A message body writer for Java type, class myPacka

Question

I am new at RESTful webservices and was trying to update my @OneToMany relationship from a standalone client application, but I am not able to do that. I am using the Jersey implementation of JAX-RS that ships with Glassfish 3.1.1.

I have a class A that has a @OneToMany relationship with class B.

MyRestClient is my standalone client that is calling my RESTful webservice which has been deployed on Glassfish 3.1.1.

MyRestClient.java

public class MyRestClient {
    public static void main(String[] args) {    
        Client client = Client.create();        
        WebResource resource = client.resource("http://localhost:8080/myapp/rest/a/update/123");    
        B b1 = new B("debris");     
        ClientResponse response = resource.put(ClientResponse.class, b1);
        System.out.println(response.getEntity(A.class).getTitle() + " has " + response.getEntity(A.class).getBList().size() + " Bs.");
    }
}

AResource is an EJB session bean which I am using as RESTful webservice.

AResource.java

@Stateless
@Path("/a")
public class AResource {

    @EJB
    private AManager aManager;

    @PUT
    @Consumes(MediaType.APPLICATION_XML)
    @Produces(MediaType.APPLICATION_XML)
    @Path("/update/{id}")
    public Response updateA(B b, @PathParam("id") int id) {
        A a = aManager.findAById(id);
        a.addB(b);
        return Response.status(Status.OK).entity(a).build();
    }
}

When I run the client I get the following error message: com.sun.jersey.api.client.ClientHandlerException: A message body writer for Java type, class myPackage.B, and MIME media type, application/octet-stream, was not found.

Following are the domain objects in my standalone client application which is making a call to the AResource EJB session bean which I am using as the RESTful webservice.

A.java

@XmlRootElement
public class A implements Serializable{ 

    private List<B> bList = new ArrayList<B>();
    public List<B> getBList() {
        return bList;
    }
    //remaining code

}

B.java

public class B implements Serializable {

    private String text;
    private A a;    


    @XmlTransient
    public A getA() {
        return a;
    }

    public void afterUnmarshal(Unmarshaller u, Object parent) {
        this.a = (A) parent;
    }
    //remaining code

}

Could someone help me understand why this is happening and how I should solve this problem?

Answer 1

This solved my issue.

http://www.markhneedham.com/blog/2012/11/28/jersey-com-sun-jersey-api-client-clienthandlerexception-a-message-body-reader-for-java-class-and-mime-media-type-applicationjson-was-not-found/

Including following dependencies in your POM.xml and run Maven -> Update also fixed my issue.

<dependency>
    <groupId>com.sun.jersey</groupId>
    <artifactId>jersey-json</artifactId>
    <version>1.19.1</version>
</dependency>
<dependency>
   <groupId>com.owlike</groupId>
   <artifactId>genson</artifactId>
   <version>0.99</version>
</dependency>

Answer 2

Adding reference to:

<dependency>
    <groupId>com.sun.jersey</groupId>
    <artifactId>jersey-json</artifactId>
    <version>${jersey1.version}</version>
</dependency>

As long as adding clientConfig.getFeatures().put(JSONConfiguration.FEATURE_POJO_MAPPING, true); on client creation solved the issue for me:

ClientConfig clientConfig = new DefaultClientConfig();
clientConfig.getFeatures().put(JSONConfiguration.FEATURE_POJO_MAPPING, true);
Client client = Client.create(clientConfig);

Answer 3

i was facing the same problem for a get method i was returning an "int" for the @get method Strangely when i change the return type to String the error was gone.Give it a try and if someone knows the logic behind it kindly share it

Answer 4

In your client code you are not specifying the content type of the data you are sending - so Jersey is not able to locate the right MessageBodyWritter to serialize the b1 object.

Modify the last line of your main method as follows:

ClientResponse response = resource.type(MediaType.APPLICATION_XML).put(ClientResponse.class, b1);

And add @XmlRootElement annotation to class B on both the server as well as the client sides.