debugproxy.java

来自「23种GOF模式的java代码实现」· Java 代码 · 共 45 行

package org.gof.structure.proxy;

public class DebugProxy
    implements java.lang.reflect.InvocationHandler {

  private Object obj;

  public static Object newInstance(Object obj) {
    return java.lang.reflect.Proxy.newProxyInstance(
        obj.getClass().getClassLoader(),
        obj.getClass().getInterfaces(),
        new DebugProxy(obj));
  }

  private DebugProxy(Object obj) {
    this.obj = obj;
  }

  public Object invoke(Object proxy, java.lang.reflect.Method m, Object[] args) throws
      Throwable {
    Object result;
    try {
      System.out.println("before method " + m.getName());
      //调用Foolmpl的方法
      result = m.invoke(obj, args);
    }
    catch (java.lang.reflect.InvocationTargetException e) {
      throw e.getTargetException();
    }
    catch (Exception e) {
      throw new RuntimeException("unexpected invocation exception: " +
                                 e.getMessage());
    }
    finally {
      System.out.println("after method " + m.getName());
    }
    return result;
  }

  public static void main(String[] args) {
    Foo foo = (Foo) DebugProxy.newInstance(new FooImpl());
    foo.bar(null);
  }
}