Composer to convert returned POJO to String

[moraleslos]

Hi,

I have a component and corresponding bean which has a method that returns a POJO.  However I have a composite service that has a REST binding which has a method that returns a String containing JSON data.  This REST method invokes the aforementioned bean that returns a POJO.  I want to have the bean implementation use POJOs internally while the composite services return only Strings (JSON data) for each method.  Now because of the mismatch return type, I was thinking that in the Composer's decompose(), I would essentially convert the POJO into JSON for each respective method, something like this:

 public RESTEasyBindingData decompose(Exchange exchange, RESTEasyBindingData target) throws Exception {
        Object content = exchange.getMessage().getContent();
        String opName = exchange.getContract().getProviderOperation().getName();
        target = super.decompose(exchange, target);
        if (target.getOperationName().equals("method1") && (content != null) && (content instanceof Pojo1) {
               exchange.getMessage().setContent(((Pojo1)content).convertToJsonString());
       }          
}

Apparently the above doesn't work and get a class cast exception:  .Pojo1 cannot be cast to java.lang.String

Any ideas on how to do this?  TIA.

[mageshbk]

The conversion from POJO to JSON should happen if the REST interface is annotated appropriately using the @Consumes and @Produces. Can you post your switchyard.xml or better still attach a simple project?

[moraleslos]

For the composite reference, it does return JSON and I have it annotated that way since the external service is REST-based. See below:

@Path("/")

public interface InvokeExternalReference {

    @POST

    @Path("/Authentication/Authenticate")

    @Produces({"application/xml","application/json"})

          String authenticate(String jsonString);

}

Now in my component service implementation (the bean) that called the above reference, I successfully get the JSON string, parse it, unmarshal it into a POJO, and returns that POJO to be used by the bean elsewhere:

@Inject

@Reference

private InvokeExternalService _ref;

@Override

          public POJO2 authenticate(POJO1 pojo) {

          String json = pojo.convertIntoJsonString();

          String result = _ref.authenticate(json);

          POJO2 pojo2 = new POJO2();

          unmarshal(pojo2, result);  // populates pojo2 with json data

          return pojo2;

   }

Now my composite service's REST binding interface that called the above authenticate(POJO1) method looks like this:

    @GET

    @Path("/authenticate/{username}/{password}")

    @Produces({"application/json"})

          String authenticate(@PathParam("username") String username, @PathParam("password") String password);

I have a CustomComposer that maps the username/password Strings into POJO1.  Now when I run the above, I get that class cast exception.  The POJO1 works fine in the bean when I need to use it, but the returned JSON string fails due to the exception.

[mageshbk]

Hi,

You really need to attach the simplified project that has the switchyard.xml. I can understand something, but I am not able to see the complete picture to help you.

thanks,

Magesh

[moraleslos]

Sorry forgot the xml (see below).  If you still need an example project, I'll need to create a new one but will do:

<?xml version="1.0" encoding="UTF-8"?>

<switchyard xmlns="urn:switchyard-config:switchyard:1.0" xmlns:bean="urn:switchyard-component-bean:config:1.0" xmlns:camel="urn:switchyard-component-camel:config:1.0" xmlns:http="urn:switchyard-component-http:config:1.0" xmlns:resteasy="urn:switchyard-component-resteasy:config:1.0" xmlns:sca="http://docs.oasis-open.org/ns/opencsa/sca/200912" xmlns:soap="urn:switchyard-component-soap:config:1.0" name="switchyard-example" targetNamespace="urn:com.example.switchyard:switchyard-example:1.0">

  <sca:composite name="switchyard-example" targetNamespace="urn:com.example.switchyard:switchyard-example:1.0">

    <sca:component name="InvokeExternalServiceBean">

      <bean:implementation.bean class="com.example.switchyard.switchyard_example.InvokeExternalServiceBean"/>

      <sca:service name="InvokeExternalService">

        <sca:interface.java interface="com.example.switchyard.switchyard_example.InvokeExternalService"/>

      </sca:service>

      <sca:reference name="ExternalService">

        <sca:interface.java interface="com.example.switchyard.switchyard_example.ExternalService"/>

      </sca:reference>

    </sca:component>

    <sca:reference name="ExternalService" multiplicity="0..1" promote="InvokeExternalServiceBean/ExternalService">

      <sca:interface.java interface="com.example.switchyard.switchyard_example.ExternalService"/>

      <resteasy:binding.rest>

        <resteasy:contextMapper/>

        <resteasy:messageComposer/>

        <resteasy:interfaces>com.example.switchyard.switchyard_example.InvokeExternalReference</resteasy:interfaces>

        <resteasy:address>http://10.62.18.2/item_admin/services/CMS</resteasy:address>

      </resteasy:binding.rest>

    </sca:reference>

    <sca:service name="InvokeExternalService" promote="InvokeExternalServiceBean/InvokeExternalService">

      <sca:interface.java interface="com.example.switchyard.switchyard_example.InvokeExternalService"/>

      <resteasy:binding.rest>

        <resteasy:contextMapper/>

        <resteasy:messageComposer class="com.example.switchyard.switchyard_example.CustomComposer"/>

        <resteasy:interfaces>com.example.switchyard.switchyard_example.ClientRestReference</resteasy:interfaces>

        <resteasy:contextPath>switchyard-example</resteasy:contextPath>

      </resteasy:binding.rest>

    </sca:service>

  </sca:composite>

</switchyard>

[mageshbk]

Your custom composer uses the name as "method1". Are you sure your method name is that and not "aunthenticate"? It is best if you attach a simple project so that we can help you further. There could be errors in copy-pasting code around.

[moraleslos]

Yes, it is the authenticate method (and not method1). Let me see if I can you a project...