基本原理：
//源接口
public interface Sourceable {
public void method();
}//实现接口类
public class Source implements Sourceable{
@Override
public void method() {
// TODO Auto-generated method stub
System.out.println("源方法");
}
}//代理对象实现类——将实现类 封装到 代理实现类，同时实现同一个接口
public class Proxy implements Sourceable{
private Sourceable source;
public Proxy(Sourceable source) {
this.source = source;
}
@Override
public void method() {
// TODO Auto-generated method stub
System.out.println("before invoke");
source.method();
System.out.println("after invoke");
}
}//测试
public class Demo {
public static void main(String[] args) {
new Proxy(new Source()).method();
}
}
综合案例：
//接口
public interface UserDao { void save(User user); void delete();}//存储User对象public class User { private String name; private Integer age; public User(){ super(); } public User(String name,Integer age){ this.name = name; this.age = age; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Integer getAge() { return age; } public void setAge(int age) { this.age = age; } @Override public String toString(){ StringBuilder tmp = new StringBuilder(); tmp.append(name); tmp.append(","); tmp.append(age); return tmp.toString(); }}
业务层：UserService
//直接调用
public static void directCall(){ User user = new User(); user.setName("macro"); user.setAge(25); //内名内部类实现 UserDao userDao = new UserDao() { @Override public void save(User user) { //入库，打印信息（简单不限制输入内容） System.out.println("保存用户信息："+user.toString()); } @Override public void delete() { } }; userDao.save(user); User user1 = new User("",20); User user2 = new User("小海",-10); userDao.save(user1); userDao.save(user2);}
静态代理——跟杨老师的Dao、Serivice、Controller 等吻合！
//将接口实现类封装到代理对象中
//接口实现类
public class UserDaoImpl implements UserDao{ @Override public void save(User user) { //入库 //初始判断条件简单 if(user.getName()==null || user.getName().length()<=0){ System.out.println("用户名输错"); return; } if(user.getAge() == null || user.getAge().intValue()<0){ System.out.println("用户年龄输错"); return; } System.out.println("入库用户信息："+user.toString()); } @Override public void delete() { System.out.println("执行删除操作"); }}//代理对象
public class StaticProxyUser implements UserDao { private UserDao target; public StaticProxyUser(UserDao userDao){ this.target = userDao; } //增加参数校验 @Override public void save(User user) { //增加判断条件 if(user.getName()==null || user.getName().length()<=0){ System.out.println("用户名称输错，入库失败"); return; } if (user.getAge()<0 ||user.getAge()>200){ System.out.println("用户年龄输错，入库失败"); return; } //调用原来的对象入库等操作 target.save(user); //System.out.println(user.toString()); } @Override public void delete() { }}//调用
public static void staticProxyCall(){ UserDaoImpl userDaoImpl = new UserDaoImpl(); StaticProxyUser staticProxyUser = new StaticProxyUser(userDaoImpl); User user = new User(); user.setName("macro"); user.setAge(25); staticProxyUser.save(user); user.setName("小海"); user.setAge(-1); staticProxyUser.save(user); User user1 = new User("",3); staticProxyUser.save(user1);}
JDK代理——缺少理论理解？？？
//实现Invocationhandler接口
public class UserInvocaHandler implements InvocationHandler { public Object object; public UserInvocaHandler(Object object){ this.object = object; } @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { //return null; System.out.println("开始执行JDKProxy"); //添加限制条件 if(args != null && args.length==1){ if(args[0] instanceof User){ User user = (User) args[0]; if (user.getName() == null || user.getName().trim().length()<=0 ){ System.out.println("姓名为空，不保存"); return false; } if (user.getAge() == null || user.getAge()<0 ){ System.out.println("年龄小于0，不保存"); return false; } } } Object result = method.invoke(object,args); System.out.println("执行结束JDKProxy"); return result; }}//调用过程public static void jdkProxy(){ User user = new User("macro",26); UserDaoImpl userDao = new UserDaoImpl(); UserInvocaHandler handler = new UserInvocaHandler(userDao); //UserDao 必须是接口 UserDao userDao1 = (UserDao) Proxy.newProxyInstance( userDao.getClass().getClassLoader(), userDao.getClass().getInterfaces(), handler ); //System.out.println("开始执行JDKProxy"); userDao1.save(user); //System.out.println("执行结束JDKProxy"); User user1 = new User("macro1",-6); User user2 = new User("",26); userDao1.save(user1); userDao1.save(user2); userDao1.delete();}
Cglib代理
//同样：实现 MethodInterceptor接口
public class User2DaoCglibProxy implements MethodInterceptor { private Object object; public User2DaoCglibProxy(Object object){ this.object = object; } public Object getProxyInstance() { Enhancer en = new Enhancer(); en.setSuperclass(object.getClass()); en.setCallback(this); return en.create(); } @Override public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable { System.out.println("开始执行"); Object result = method.invoke(object,objects); System.out.println("结束执行"); return result; //return null; } /*@Override public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable { return null; }*/}//调用该代理方法public static void cglibProxy(){ User user = new User("macro",26); User2Dao user2Dao = new User2Dao(); //UserInvocaHandler handler = new UserInvocaHandler(userDao); User2DaoCglibProxy cglibProxy = new User2DaoCglibProxy(user2Dao); User2Dao user2DaoProxy = (User2Dao) cglibProxy.getProxyInstance(); user2DaoProxy.save(user); User user1 = new User("",26); user2DaoProxy.save(user1); User user12 = new User("hr",-6); user2DaoProxy.save(user12);}
来源：https://www.cnblogs.com/macro-renzhansheng/p/12536496.html