json - Jersey Exception : SEVERE: A message body reader for Java class

Question

I have a Jersey based Rest WS which outputs JSON. I am implementing a Jersey Client to invoke the WS and consume the JSON response. The client code I have is below

WebResource r = restClient.resource(UriBuilder.fromUri("http://localhost/").port(8080).build());
String resp = r.path("/user").accept(MediaType.APPLICATION_JSON).get(String.class);
User[] users = r.path("/user").accept(MediaType.APPLICATION_JSON).get(User[].class);

The 2nd line outputs the JSON string response correctly, however the 3rd line to marshal JSON to the POJO is not happening and I get the following exception stacktrace

SEVERE: A message body reader for Java class [Lorg.shoppingsite.model.entity.jpa.User;, and Java type class [Lorg.shoppingsite.model.entity.jpa.User;, and MIME media type application/json was not found
Dec 21, 2011 11:32:01 AM com.sun.jersey.api.client.ClientResponse getEntity
SEVERE: The registered message body readers compatible with the MIME media type are:
*/* ->
  com.sun.jersey.core.impl.provider.entity.FormProvider
  com.sun.jersey.core.impl.provider.entity.StringProvider
  com.sun.jersey.core.impl.provider.entity.ByteArrayProvider
  com.sun.jersey.core.impl.provider.entity.FileProvider
  com.sun.jersey.core.impl.provider.entity.InputStreamProvider
  com.sun.jersey.core.impl.provider.entity.DataSourceProvider
  com.sun.jersey.core.impl.provider.entity.XMLJAXBElementProvider$General
  com.sun.jersey.core.impl.provider.entity.ReaderProvider
  com.sun.jersey.core.impl.provider.entity.DocumentProvider
  com.sun.jersey.core.impl.provider.entity.SourceProvider$StreamSourceReader
  com.sun.jersey.core.impl.provider.entity.SourceProvider$SAXSourceReader
  com.sun.jersey.core.impl.provider.entity.SourceProvider$DOMSourceReader
  com.sun.jersey.core.impl.provider.entity.XMLRootElementProvider$General
  com.sun.jersey.core.impl.provider.entity.XMLListElementProvider$General
  com.sun.jersey.core.impl.provider.entity.XMLRootObjectProvider$General
  com.sun.jersey.core.impl.provider.entity.EntityHolderReader

I have the correct MIME TYPES in my request. My POJO has been annotated with XMLRootElement. What am I missing.

Thank you

Answer 1

To make it work you only need two things. Check if you are missing:

1. First of all, you need @XmlRootElement annotation for your object class/entity.

2. You need to add dependency for jersey-json if you are missing.For your reference I added this dependency into my pom.xml.

   <dependency>
       <groupId>com.sun.jersey</groupId>
       <artifactId>jersey-json</artifactId>
       <version>1.17.1</version>
   </dependency>