转账问题演示及解决（Aop的引出：ConnectionUtils（ThreadLocal）+TransactionManager）

转账问题分析事务

accountDao中的使用的是Jdbctemplate
由于更新中途出现异常，导致source的金钱扣了却没有转账到target账户上！！！

转账问题解决

该解决方法代码量冗余，配置文件逻辑复杂，仍有巨大优化空间(代理模式加强方法)

工具类部分（通过ThreadLocal绑定线程上的Connection）

ConnectionUtils(通过ThreadLocal绑定对象)

package com.czy.utils;

import javax.sql.DataSource;
import java.sql.Connection;

/**
 * 连接工具类
 * 它用于从数据源获取一个连接，并且实现和线程的绑定
 */

public class ConnectionUtils {
    private ThreadLocal tl = new ThreadLocal();

    //用spring注入此对象
    private DataSource dataSource;

    public void setDataSource(DataSource dataSource) {
        this.dataSource = dataSource;
    }

    /**
     * 获取当前线程上的连接
     * @return
     */
    public Connection getThreadConnection(){
        //1.先从ThreadLocal上获取
        Connection conn = tl.get();
        try {
            //2.判断当前线程上是否有连接
            if (conn == null) {
                //3.从数据源获取一个连接,并且和线程绑定(存入ThreadLocal中)
                conn = dataSource.getConnection();
                tl.set(conn);
            }
        }catch (Exception exception){
            throw new RuntimeException(exception);
        }
        //4.返回当前线程上的连接
        return conn;
    }

    /**
     * 把连接和线程解绑
     */
    public void removeConnection(){
        tl.remove();
    }
}

TransactionManager(管理事务)

package com.czy.utils;

import java.sql.SQLException;

/**
 * 事务管理相关的工具类,包含了开启事务，提交事务，回滚事务和释放连接
 */
public class TransactionManager {

    //使用spring注入
    private ConnectionUtils connectionUtils;

    public void setConnectionUtils(ConnectionUtils connectionUtils) {
        this.connectionUtils = connectionUtils;
    }

    /**
     * 开启事务
     */
    public void beginTransaction(){
        try {
            connectionUtils.getThreadConnection().setAutoCommit(false);
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
    }

    /**
     * 提交事务
     */
    public void commit(){
        try {
            connectionUtils.getThreadConnection().commit();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
    }

    /**
     * 回滚事务
     */
    public void rollback(){
        try {
            connectionUtils.getThreadConnection().rollback();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
    }

    /**
     * 释放连接
     */
    public void release(){
        try {
            connectionUtils.getThreadConnection().close();  //Connection还回连接池中
            connectionUtils.removeConnection();
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
    }
}

dao

package com.czy.dao.impl;

import com.czy.dao.AccountDao;
import com.czy.domain.Account;
import com.czy.utils.ConnectionUtils;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;

import java.util.List;

/**
 * 账户的持久层实现类
 */

public class AccountDaoImpl implements AccountDao {

    private JdbcTemplate template;
    private ConnectionUtils connectionUtils;

    public void setConnectionUtils(ConnectionUtils connectionUtils) {
        this.connectionUtils = connectionUtils;
    }

    public void setTemplate(JdbcTemplate template) {
        this.template = template;
    }

    public List findAllAccount() {
        return template.query("select * from account",new BeanPropertyRowMapper(Account.class),connectionUtils.getThreadConnection());
    }

    public Account findAccountById(Integer id) {
        return template.queryForObject("select * from account where id = ?",new BeanPropertyRowMapper(Account.class),id,connectionUtils.getThreadConnection());
    }

    public void saveAccount(Account account) {
        template.update("insert into account(name,money) values (?,?)",account.getName(),account.getMoney(),connectionUtils.getThreadConnection());
    }

    public void updateAccount(Account account) {
        template.update("update account set name = ?,money = ? where id = ?",account.getName(),account.getMoney(),account.getId(),connectionUtils.getThreadConnection());
    }

    public void deleteAccount(Integer id) {
        template.update("delete from account where id = ?",id);
    }

    public Account findAccountByName(String accountName) {
        List accounts = template.query("select * from account where name = ?",new BeanPropertyRowMapper(Account.class),accountName,connectionUtils.getThreadConnection());
        if(accounts == null || accounts.size() == 0)
            return null;
        else if(accounts.size() > 1)
            throw new RuntimeException("结果集不唯一");
        return accounts.get(0);
    }
}

service

package com.czy.service.impl;

import com.czy.dao.AccountDao;
import com.czy.domain.Account;
import com.czy.service.AccountService;
import com.czy.utils.TransactionManager;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

public class AccountServiceImpl implements AccountService {

    private AccountDao dao;

    private TransactionManager txManager;

    public void setTxManager(TransactionManager txManager) {
        this.txManager = txManager;
    }

    public void setDao(AccountDao dao) {
        this.dao = dao;
    }

    public List findAllAccount() {
        try{
            //1.开启事务
            txManager.beginTransaction();
            //2.执行操作
            List accounts = dao.findAllAccount();
            //3.提交事务
            txManager.commit();
            //4.返回结果
            return accounts;
        }catch(Exception e){
            //5.回滚操作
            txManager.rollback();
            throw new RuntimeException(e);
        }finally {
            //6.释放资源
            txManager.release();
        }

    }

    public Account findAccountById(Integer id) {
        try{
            //1.开启事务
            txManager.beginTransaction();
            //2.执行操作
            Account account = dao.findAccountById(id);
            //3.提交事务
            txManager.commit();
            //4.返回结果
            return account;
        }catch(Exception e){
            //5.回滚操作
            txManager.rollback();
            throw new RuntimeException(e);
        }finally {
            //6.释放资源
            txManager.release();
        }
    }

    public void saveAccount(Account account) {
        try{
            //1.开启事务
            txManager.beginTransaction();
            //2.执行操作
            dao.saveAccount(account);
            //3.提交事务
            txManager.commit();
            //4.返回结果
        }catch(Exception e){
            //5.回滚操作
            txManager.rollback();
        }finally {
            //6.释放资源
            txManager.release();
        }
    }


    public void transfer(String sourceName, String targetName, Float money) {

        try{
            //1.开启事务
            txManager.beginTransaction();
            //2.执行操作

            //根据名称查询转出账户
            Account source = dao.findAccountByName(sourceName);
            //根据名称查询转入账户
            Account target = dao.findAccountByName(targetName);
            //转出账户减钱
            source.setMoney(source.getMoney()-money);
            //转入账户减钱
            target.setMoney(target.getMoney()+money);
            //更新两者
            dao.updateAccount(source);

            int i = 1/0;

            dao.updateAccount(target);

            //3.提交事务
            txManager.commit();
            //4.返回结果
        }catch(Exception e){
            //5.回滚操作
            txManager.rollback();
            e.printStackTrace();
        }finally {
            //6.释放资源
            txManager.release();
        }

    }
}

配置文件(依赖注入)

<?xml version="1.0" encoding="UTF-8"?>


    
        
    

    
        
    

    

    

    
    
        
        
    

    
        
        
    

    
        
        
    

动态代理优化

package com.czy.factory;

import com.czy.domain.Account;
import com.czy.service.AccountService;
import com.czy.utils.TransactionManager;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.List;

/**
 * 用于创建Service的代理对象的工厂
 */
public class BeanFactory {
    //通过spring获取
    private AccountService accountService;

    private TransactionManager txManager;

    public void setTxManager(TransactionManager txManager) {
        this.txManager = txManager;
    }


    public void setAccountService(AccountService accountService) {
        this.accountService = accountService;
    }

    public AccountService getAccountService(){
        final AccountService service = (AccountService) Proxy.newProxyInstance(accountService.getClass().getClassLoader(), accountService.getClass().getInterfaces(), new InvocationHandler() {
            /**
             * 添加事务的支持
             * @param proxy
             * @param method
             * @param args
             * @return
             * @throws Throwable
             */
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                Object rtValue = null;
                try{
                    //1.开启事务
                    txManager.beginTransaction();
                    //2.执行操作
                    rtValue = method.invoke(accountService,args);
                    //3.提交事务
                    txManager.commit();
                    //4.返回结果
                    return rtValue;
                }catch(Exception e){
                    //5.回滚操作
                    txManager.rollback();
                    throw new RuntimeException(e);
                }finally {
                    //6.释放资源
                    txManager.release();
                }
            }
        });
        return service;
    }
}