黑马程序员_动态代理入门讲解

动态代理讲解

<span style="font-size:18px;"><strong>import java.lang.reflect.Method;
public interface Advice {

public void beforeMethod(Method method);
public void afterMethod(Method method);
}
</strong></span>

<span style="font-size:18px;"><strong>import java.lang.reflect.Method;
public interface Advice {

public void beforeMethod(Method method);
public void afterMethod(Method method);
}
</strong></span>

<span style="font-size:18px;"><strong>创建一个实现接口的类
import java.lang.reflect.Method;
public class MyAdvice implements Advice{

long beginTime = 0;

public void afterMethod(Method method) {
System.out.println("学习结束了");
long endTime = System.currentTimeMillis();
System.out.println(method.getName() + " 运行时间"
+ (endTime - beginTime));
}
public void beforeMethod(Method method) {
System.out.println("开始学习了");
beginTime = System.currentTimeMillis();

}  <span style="font-size:18px;"><strong>import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.ArrayList;
import java.util.Collection;
public class ProxyText {

public static void main(String[] args) throws Exception,
NoSuchMethodException {
// 获取字节码
Class clazzProxy1 = Proxy.getProxyClass(Collection.class
.getClassLoader(), Collection.class);
System.out.println(clazzProxy1.getName());

System.out.println("----------begin constructors list------------");
/*
* $Proxy0() $Proxy0(InvocationHandier,int)
*/
// 获取所有构造方法
Constructor[] constructors = clazzProxy1.getConstructors();
for (Constructor constructor : constructors) {

String name = constructor.getName();
StringBuilder sBuilder = new StringBuilder(name);
sBuilder.append("(");
Class[] clazzPrams = constructor.getParameterTypes();
for (Class clazzPram : clazzPrams) {
if (clazzPrams != null && clazzPrams.length != 0) {
sBuilder.append(clazzPram.getName()).append(",");
}
}
sBuilder.append(")");
System.out.println(sBuilder.toString());

System.out.println("-----------begin methods llist------------");
// 获得所有的方法
Method[] methods = clazzProxy1.getMethods();
for (Method method : methods) {// 遍历数组
String name1 = method.getName();// 获取方法名
StringBuilder sBuilder1 = new StringBuilder(name1);// 添加容器
sBuilder1.append("(");
Class[] clazzPrams1 = method.getParameterTypes();// 返回描述了此
// Method
// 对象所表示的方法的形参类型
for (Class clazzPram1 : clazzPrams1) {
sBuilder1.append(clazzPram1.getName());
}
sBuilder1.append(")");
System.out.println(sBuilder1.toString());
}

System.out
.println("-----------begin create instance object-----------");
// 创建InvocationHandler的实例对象
Constructor constructor1 = clazzProxy1
.getConstructor(InvocationHandler.class);

// 第一种方法 创建MyInvocationHandler1并实现InvocationHandler接口
class MyInvocationHandler1 implements InvocationHandler {

public Object invoke(Object proxy, Method method, Object[] args)
throws Throwable {

return null;
}
}

Collection proxy1 = (Collection) constructor1
.newInstance(new MyInvocationHandler1());

// 第二种创建方法：用匿名内部类
Collection proxy2 = (Collection) constructor1
.newInstance(new InvocationHandler() {

public Object invoke(Object proxy, Method method,
Object[] args) throws Throwable {
return null;
}
});

final ArrayList al = new ArrayList();
Collection proxy3 = (Collection) getProxy(al,new MyAdvice());
//          proxy3.add("abc");
//          proxy3.add("bcd");
//          proxy3.add("cde");
System.out.println(proxy3.size());
}
}

// //第三种创建的方法：使用newProxyInstance方法 (抽取方法)
private static Object getProxy(final Object target, final Advice advice) {
Object proxy3 = Proxy.newProxyInstance(

target.getClass().getClassLoader(),

// new Class[]{Collection.class},
target.getClass().getInterfaces(),

new InvocationHandler() {

public Object invoke(Object proxy, Method method,
Object[] args) throws Throwable {

/*
* long beginTime = System.currentTimeMillis(); Object
* retVal = method.invoke(target, args); long endTime =
* System.currentTimeMillis();
*
* System.out.println(method.getName() + " 运行时间" +
* (endTime - beginTime)); return retVal;
*/

advice.beforeMethod(method);

Object retVal = method.invoke(target, args);

advice.afterMethod(method);

return retVal;
}
});
return proxy3;
}
}
</strong></span>