RESTEasy Mock vs. Exception Mapper vs. Context

Question

RESTEasy mock framework works fine without exception mapper--request is received and entity is returned with expected contents.

After registering exception mapper and forcing an exception, call fails when innards of RESTEasy call ResteasyProviderFactory.getContextData(type), which returns null, resulting in unexpected error message: "Unable to find contextual data of type: javax.servlet.http.HttpServletRequest".

Couldn't find any examples anywhere online of RESTEasy mock plus an exception mapper, and couldn't find anything useful about the error either.

Client class:

package com.foo;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;

@XmlAccessorType(XmlAccessType.FIELD)
@XmlType(name = "foo-type", propOrder = {
    "name"
})
@XmlRootElement(name = "foo")
public class Foo {

    protected String name;

    public String getName() {
        return name;
    }

    public void setName(String value) {
        this.name = value;
    }
}

Object factory:

package com.foo;

import javax.xml.bind.annotation.XmlRegistry;

@XmlRegistry
public class ObjectFactory {

    public ObjectFactory() {
    }

    public Foo createFoo() {
        return new Foo();
    }
}

Validation exception:

package com.foo;

public class ValidationException extends RuntimeException {

    private static final long serialVersionUID = -8100360206713223313L;

    public ValidationException(String message) {
        super(message);
    }

    public ValidationException(Exception innerException) {
        super(innerException);
    }

    public ValidationException(String message, Exception innerException) {
        super(message, innerException);
    }
}

Service endpoint:

package com.foo;

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;

@Path("/rest/v1")
public class FooService {

    @GET
    @Path("/foo")
    @Produces("application/xml")
    public Foo alwaysBlowUp() throws ValidationException {
        if (System.currentTimeMillis() > 0) {
            throw new ValidationException("FOO");
        }
        return null;
    }
}

Exception mapper:

package com.foo;

import javax.servlet.http.HttpServletRequest;
import javax.ws.rs.core.Context;
import javax.ws.rs.core.HttpHeaders;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;
import javax.ws.rs.core.Response.ResponseBuilder;
import javax.ws.rs.core.Response.Status;
import javax.ws.rs.ext.ExceptionMapper;
import javax.ws.rs.ext.Provider;

@Provider
public class FooExceptionMapper implements ExceptionMapper<ValidationException> {

    @Context
    private static HttpServletRequest request;
    @Context
    private static HttpHeaders headers;

    @Override
    public Response toResponse(ValidationException exception) {
        MediaType mediaType = null;

/*
Set breakpoint on line below.
Step over line and you get the exception in the logs.
Step into the line and the problem is in ResteasyProviderFactory:

public static <T> T getContextData(Class<T> type)
{
    return (T) getContextDataMap().get(type); <<< type == javax.servlet.http.HttpServletRequest
}

The type is not in the map, so it returns null.

The null results in this error in ContextParameterInjector:

private class GenericDelegatingProxy implements InvocationHandler
{
    public Object invoke(Object o, Method method, Object[] objects) throws Throwable
    {
        try
        {
            Object delegate = ResteasyProviderFactory.getContextData(type);
            if (delegate == null)
               throw new LoggableFailure("Unable to find contextual data of type: " + type.getName()); <<< ERROR IN LOGS
*/

        String acceptHeader = request.getHeader("accept");

        if (MediaType.APPLICATION_XML.equals(acceptHeader)) {
            mediaType = MediaType.APPLICATION_XML_TYPE;
        } else if (MediaType.APPLICATION_JSON.equals(acceptHeader)) {
            mediaType = MediaType.APPLICATION_JSON_TYPE;
        } else {
            mediaType = headers.getMediaType();

            if (mediaType == null) {
                mediaType = MediaType.APPLICATION_XML_TYPE;
            }
        }

        ResponseBuilder builder = Response.status(Status.BAD_REQUEST);
        builder.type(mediaType);
        return builder.build();
    }
}

Test:

package com.foo;

import java.net.URISyntaxException;

import org.jboss.resteasy.core.Dispatcher;
import org.jboss.resteasy.mock.MockDispatcherFactory;
import org.jboss.resteasy.mock.MockHttpRequest;
import org.jboss.resteasy.mock.MockHttpResponse;
import org.jboss.resteasy.plugins.server.resourcefactory.POJOResourceFactory;

public final class TestFooExceptionMapper {

    public static void main(String[] args) throws URISyntaxException {
        Dispatcher dispatcher = MockDispatcherFactory.createDispatcher();
        dispatcher.getRegistry().addResourceFactory(new POJOResourceFactory(FooService.class));
        dispatcher.getProviderFactory().addExceptionMapper(FooExceptionMapper.class);

        MockHttpRequest request = MockHttpRequest.get("/rest/v1/foo");
        MockHttpResponse response = new MockHttpResponse();
        dispatcher.invoke(request, response);
    }
}

Error:

Aug 26, 2012 10:44:26 PM org.jboss.resteasy.core.SynchronousDispatcher 
SEVERE: Failed executing GET /rest/v1/foo
org.jboss.resteasy.spi.LoggableFailure: Unable to find contextual data of type: javax.servlet.http.HttpServletRequest
    at org.jboss.resteasy.core.ContextParameterInjector$GenericDelegatingProxy.invoke(ContextParameterInjector.java:56)
    at $Proxy18.getHeader(Unknown Source)
    at com.foo.FooExceptionMapper.toResponse(FooExceptionMapper.java:51)
    at com.foo.FooExceptionMapper.toResponse(FooExceptionMapper.java:1)
    at org.jboss.resteasy.core.SynchronousDispatcher.executeExceptionMapper(SynchronousDispatcher.java:330)
    at org.jboss.resteasy.core.SynchronousDispatcher.unwrapException(SynchronousDispatcher.java:359)
    at org.jboss.resteasy.core.SynchronousDispatcher.handleApplicationException(SynchronousDispatcher.java:348)
    at org.jboss.resteasy.core.SynchronousDispatcher.handleException(SynchronousDispatcher.java:220)
    at org.jboss.resteasy.core.SynchronousDispatcher.handleInvokerException(SynchronousDispatcher.java:196)
    at org.jboss.resteasy.core.SynchronousDispatcher.getResponse(SynchronousDispatcher.java:551)
    at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:513)
    at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:125)
    at com.foo.TestFooExceptionMapper.main(TestFooExceptionMapper.java:20)

Answer 1

The problem is that the 'mock framework' does not supply a HttpServletRequest to the context. It's not directly related to the ExceptionMapper.

Resteasy injects @Context fields based on data that is present in the ResteasyProviderFactory.getContextDataMap(). When this map does not contain an instance of HttpServletRequest, it blows up whith the error 'Unable to find contextual data of type...'

I have worked around this by putting a mock HttpServletRequest into the resteasy context:

Dispatcher dispatcher = MockDispatcherFactory.createDispatcher();
dispatcher.getRegistry().addSingletonResource(new Service());

ResteasyProviderFactory
        .getContextDataMap()
        .put(HttpServletRequest.class, new MockHttpServletRequest());

MockHttpResponse response = new MockHttpResponse();

dispatcher.invoke(
    MockHttpRequest.get("/"),
    response
);