【Java SE】代理

代理会在运行时创建一个实现了一组给定接口的新类。
创建的代理类名字以$Proxy开头，并且是public和final的。
创建代理类时需要提供一个实现了InvocationHandler接口的调用处理器，
无论何时调用代理对象的方法，调用处理器的invoke方法都会被调用，并向其传递Method和原始对象的调用参数

自定义接口

public interface MyInterface {
    void showMessage(String msg);
}
public class MyHandler implements InvocationHandler {
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        System.out.println("执行invoke");
        if (args != null && args.length > 0) {
            for (int i = 0; i < args.length; i++) {
                System.out.println(" 参数: " + args[i]);
            }
        }
        return null;
    }
}
public class YProxy {
    public static void main(String[] mainArgs) {
        MyInterface proxyObject = (MyInterface) Proxy.newProxyInstance(Thread.currentThread().getContextClassLoader(), new Class[] {MyInterface.class}, new MyHandler());
        proxyObject.showMessage("Hello World!");
    }
}

Comparable接口

public class YProxy {
    public static void main(String[] mainArgs) {
        // 1,2,3,4,5,6,7,8,9,10
        Object[] elements = new Object[10];
        for (int i = 0; i < elements.length; i++) {
            Integer value = i + 1;
            InvocationHandler handler = new TraceHandler(value);
            Object proxy = Proxy.newProxyInstance(null, new Class[] { Comparable.class }, handler);
            elements[i] = proxy;
        }
        // 二分法检索
        int result = Arrays.binarySearch(elements, 3);
        System.out.println("结果: " + elements[result]);
    }
    // 显示比较过程
    static class TraceHandler implements InvocationHandler {
        private Object target;
        TraceHandler(Object value) {
            target = value;
        }
        @Override
        public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
            if (args != null) {
                System.out.println(target + "." + method.getName() + "(" + args[0] + ")");
            }
            return method.invoke(target, args);
        }
    }
}
5.compareTo(3)
2.compareTo(3)
3.compareTo(3)
结果: 3