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Java example source code file (MethodInterceptionTest.java)

This example Java source code file (MethodInterceptionTest.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

abstractmodule, calllaterinterceptor, constructorbinding, countinginterceptor, exception, injector, interceptable, interface, list, methodinterceptor, namedinterceptor, object, reflection, returnnullinterceptor, throwable, util

The MethodInterceptionTest.java Java example source code

/**
 * Copyright (C) 2008 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.inject;

import static com.google.inject.matcher.Matchers.only;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Iterables;
import com.google.common.collect.Lists;
import com.google.inject.matcher.AbstractMatcher;
import com.google.inject.matcher.Matchers;
import com.google.inject.spi.ConstructorBinding;

import junit.framework.TestCase;

import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;

import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.List;
import java.util.Queue;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReference;

/**
 * @author jessewilson@google.com (Jesse Wilson)
 */
public class MethodInterceptionTest extends TestCase {

  private AtomicInteger count = new AtomicInteger();

  private final class CountingInterceptor implements MethodInterceptor {
    public Object invoke(MethodInvocation methodInvocation) throws Throwable {
      count.incrementAndGet();
      return methodInvocation.proceed();
    }
  }

  private final class ReturnNullInterceptor implements MethodInterceptor {
    public Object invoke(MethodInvocation methodInvocation) throws Throwable {
      return null;
    }
  }
  
  private final class NoOpInterceptor implements MethodInterceptor {
    public Object invoke(MethodInvocation methodInvocation) throws Throwable {
      return methodInvocation.proceed();
    }
  }

  public void testSharedProxyClasses() {
    Injector injector = Guice.createInjector(new AbstractModule() {
      protected void configure() {
        bindInterceptor(Matchers.any(), Matchers.returns(only(Foo.class)),
            new ReturnNullInterceptor());
      }
    });

    Injector childOne = injector.createChildInjector(new AbstractModule() {
      protected void configure() {
        bind(Interceptable.class);
      }
    });

    Interceptable nullFoosOne = childOne.getInstance(Interceptable.class);
    assertNotNull(nullFoosOne.bar());
    assertNull(nullFoosOne.foo()); // confirm it's being intercepted

    Injector childTwo = injector.createChildInjector(new AbstractModule() {
      protected void configure() {
        bind(Interceptable.class);
      }
    });

    Interceptable nullFoosTwo = childTwo.getInstance(Interceptable.class);
    assertNull(nullFoosTwo.foo()); // confirm it's being intercepted

    assertSame("Child injectors should share proxy classes, otherwise memory leaks!",
        nullFoosOne.getClass(), nullFoosTwo.getClass());
    
    Injector injector2 = Guice.createInjector(new AbstractModule() {
      protected void configure() {
        bindInterceptor(Matchers.any(), Matchers.returns(only(Foo.class)),
            new ReturnNullInterceptor());
      }
    });
    Interceptable separateNullFoos = injector2.getInstance(Interceptable.class);
    assertNull(separateNullFoos.foo()); // confirm it's being intercepted
    assertSame("different injectors should share proxy classes, otherwise memory leaks!",
        nullFoosOne.getClass(), separateNullFoos.getClass());
  }

  public void testGetThis() {
    final AtomicReference<Object> lastTarget = new AtomicReference();

    Injector injector = Guice.createInjector(new AbstractModule() {
      protected void configure() {
        bindInterceptor(Matchers.any(), Matchers.any(), new MethodInterceptor() {
          public Object invoke(MethodInvocation methodInvocation) throws Throwable {
            lastTarget.set(methodInvocation.getThis());
            return methodInvocation.proceed();
          }
        });
      }
    });

    Interceptable interceptable = injector.getInstance(Interceptable.class);
    interceptable.foo();
    assertSame(interceptable, lastTarget.get());
  }

  public void testInterceptingFinalClass() {
    Injector injector = Guice.createInjector(new AbstractModule() {
      protected void configure() {
        bindInterceptor(Matchers.any(), Matchers.any(), new MethodInterceptor() {
          public Object invoke(MethodInvocation methodInvocation) throws Throwable {
            return methodInvocation.proceed();
          }
        });
      }
    });
    try {
      injector.getInstance(NotInterceptable.class);
      fail();
    } catch(ConfigurationException ce) {
      assertEquals("Unable to method intercept: " + NotInterceptable.class.getName(),
          Iterables.getOnlyElement(ce.getErrorMessages()).getMessage().toString());
      assertEquals("Cannot subclass final class " + NotInterceptable.class.getName(),
          ce.getCause().getMessage());
    }
  }

  public void testSpiAccessToInterceptors() throws NoSuchMethodException {
    final MethodInterceptor countingInterceptor = new CountingInterceptor();
    final MethodInterceptor returnNullInterceptor = new ReturnNullInterceptor();
    Injector injector = Guice.createInjector(new AbstractModule() {
      protected void configure() {
        bindInterceptor(Matchers.any(),Matchers.returns(only(Foo.class)),
            countingInterceptor);
        bindInterceptor(Matchers.any(), Matchers.returns(only(Foo.class).or(only(Bar.class))),
            returnNullInterceptor);
      }
    });

    ConstructorBinding<?> interceptedBinding
        = (ConstructorBinding<?>) injector.getBinding(Interceptable.class);
    Method barMethod = Interceptable.class.getMethod("bar");
    Method fooMethod = Interceptable.class.getMethod("foo");
    assertEquals(ImmutableMap.<Method, Listof(
        fooMethod, ImmutableList.of(countingInterceptor, returnNullInterceptor),
        barMethod, ImmutableList.of(returnNullInterceptor)),
        interceptedBinding.getMethodInterceptors());

    ConstructorBinding<?> nonInterceptedBinding
        = (ConstructorBinding<?>) injector.getBinding(Foo.class);
    assertEquals(ImmutableMap.<Method, Listof(),
        nonInterceptedBinding.getMethodInterceptors());

    injector.getInstance(Interceptable.class).foo();
    assertEquals("expected counting interceptor to be invoked first", 1, count.get());
  }

  public void testInterceptedMethodThrows() throws Exception {
    Injector injector = Guice.createInjector(new AbstractModule() {
      protected void configure() {
        bindInterceptor(Matchers.any(), Matchers.any(), new CountingInterceptor());
        bindInterceptor(Matchers.any(), Matchers.any(), new CountingInterceptor());
      }
    });

    Interceptable interceptable = injector.getInstance(Interceptable.class);
    try {
      interceptable.explode();
      fail();
    } catch (Exception e) {
      // validate all causes.
      for (Throwable t = e; t != null; t = t.getCause()) {
        StackTraceElement[] stackTraceElement = t.getStackTrace();
        assertEquals("explode", stackTraceElement[0].getMethodName());
        assertEquals("invoke", stackTraceElement[1].getMethodName());
        assertEquals("invoke", stackTraceElement[2].getMethodName());
        assertEquals("testInterceptedMethodThrows", stackTraceElement[3].getMethodName());
      }
    }
  }
  
  public void testNotInterceptedMethodsInInterceptedClassDontAddFrames() {
    Injector injector = Guice.createInjector(new AbstractModule() {
      protected void configure() {
        bindInterceptor(Matchers.any(), Matchers.returns(only(Foo.class)),
            new NoOpInterceptor());
      }
    });

    Interceptable interceptable = injector.getInstance(Interceptable.class);
    assertNull(interceptable.lastElements);
    interceptable.foo();
    boolean cglibFound = false;
    for (int i = 0; i < interceptable.lastElements.length; i++) {
      if (interceptable.lastElements[i].toString().contains("cglib")) {
        cglibFound = true;
        break;
      }
    }
    assertTrue(Arrays.toString(interceptable.lastElements), cglibFound);
    cglibFound = false;
    
    interceptable.bar();
    for (int i = 0; i < interceptable.lastElements.length; i++) {
      if (interceptable.lastElements[i].toString().contains("cglib")) {
        cglibFound = true;
        break;
      }
    }
    assertFalse(Arrays.toString(interceptable.lastElements), cglibFound);
  }

  static class Foo {}
  static class Bar {}

  public static class Interceptable {
    StackTraceElement[] lastElements; 
    
    public Foo foo() {
      lastElements = Thread.currentThread().getStackTrace();
      return new Foo() {};
    }
    public Bar bar() {
      lastElements = Thread.currentThread().getStackTrace();
      return new Bar() {};
    }
    public String explode() throws Exception {
      lastElements = Thread.currentThread().getStackTrace();
      throw new Exception("kaboom!", new RuntimeException("boom!"));
    }
  }

  public static final class NotInterceptable {}
  
  public void testInterceptingNonBridgeWorks() {
    Injector injector = Guice.createInjector(new AbstractModule() {
      @Override
      protected void configure() {
        bind(Interface.class).to(Impl.class);
        bindInterceptor(Matchers.any(), new AbstractMatcher<Method>() {
          public boolean matches(Method t) {
            return !t.isBridge() && t.getDeclaringClass() != Object.class;
          }
        }, new CountingInterceptor());
      }
    });
    Interface intf = injector.getInstance(Interface.class);
    assertEquals(0, count.get());
    intf.aMethod(null);
    assertEquals(1, count.get());
  }
  
  static class ErasedType {}
  static class RetType extends ErasedType {}  
  static abstract class Superclass<T extends ErasedType> {
      public T aMethod(T t) { return null; }
  }
  public interface Interface {
      RetType aMethod(RetType obj);
  }
  public static class Impl extends Superclass<RetType> implements Interface {
  }
  
  public void testInterceptionOrder() {
    final List<String> callList = Lists.newArrayList();
    Injector injector = Guice.createInjector(new AbstractModule() {
      protected void configure() {
        bindInterceptor(Matchers.any(), Matchers.any(), 
          new NamedInterceptor("a", callList),
          new NamedInterceptor("b", callList),
          new NamedInterceptor("c", callList));
      }
    });

    Interceptable interceptable = injector.getInstance(Interceptable.class);
    assertEquals(0, callList.size());
    interceptable.foo();
    assertEquals(Arrays.asList("a", "b", "c"), callList);
  }
  
  private final class NamedInterceptor implements MethodInterceptor {
    private final String name;
    final List<String> called;
    
    NamedInterceptor(String name, List<String> callList) {
      this.name = name;
      this.called = callList;
    }
    
    public Object invoke(MethodInvocation methodInvocation) throws Throwable {
      called.add(name);
      return methodInvocation.proceed();
    }
  }
  
  public void testDeDuplicateInterceptors() throws Exception {
    Injector injector = Guice.createInjector(new AbstractModule() {
      @Override protected void configure() {
        CountingInterceptor interceptor = new CountingInterceptor();
        bindInterceptor(Matchers.any(), Matchers.any(), interceptor);
        bindInterceptor(Matchers.any(), Matchers.any(), interceptor);
      }
    });

    Interceptable interceptable = injector.getInstance(Interceptable.class);
    interceptable.foo();
    assertEquals(1, count.get());
  }

  public void testCallLater() {
    final Queue<Runnable> queue = Lists.newLinkedList();
    Injector injector = Guice.createInjector(new AbstractModule() {
      protected void configure() {
        bindInterceptor(Matchers.any(), Matchers.any(), new CallLaterInterceptor(queue));
      }
    });

    Interceptable interceptable = injector.getInstance(Interceptable.class);
    interceptable.foo();
    assertNull(interceptable.lastElements);
    assertEquals(1, queue.size());

    queue.remove().run();
    assertNotNull(interceptable.lastElements);
  }

  private final class CallLaterInterceptor implements MethodInterceptor {
    private final Queue<Runnable> queue;

    public CallLaterInterceptor(Queue<Runnable> queue) {
      this.queue = queue;
    }

    public Object invoke(final MethodInvocation methodInvocation) throws Throwable {
      queue.add(new Runnable() {
        @Override
        public void run() {
          try {
            methodInvocation.proceed();
          } catch (Throwable t) {
            throw new RuntimeException(t);
          }
        }
      });
      return null;
    }
  }
}




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