GuicedServletAssertion.java

package jerseyandguice;

import static org.testng.Assert.assertNotNull;
import static org.testng.Assert.assertTrue;

import java.util.concurrent.atomic.AtomicReference;

import javax.servlet.FilterChain;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;

import org.jmock.Expectations;
import org.jmock.Mockery;

import com.google.inject.Injector;
import com.google.inject.servlet.GuiceFilter;

public class GuicedServletAssertion {

  public static void assertProvisioningType(final Injector injector,
      final Class<?> requestedType, final Class<?> expectedImplementation)
      throws Exception {
    applyFilterChainAssertion(new FilterChain() {
      public void doFilter(ServletRequest servletRequest,
          ServletResponse servletResponse) {
        assertTrue(requestedType
            .isInstance(injector.getInstance(requestedType)));
        assertTrue(expectedImplementation.isInstance(injector
            .getInstance(requestedType)));
      }
    });
  }

  public static void assertInstantiablity(final Injector injector,
      final Class<?> clazz) throws Exception {
    applyFilterChainAssertion(new FilterChain() {
      public void doFilter(ServletRequest servletRequest,
          ServletResponse servletResponse) {
        assertNotNull(injector.getInstance(clazz));
      }
    });
  }

  public static void applyFilterChainAssertion(FilterChain filterChain)
      throws Exception {
    Mockery context = new Mockery();
    GuiceFilter filter = new GuiceFilter();
    final HttpServletRequest request = context.mock(HttpServletRequest.class);

    context.checking(new Expectations() {
      {
        allowing(request).getAttribute(with(any(String.class)));
        will(returnValue(null));
        allowing(request).setAttribute(with(any(String.class)),
            with(any(Class.class)));
        oneOf(request).getServletPath();
      }
    });

    filter.doFilter(request, null, filterChain);
  }

  public static <T> T expose(final Injector injector, final Class<?> clazz)
      throws Exception {
    final AtomicReference<T> ref = new AtomicReference<T>();
    applyFilterChainAssertion(new FilterChain() {
      @SuppressWarnings("unchecked")
      public void doFilter(ServletRequest servletRequest,
          ServletResponse servletResponse) {
        ref.set((T) injector.getInstance(clazz));
      }
    });
    return ref.get();
  }

}