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WSO2 EI provides support for JavaScript Object Notation (JSON) payloads in messages. The following sections describe how to work with JSON in the EI:

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If you want to convert the JSON representation to XML before the mediation flow begins, you need to add the message builder and formatter shown below. Note that some data loss can occur during the JSON to XML to JSON conversion process.

• <parameter name="passthruJsonBuilder">org.apache.synapse.commons.json.JsonBuilder</parameter>

• <parameter name="passthruJsonFormatter">org.apache.synapse.commons.json.JsonFormatter</parameter>

The following builders and formatters can be enabled for JSON mapping in data services.

• <parameter name="dsJsonBuilder">org.apache.axis2.json.gson.JsonBuilder</parameter>
• <parameter name="dsJsonFormatter">org.apache.axis2.json.JSONMessageFormatter</parameter>

The following builders and formatters can also enabled. Note that this is necessary for compatibility with previous versions of the EI (WSO2 ESB):

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Note the addition of xml-multiple processing instructions to the XML payloads whose JSON representations contain arrays. JsonBuilder (via StAXON) adds these instructions to the XML payload that it builds during the JSON to XML conversion so that during the XML to JSON conversion, JsonFormatter can reconstruct the arrays that are present in the original JSON payload. JsonFormatter interprets the elements immediately following a processing instruction to construct an array.

Special characters

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Special characters

When building XML elements, the EI handles the ‘$’ character and digits in a special manner when they appear as the first character of a JSON key. Following are examples of two such occurrences. Note the addition of the _JsonReader_PS_ and _JsonReader_PD_ prefixes in place of the ‘$’ and digit characters, respectively.

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You can use JSON path expressions with following mediators:

<log>
    <property name="location" 
              expression="json-eval($.coordinates.location[0].name)"/>
</log>

<property name="location" 
              expression="json-eval($.coordinates.location[0].name)"/>

<payloadFactory media-type="json">
    <format>{"RESPONSE":"$1"}</format>
    <args>
        <arg evaluator="json" expression="$.coordinates.location[0].name"/>
    </args>
</payloadFactory>

<switch source="json-eval($.coordinates.location[0].name)">

<filter source="json-eval($.coordinates.location[0].name)" 
        regex="Eiffel.*">

JSON path syntax

Suppose we have the following payload:

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The following table summarizes sample JSONPath expressions and their outputs:

$.

{ "id":12345, "id_str":"12345", "array":[1, 2, [[],[{"inner_id":6789}]]], "name":null, "object":{}, "$schema_location":"unknown", "12X12":"image12x12.png"}

$.id

12345

$.name

null

$.object

{}

$.['$schema_location']

unknown

$.12X12

image12x12.png

$.array

[1, 2, [[],[{"inner_id":6789}]]]

$.array[2][1][0].inner_id

6789

You can learn more about JSONPath syntax here.

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XML to JSON transformation parameters

You can use XML to JSON transformation parameters add the parameters listed below to the synapse.properties file (stored in the <EI_HOME>/conf/ directory) when you need to transform XML formatted data into the JSON format.Following are the XML to JSON transformation parameters and their descriptions:

synapse.json.to.

xml.

processing.

instruction.

enabled

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The parameters available in this section are as follows.

Following example use the below sample schema  StockQuoteSchema.json file. Add this sample schema file (i.e. StockQuoteSchema.json) to the following Registry path:  conf:/schema/StockQuoteSchema.json. For instructions on adding the schema file to the Registry path, see Adding a Resource.

{
  "$schema": "http://json-schema.org/draft-04/schema#",
  "type": "object",
  "properties": {
    "getQuote": {
      "type": "object",
      "properties": {
        "request": {
          "type": "object",
          "properties": {
            "symbol": {
              "type": "string"
            }
          },
          "required": [
            "symbol"
          ]
        }
      },
      "required": [
        "request"
      ]
    }
  },
  "required": [
    "getQuote"
  ]
}
 

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