Java代理和动态代理

code from 《Thinking in java》

代理模式

interface Interface {
void doSomething();
void somethingElse(String arg);
}

class RealObject implements Interface {

@Override
public void doSomething() {
System.out.println("doSomething.");
}

@Override
public void somethingElse(String arg) {
System.out.println("somethingElse " + arg);
}
}

class SimpleProxy implements Interface {

private Interface proxy;

public SimpleProxy(Interface proxy) {
this.proxy = proxy;
}

@Override
public void doSomething() {
System.out.println("SimpleProxy doSomething.");
proxy.doSomething();
}

@Override
public void somethingElse(String arg) {
System.out.println("SimpleProxy somethingElse " + arg);
proxy.somethingElse(arg);
}
}

public class SimpleProxyDemo {

public static void consumer(Interface iface) {
iface.doSomething();
iface.somethingElse("bonobo");
}

public static void main(String[] args) {
consumer(new RealObject());
consumer(new SimpleProxy(new RealObject()));
}

}

输出：

doSomething.
somethingElse bonobo
SimpleProxy doSomething.
doSomething.
SimpleProxy somethingElse bonobo
somethingElse bonobo

动态代理

class DynamicProxyHandler implements InvocationHandler {

private Object proxy;

public DynamicProxyHandler(Object proxy) {
this.proxy = proxy;
}

@Override
public Object invoke(Object proxy, Method method, Object[] args)
throws Throwable {
System.out.println("*** proxy: " + proxy.getClass() +
". method: " + method + ". args: " + args);
if(args != null) {
for(Object arg : args)
System.out.println(" " + arg);
}
return method.invoke(this.proxy, args);
}
}

public class SimpleDynamicProxy {

public static void consumer(Interface iface) {
iface.doSomething();
iface.somethingElse("bonobo");
}

public static void main(String[] args) {
RealObject real = new RealObject();
consumer(real);
// insert a proxy and call again:
Interface proxy = (Interface)Proxy.newProxyInstance(
Interface.class.getClassLoader(),
new Class[]{ Interface.class },
new DynamicProxyHandler(real));

consumer(proxy);
}

}

输出：

doSomething.
somethingElse bonobo
*** proxy: class typeinfo.\$Proxy0. method: public abstract void typeinfo.Interface.doSomething(). args: null
doSomething.
*** proxy: class typeinfo.\$Proxy0. method: public abstract void typeinfo.Interface.somethingElse(java.lang.String). args: [Ljava.lang.Object;@6a8814e9
bonobo
somethingElse bonobo

二者最大的区别 动态代理 将代理类和实际执行类 解耦了

代理类持有的是Object类型的引用 也就是说此时该代理类可以代理不同类型的实际执行类

只需要在客户端实例化不同的实际执行类 再传入代理类中即可

key thinking ：解耦