【spring】事务学习笔记
举例说明：转账案例
一、编程式事务控制
1、没有事务控制的代码
如下AccountServiceImpl，查询用户和更新账户，每一行代码都是独立的线程，代码中出现错误（/0）
报错前的代码已被执行，报错后的代码不会被执行，导致程序业务逻辑出错。
2、演示代码
AccountServiceImpl.java
public class AccountServiceImpl implements AccountService {
private AccountDao accountDao;
public void setAccountDao(AccountDao accountDao) {
this.accountDao = accountDao;
}
public void transfer(String sourceName, String targetName, Float money) {
System.out.println("transfer....");
//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);
}
}
AccountDaoImpl.java
public class AccountDaoImpl implements AccountDao {
private QueryRunner queryRunner;
public void setQueryRunner(QueryRunner queryRunner) {
this.queryRunner = queryRunner;
}
public void updateAccount(Account account) {
try {
queryRunner.update(connectionUtils.getThreadConnection(),"update account set name=?,money=? where id=?", account.getName(), account.getMoney(), account.getId());
} catch (Exception e) {
throw new RuntimeException(e);
}
}
public Account findAccountByName(String accountName) {
try {
List<Account> accounts = queryRunner.query(connectionUtils.getThreadConnection(),"select * from account where name = ? ", new BeanListHandler<Account>(Account.class), accountName);
if (accounts == null || accounts.size() == 0) {
return null;
}
if (accounts.size() > 1) {
throw new RuntimeException("结果集不唯一，数据有问题");
}
return accounts.get(0);
} catch (Exception e) {
throw new RuntimeException(e);
}
}
}
applicationContext.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd">
<!-- 配置Service -->
<bean id="accountService" class="com.donglei.service.AccountServiceImpl">
<!-- 注入dao -->
<property name="accountDao" ref="accountDao"></property>
</bean>
<!--配置Dao对象-->
<bean id="accountDao" class="com.donglei.dao.AccountDaoImpl">
<!-- 注入QueryRunner -->
<property name="queryRunner" ref="runner"></property>
</bean>
<!--配置QueryRunner-->
<bean id="runner" class="org.apache.commons.dbutils.QueryRunner" scope="prototype">
<constructor-arg name="ds" ref="dataSource"></constructor-arg>
</bean>
<!-- 配置数据源 -->
<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
<!--连接数据库的必备信息-->
<property name="driverClass" value="com.mysql.jdbc.Driver"></property>
<property name="jdbcUrl" value="jdbc:mysql:///donglei"></property>
<property name="user" value="root"></property>
<property name="password" value="root"></property>
</bean>
</beans>
Test.java
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath:applicationContext.xml")
public class AccountServiceTest {
@Autowired
private AccountService as;
@Test
public void testTransfer(){
as.transfer("aaa","bbb",100f);
}
}
3、分析原因
DBUtils每个操作数据都是获取一个连接，每个连接的事务都是独立的，且默认是自动提交。
4、解决方案
需要使用ThreadLocal对象吧Connection和当前线程绑定，从而使一个线程中只能一个能控制事务的连接对象。
5、解决方案代码
ConnectionUtils.java
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
* @return
*/
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（在当前线程结束的时候执行）
*/
public void removeConnection(){
tl.remove();
}
}
TransactionManager.java
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 {
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();//把连接还回连接池中
connectionUtils.removeConnection();//线程和连接解绑
}catch (Exception e){
e.printStackTrace();
}
}
}
修改AccountDaoImpl.java
queryRunner的操作中指定连接conn，获取本地线程中同一个连接
public class AccountDaoImpl implements AccountDao {
private QueryRunner queryRunner;
private ConnectionUtils connectionUtils;
public void setConnectionUtils(ConnectionUtils connectionUtils) {
this.connectionUtils = connectionUtils;
}
public void setQueryRunner(QueryRunner queryRunner) {
this.queryRunner = queryRunner;
}
public void updateAccount(Account account) {
try {
queryRunner.update(connectionUtils.getThreadConnection(),"update account set name=?,money=? where id=?", account.getName(), account.getMoney(), account.getId());
} catch (Exception e) {
throw new RuntimeException(e);
}
}
}
修改AccountServiceImpl.java
事务操作一定需要在Service层控制，通过事务管理器控制事务
public class AccountServiceImpl implements AccountService {
private AccountDao accountDao;
private TransactionManager txManager;
public void setTxManager(TransactionManager txManager) {
this.txManager = txManager;
}
public void setAccountDao(AccountDao accountDao) {
this.accountDao = accountDao;
}
public void transfer(String sourceName, String targetName, Float money) {
try {
//1.开启事务
txManager.beginTransaction();
System.out.println("transfer....");
//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();
}
}
}
修改applicationContext.xml
dao中注入连接管理工具，service中注入事务管理器，在连接工具中注入数据库而不是在queryRunner中
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd">
<!-- 配置Service -->
<bean id="accountService" class="com.donglei.service.AccountServiceImpl">
<!-- 注入dao -->
<property name="accountDao" ref="accountDao"></property>
<!--注入事务管理器-->
<property name="txManager" ref="txManager"></property>
</bean>
<!--配置Dao对象-->
<bean id="accountDao" class="com.donglei.dao.AccountDaoImpl">
<!-- 注入QueryRunner -->
<property name="queryRunner" ref="runner"></property>
<!-- 注入ConnectionUtils -->
<property name="connectionUtils" ref="connectionUtils"></property>
</bean>
<!--配置QueryRunner-->
<bean id="runner" class="org.apache.commons.dbutils.QueryRunner" scope="prototype">
<!--<constructor-arg name="ds" ref="dataSource"></constructor-arg>-->
</bean>
<!-- 配置数据源 -->
<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
<!--连接数据库的必备信息-->
<property name="driverClass" value="com.mysql.jdbc.Driver"></property>
<property name="jdbcUrl" value="jdbc:mysql:///donglei"></property>
<property name="user" value="root"></property>
<property name="password" value="root"></property>
</bean>
<!-- 配置Connection的工具类 ConnectionUtils -->
<bean id="connectionUtils" class="com.donglei.util.ConnectionUtils">
<!-- 注入数据源-->
<property name="dataSource" ref="dataSource"></property>
</bean>
<!-- 配置事务管理器-->
<bean id="txManager" class="com.donglei.util.TransactionManager">
<!-- 注入ConnectionUtils -->
<property name="connectionUtils" ref="connectionUtils"></property>
</bean>
</beans>
6、问题来了
代码耦合，业务层方法里面充斥着很多重复代码。
二、AOP JDK代理
7、代理模式
public class BeanFactory {
private AccountService accountService;
private TransactionManager txManager;
public void setTxManager(TransactionManager txManager) {
this.txManager = txManager;
}
public final void setAccountService(AccountService accountService) {
this.accountService = accountService;
}
public AccountService getAccountService() {
return (AccountService) Proxy.newProxyInstance(accountService.getClass().getClassLoader(),
accountService.getClass().getInterfaces(),
new InvocationHandler() {
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.释放连接
txManager.release();
}
}
});
}
}
此时serviceImpl中就不用注入事务控制器，修改applicationContext.xml增加代理service
<!--配置代理的service-->
<bean id="proxyAccountService" factory-bean="beanFactory" factory-method="getAccountService"></bean>
<!--配置beanfactory-->
<bean id="beanFactory" class="com.donglei.util.BeanFactory">
<!-- 注入service -->
<property name="accountService" ref="accountService"></property>
<!-- 注入事务管理器 -->
<property name="txManager" ref="txManager"></property>
</bean>
在测试方法中注意代理service
因为spring容器中出现了2个AccountService的类型，所以使用@Qualifier(“proxyAccountService”)指定想要的类型
@Autowired
@Qualifier("proxyAccountService")
private AccountService as;
