JSON Class

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The JSON class can be used to parse and write JSON documents.

Syntax

ipworksiot.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 that 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, it may be navigated by setting XPath if BuildDOM is True (default). If BuildDOM is False, parsed data are accessible only through the events.

The following events will fire during parsing:

• StartElement
• Characters
• EndElement
• IgnorableWhitespace

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. Because 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 before parsing the document for the XPath functionality to be available.

The XPath property accepts both XPath and JSONPath formats. Please review the following notes 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:

• XElement
• XElementType
• XParent
• XText
• XSubTree
• XChildren

BuildDOM must be set to True before parsing the document for the XPath functionality to be available.

Simple JSON Document

{
  "firstlevel": {
    "one": "value",
    "two": ["first", "second"],
    "three": "value three"
  }
}

JSONPath

The JSONPath is a series of one or more accessors in either dot-notation

$.store.book[0].title

$['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
        }
    },
}

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:

• SetInputStream
• InputFile
• InputData

If parsing multiple documents, call Reset between documents to reset the parser.

Writing JSON

The JSON class also can 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:

• SetOutputStream
• OutputFile
• OutputData: The output data are written to this property if no other destination is specified.

Example. Writing a JSON Document:

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 edited. The class supports inserting new values, renaming or overwriting existing values, and removing values. After editing is complete, call Save to output the updated JSON document.

The following methods are applicable when modifying a JSON document:

• InsertProperty
• InsertValue
• Remove
• Save
• SetName
• SetValue

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:

• SetOutputStream
• OutputFile
• OutputData: The output data are written to this property if no other destination is specified.

Example 1. 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 these methods specifies the type of the value. Possible values are as follows:

• 0 (Object)
• 1 (Array)
• 2 (String)
• 3 (Number)
• 4 (Bool)
• 5 (Null)
• 6 (Raw)

The Position parameter of these methods specifies the position of Value. Possible values are as follows:

• 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();

Produces 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
    }
    ]
  }
}

Example 2. Removing Values:

To remove existing values, set XPath and call the Remove method. Continuing with example 1, 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
    }
    ]
  }
}

Example 3. Updating Existing Names and Values:

The SetName and SetValue methods may be used to modify existing names and values. Continuing with the preceding JSON in example 2, 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.

Method List

The following is the full list of the methods of the class with short descriptions. Click on the links for further details.

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.

Config Settings

The following is a list of config settings for the class with short descriptions. Click on the links for further details.

BuildDOM Property (JSON Class)

When True, an internal object model of the JSON document is created.

Syntax

public boolean isBuildDOM();
public void setBuildDOM(boolean buildDOM);

Default Value

True

Remarks

Set this property to True when you need to browse the current document through XPath.

InputData Property (JSON Class)

This property includes the JSON data to parse.

Syntax

public String getInputData();
public void setInputData(String inputData);

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:

• SetInputStream
• InputFile
• InputData

InputFile Property (JSON Class)

This property specifies the file to process.

Syntax

public String getInputFile();
public void setInputFile(String inputFile);

Default Value

""

Remarks

This property specifies the file to be processed. Set this property to the full or relative path to the file that 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:

• SetInputStream
• InputFile
• InputData

OutputData Property (JSON Class)

This property includes the output JSON after processing.

Syntax

public String getOutputData();
public void setOutputData(String outputData);

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:

• SetOutputStream
• OutputFile
• OutputData: The output data are written to this property if no other destination is specified.

OutputFile Property (JSON Class)

This is the path to a local file where the output will be written.

Syntax

public String getOutputFile();
public void setOutputFile(String outputFile);

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:

• SetOutputStream
• OutputFile
• OutputData: The output data are written to this property if no other destination is specified.

Overwrite Property (JSON Class)

This property indicates whether or not the class should overwrite files.

Syntax

public boolean isOverwrite();
public void setOverwrite(boolean overwrite);

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.

Validate Property (JSON Class)

This property controls whether documents are validated during parsing.

Syntax

public boolean isValidate();
public void setValidate(boolean validate);

Default Value

True

Remarks

When true (default), the document will be validated during parsing. To disable validation set Validate to false. Disabling validation may be useful in cases in which data can still be parsed even if the document is not well formed.

XChildren Property (JSON Class)

This property includes a collection of child elements of the current element.

Syntax

public JSONElementList getXChildren();
public void setXChildren(JSONElementList XChildren);

Remarks

This property contains a collection of child elements of the current element. The elements are provided in the collection in the same order they are found in the document.

This collection is indexed from 0 to size -1.

This property is not available at design time.

XElement Property (JSON Class)

This property includes the name of the current element.

Syntax

public String getXElement();
public void setXElement(String XElement);

Default Value

""

Remarks

This property contains the name of the current element. The current element is specified through the XPath property.

XElementType Property (JSON Class)

This property indicates the data type of the current element.

Syntax

public int getXElementType();

Enumerated values:
  public final static int etObject = 0;
  public final static int etArray = 1;
  public final static int etString = 2;
  public final static int etNumber = 3;
  public final static int etBool = 4;
  public final static int etNull = 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 as follows:

• 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.

XErrorPath Property (JSON Class)

This property includes an XPath to check the server response for errors.

Syntax

public String getXErrorPath();
public void setXErrorPath(String XErrorPath);

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.

XParent Property (JSON Class)

The parent of the current element.

Syntax

public String 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.

XPath Property (JSON Class)

This property provides a way to point to a specific element in the response.

Syntax

public String getXPath();
public void setXPath(String XPath);

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. Because 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 before parsing the document for the XPath functionality to be available.

The XPath property accepts both XPath and JSONPath formats. Please review the following notes 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:

• XElement
• XElementType
• XParent
• XText
• XSubTree
• XChildren

BuildDOM must be set to True before parsing the document for the XPath functionality to be available.

Simple JSON Document

{
  "firstlevel": {
    "one": "value",
    "two": ["first", "second"],
    "three": "value three"
  }
}

JSONPath

The JSONPath is a series of one or more accessors in either dot-notation

$.store.book[0].title

$['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
        }
    },
}

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 // }

XSubTree Property (JSON Class)

This property includes a snapshot of the current element in the document.

Syntax

public String getXSubTree();

Default Value

""

Remarks

The current element is specified through this property. For this property to work, you must have the CacheContent set to True.

This property is read-only.

XText Property (JSON Class)

This property includes the text of the current element.

Syntax

public String getXText();
public void setXText(String XText);

Default Value

""

Remarks

This property contains the text of the current element. The current element is specified through the XPath property.

Config Method (JSON Class)

Sets or retrieves a configuration setting.

Syntax

public String config(String configurationString);

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.

EndArray Method (JSON Class)

This method writes the closing bracket of a JSON array.

Syntax

public void 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.

EndObject Method (JSON Class)

This method writes the closing brace of a JSON object.

Syntax

public void endObject();

Remarks

This method writes the closing brace of a JSON object. An object must have been started previously by calling StartObject.

Flush Method (JSON Class)

This method flushes the parser's or writer's buffers.

Syntax

public void flush();

Remarks

When Flush is called, the component flushes all of its buffers, firing events as necessary.

When parsing, 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:

• SetOutputStream
• OutputFile
• OutputData: The output data are written to this property if no other destination is specified.

HasXPath Method (JSON Class)

This method determines whether a specific element exists in the document.

Syntax

public boolean hasXPath(String XPath);

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 through XPath.

This method returns True if the xpath exists, and False if not.

See XPath for details on the XPath syntax.

InsertProperty Method (JSON Class)

This method inserts the specified name and value at the selected position.

Syntax

public void insertProperty(String name, String value, int valueType, int position);

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 as follows:

• 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 as follows:

• 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.

InsertValue Method (JSON Class)

This method inserts the specified value at the selected position.

Syntax

public void insertValue(String value, int valueType, int position);

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 as follows:

• 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 as follows:

• 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.

Parse Method (JSON Class)

This method parses the specified JSON data.

Syntax

public void 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, it may be navigated by setting XPath if BuildDOM is True (default). If BuildDOM is False, parsed data are accessible only through the events.

The following events will fire during parsing:

• StartElement
• Characters
• EndElement
• IgnorableWhitespace

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. Because 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 before parsing the document for the XPath functionality to be available.

The XPath property accepts both XPath and JSONPath formats. Please review the following notes 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:

• XElement
• XElementType
• XParent
• XText
• XSubTree
• XChildren

BuildDOM must be set to True before parsing the document for the XPath functionality to be available.

Simple JSON Document

{
  "firstlevel": {
    "one": "value",
    "two": ["first", "second"],
    "three": "value three"
  }
}

JSONPath

The JSONPath is a series of one or more accessors in either dot-notation

$.store.book[0].title

$['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
        }
    },
}

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:

• SetInputStream
• InputFile
• InputData

If parsing multiple documents, call Reset between documents to reset the parser.

PutName Method (JSON Class)

This method writes the name of a property.

Syntax

public void putName(String name);

Remarks

This method writes the name of a property. The Name parameter specifies the value to write.

PutProperty Method (JSON Class)

This method writes a property and value.

Syntax

public void putProperty(String name, String value, int valueType);

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 as follows:

• 0 (Object)
• 1 (Array)
• 2 (String)
• 3 (Number)
• 4 (Bool)
• 5 (Null)
• 6 (Raw)

PutRaw Method (JSON Class)

This method writes a raw JSON fragment.

Syntax

public void putRaw(String text);

Remarks

This method writes raw data to the output. This may be used to write any data of any format directly to the output.

PutValue Method (JSON Class)

This method writes a value of a property.

Syntax

public void putValue(String value, int valueType);

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 as follows:

• 0 (Object)
• 1 (Array)
• 2 (String)
• 3 (Number)
• 4 (Bool)
• 5 (Null)
• 6 (Raw)

Remove Method (JSON Class)

This method removes the element or value set in XPath.

Syntax

public void 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.

Reset Method (JSON Class)

This method resets the class.

Syntax

public void reset();

Remarks

This method resets the JSON parser.

Save Method (JSON Class)

This method saves the modified JSON document.

Syntax

public void 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 edited. The class supports inserting new values, renaming or overwriting existing values, and removing values. After editing is complete, call Save to output the updated JSON document.

The following methods are applicable when modifying a JSON document:

• InsertProperty
• InsertValue
• Remove
• Save
• SetName
• SetValue

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:

• SetOutputStream
• OutputFile
• OutputData: The output data are written to this property if no other destination is specified.

Example 1. 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 these methods specifies the type of the value. Possible values are as follows:

• 0 (Object)
• 1 (Array)
• 2 (String)
• 3 (Number)
• 4 (Bool)
• 5 (Null)
• 6 (Raw)

The Position parameter of these methods specifies the position of Value. Possible values are as follows:

• 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();

Produces 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
    }
    ]
  }
}

Example 2. Removing Values:

To remove existing values, set XPath and call the Remove method. Continuing with example 1, 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
    }
    ]
  }
}

Example 3. Updating Existing Names and Values:

The SetName and SetValue methods may be used to modify existing names and values. Continuing with the preceding JSON in example 2, 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
    }
    ]
  }
}

SetInputStream Method (JSON Class)

This method sets the stream from which the class will read data to parse.

Syntax

public void setInputStream(java.io.InputStream inputStream);

Remarks

This method specifies a stream from which data will be read when Parse is called.

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:

• SetInputStream
• InputFile
• InputData

SetName Method (JSON Class)

This method sets a new name for the element specified by XPath.

Syntax

public void setName(String name);

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.

SetOutputStream Method (JSON Class)

This method sets the stream to which the class will write the JSON.

Syntax

public void setOutputStream(java.io.OutputStream outputStream);

Remarks

This method sets the stream to which the output will be written when writing data.

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:

• SetOutputStream
• OutputFile
• OutputData: The output data are written to this property if no other destination is specified.

SetValue Method (JSON Class)

This method sets a new value for the element specified by XPath.

Syntax

public void setValue(String value, int valueType);

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 as follows:

• 0 (Object)
• 1 (Array)
• 2 (String)
• 3 (Number)
• 4 (Bool)
• 5 (Null)
• 6 (Raw)

See Save for details.

StartArray Method (JSON Class)

This method writes the opening bracket of a JSON array.

Syntax

public void startArray();

Remarks

This method writes the opening bracket of a JSON array to the output. To close the array, call EndArray.

StartObject Method (JSON Class)

This event writes the opening brace of a JSON object.

Syntax

public void startObject();

Remarks

This method writes the opening brace of a JSON object to the output. To close the object, call EndObject.

TryXPath Method (JSON Class)

This method navigates to the specified XPath if it exists.

Syntax

public boolean tryXPath(String xpath);

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.

Characters Event (JSON Class)

This event is fired for plaintext segments of the input stream.

Syntax

public class DefaultJSONEventListener implements JSONEventListener {
  ...
  public void characters(JSONCharactersEvent e) {}
  ...
}

public class JSONCharactersEvent {
  public String text;
}

Remarks

The Characters event provides the plaintext 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)

This event fires when the end of a JSON document is encountered.

Syntax

public class DefaultJSONEventListener implements JSONEventListener {
  ...
  public void endDocument(JSONEndDocumentEvent e) {}
  ...
}

public class JSONEndDocumentEvent {
}

Remarks

This event fires when parsing of a JSON document ends. This event may fire multiple times if InputFormat is set to a value that accepts multiple JSON documents.

EndElement Event (JSON Class)

This event is fired when an end-element tag is encountered.

Syntax

public class DefaultJSONEventListener implements JSONEventListener {
  ...
  public void endElement(JSONEndElementEvent e) {}
  ...
}

public class JSONEndElementEvent {
  public String element;
}

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)

Fired when information is available about errors during data delivery.

Syntax

public class DefaultJSONEventListener implements JSONEventListener {
  ...
  public void error(JSONErrorEvent e) {}
  ...
}

public class JSONErrorEvent {
  public int errorCode;
  public String description;
}

Remarks

The Error event is fired in case of exceptional conditions during message processing. Normally the class throws an exception.

The ErrorCode parameter contains an error code, and the Description parameter 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)

This event is fired when a section of ignorable whitespace is encountered.

Syntax

public class DefaultJSONEventListener implements JSONEventListener {
  ...
  public void ignorableWhitespace(JSONIgnorableWhitespaceEvent e) {}
  ...
}

public class JSONIgnorableWhitespaceEvent {
  public String text;
}

Remarks

The ignorable whitespace section is provided by the Text parameter.

JSON Event (JSON Class)

This event fires with the JSON data being written.

Syntax

public class DefaultJSONEventListener implements JSONEventListener {
  ...
  public void JSON(JSONJSONEvent e) {}
  ...
}

public class JSONJSONEvent {
  public String text;
}

Remarks

This event fires when output data are written.

Text contains the JSON data currently being written.

StartDocument Event (JSON Class)

This event fires when the start of a new JSON document is encountered.

Syntax

public class DefaultJSONEventListener implements JSONEventListener {
  ...
  public void startDocument(JSONStartDocumentEvent e) {}
  ...
}

public class JSONStartDocumentEvent {
}

Remarks

This event fires when parsing of a JSON document begins. This event may fire multiple times if InputFormat is set to a value that accepts multiple JSON documents.

StartElement Event (JSON Class)

This event is fired when a new element is encountered in the document.

Syntax

public class DefaultJSONEventListener implements JSONEventListener {
  ...
  public void startElement(JSONStartElementEvent e) {}
  ...
}

public class JSONStartElementEvent {
  public String element;
}

Remarks

The StartElement event is fired when a new element is found in the document.

The element name is provided through the Element parameter.

JSONElement Type

This type describes an element contained within the JSON document.

Remarks

This type describes a JSON element.

The elements are inserted into the array in the same order they are found in the document.

Fields

Constructors

public JSONElement();

Config Settings (JSON Class)

JSON Config Settings

{"data":{"id":3,"first_name":"Emma","last_name":"Wong","avatar":"https:\/\/s3.amazonaws.com\/uifaces\/faces\/twitter\/olegpogodaev\/128.jpg"}}

{
  "data": {
    "id": 3,
    "first_name": "Emma",
    "last_name": "Wong",
    "avatar": "https:\/\/s3.amazonaws.com\/uifaces\/faces\/twitter\/olegpogodaev\/128.jpg"
  }
}

"example" : "value\ntest"

"value\ntest"

value\ntest

"value
test"

value
test

Base Config Settings

Trappable Errors (JSON Class)

JSON Errors

XML Errors