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To read data from regular name-value pairs, first remember to set your position in the JSON structure to a correct depth - e.g. <Context xpath="zoo/animals/tiger">.

Optionally, you can map the subtree of <Context> to the output port - e.g. <Context xpath="childObjects" outPort="2">.

Do the <Mapping>: select a name-value pair in xpath. Next, send the value to Clover using cloverField; e.g.: <Mapping cloverField="id" xpath="nestedObject">.

Example JSON:

		
{ 
  "property" : 1,
  "innerObject" : {
      "property" : 2
  }
}
		

JSONReader mapping:

		
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<Context outPort="0" xpath="/root/object">
   <Mapping cloverField="property" xpath="property"/>
   <Context xpath="innerObject">
      <Mapping cloverField="propertyOfInnerObject" xpath="property"/>
   </Context>
</Context>
		
		

Remember that you do not use the @ symbol to access 'attributes' as there are none. In order to select objects with specific values you will write mapping in a way like:

				
<Context xpath="//website[uri='http://www.w3.org/']" outPort="1"> 
   <Mapping cloverField="dateUpdated" xpath="dateUpdated" />
   <Mapping cloverField="title" xpath="title"/>
</Context>
			    
				

The XPath in the example selects all elements website (no matter how deep in the JSON they are) whose uri matches the given string. Next, it sends its two elements (dateUpdated and title) to respective metadata fields on port 1.

As has already been mentioned, JSON is internally converted into a XML DOM. Since not all JSON names are valid XML element names, the names are encoded. Invalid characters are replaced with with escape sequences of the form _xHHHH where HHHH is a hexadecimal Unicode code point. These sequences must therefore also be used in JSONReader's XPath expressions.

The XPath name() function can be used to read the names of properties of JSON objects (for a description of XPath functions on nodes, see http://www.w3schools.com/xpath/xpath_functions.asp#node). However, the names may contain escape sequences, as described above. JSONReader offers two functions to deal with them, the functions are available from http://www.cloveretl.com/ns/TagNameEncoder namespace which has to be declared using the namespacePaths attribute, as will be shown below. These functions are the decode(string) function, which can be used to decode _xHHHH escape sequences, and its counterpart, the encode(string) function, which escapes invalid characters.

For example, let's try to process the following structure:

{"map" : { "0" : 2 , "7" : 1 , "16" : 1 , "26" : 3 , "38" : 1 }}
				

A suitable mapping could look like this:

				
<Context xpath="/root/object/map/*" outPort="0" namespacePaths='tag="http://www.cloveretl.com/ns/TagNameEncoder"'>
   <Mapping cloverField="key" xpath="tag:decode(name())" />
   <Mapping cloverField="value" xpath="." />
</Context>
			    
				

The mapping maps the names of properties of "map" ("0", "7", "16", "26" and "38") to the field "key" and their values (2, 1, 1, 3 and 1, resp.) to the field "value".

If you switch the component's attribute Implicit mapping to true, you can save a lot of space because mapping of JSON structures to fields of the same name:

			<Mapping cloverField="salary" xpath="salary"/>
			

will be performed automatically (i.e. you do not write the mapping code above).