@Override
public void transfer(String sourceName, String targetName, Float money) {
System.out.println("transfer....");
//1、根据名称查询转出账户
Account source = accountDao.findAccountByName(sourceName);
//2、根据名称查询转入账户
Account target = accountDao.findAccountByName(targetName);
//3、转出账户减钱
source.setMoney(source.getMoney()-money);
//4、转入账户加钱
target.setMoney(target.getMoney()+money);
//5、更新转出账户
accountDao.updateAccount(source);
int i=1/0;
//6、更新转入账户
accountDao.updateAccount(target); 在上述代码中，我们会发现钱从转成账户转出，中间出现了异常，没有转入到转入账户中，造成了事务的不一致性。
//2.1根据名称查询转出账户 Account source = accountDao.findAccountByName(sourceName); //2.2根据名称查询转入账户 Account target = accountDao.findAccountByName(targetName); //2.5更新转出账户 accountDao.updateAccount(source); //2.6更新转入账户 accountDao.updateAccount(target);
上面四行代码总共获取了四次连接，我们应该使上述四行代码使用同一个连接Connection，那么如何使上述四个操作都使用同一个Connection哪？
需要ThreadLocal对象把Connection和当前线程绑定，从而使一个线程中只有一个能控制事务的对象。
在utils包下创建两个类：
package com.zzu.utils;
import javax.sql.DataSource;
import java.sql.Connection;
//连接的工具类，它用于从数据源中获取一个连接，并且实现和线程的绑定
public class ConnectionUtils {
private ThreadLocal<Connection> tl = new ThreadLocal<Connection>();
private DataSource dataSource;
public void setDataSource(DataSource dataSource) {
this.dataSource = dataSource;
}
//获取当前线程上的连接
public Connection getThreadConnection() {
try{
//1.先从ThreadLocal上获取
Connection conn = tl.get();
//2.判断当前线程上是否有连接
if (conn == null) {
//3.从数据源中获取一个连接，并且存入ThreadLocal中
conn = dataSource.getConnection();
tl.set(conn);
}
//4.返回当前线程上的连接
return conn;
}catch (Exception e){
throw new RuntimeException(e);
}
}
//把连接和线程解绑
public void removeConnection(){
tl.remove();
}
} package com.zzu.utils;
//和事务管理相关的工具类，它包含了，开启事务，提交事务，回滚事务和释放连接
public class TransactionManager {
private ConnectionUtils connectionUtils;
public void setConnectionUtils(ConnectionUtils connectionUtils) {
this.connectionUtils = connectionUtils;
}
//开启事务
public void beginTransaction(){
try {
connectionUtils.getThreadConnection().setAutoCommit(false);
}catch (Exception e){
e.printStackTrace();
}
}
//提交事务
public void commit(){
try {
connectionUtils.getThreadConnection().commit();
}catch (Exception e){
e.printStackTrace();
}
}
//回滚事务
public void rollback(){
try {
connectionUtils.getThreadConnection().rollback();
}catch (Exception e){
e.printStackTrace();
}
}
//释放连接
public void release(){
try {
connectionUtils.getThreadConnection().close();//还回连接池中
connectionUtils.removeConnection();
}catch (Exception e){
e.printStackTrace();
}
}
}
package com.itheima.service.impl;
import com.itheima.dao.IAccountDao;
import com.itheima.domain.Account;
import com.itheima.service.IAccountService;
import com.itheima.utils.TransactionManager;
import java.util.List;
/**
* 账户的业务层实现类
*
* 事务控制应该都是在业务层
*/
public class AccountServiceImpl_OLD implements IAccountService{
private IAccountDao accountDao;
private TransactionManager txManager;
public void setTxManager(TransactionManager txManager) {
this.txManager = txManager;
}
public void setAccountDao(IAccountDao accountDao) {
this.accountDao = accountDao;
}
@Override
public List<Account> findAllAccount() {
try {
//1.开启事务
txManager.beginTransaction();
//2.执行操作
List<Account> accounts = accountDao.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.释放连接
txManager.release();
}
}
@Override
public Account findAccountById(Integer accountId) {
try {
//1.开启事务
txManager.beginTransaction();
//2.执行操作
Account account = accountDao.findAccountById(accountId);
//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.释放连接
txManager.release();
}
}
@Override
public void saveAccount(Account account) {
try {
//1.开启事务
txManager.beginTransaction();
//2.执行操作
accountDao.saveAccount(account);
//3.提交事务
txManager.commit();
}catch (Exception e){
//4.回滚操作
txManager.rollback();
}finally {
//5.释放连接
txManager.release();
}
}
@Override
public void updateAccount(Account account) {
try {
//1.开启事务
txManager.beginTransaction();
//2.执行操作
accountDao.updateAccount(account);
//3.提交事务
txManager.commit();
}catch (Exception e){
//4.回滚操作
txManager.rollback();
}finally {
//5.释放连接
txManager.release();
}
}
@Override
public void deleteAccount(Integer acccountId) {
try {
//1.开启事务
txManager.beginTransaction();
//2.执行操作
accountDao.deleteAccount(acccountId);
//3.提交事务
txManager.commit();
}catch (Exception e){
//4.回滚操作
txManager.rollback();
}finally {
//5.释放连接
txManager.release();
}
}
@Override
public void transfer(String sourceName, String targetName, Float money) {
try {
//1.开启事务
txManager.beginTransaction();
//2.执行操作
//2.1根据名称查询转出账户
Account source = accountDao.findAccountByName(sourceName);
//2.2根据名称查询转入账户
Account target = accountDao.findAccountByName(targetName);
//2.3转出账户减钱
source.setMoney(source.getMoney()-money);
//2.4转入账户加钱
target.setMoney(target.getMoney()+money);
//2.5更新转出账户
accountDao.updateAccount(source);
int i=1/0;
//2.6更新转入账户
accountDao.updateAccount(target);
//3.提交事务
txManager.commit();
}catch (Exception e){
//4.回滚操作
txManager.rollback();
e.printStackTrace();
}finally {
//5.释放连接
txManager.release();
}
}
}
未完，待续...
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