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Java example source code file (DefaultConstructionProxyFactory.java)

This example Java source code file (DefaultConstructionProxyFactory.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

assertionerror, constructionproxy, constructor, defaultconstructionproxyfactory, fastclassproxy, illegalaccessexception, immutablemap, injectionpoint, instantiationexception, invocationtargetexception, override, reflection, reflectiveproxy, suppresswarnings, util

The DefaultConstructionProxyFactory.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.base.Preconditions;
import com.google.common.collect.ImmutableMap;
import com.google.inject.spi.InjectionPoint;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.List;

/**
 * Produces construction proxies that invoke the class constructor.
 *
 * @author crazybob@google.com (Bob Lee)
 */
final class DefaultConstructionProxyFactory<T> implements ConstructionProxyFactory {

  private final InjectionPoint injectionPoint;

  /**
   * @param injectionPoint an injection point whose member is a constructor of {@code T}.
   */
  DefaultConstructionProxyFactory(InjectionPoint injectionPoint) {
    this.injectionPoint = injectionPoint;
  }

  @Override
  public ConstructionProxy<T> create() {
    @SuppressWarnings("unchecked") // the injection point is for a constructor of T
    final Constructor<T> constructor = (Constructor) injectionPoint.getMember();

    /*if[AOP]*/
    try {
      net.sf.cglib.reflect.FastClass fc =
          BytecodeGen.newFastClassForMember(constructor);
      if (fc != null) {
        int index = fc.getIndex(constructor.getParameterTypes());
        // We could just fall back to reflection in this case but I believe this should actually
        // be impossible.
        Preconditions.checkArgument(index >= 0,
            "Could not find constructor %s in fast class",
            constructor);
        return new FastClassProxy<T>(injectionPoint, constructor, fc, index);
      }
    } catch (net.sf.cglib.core.CodeGenerationException e) {/* fall-through */}
    /*end[AOP]*/

    return new ReflectiveProxy<T>(injectionPoint, constructor);
  }

  /*if[AOP]*/
  /** A {@link ConstructionProxy} that uses FastClass to invoke the constructor. */
  private static final class FastClassProxy<T> implements ConstructionProxy {
    final InjectionPoint injectionPoint;
    final Constructor<T> constructor;
    final net.sf.cglib.reflect.FastClass fc;
    final int index;

    private FastClassProxy(InjectionPoint injectionPoint, Constructor<T> constructor,
        net.sf.cglib.reflect.FastClass fc, int index) {
      this.injectionPoint = injectionPoint;
      this.constructor = constructor;
      this.fc = fc;
      this.index = index;
    }

    @Override
    @SuppressWarnings("unchecked")
    public T newInstance(Object... arguments) throws InvocationTargetException {
      // Use this method instead of FastConstructor to save a stack frame
      return (T) fc.newInstance(index, arguments);
    }

    @Override
    public InjectionPoint getInjectionPoint() {
      return injectionPoint;
    }

    @Override
    public Constructor<T> getConstructor() {
      return constructor;
    }

    @Override
    public ImmutableMap<Method, List
        getMethodInterceptors() {
      return ImmutableMap.of();
    }
  }
  /*end[AOP]*/

  private static final class ReflectiveProxy<T> implements ConstructionProxy {
    final Constructor<T> constructor;
    final InjectionPoint injectionPoint;

    ReflectiveProxy(InjectionPoint injectionPoint, Constructor<T> constructor) {
      if (!Modifier.isPublic(constructor.getDeclaringClass().getModifiers())
          || !Modifier.isPublic(constructor.getModifiers())) {
        constructor.setAccessible(true);
      }
      this.injectionPoint = injectionPoint;
      this.constructor = constructor;
    }

    @Override
    public T newInstance(Object... arguments) throws InvocationTargetException {
      try {
        return constructor.newInstance(arguments);
      } catch (InstantiationException e) {
        throw new AssertionError(e); // shouldn't happen, we know this is a concrete type
      } catch (IllegalAccessException e) {
        throw new AssertionError(e); // a security manager is blocking us, we're hosed
      }
    }

    @Override
    public InjectionPoint getInjectionPoint() {
      return injectionPoint;
    }

    @Override
    public Constructor<T> getConstructor() {
      return constructor;
    }

    /*if[AOP]*/
    @Override
    public ImmutableMap<Method, List
        getMethodInterceptors() {
      return ImmutableMap.of();
    }
    /*end[AOP]*/
  }
}

Other Java examples (source code examples)

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