via the XPath property.
Data Type
String
Config Method (JSON Class)
Sets or retrieves a configuration setting.
Syntax
QString Config(const QString& qsConfigurationString);
Remarks
Config is a generic method available in every class. It is used to set and retrieve configuration settings for the class.
These settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the class, access to these internal properties is provided through the Config method.
To set a configuration setting named PROPERTY, you must call Config("PROPERTY=VALUE"), where VALUE is the value of the setting expressed as a string. For boolean values, use the strings "True", "False", "0", "1", "Yes", or "No" (case does not matter).
To read (query) the value of a configuration setting, you must call Config("PROPERTY"). The value will be returned as a string.
Error Handling
This method returns a String value; after it returns, call the GetLastErrorCode() method to obtain its result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message.
EndArray Method (JSON Class)
Writes the closing bracket of a JSON array.
Syntax
int EndArray();
Remarks
This method writes the closing bracket of a JSON array to the output. An array must already have been opened by calling StartArray.
Error Handling
This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)
EndObject Method (JSON Class)
Writes the closing brace of a JSON object.
Syntax
int EndObject();
Remarks
This method writes the closing brace of a JSON object. A object must have previously been started by calling StartObject.
Error Handling
This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)
Flush Method (JSON Class)
Flushes the parser's or writer's buffers.
Syntax
int Flush();
Remarks
When Flush is called, the component flushes all its buffers, firing events as necessary.
When parsing, then the end state of the JSON is checked. If Validate is also true, the parser verifies that all open elements were closed, returning an error if not.
When writing, the resultant JSON is available in one of the output properties.
Output Properties
The class will determine the destination of the output based on which properties are set.
The order in which the output properties are checked is as follows:
- OutputFile
- OutputData: The output data is written to this property if no other destination is specified.
Error Handling
This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)
HasXPath Method (JSON Class)
Determines whether a specific element exists in the document.
Syntax
bool HasXPath(const QString& qsXPath);
Remarks
This method determines whether a particular XPath exists within the document. This may be used to check if a path exists before setting it via XPath.
This method returns True if the xpath exists, False if not.
See XPath for details on the XPath syntax.
Error Handling
This method returns a Boolean value; after it returns, call the GetLastErrorCode() method to obtain its result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message.
InsertProperty Method (JSON Class)
This method inserts the specified name and value at the selected position.
Syntax
int InsertProperty(const QString& qsName, const QString& qsValue, int iValueType, int iPosition);
Remarks
This method inserts a property and its corresponding value relative to the element specified by XPath. Before calling this method a valid JSON document must first be loaded by calling Parse.
The Name parameter specifies the name of the property.
The Value parameter specifies the value of the property.
The ValueType parameter specifies the type of the value. Possible values are:
- 0 (Object)
- 1 (Array)
- 2 (String)
- 3 (Number)
- 4 (Bool)
- 5 (Null)
- 6 (Raw)
The Position parameter specifies the position of Value relative to the element specified by XPath. Possible values are:
- 0 (Before the current element)
- 1 (After the current element)
- 2 (The first child of the current element)
- 3 (The last child of the current element)
See Save for details.
Error Handling
This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)
InsertValue Method (JSON Class)
This method inserts the specified value at the selected position.
Syntax
int InsertValue(const QString& qsValue, int iValueType, int iPosition);
Remarks
This method inserts a value relative to the element specified by XPath. Before calling this method a valid JSON document must first be loaded by calling Parse.
The Value parameter specifies the value of the property.
The ValueType parameter specifies the type of the value. Possible values are:
- 0 (Object)
- 1 (Array)
- 2 (String)
- 3 (Number)
- 4 (Bool)
- 5 (Null)
- 6 (Raw)
The Position parameter specifies the position of Value relative to the element specified by XPath. Possible values are:
- 0 (Before the current element)
- 1 (After the current element)
- 2 (The first child of the current element)
- 3 (The last child of the current element)
See Save for details.
Error Handling
This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)
Parse Method (JSON Class)
This method parses the specified JSON data.
Syntax
int Parse();
Remarks
This method parses the specified JSON data.
When parsing a document events will fire to provide information about the parsed data. After Parse returns the document may be navigated by setting XPath if BuildDOM is True (default). If BuildDOM is False parsed data is only accessible through the events.
The following events will fire during parsing:
If BuildDOM is True (default), XPath may be set after this method returns. XPath may be set to navigate to specific elements within the JSON document. This will be the path to a specified value within the document. Since arrays in JSON only contain values, and no associated object name, an empty name will be used for these values. To reach an array element at position 1, the path must be set to "[1]". In addition, a root element named "json" will be added to each JSON document in the parser.
BuildDOM must be set to True prior to parsing the document for the XPath functionality to be available.
The XPath property accepts both XPath and JSONPath formats. Please see notes below on both formats.
XPath
The path is a series of one or more element accessors separated by '/'. The path can be absolute (starting with '/') or relative to the current XPath location.
The following are possible values for an element accessor:
| 'name' | A particular element name. |
| [i] | The i-th subelement of the current element. |
| .. | the parent of the current element. |
When XPath is set to a valid path the following properties are updated:
- XElement
- XElementType
- XParent
- XText
- XSubTree
- XChildren*
BuildDOM must be set to True prior to parsing the document for the XPath functionality to be available.
Simple JSON document
{
"firstlevel": {
"one": "value",
"two": ["first", "second"],
"three": "value three"
}
}
Example (Setting XPath)
| Document root | JsonControl.XPath = "/" |
| Specific Element | JsonControl.XPath = "/json/firstlevel/one/" |
| i-th Child | JsonControl.XPath = "/json/firstlevel/two/[i]/" |
Note: When using XPath notation the root element is always referred to as "json". As in the above examples this means all paths will begin with "/json".
JSONPath
This property implements a subset of the JSONPath notation. This may be set to point to a specific element in the JSON document.The JSONPath is a series of one or more accessors in either dot-notation
$.store.book[0].titleOr bracket-notation
$['store']['book'][0]['title']
After setting XPath the following properties are populated:
- XChildren
- XElement
- XElementType
- XSubTree
- XText
Given the following JSON document:
{
"store": {
"book": [
{
"category": "reference",
"author": "Nigel Rees",
"title": "Sayings of the Century",
"price": 8.95
},
{
"category": "fiction",
"author": "Evelyn Waugh",
"title": "Sword of Honour",
"price": 12.99
},
{
"category": "fiction",
"author": "Herman Melville",
"title": "Moby Dick",
"isbn": "0-553-21311-3",
"price": 8.99
},
{
"category": "fiction",
"author": "J. R. R. Tolkien",
"title": "The Lord of the Rings",
"isbn": "0-395-19395-8",
"price": 22.99
}
],
"bicycle": {
"color": "red",
"price": 19.95
}
},
}
The following code shows several examples.
Get the first book's author:
json.XPath = "$.store.book[0].author";
Console.WriteLine(json.XText);
//Output
//"Nigel Rees"
Select the first book and inspect the children:
json.XPath = "$.store.book[0]";
Console.WriteLine("Child Count: " + json.XChildren.Count);
Console.WriteLine(json.XChildren[1].Name + ": " + json.XChildren[1].XText);
//Output
//Child Count: 4
//author: "Nigel Rees"
Get the price of the second book:
json.XPath = "$['store']['book'][1]['price']";
Console.WriteLine(json.XText);
//Output
//12.99
Get the second to last book's author:
json.XPath = "$['store']['book'][last() - 1]['author']";
Console.WriteLine(json.XText);
Console.WriteLine(json.XPath); //Note that "last() - 1" is resolved to "3".
//Output
//"Herman Melville"
//$['store']['book'][3]['author']
Display the full subtree at the current path:
json.XPath = "$.store.book[0]";
Console.WriteLine(json.XSubTree);
//Output
// {
// "category": "reference",
// "author": "Nigel Rees",
// "title": "Sayings of the Century",
// "price": 8.95
// }
Input Properties
The class will determine the source of the input based on which properties are set.
The order in which the input properties are checked is as follows:
When a valid source is found the search stops.If parsing multiple documents call Reset between documents to reset the parser.
Error Handling
This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)
PutName Method (JSON Class)
Writes the name of a property.
Syntax
int PutName(const QString& qsName);
Remarks
This method writes the name of a property. The Name parameter specifies the value to write.
Error Handling
This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)
PutProperty Method (JSON Class)
Write a property and value.
Syntax
int PutProperty(const QString& qsName, const QString& qsValue, int iValueType);
Remarks
This method writes a property and its corresponding value to the output.
The Name parameter specifies the name of the property.
The Value parameter specifies the value of the property.
The ValueType parameter specifies the type of the value. Possible values are:
- 0 (Object)
- 1 (Array)
- 2 (String)
- 3 (Number)
- 4 (Bool)
- 5 (Null)
- 6 (Raw)
Error Handling
This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)
PutRaw Method (JSON Class)
Writes a raw JSON fragment.
Syntax
int PutRaw(const QString& qsText);
Remarks
This method writes raw data to the output. This may be used to write any data of any format directly to the output.
Error Handling
This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)
PutValue Method (JSON Class)
Writes a value of a property.
Syntax
int PutValue(const QString& qsValue, int iValueType);
Remarks
This method writes the value of a property to the output. The Value parameter specifies the value. The ValueType parameter specifies the type of data. Possible values are:
- 0 (Object)
- 1 (Array)
- 2 (String)
- 3 (Number)
- 4 (Bool)
- 5 (Null)
- 6 (Raw)
Error Handling
This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)
Remove Method (JSON Class)
Removes the element or value set in XPath.
Syntax
int Remove();
Remarks
This method removes the current object at the specified XPath. This is used when editing previously loaded JSON documents.
See Save for details.
Error Handling
This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)
Reset Method (JSON Class)
Resets the class.
Syntax
int Reset();
Remarks
This method resets the JSON parser.
Error Handling
This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)
Save Method (JSON Class)
Saves the modified JSON document.
Syntax
int Save();
Remarks
This method saves the modified JSON data. This is used after editing a previously loaded JSON document.
After loading a JSON document with Parse the document may be editted. The class supports inserting new values, renaming or overwriting existing values, and removing values. After editting is complete call Save to output the updated JSON document.
The following methods are applicable when modifying a JSON document:
When Save is called the modified JSON is written to the specified output location.
Output Properties
The class will determine the destination of the output based on which properties are set.
The order in which the output properties are checked is as follows:
- OutputFile
- OutputData: The output data is written to this property if no other destination is specified.
Inserting New Values
To insert new values in a JSON document first load the existing document with Parse. Next set XPath to the sibling or parent of the data to be inserted. Call InsertProperty or InsertValue and pass the ValueType and Position parameters to indicate the type of data being inserted and the position.
The ValueType parameter of the above methods specifies the type of the value. Possible values are:
- 0 (Object)
- 1 (Array)
- 2 (String)
- 3 (Number)
- 4 (Bool)
- 5 (Null)
- 6 (Raw)
The Position parameter of the above methods specifies the position of Value. Possible values are:
- 0 (Before the current element)
- 1 (After the current element)
- 2 (The first child of the current element)
- 3 (The last child of the current element)
For example:
Given the following JSON:
{
"store": {
"books": [
{
"category": "reference",
"author": "Nigel Rees",
"title": "Sayings of the Century",
},
{
"category": "fiction",
"author": "Evelyn Waugh",
"title": "Sword of Honour",
}
]
}
}
Insert a new property "price" for each book:
json.XPath = "/json/store/books/[1]";
json.InsertProperty("price", "8.95", 3, 3); //3 - Number, 3 - Last Child
json.XPath = "/json/store/books/[2]";
json.InsertProperty("price", "12.99", 3, 3); //3 - Number, 3 - Last Child
json.Save();
Produces the JSON:
{
"store": {
"books": [
{
"category": "reference",
"author": "Nigel Rees",
"title": "Sayings of the Century",
"price": 8.95
},
{
"category": "fiction",
"author": "Evelyn Waugh",
"title": "Sword of Honour",
"price": 12.99
}
]
}
}
To add a new book to the array:
json.XPath = "/json/store/books";
json.InsertValue("", 0, 3); //0 - Object, 3 - Last Child
json.XPath = "/json/store/books/[3]";
json.InsertProperty("category", "fiction", 2, 3); //2 - String, 3 - Last Child
json.InsertProperty("author", "Herman Melville", 2, 3); //2 - String, 3 - Last Child
json.InsertProperty("title", "Moby Dick", 2, 3); //2 - String, 3 - Last Child
json.InsertProperty("price", "8.99", 3, 3); //3 - Number, 3 - Last Child
json.Save();
Produces the JSON:
{
"store": {
"books": [
{
"category": "reference",
"author": "Nigel Rees",
"title": "Sayings of the Century",
"price": 8.95
},
{
"category": "fiction",
"author": "Evelyn Waugh",
"title": "Sword of Honour",
"price": 12.99
},
{
"category": "fiction",
"author": "Herman Melville",
"title": "Moby Dick",
"price": 8.99
}
]
}
}
To add a new array property to each book:
json.XPath = "/json/store/books/[1]";
json.InsertProperty("tags", "", 1, 2); //1 - Array, 2 - First Child
json.XPath = "/json/store/books/[1]/tags";
json.InsertValue("quotes", 2, 3); //2 - String, 3 - Last Child
json.InsertValue("british", 2, 3); //2 - String, 3 - Last Child
json.XPath = "/json/store/books/[2]";
json.InsertProperty("tags", "", 1, 2); //1 - Array, 2 - First Child
json.XPath = "/json/store/books/[2]/tags";
json.InsertValue("trilogy", 2, 3); //2 - String, 3 - Last Child
json.InsertValue("war", 2, 3); //2 - String, 3 - Last Child
json.XPath = "/json/store/books/[3]";
json.InsertProperty("tags", "", 1, 2); //1 - Array, 2 - First Child
json.XPath = "/json/store/books/[3]/tags";
json.InsertValue("classic", 2, 3); //2 - String, 3 - Last Child
json.InsertValue("whales", 2, 3); //2 - String, 3 - Last Child
json.Save();
Producse the JSON:
{
"store": {
"books": [
{
"tags": ["quotes", "british"],
"category": "reference",
"author": "Nigel Rees",
"title": "Sayings of the Century",
"price": 8.95
},
{
"tags": ["trilogy", "war"],
"category": "fiction",
"author": "Evelyn Waugh",
"title": "Sword of Honour",
"price": 12.99
},
{
"tags": ["classic", "whales"],
"category": "fiction",
"author": "Herman Melville",
"title": "Moby Dick",
"price": 8.99
}
]
}
}
Removing Values
To remove existing values set XPath and call the Remove method. Continuing with the example above, to remove
the first book:
json.XPath = "/json/store/books/[1]";
json.Remove();
json.Save();
Produces the JSON:
{
"store": {
"books": [
{
"tags": ["trilogy", "war"],
"category": "fiction",
"author": "Evelyn Waugh",
"title": "Sword of Honour",
"price": 12.99
},
{
"tags": ["classic", "whales"],
"category": "fiction",
"author": "Herman Melville",
"title": "Moby Dick",
"price": 8.99
}
]
}
}
To remove the "category" properties from each book:
json.XPath = "/json/store/books/[1]/category";
json.Remove();
json.XPath = "/json/store/books/[2]/category";
json.Remove();
json.Save();
Produces the JSON:
{
"store": {
"books": [
{
"tags": ["trilogy", "war"],
"author": "Evelyn Waugh",
"title": "Sword of Honour",
"price": 12.99
},
{
"tags": ["classic", "whales"],
"author": "Herman Melville",
"title": "Moby Dick",
"price": 8.99
}
]
}
}
Updating Existing Names and Values
The SetName and SetValue methods may be used to modify existing names and values. Continuing with the JSON directly above, to rename "tags" to "meta" and update values within the array and prices:
//Rename "tags" to "meta" for 1st book
json.XPath = "/json/store/books/[1]/tags";
json.SetName("meta");
//Update Price
json.XPath = "/json/store/books/[1]/price";
json.SetValue("13.99", 3); //3 - Number
//Rename "tags" to "meta" for 2nd book
json.XPath = "/json/store/books/[2]/tags";
json.SetName("meta");
//Update tag "whales" to "revenge"
json.XPath = "/json/store/books/[2]/meta/[2]";
json.SetValue("revenge", 2); //2 - String
//Update Price
json.XPath = "/json/store/books/[2]/price";
json.SetValue("9.99", 3); //3 - Number
json.Save();
Produces the JSON:
{
"store": {
"books": [
{
"meta": ["trilogy", "war"],
"author": "Evelyn Waugh",
"title": "Sword of Honour",
"price": 13.99
},
{
"meta": ["classic", "revenge"],
"author": "Herman Melville",
"title": "Moby Dick",
"price": 9.99
}
]
}
}
Error Handling
This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)
SetName Method (JSON Class)
Sets a new name for the element specified by XPath.
Syntax
int SetName(const QString& qsName);
Remarks
This method sets a new name for the element specified in XPath. This is used to modify an existing JSON document.
The Name parameter specifies the new name of the element.
See Save for details.
Error Handling
This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)
SetValue Method (JSON Class)
Sets a new value for the element specified by XPath.
Syntax
int SetValue(const QString& qsValue, int iValueType);
Remarks
This method sets a new value for the element specified in XPath. This is used to modify an existing JSON document.
Value specifies the new value.
ValueType specifies the type of the value. Possible values are:
- 0 (Object)
- 1 (Array)
- 2 (String)
- 3 (Number)
- 4 (Bool)
- 5 (Null)
- 6 (Raw)
See Save for details.
Error Handling
This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)
StartArray Method (JSON Class)
Writes the opening bracket of a JSON array.
Syntax
int StartArray();
Remarks
This method writes the opening bracket of a JSON array to the output. To close the array call EndArray.
Error Handling
This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)
StartObject Method (JSON Class)
Writes the opening brace of a JSON object.
Syntax
int StartObject();
Remarks
This method writes the opening brace of a JSON object to the output. To close the object call EndObject.
Error Handling
This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)
TryXPath Method (JSON Class)
Navigates to the specified XPath if it exists.
Syntax
bool TryXPath(const QString& qsxpath);
Remarks
This method will attempt to navigate to the specified XPath parameter if it exists within the document.
If the XPath exists the XPath property will be updated and this method returns True.
If the XPath does not exist the XPath property is not updated and this method returns False.
Error Handling
This method returns a Boolean value; after it returns, call the GetLastErrorCode() method to obtain its result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message.
Characters Event (JSON Class)
Fired for plain text segments of the input stream.
Syntax
class JSONCharactersEventParams {
public:
const QString &Text();
int EventRetVal();
void SetEventRetVal(int iRetVal);
};
// To handle, connect one or more slots to this signal.
void Characters(JSONCharactersEventParams *e);
// Or, subclass JSON and override this emitter function.
virtual int FireCharacters(JSONCharactersEventParams *e) {...}
Remarks
The Characters event provides the plain text content of the JSON document (i.e. the text inside the elements). The text is provided through the Text parameter.
The text includes white space as well as end of line characters, except for ignorable whitespace which is fired through the IgnorableWhitespace event.
EndDocument Event (JSON Class)
Fires when the end of a JSON document is encountered.
Syntax
class JSONEndDocumentEventParams {
public:
int EventRetVal();
void SetEventRetVal(int iRetVal);
};
// To handle, connect one or more slots to this signal.
void EndDocument(JSONEndDocumentEventParams *e);
// Or, subclass JSON and override this emitter function.
virtual int FireEndDocument(JSONEndDocumentEventParams *e) {...}
Remarks
This event fires when parsing of a JSON document ends. This event may fire multiple times if InputFormat is set to a value which accepts multiple JSON documents.
EndElement Event (JSON Class)
Fired when an end-element tag is encountered.
Syntax
class JSONEndElementEventParams {
public:
const QString &Element();
int EventRetVal();
void SetEventRetVal(int iRetVal);
};
// To handle, connect one or more slots to this signal.
void EndElement(JSONEndElementEventParams *e);
// Or, subclass JSON and override this emitter function.
virtual int FireEndElement(JSONEndElementEventParams *e) {...}
Remarks
The EndElement event is fired when the end of an element is found in the document.
The element name is provided by the Element parameter.
Error Event (JSON Class)
Information about errors during data delivery.
Syntax
class JSONErrorEventParams {
public:
int ErrorCode();
const QString &Description();
int EventRetVal();
void SetEventRetVal(int iRetVal);
};
// To handle, connect one or more slots to this signal.
void Error(JSONErrorEventParams *e);
// Or, subclass JSON and override this emitter function.
virtual int FireError(JSONErrorEventParams *e) {...}
Remarks
The Error event is fired in case of exceptional conditions during message processing. Normally the class fails with an error.
ErrorCode contains an error code and Description contains a textual description of the error. For a list of valid error codes and their descriptions, please refer to the Error Codes section.
IgnorableWhitespace Event (JSON Class)
Fired when a section of ignorable whitespace is encountered.
Syntax
class JSONIgnorableWhitespaceEventParams {
public:
const QString &Text();
int EventRetVal();
void SetEventRetVal(int iRetVal);
};
// To handle, connect one or more slots to this signal.
void IgnorableWhitespace(JSONIgnorableWhitespaceEventParams *e);
// Or, subclass JSON and override this emitter function.
virtual int FireIgnorableWhitespace(JSONIgnorableWhitespaceEventParams *e) {...}
Remarks
The ignorable whitespace section is provided by the Text parameter.
JSON Event (JSON Class)
Fires with the JSON data being written.
Syntax
class JSONJSONEventParams {
public:
const QString &Text();
int EventRetVal();
void SetEventRetVal(int iRetVal);
};
// To handle, connect one or more slots to this signal.
void JSONEvt(JSONJSONEventParams *e);
// Or, subclass JSON and override this emitter function.
virtual int FireJSON(JSONJSONEventParams *e) {...}
Remarks
This event fires when output data is written.
Text contains the JSON data currently being written.
StartDocument Event (JSON Class)
Fires when the start of a new JSON document is encountered.
Syntax
class JSONStartDocumentEventParams {
public:
int EventRetVal();
void SetEventRetVal(int iRetVal);
};
// To handle, connect one or more slots to this signal.
void StartDocument(JSONStartDocumentEventParams *e);
// Or, subclass JSON and override this emitter function.
virtual int FireStartDocument(JSONStartDocumentEventParams *e) {...}
Remarks
This event fires when parsing of a JSON document begins. This event may fire multiple times if InputFormat is set to a value which accepts multiple JSON documents.
StartElement Event (JSON Class)
Fired when a new element is encountered in the document.
Syntax
class JSONStartElementEventParams {
public:
const QString &Element();
int EventRetVal();
void SetEventRetVal(int iRetVal);
};
// To handle, connect one or more slots to this signal.
void StartElement(JSONStartElementEventParams *e);
// Or, subclass JSON and override this emitter function.
virtual int FireStartElement(JSONStartElementEventParams *e) {...}
Remarks
The StartElement event is fired when a new element is found in the document.
The element name is provided through the Element parameter.
Configuration Settings (JSON Class)
The class accepts one or more of the following configuration settings. Configuration settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the class, access to these internal properties is provided through the Config method.JSON Configuration Settings | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| CacheContent:
If true, the original JSON is stored internally in a buffer. This config controls whether or not the class retains the entire original JSON data in a buffer. This is used to retain the original JSON as opposed to returning generated JSON after parsing. The default value is true. |
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| ElementXPath:
The XPath value for the current element in the document. This setting holds the current XPath value when the document is parsed. When queried from inside the StartElement event, the corresponding element's XPath value will be returned. For instance:
Note: The BuildDOM property must be set to false. |
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| EscapeForwardSlashes:
Whether to escape forward slashes when writing a JSON object. This setting specifies whether forward slashes (/) are escaped when creating a JSON object using the class. This does not affect parsing of JSON, only when JSON values are written. |
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| InputFormat:
Specifies the input format used in JSON streaming. This setting specifies how JSON documents are formatted as they are input to the class. This setting is designed for use when data is provided via JSON streaming. This means multiple documents may be parsed by the class. This setting is only applicable when BuildDOM is set to False. Possible values are:
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| PrettyPrint:
Determines whether output is on one line or "pretty printed". The value of this configuration setting determines whether output is generated as a single line of JSON or
multiple, "pretty printed" lines.
For a better understanding please take the example code below:
{"data":{"id":3,"first_name":"Emma","last_name":"Wong","avatar":"https:\/\/s3.amazonaws.com\/uifaces\/faces\/twitter\/olegpogodaev\/128.jpg"}}
With PrettyPrint set to True the output would instead be this:
{
"data": {
"id": 3,
"first_name": "Emma",
"last_name": "Wong",
"avatar": "https:\/\/s3.amazonaws.com\/uifaces\/faces\/twitter\/olegpogodaev\/128.jpg"
}
}
The default value is False.
|
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| RecordEndDelimiter:
The character sequence after the end of a JSON document. This setting is used in conjunction with InputFormat to specify the character sequence that is expected after the end of a JSON document. |
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| RecordStartDelimiter:
The character sequence before the start of a JSON document. This setting is used in conjunction with InputFormat to specify the character sequence that is expected before the start of a JSON document. |
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| StringProcessingOptions:
Defines options to use when processing string values. This setting determines what additional processing is performed on string values during parsing. By default no additional processing is performed and the string is returned as is from the document. Strings may also be unquoted, unescaped, or both. Possible values are:
For instance, given the JSON element: "example" : "value\ntest"The following table shows the resulting value for the XText of the element.
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| XPathNotation:
Specifies the expected format when setting XPath. This setting optionally specifies the expected input format when setting XPath. Possible values are:
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Base Configuration Settings | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| BuildInfo:
Information about the product's build. When queried, this setting will return a string containing information about the product's build. |
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| CodePage:
The system code page used for Unicode to Multibyte translations. The default code page is Unicode UTF-8 (65001). The following is a list of valid code page identifiers:
The following is a list of valid code page identifiers for Mac OS only:
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| LicenseInfo:
Information about the current license. When queried, this setting will return a string containing information about the license this instance of a class is using. It will return the following information:
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| UseInternalSecurityAPI:
Tells the class whether or not to use the system security libraries or an internal implementation. By default the class will use the system security libraries to perform cryptographic functions where applicable. Setting this to true tells the class to use the internal implementation instead of using the system's security API. |
Trappable Errors (JSON Class)
JSON Errors
| 10231 Unbalanced element tag. | |
| 10232 Invalid JSON markup. | |
| 10233 Invalid XPath. | |
| 10234 DOM tree unavailable (set BuildDOM to true and reparse). |
XML Errors
| 101 Invalid attribute index. | |
| 102 No attributes available. | |
| 103 Invalid namespace index. | |
| 104 No namespaces available. | |
| 105 Invalid element index. | |
| 106 No elements available. | |
| 107 Attribute does not exist. | |
| 201 Unbalanced element tag. | |
| 202 Unknown element prefix (can't find namespace). | |
| 203 Unknown attribute prefix (can't find namespace). | |
| 204 Invalid XML markup. | |
| 205 Invalid end state for parser. | |
| 206 Document contains unbalanced elements. | |
| 207 Invalid XPath. | |
| 208 No such child. | |
| 209 Top element does not match start of path. | |
| 210 DOM tree unavailable (set BuildDOM to true and reparse). | |
| 302 Can't open file. | |
| 401 Invalid XML would be generated. | |
| 402 An invalid XML name has been specified. |