java反射

java反射

• Class.forName("java.lang.System")

  Method[] m=c.getDeclareMethods();方法列表

  Constructor构造

  Modifier修饰符  Field字段

  java动态代理

  案例

  定义接口和实现类

  public interface Hello {

  ....public void say();

  }

  public class HelloWorld implements Hello{

  ....public void say() {

  ........System.out.println("hello world");

  ....}

  }

  public class HelloChina implements Hello {

  ....public void say() {

  ........System.out.println("hello china");

  ....}

  }

  动态代理类

  import java.lang.reflect.InvocationHandler;

  import java.lang.reflect.Method;

  public class HelloHandler implements InvocationHandler {

  ....private Object proxyed;

  ....

  ....// 被代理的对象

  ....public HelloHandler(Object o)

  ....{

  ........this.proxyed = o;

  ....}

  ....

  ....public Object invoke(Object arg0, Method arg1, Object[] arg2)

  ............throws Throwable {

  ........Object result;

  ........// 方法调用之前

  ........System.out.println("start to say");

  ........// 反射invoke出方法列表,调用原始对象的方法

  ........result=arg1.invoke(this.proxyed, arg2);

  ........System.out.println("end say");

  ........return result;

  ....}

  }

  具体的使用

  Hello hw =new HelloWorld();

  // 代理调用world

  InvocationHandler hander1=new HelloHandler(hw);

  Hello proxy1=(Hello)Proxy.newProxyInstance(hw.getClass().getClassLoader(), hw.getClass().getInterfaces(), hander1);

  proxy1.say();

  // 代理调用china

  Hello hc =new HelloChina();

  InvocationHandler hander2=new HelloHandler(hc);

  Hello proxy2=(Hello)Proxy.newProxyInstance(hc.getClass().getClassLoader(),hc.getClass().getInterfaces(), hander2);

  proxy2.say();