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Java静态代理和动态代理总结

2019年07月22日  | 移动技术网IT编程  | 我要评论

静态代理

第一种实现(基于接口)：

1》接口

public interface hello {
 void say(string msg);
}

2》目标类，至少实现一个接口

public class helloimpl implements hello {
 public void say(string msg) {
  system.out.println("hi,"+msg);
 }
}

3》代理类(与目标类实现相同接口，从而保证功能一致)

public class helloproxy implements hello{
 private hello hello;
 public helloproxy(hello hello){
  this.hello = hello;
 }
 public void say(string msg){
  before();
  hello.say(msg);
  after();
 }
 private void before(){
  system.out.println("before");
 }
 private void after(){
  system.out.println("after");
 }
}

3》测试

/**
 * @author lzhl
 * @create 2017-02-19 10:26
 * @description
 */
public class main {
 public static void main(string[] args) throws exception {
  helloimpl target = new helloimpl();
  helloproxy proxy = new helloproxy(target);
  proxy.say("lzhl");
 }
}

第二种实现(基于目标类)：

1>目标类

public class hellotarget {
 public void sayhello(string name){
  system.out.println("hi,"+name);
 }
}

2>代理类(通过继承目标类，保证功能一致)

public class helloproxy extends hellotarget{
　　private hellotarget target;
　　public helloproxy(hellotarget target){
　　　　this.target = target;
　　} 
　　@override
 public void sayhello(string name) {
  this.before();
  target.sayhello(name);
  this.after();
 }
 private void before(){
  system.out.println("before");
 }
 private void after(){
  system.out.println("after");
 }
}

3>测试

public class main {
 public static void main(string[] args) throws exception {
  hellotarget target = new hellotarget(); 
　　　　helloproxy proxy= new helloproxy(target);
  proxy.sayhello("lzhl");
 }
}

动态代理

动态代理的代理类是在程序运行期间动态生成的，也有两种实现，一种是jdk动态代理，一种是cglib动态代理

1》jdk动态代理(基于接口实现，与目标类实现相同接口，从而保证功能一致)

/**
 * @author lzhl
 * @create 2017-02-19 12:46
 * @description
 */
public class main {
 public static void main(string[] args){
  final helloimpl target = new helloimpl();
  object proxyinstance = proxy.newproxyinstance(target.getclass().getclassloader(), target.getclass().getinterfaces(), new invocationhandler() {
   /*
    * proxy: 代理对象
    * method: 目标对象的方法对象
    * args: 目标对象方法的参数
    * return: 目标对象方法的返回值
    */
   public object invoke(object proxy, method method, object[] args) throws throwable {
    system.out.println("before");
    object retvalue = method.invoke(target, args);
    system.out.println("after");
    return retvalue;
   }
  });
  hello proxy = (hello) proxyinstance;
  proxy.say("lyx");
  //可以把invocationhandler提取出来，单独写一个类，为了方便大家看，这里我用内部类的形式
  class jdkproxy implements invocationhandler {
   private object target;
   public jdkproxy(object target){
    this.target = target;
   }
   public object invoke(object proxy, method method, object[] args) throws throwable {
    before();
    object result = method.invoke(target, args);
    after();
    return result;
   }
   private void before(){
    system.out.println("before");
   }
   private void after(){
    system.out.println("after");
   }
  }
  invocationhandler ih = new jdkproxy(target);
  object proxyinstance2 = proxy.newproxyinstance(target.getclass().getclassloader(), target.getclass().getinterfaces(), ih);
  hello proxy2 = (hello) proxyinstance2;
  proxy2.say("lzhl");
 }
}

2》cglib动态代理(基于目标类，通过继承目标类，从而保证功能一致)，需要导入cglib-3.2.4.jar包

pom.xml

<dependencies>
 <!-- https://mvnrepository.com/artifact/cglib/cglib -->
 <dependency>
  <groupid>cglib</groupid>
  <artifactid>cglib</artifactid>
  <version>3.2.4</version>
 </dependency>
</dependencies>

1)目标类

public class hi {
 public void sayhi(string msg){
  system.out.println("hi,"+msg);
 }
}

2)测试

/**
 * @author lzhl
 * @create 2017-02-19 13:19
 * @description
 */
public class main {
 public static void main(string[] args) {
  enhancer enhancer = new enhancer();
  //设置父类
  enhancer.setsuperclass(hi.class);
  //设置回调函数
  enhancer.setcallback(new methodinterceptor() {
   public object intercept(object target, method method, object[] args, methodproxy methodproxy) throws throwable {
    system.out.println("before");
    object retvalue = methodproxy.invokesuper(target, args);
    system.out.println("after");
    return retvalue;
   }
  });
  object proxy = enhancer.create();
  hi hi = (hi) proxy;
  hi.sayhi("lxy");
  //可以把methodinterceptor提取出来，单独写一个类，为了方便大家看，这里我用内部类的形式
  class cglibproxy implements methodinterceptor {
   public <t> t getproxy(class<t> clazz){
    return (t) enhancer.create(clazz, this);
   }
   public object intercept(object target, method method, object[] args, methodproxy proxy) throws throwable {
    before();
    object result = proxy.invokesuper(target, args);
    after();
    return result;
   }
   private void before(){
    system.out.println("before");
   }
   private void after(){
    system.out.println("after");
   }
  }
  cglibproxy cglibproxy = new cglibproxy();
  hi hi2 = cglibproxy.getproxy(hi.class);
  hi2.sayhi("lzhl");
 }
}

以上所述是小编给大家介绍的java静态代理和动态代理总结，希望对大家有所帮助

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