用處：aop,日志，程序用時(shí)...
分類：
靜態(tài)代理
動(dòng)態(tài)代理：JDK動(dòng)態(tài)代理，Cglib動(dòng)態(tài)代理等(底層都是用asm實(shí)現(xiàn)，直接操作class文件碼)
先上類圖
代理模式.jpg
案例代碼
靜態(tài)代理
類似裝飾者模式，將被代理接口聚合在代理中。
package com.wwj.proxymode;
public class StaticProxy {
public static void main(String[] args) {
//new Car().run();
new StaticLogProxy(new Car()).run();
}
}
/**
* 定義交通工具接口
*/
interface Vehicle{
void run();
}
/**
* 定義被代理對(duì)象
*/
class Car implements Vehicle{
@Override
public void run(){
System.out.println("10m/s的速度前進(jìn)!!!!!");
}
}
/**
* 以打印日志為例
*/
class StaticLogProxy implements Vehicle{
Vehicle vehicle;
public StaticLogProxy(Vehicle vehicle) {
this.vehicle = vehicle;
}
@Override
public void run() {
System.out.println("日志打印開始===========");
vehicle.run();
System.out.println("日志打印結(jié)束===========");
}
}
JDK動(dòng)態(tài)代理
- spring AOP 被代理對(duì)象是接口默認(rèn)使用JDK的動(dòng)態(tài)代理
- JDK的動(dòng)態(tài)代理
- 代理類自動(dòng)生成，且實(shí)現(xiàn)指定的接口
- 利用asm生成
- 局限性:被代理對(duì)象必須實(shí)現(xiàn)接口
package com.wwj.proxymode;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
/**
* spring AOP 被代理對(duì)象是接口默認(rèn)使用JDK的動(dòng)態(tài)代理
* JDK的動(dòng)態(tài)代理
* 代理類自動(dòng)生成，且實(shí)現(xiàn)指定的接口
* 利用asm生成
* 局限性:被代理對(duì)象必須實(shí)現(xiàn)接口
*/
public class JDKDynamicProxy {
public static void main(String[] args) {
JDKCar jdkCar = new JDKCar();
//配置自動(dòng)生成的反射對(duì)象保留在代碼中，方便理解
System.getProperties().put("sun.misc.ProxyGenerator.saveGeneratedFiles","true");
//利用JDK自動(dòng)生成代理對(duì)象
JDKVehicle JDKVehicle = (JDKVehicle)Proxy.newProxyInstance(
JDKCar.class.getClassLoader(),
new Class[]{JDKVehicle.class},
new MyInvocationHandler(jdkCar));
JDKVehicle.run();
}
}
class MyInvocationHandler implements InvocationHandler{
/**
* 聚合被代理接口
*/
JDKVehicle jdkVehicle;
public MyInvocationHandler(JDKVehicle jdkVehicle) {
this.jdkVehicle = jdkVehicle;
}
/**
* 自動(dòng)生成的代理對(duì)象會(huì)調(diào)用invoke方法
* @param proxy
* @param method
* @param args
* @return
* @throws Throwable
*/
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
System.out.println("日志打印開始===========");
Object invoke = method.invoke(jdkVehicle, args);
System.out.println("日志打印結(jié)束===========");
return invoke;
}
}
/**
* 定義交通工具接口
*/
interface JDKVehicle{
void run();
}
/**
* 定義被代理對(duì)象
*/
class JDKCar implements JDKVehicle{
@Override
public void run(){
System.out.println("10m/s的速度前進(jìn)!!!!!");
}
}
這里可以看到內(nèi)存中自動(dòng)生成的代理對(duì)象(正常在源碼中是看不到的)：
//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//
package com.wwj.proxymode;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.lang.reflect.UndeclaredThrowableException;
final class $Proxy0 extends Proxy implements JDKVehicle {
private static Method m1;
private static Method m3;
private static Method m2;
private static Method m0;
public $Proxy0(InvocationHandler var1) throws {
super(var1);
}
public final boolean equals(Object var1) throws {
try {
return (Boolean)super.h.invoke(this, m1, new Object[]{var1});
} catch (RuntimeException | Error var3) {
throw var3;
} catch (Throwable var4) {
throw new UndeclaredThrowableException(var4);
}
}
public final void run() throws {
try {
super.h.invoke(this, m3, (Object[])null);
} catch (RuntimeException | Error var2) {
throw var2;
} catch (Throwable var3) {
throw new UndeclaredThrowableException(var3);
}
}
public final String toString() throws {
try {
return (String)super.h.invoke(this, m2, (Object[])null);
} catch (RuntimeException | Error var2) {
throw var2;
} catch (Throwable var3) {
throw new UndeclaredThrowableException(var3);
}
}
public final int hashCode() throws {
try {
return (Integer)super.h.invoke(this, m0, (Object[])null);
} catch (RuntimeException | Error var2) {
throw var2;
} catch (Throwable var3) {
throw new UndeclaredThrowableException(var3);
}
}
static {
try {
m1 = Class.forName("java.lang.Object").getMethod("equals", Class.forName("java.lang.Object"));
m3 = Class.forName("com.wwj.proxymode.JDKVehicle").getMethod("run");
m2 = Class.forName("java.lang.Object").getMethod("toString");
m0 = Class.forName("java.lang.Object").getMethod("hashCode");
} catch (NoSuchMethodException var2) {
throw new NoSuchMethodError(var2.getMessage());
} catch (ClassNotFoundException var3) {
throw new NoClassDefFoundError(var3.getMessage());
}
}
}
Cglib動(dòng)態(tài)代理
- spring AOP 被代理對(duì)象不是接口默認(rèn)使用Cglib的動(dòng)態(tài)代理
- Cglib的動(dòng)態(tài)代理
- 代理類自動(dòng)生成，且繼承被代理類指定的接口
- 利用asm生成
package com.wwj.proxymode;
import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;
import java.lang.reflect.Method;
/**
* spring AOP 被代理對(duì)象不是接口默認(rèn)使用Cglib的動(dòng)態(tài)代理
* * Cglib的動(dòng)態(tài)代理
* * 代理類自動(dòng)生成，且繼承被代理類指定的接口
* * 利用asm生成
*/
public class CglibDynamicProxy {
public static void main(String[] args) {
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(CglibCar.class);
enhancer.setCallback(new MyMethodInterceptor());
CglibCar cglibCar = (CglibCar)enhancer.create();
cglibCar.run();
}
}
/**
* 自定義回調(diào)接口
*/
class MyMethodInterceptor implements MethodInterceptor {
@Override
public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
System.out.println("日志打印開始===========");
Object invoke = methodProxy.invokeSuper(o, objects);
System.out.println("日志打印結(jié)束===========");
return invoke;
}
}
/**
* 定義被代理對(duì)象
*/
class CglibCar{
public void run(){
System.out.println("10m/s的速度前進(jìn)!!!!!");
}
}
