设计模式——代理模式

Posted 2021-03-04 macro-renzhansheng

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);
}