How to get json property when I use the Property Mediator? - wso2

Question

I use the Property Mediator to get a registry resource, it returns me a json string, but how can I get the property in the json string?
my code example:
test-file.json like so
{
"mappings": {
"mapping": {
"ep_1": "http://localhost:8280/services/ep_1",
"ep_2": "http://localhost:8280/services/ep_2",
"ep_3": "http://localhost:8280/services/ep_3"
}
}
}
I do like this:
<property expression="get-property('registry','conf:customresource/test-file.json')" name="JsonContent" scope="default" type="STRING"/>
<property expression="????" name="endpointUrl" />
how to get the property 'ep_1' in the 'endpointUrl' Or is there any other way to get the property 'ep_1'? thx

Answer 1

Try the following.
expression="json-eval($ctx:JsonContent.mappings.mapping.ep_1)"
If above does not work, try this.
expression="$ctx:JsonContent//mappings/mapping/ep_1"

Answer 2

Saving the input JSON to a property:
<property expression="json-eval($)" name="var_in_JSON" scope="default" type="STRING"/>
!!! Don't use dots (.) in the json property name !!!
...
Using data from a saved json property:
<property expression="json-eval($ctx:var_in_JSON.sub_param)" name="sub_param" scope="default" type="STRING"/>
The answer in your case:
<property expression="json-eval($ctx:JsonContent.ep_1)" name="ep_1" scope="default" type="STRING"/>

Answer 3

You can load json file from registry to payload, and make json-eval on payload. It is dirty solution, but it works ;):
<property expression="base64Decode(get-property('registry','conf:customresource/test-file.json'))" name="JsonContent" scope="default" type="STRING"/>
<payloadFactory description="Build Payload Response" media-type="json">
<format>$1</format>
<args>
<arg evaluator="xml" expression="$ctx:JsonContent" xmlns:payload="http://ws.apache.org/commons/ns/payload"/>
</args>
</payloadFactory>
<property expression="json-eval($.mappings.mapping.ep_1)" name="endpointUrl" scope="default" type="STRING"/>
Best regards

Answer 4

I have done with this question.You have to use XML content instead of JSON, then set content into a Property Mediator which type filed is OM, and you can use xpath expression to get any value you want in your XML content.
code example
XML content:
<mappings>
<mapping>
<ep_1>http://localhost:8280/services/ep_1</ep_1>
<ep_2>http://localhost:8280/services/ep_2</ep_2>
<ep_3>http://localhost:8280/services/ep_3</ep_3>
</mapping>
</mappings>
<property expression="get-property('registry','conf:customresource/test-file.xml')" name="XmlContent" scope="default" type="OM"/>
<property expression="$ctx:XmlContent/mapping/ep_1" name="endpointUrl" />
After that, the value will been set into the property named endpointUrl.
Last, please note the expression of second Property mediator,you get black value if you do like this $ctx:XmlContent/mappings/mapping/ep_1.Hope its helpful for someone.