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Dozer is a powerful Java Bean to Java Bean mapper that recursively copies data from one object to another
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/*
 * Copyright 2005-2009 the original author or authors.
 *
 * 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 org.dozer.util;

import java.lang.reflect.Method;

/**
 * Utility class to find methods that are bridged by other methods (bridge methods)
 *
 * @author andor.greissl
 */
public final class BridgedMethodFinder {

  /** utility class constructor */
  private BridgedMethodFinder() {}

  /**
   * Find the original method for the Java5 bridge Method. If the supplied method
   * is not a bridge method then the supplied method is returned.
   * If the supplied method is a bridge method, the algorithm tries to find a more
   * specific method with parameters and return types that can be assigned to the
   * the supplied method parameters and return type.
   *
   * Informally, method A is more specific than method B if
   * any invocation handled by method A can also be handled by method B.
   *
   * @param bridgeMethod the bridge method (Java 5 specific)
   * @param targetClass the class the method belongs to
   * @return the original method or a more specific method if available
   */
  public static Method findMethod(final Method bridgeMethod, final Class< ? > targetClass) {
    if (bridgeMethod == null || targetClass == null)
      return bridgeMethod;

    if (!bridgeMethod.isBridge())
      return bridgeMethod;

    Method[] methods = bridgeMethod.getDeclaringClass().getDeclaredMethods();
    for (Method method : methods) {
      // don't care about methods that are bridge methods
      if (method.isBridge())
        continue;

      // check if the method is more specific
      if (isAssignable(method, bridgeMethod))
        return method;
    }
    return bridgeMethod;
  }

  /**
   * returns true if the supplied method can handle the invocation
   * of the candidate Method.
   *
   * @param candidate the method to inspect
   * @param method the proposed bridge method
   * @return
   *   true if the supplied method can handle the invocation
   *   of the candidate Method.
   */
  private static boolean isAssignable(final Method candidate, final Method method) {
    if (!method.getName().equals(candidate.getName()))
      return false;
    if (method.getParameterTypes().length != candidate.getParameterTypes().length)
      return false;
    if (!isAssignable(method.getReturnType(), candidate.getReturnType()))
      return false;
    if (!isAssignable(method.getParameterTypes(), candidate.getParameterTypes()))
      return false;

    return true;
  }

  /**
   * Returns true if all the classes supplied as a's can be assigned
   * to the classes supplied as b's
   */
  private static boolean isAssignable(final Class< ? >[] as, final Class< ? >[] bs) {
    if (as == null && bs == null)
      return true;
    if (as == null || bs == null)
      return false;
    if (as.length != bs.length)
      return false;

    for (int i = 0; i < as.length; i++) {
      if (!isAssignable(as[i], bs[i]))
        return false;
    }
    return true;
  }

  /**
   * Returns true if all the class supplied as a can be assigned
   * from b
   */
  private static boolean isAssignable(final Class< ? > a, final Class< ? > b) {
    if (a == null && b == null)
      return true;
    if (a == null || b == null)
      return false;

    return a.isAssignableFrom(b);
  }

}