A message body writer for Java type was not found - web-services

Question

I am receiving following exception:
ClientHandlerException: A message body writer for Java type,
class com.company.testing.repo.model.Privilege,
and MIME media type,
application/octet-stream, was not found
Privilege is an ENUM class:
public enum Privilege {
READ,
WRITE;
}
Resource entry is this:
#Path("repoPrivs")
#POST
#Consumes(MediaType.APPLICATION_JSON)
#Produces(MediaType.APPLICATION_JSON)
Response getGroups(Privilege privilege);
my client code is this:
#Override
public List<MyGroup> getGroups(Privilege privilege) {
IWebParamaterProvider provider = WebParamaterFactory.create("repo-mapping/repoPrivs", //$NON-NLS-1$
SecureAction.READ, webProxy);
provider = provider.setType(MediaType.APPLICATION_JSON);
provider = provider.setAccept(MediaType.APPLICATION_JSON);
List<MyGroup> groups = null;
groups = webProxy.post(provider, new GenericTypeFactory<MyGroup>(), MyGroup.class, privilege);
return groups;
}
Override
public final <T> List<T> post(IWebParamaterProvider provider, GenericTypeFactory<T> genericsFactory,
Class<T> clazz, Object requestEntity){
WebResource resource = ((IWebResourceProvider) provider).getWebResource();
TRACER.trace("POST: " + resource.getURI().toString()); //$NON-NLS-1$
return resource.post(genericsFactory.create(clazz), requestEntity);
}
public GenericType<List<T>> create(final Class<T> clazz) {
ParameterizedType genericType = new ParameterizedType() {
#Override
public Type[] getActualTypeArguments() {
return new Type[] { clazz };
}
#Override
public Type getOwnerType() {
return List.class;
}
#Override
public Type getRawType() {
return List.class;
}
};
return new GenericType<List<T>>(genericType) {
};
}
What is that I am missing

Answer 1

It is very important to provide complete minimal example so other people can help you.
Below you have Jersey 2 and Jersey 1 example and both of them uses in memory test container. Make sure to get the all the required dependencies based on the version.
Jersey 2
import com.fasterxml.jackson.annotation.JsonAutoDetect;
import org.glassfish.jersey.jackson.JacksonFeature;
import org.glassfish.jersey.server.ResourceConfig;
import org.glassfish.jersey.test.JerseyTest;
import org.glassfish.jersey.test.inmemory.InMemoryTestContainerFactory;
import org.glassfish.jersey.test.spi.TestContainerFactory;
import org.junit.Test;
import javax.ws.rs.Consumes;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.client.Entity;
import javax.ws.rs.core.Application;
import javax.ws.rs.core.GenericType;
import javax.ws.rs.core.MediaType;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.List;
import static javax.ws.rs.core.MediaType.APPLICATION_JSON;
import static org.junit.Assert.*;
public class JerseyVersion2Test extends JerseyTest {
#Path("hello")
public static class HelloResource {
#POST
#Produces(APPLICATION_JSON)
#Consumes(APPLICATION_JSON)
public List<MyGroup> doPost(Privilege privilege) {
List<MyGroup> myGroups = new ArrayList<>();
MyGroup myGroup = new MyGroup();
myGroup.name = "jersey";
myGroup.version = 2;
myGroups.add(myGroup);
return myGroups;
}
}
#Override
protected Application configure() {
return new ResourceConfig(HelloResource.class);
}
#Override
protected TestContainerFactory getTestContainerFactory() {
return new InMemoryTestContainerFactory();
}
#Test
public void testPost() {
List<MyGroup> myGroups = getGroups();
assertEquals(1, myGroups.size());
}
public enum Privilege {
READ,
WRITE;
}
public List<MyGroup> getGroups() {
List<MyGroup> groups = target("hello").request().
accept(MediaType.APPLICATION_JSON).
post(Entity.json(Privilege.READ)).
readEntity(new GenericTypeFactory<MyGroup>().create(MyGroup.class));
return groups;
}
#JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.ANY)
public static class MyGroup {
private String name;
private double version;
}
public class GenericTypeFactory<T> {
public GenericType<List<T>> create(final Class<T> clazz) {
ParameterizedType genericType = new ParameterizedType() {
#Override
public Type[] getActualTypeArguments() {
return new Type[]{clazz};
}
#Override
public Type getOwnerType() {
return List.class;
}
#Override
public Type getRawType() {
return List.class;
}
};
return new GenericType<List<T>>(genericType) {
};
}
}
}
Jersey 1
import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.sun.jersey.api.client.GenericType;
import com.sun.jersey.api.client.WebResource;
import com.sun.jersey.test.framework.AppDescriptor;
import com.sun.jersey.test.framework.JerseyTest;
import com.sun.jersey.test.framework.LowLevelAppDescriptor;
import com.sun.jersey.test.framework.spi.container.TestContainerFactory;
import com.sun.jersey.test.framework.spi.container.inmemory.InMemoryTestContainerFactory;
import org.junit.Test;
import javax.ws.rs.Consumes;
import javax.ws.rs.POST;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.List;
import static javax.ws.rs.core.MediaType.APPLICATION_JSON;
import static org.junit.Assert.assertEquals;
public class JerseyVersion1Test extends JerseyTest {
#Path("hello")
public static class HelloResource {
#POST
#Produces(APPLICATION_JSON)
#Consumes(APPLICATION_JSON)
public List<MyGroup> doPost(Privilege privilege) {
List<MyGroup> myGroups = new ArrayList<>();
MyGroup myGroup = new MyGroup();
myGroup.name = "jersey";
myGroup.version = 1.12;
myGroups.add(myGroup);
return myGroups;
}
}
#Override
protected AppDescriptor configure() {
return new LowLevelAppDescriptor.Builder(HelloResource.class).build();
}
#Override
protected TestContainerFactory getTestContainerFactory() {
return new InMemoryTestContainerFactory();
}
#Test
public void testPost() {
List<MyGroup> myGroups = getGroups();
assertEquals(1, myGroups.size());
}
public enum Privilege {
READ,
WRITE;
}
public List<MyGroup> getGroups() {
WebResource webResource = resource();
List<MyGroup> groups = webResource.path("hello").
accept(MediaType.APPLICATION_JSON).
type(MediaType.APPLICATION_JSON).
post(new GenericTypeFactory<MyGroup>().create(MyGroup.class), Privilege.READ);
return groups;
}
#JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.ANY)
public static class MyGroup {
private String name;
private double version;
}
public class GenericTypeFactory<T> {
public GenericType<List<T>> create(final Class<T> clazz) {
ParameterizedType genericType = new ParameterizedType() {
#Override
public Type[] getActualTypeArguments() {
return new Type[]{clazz};
}
#Override
public Type getOwnerType() {
return List.class;
}
#Override
public Type getRawType() {
return List.class;
}
};
return new GenericType<List<T>>(genericType) {
};
}
}
}

Answer 2

javax.xml.bind.annotation.XmlRootElement
Java doc:
The #XmlRootElement annotation can be used with the following program
elements:
a top level class
an enum type
[...]
When a top level class or an enum type is annotated with the #XmlRootElement annotation, then its value is represented as XML element in an XML document.
in your case it is clear that Jersey unable to unmarshall the incoming JSON payload to your object, thus the exception
A message body writer for Java type, class com.company.testing.repo.model.Privilege
annotating your Enum (Privilege) with #XmlRootElement should solve the issue.
#XmlRootElement
public enum Privilege {
READ,
WRITE;
}