Java动态代理 - 如何参考具体类 [英] Java Dynamic Proxy - How reference concrete class

问题描述

假设我有一个名为 Foo 的界面，一个方法执行和class FooImpl实现Foo 。

当我为 Foo 创建一个代理，我有一些类似的东西：

  Foo f =（Foo）Proxy.newProxyInstance（Foo.class.getClassLoader（），
 new Class [] {Foo.class}，
 handler）; 
  

假设我的调用处理程序如下所示：

  public class FooHandler实现InvocationHandler {
 public Object invoke（Object proxy，Method method，Object [] args）{
 ... 
} 
} 
  

如果我的调用代码看起来像

  Foo proxyFoo =（Foo）Proxy.newInstance（Foo.getClass（）。getClassLoader（），
 new Class [] {Foo.class}，
 new FooHandler（））; 
 proxyFoo.execute（）; 
  

如果代理可以拦截上述调用执行从 Foo 界面， FooImpl 进入哪里？也许我以错误的方式看动态代理。我想要的是从 Foo 的具体实现中获取执行调用，例如 FooImpl 。可以这样做吗？

非常感谢

解决方案

使用动态代理的截取方法是：

  public class FooHandler implements InvocationHandler {
 private Object realObject; 
 
 public FooHandler（Object real）{
 realObject = real; 
} 
 
 
 public Object invoke（Object target，Method method，Object [] arguments）throws Throwable {
 if（execute.equals（method.getName （））{
 //截取方法名为execute
} 
 
 //调用原始方法
 return method.invoke（realObject，arguments）; 
} 
} 
  

通过以下方式调用代理：

  Foo foo =（Foo）Proxy.newProxyInstance（
 Foo.class.getClassLoader（），
 new Class [] {Foo。 class}，
 new FooHandler（new FooImpl（）））; 
  

I have a question relating to dynamic proxies in java.

Suppose I have an interface called Foo with a method execute and class FooImpl implements Foo.

When I create a proxy for Foo and I have something like:

Foo f = (Foo) Proxy.newProxyInstance(Foo.class.getClassLoader(),
                                     new Class[] { Foo.class },
                                     handler);

Suppose my invocation handler looks like:

public class FooHandler implements InvocationHandler {
    public Object invoke(Object proxy, Method method, Object[] args) {
        ...
    }
}

If my invocation code looks something like

Foo proxyFoo = (Foo) Proxy.newInstance(Foo.getClass().getClassLoader(),
                                       new Class[] { Foo.class },
                                       new FooHandler());
proxyFoo.execute();

If the proxy can intercept the aforementioned call execute from the Foo interface, where does the FooImpl come in to play? Maybe I am looking at dynamic proxies in the wrong way. What I want is to be able to catch the execute call from a concrete implementation of Foo, such as FooImpl. Can this be done?

Many thanks

解决方案

The way to intercept methods using dynamic proxies are by:

public class FooHandler implements InvocationHandler {
    private Object realObject;

    public FooHandler (Object real) {
        realObject=real;
    }


    public Object invoke(Object target, Method method, Object[] arguments) throws Throwable {
        if ("execute".equals(method.getName()) {
            // intercept method named "execute"
        }

        // invoke the original methods
        return method.invoke(realObject, arguments);
    }
}

Invoke the proxy by:

Foo foo = (Foo) Proxy.newProxyInstance(
            Foo.class.getClassLoader(),
            new Class[] {Foo.class}, 
            new FooHandler(new FooImpl()));

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