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Java example source code file (InterceptorStackCallback.java)

This example Java source code file (InterceptorStackCallback.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

accessibleobject, aop_internal_classes, enhancerbyguice, interceptedmethodinvocation, interceptorstackcallback, list, method, methodinterceptor, methodproxy, object, reflection, set, stacktraceelement, string, throwable, util

The InterceptorStackCallback.java Java example source code

/**
 * Copyright (C) 2006 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.internal;

import com.google.common.collect.Lists;

import net.sf.cglib.proxy.MethodProxy;

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

import java.lang.reflect.AccessibleObject;
import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

/**
 * Intercepts a method with a stack of interceptors.
 *
 * @author crazybob@google.com (Bob Lee)
 */
final class InterceptorStackCallback implements net.sf.cglib.proxy.MethodInterceptor {
  private static final Set<String> AOP_INTERNAL_CLASSES = new HashSet(Arrays.asList(
      InterceptorStackCallback.class.getName(),
      InterceptedMethodInvocation.class.getName(),
      MethodProxy.class.getName()));

  final MethodInterceptor[] interceptors;
  final Method method;

  public InterceptorStackCallback(Method method,
      List<MethodInterceptor> interceptors) {
    this.method = method;
    this.interceptors = interceptors.toArray(new MethodInterceptor[interceptors.size()]);
  }

  public Object intercept(Object proxy, Method method, Object[] arguments,
      MethodProxy methodProxy) throws Throwable {
    return new InterceptedMethodInvocation(proxy, methodProxy, arguments, 0).proceed();
  }

  private class InterceptedMethodInvocation implements MethodInvocation {

    final Object proxy;
    final Object[] arguments;
    final MethodProxy methodProxy;
    final int index;

    public InterceptedMethodInvocation(Object proxy, MethodProxy methodProxy,
        Object[] arguments, int index) {
      this.proxy = proxy;
      this.methodProxy = methodProxy;
      this.arguments = arguments;
      this.index = index;
    }

    public Object proceed() throws Throwable {
      try {
        return index == interceptors.length
            ? methodProxy.invokeSuper(proxy, arguments)
            : interceptors[index].invoke(
                new InterceptedMethodInvocation(proxy, methodProxy, arguments, index + 1));
      } catch (Throwable t) {
        pruneStacktrace(t);
        throw t;
      }
    }

    public Method getMethod() {
      return method;
    }

    public Object[] getArguments() {
      return arguments;
    }

    public Object getThis() {
      return proxy;
    }

    public AccessibleObject getStaticPart() {
      return getMethod();
    }
  }

  /**
   * Removes stacktrace elements related to AOP internal mechanics from the
   * throwable's stack trace and any causes it may have.
   */
  private void pruneStacktrace(Throwable throwable) {
    for(Throwable t = throwable; t != null; t = t.getCause()) {
      StackTraceElement[] stackTrace = t.getStackTrace();
      List<StackTraceElement> pruned = Lists.newArrayList();
      for (StackTraceElement element : stackTrace) {
        String className = element.getClassName();
        if (!AOP_INTERNAL_CLASSES.contains(className) && !className.contains("$EnhancerByGuice$")) {
          pruned.add(element);
        }
      }
      t.setStackTrace(pruned.toArray(new StackTraceElement[pruned.size()]));
    }
  }
}

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