关于后端:JDK和CGLIB动态代理实现AOP控制事务

JDK和CGLIB动静代理实现AOP管制事务

前言

还是接着xml形式自定义实现Ioc容器

这个实例中,没有进行事务得操作,不能放弃一个线程操作中事务得一致性;

  @Override
    public void transfer(String fromCardNo, String toCardNo, int money) throws Exception {

            Account from = accountDao.queryAccountByCardNo(fromCardNo);
            Account to = accountDao.queryAccountByCardNo(toCardNo);

            from.setMoney(from.getMoney()-money);
            to.setMoney(to.getMoney()+money);

            accountDao.updateAccountByCardNo(to);
            //模仿异样代码
            int c = 1/0;
            accountDao.updateAccountByCardNo(from);

    }

service 层没有增加事务管制,这样会呈现脏数据,可能会呈现以下场景:

  • 1 没扣钱 ,他人账户加了钱
  • 2 扣了钱,他人账户没加上钱

解决这种脏数据问题是给service加上事务操作,如果出现异常,咱们就让他回滚,如果没有咱们就手动提交事务;

以后线程2个update操作内的数据库操作属于同一个线程内执行调用,能够让这个线程应用同一个数据库连贯

1 如何让两个Update语句再同一个事务中呢!

在JDBC的事务操作中,必须操作的是同一个Connection连贯

咱们能够让两个update语句应用同一个数据库连贯!

2 如何让让两个update语句应用同一个数据库连贯?

Java中应用ThreadLocal给以后线程绑定同一个对象

 ThreadLocal<T> threadLocal = new ThreadLocal<>();

所以咱们来批改一下这行代码

Connection con = DruidUtils.getInstance().getConnection();

将获取连贯局部抽离进去,定义一个连贯工厂ConnetionUtil类,单例它,放弃一个对象,防止不同得连贯对事务影响;

public class ConnetionUtil {

    //单例 放弃惟一
    private ConnetionUtil(){}

    private static ConnetionUtil connetionUtil = new ConnetionUtil();


    public static ConnetionUtil getconnetionUtil(){
        return connetionUtil;
    }



    private  ThreadLocal<Connection> threadLocal = new ThreadLocal<>();


    public  Connection getConnection() throws SQLException {
        Connection connection = threadLocal.get();
        if (threadLocal.get()==null){
             connection = DruidUtils.getInstance().getConnection();
            //绑定以后线程 数据库连贯
            threadLocal.set(connection);
        }
        //存在间接返回这个连贯
        return connection;

    }


    //开启事务
   public void start() throws SQLException {
        //不主动提交
       getConnection().setAutoCommit(false);
    }

    //提交事务
    public void commit() throws SQLException {
        getConnection().commit();
    }
    //敞开事务  回滚事务
    public  void rowback() throws SQLException {
        getConnection().rollback();
    }

    public  void close() throws SQLException {
        getConnection().close();
    }
}

而后再dao层去更改一下获取连贯的中央

Connection con = ConnetionUtil.getconnetionUtil().getConnection();

而后再service层去管制事务,敞开主动事务提交,应用try..catch 捕捉极可;

     try {

            //开启事务
            TransferServicemanager.get().start();


            Account from = accountDao.queryAccountByCardNo(fromCardNo);
            Account to = accountDao.queryAccountByCardNo(toCardNo);

            from.setMoney(from.getMoney()-money);
            to.setMoney(to.getMoney()+money);

            accountDao.updateAccountByCardNo(to);
            //模仿异样代码
            int c = 1/0;
            accountDao.updateAccountByCardNo(from);
            //提交事务
            TransferServicemanager.get().commit();
        }catch (Exception e){
            //回滚事务
            TransferServicemanager.get().rowback();
            System.out.println(e.getStackTrace());
            throw new RuntimeException("失败!");
        }finally {
            //敞开连贯
            System.out.println(ConnetionUtil.getconnetionUtil());
            ConnetionUtil.getconnetionUtil().close();
        }

这样就能够实现手动管制事务,从而进一步保证数据一致性;

思考一下,平时工作中零碎中有很多得写语句,那么每一个业务层咱们都手动去加一下,事务控制代码,那不得被累死;

咱们须要革新一下,这块代码,应用代理去实现这块,动静的生成一个代理类去执行这块业务逻辑

基于类的职责,咱们定义一个事务管理器类TransferServicemanager,将事务代码剥离进去,专门去治理事务操作!

public class TransferServicemanager {

    private TransferServicemanager(){}

    //单例
    private static TransferServicemanager t =  new TransferServicemanager();

    //对外提供对象接口
    public static TransferServicemanager get(){
        return t;
    }


    //开启事务
    public  void start() throws SQLException {
        //不主动提交
        ConnetionUtil.getconnetionUtil().start();
    }

    //提交事务
    public void commit() throws SQLException {
        ConnetionUtil.getconnetionUtil().commit();
    }


    //敞开事务  回滚事务
    public  void rowback() throws SQLException {
        ConnetionUtil.getconnetionUtil().rowback();
    }


}

定义动静代理工厂ProxyFactory类,这里通过传入的被代理对象,应用JDK和CGLIB去生成代理对象!

public class ProxyFactory {

    //单例
    private ProxyFactory() {
    }

    private static ProxyFactory jdkProxy = new ProxyFactory();

    //对外提供接口
    public static ProxyFactory getJdkProxy() {
        return jdkProxy;
    }


    /**
     * Jdk动静代理
     *
     * @param obj 被代理的对象
     * @return 返回代理对象
     */
    public Object getJdkProxy(Object obj) {

        //生成代理对象

        return Proxy.newProxyInstance(obj.getClass().getClassLoader(), obj.getClass().getInterfaces(), new InvocationHandler() {
            @Override
            public Object invoke(Object o, Method method, Object[] objects) throws Throwable {

                Object result = null;

                try {

                    //开启事务
                    TransferServicemanager.get().start();

                    result = method.invoke(obj, objects);

                    //提交事务
                    TransferServicemanager.get().commit();
                } catch (Exception e) {
                    //回滚事务
                    TransferServicemanager.get().rowback();
                    System.out.println(e.getStackTrace());
                    throw new RuntimeException("失败!");
                } finally {
                    //敞开连贯
                    System.out.println(ConnetionUtil.getconnetionUtil());
                    ConnetionUtil.getconnetionUtil().close();
                }

                return result;
            }
        });


    }


    /**
     * Jdk动静代理
     *
     * @param object 被代理的对象
     * @return 返回代理对象
     */
    public Object getCglibProxy(Object object) {

        //生成代理对象
        return Enhancer.create(object.getClass(), new MethodInterceptor() {

            @Override
            public Object intercept(Object o, Method method, Object[] objects, MethodProxy methodProxy) throws Throwable {
                Object result = null;

                try {

                    //开启事务
                    TransferServicemanager.get().start();

                    result = method.invoke(object, objects);

                    //提交事务
                    TransferServicemanager.get().commit();
                } catch (Exception e) {
                    //回滚事务
                    TransferServicemanager.get().rowback();
                    System.out.println(e.getStackTrace());
                    throw new RuntimeException("失败!");
                } finally {
                    //敞开连贯
                    System.out.println(ConnetionUtil.getconnetionUtil());
                    ConnetionUtil.getconnetionUtil().close();
                }
                return result;
            }


        });

    }

}

在代理类里执行原对象办法前后管制事务操作;

 try {

                    //开启事务
                    TransferServicemanager.get().start();

                    result = method.invoke(object, objects);

                    //提交事务
                    TransferServicemanager.get().commit();
                } catch (Exception e) {
                    //回滚事务
                    TransferServicemanager.get().rowback();
                    System.out.println(e.getStackTrace());
                    throw new RuntimeException("失败!");
                } finally {
                    //敞开连贯
                    System.out.println(ConnetionUtil.getconnetionUtil());
                    ConnetionUtil.getconnetionUtil().close();
                }
                return result;
            }

最初在管制层去获取找个代理对象去执行办法

委托对象是加强了事务管制的性能(这个对象就曾经加强了事务操作)

    // 3 从工厂获取
    // 3.1 获取jdk代理对象 ProxyFactory
    private TransferService transferService = (TransferService) ProxyFactory.getJdkProxy().getJdkProxy(BeanFactorys.getBean("transferService"));

     // 3.2 获取cglib 代理对象 ProxyFactory
    // private TransferServiceImpl transferService = (TransferServiceImpl) ProxyFactory.getJdkProxy().getCglibProxy(BeanFactorys.getBean("transferService"));

须要的cglib依赖

    <!--引入cglib依赖包-->
    <dependency>
      <groupId>cglib</groupId>
      <artifactId>cglib</artifactId>
      <version>2.1_2</version>
    </dependency>

源码地址

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本文由乐趣区整理发布,转载请注明出处,谢谢。

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