代理模式实例

public interface PersonDao {    public void savePerson();}

public class PersonDaoImpl implements PersonDao{    public void savePerson() {        System.out.println("save person");    }}

public class Transaction {    public void beginTransaction(){        System.out.println("begin transaction");    }        public void commit(){        System.out.println("commit");    }}

public class PersonDaoProxy implements PersonDao{    private PersonDao personDao;    private Transaction transaction;    public PersonDaoProxy(PersonDao personDao, Transaction transaction) {        super();        this.personDao = personDao;        this.transaction = transaction;    }    public void savePerson() {        this.transaction.beginTransaction();        this.personDao.savePerson();        this.transaction.commit();    }}

/** * 静态代理模式的缺点 *    1、只要写一个dao的是实现类就会写一个代理类 *    2、如果接口中的方法比较多，那么代理类中的方法就比较多，每个方法都需要开启事务、事务的提交 *        所以没有简化开发，没有做到业务逻辑与事务的松耦合 * @author zd * */public class StaticProxyTest {    @Test    public void testProxy(){        PersonDao personDao = new PersonDaoImpl();        Transaction transaction = new Transaction();        PersonDaoProxy proxy = new PersonDaoProxy(personDao, transaction);        proxy.savePerson();    }}

1.jdk动态代理(接口代理)

public interface PersonDao {    public void savePerson();    public void updatePerson();}

public class PersonDaoImpl implements PersonDao{    public void savePerson() {        System.out.println("save person");    }    public void updatePerson() {        // TODO Auto-generated method stub        System.out.println("update person");    }}

public class Transaction {    public void beginTransaction(){        System.out.println("begin transaction");    }        public void commit(){        System.out.println("commit");    }}

/** * 1、引入目标类和事务类 * 2、完成invoke * @author zd * */public class MyInterceptor implements InvocationHandler{    private Object target;    private Transaction transaction;        public MyInterceptor(Object target, Transaction transaction) {        super();        this.target = target;        this.transaction = transaction;    }    public Object invoke(Object proxy, Method method, Object[] args)            throws Throwable {        this.transaction.beginTransaction();        method.invoke(this.target, args);        this.transaction.commit();        return null;    }}

/** * 1、产生的代理类与接口是什么关系？ *     代理类实现了接口 * 2、代理类的方法体的内容是什么？ *     方法体的内容就是拦截器中invoke方法体的内容 * 3、拦截器的作用是什么? *     完成invoke方法体中的内容 * 4、拦截器中的invoke方法的参数method *     客户端调用哪个方法，method就代理哪个方法 * 5、拦截器中的invoke方法是什么？ *     是代理类的方法 * @author zd * */public class JDKProxyTest {    @Test    public void testJDKProxy(){        Object target = new PersonDaoImpl();        Transaction transaction = new Transaction();        MyInterceptor interceptor = new MyInterceptor(target, transaction);        //产生代理对象        /**         * 第一个参数         *    类加载器         * 第二个参数         *    目标类实现的所有的接口         * 第三个参数         *    拦截器          */        PersonDao personDao = (PersonDao)Proxy.newProxyInstance(target.getClass().getClassLoader(),                 target.getClass().getInterfaces(), interceptor);        personDao.updatePerson();            }}

 2.cglib动态代理(子类代理)

public class Transaction {    public void beginTransaction(){        System.out.println("begin transaction");    }        public void commit(){        System.out.println("commit");    }}

public class PersonDaoImpl{    public void savePerson() {        System.out.println("save person");    }}

import java.lang.reflect.Method;import net.sf.cglib.proxy.Enhancer;import net.sf.cglib.proxy.MethodInterceptor;import net.sf.cglib.proxy.MethodProxy;public class PersonDaoInterceptor implements MethodInterceptor{    private Object target;    private Transaction transact��ȫ,ƽ��ion;        public PersonDaoInterceptor(Object target, Transaction transaction) {        super();        this.target = target;        this.transaction = transaction;    }        /**     * 用来产生代理对象     */    public Object createProxy(){        Enhancer enhancer = new Enhancer();        enhancer.setCallback(this);        //设置代理类的父类        enhancer.setSuperclass(PersonDaoImpl.class);        return enhancer.create();    }    public Object intercept(Object arg0, Method method, Object[] arg2,            MethodProxy arg3) throws Throwable {        this.transaction.beginTransaction();        method.invoke(target, arg2);        this.transaction.commit();        return null;    }}

/** * 使用cglib产生的代理类，其代理类是目标类的子类 * @author zd * */public class PersonDaoTest {    @Test    public void testPersonDaoProxy(){        Object target = new PersonDaoImpl();        Transaction transaction = new Transaction();        PersonDaoInterceptor interceptor = new PersonDaoInterceptor(target, transaction);        PersonDaoImpl daoImpl = (PersonDaoImpl)interceptor.createProxy();        daoImpl.savePerson();    }}