spring基于编程式的事务控制【了解】
DataSourceTransactionManager类中有个属性nestedTransactionAllowed ，表示允许【嵌套事务】，基于此原理，然后再基于切面编程(被代理方法前后增强)，实现嵌套事务！
此种方式只是了解，因为这种方式写出来的事务，每个需要事务的切入点都需要这样配，通用性很不好！
一、基于编程的事务控制编写核心流程
1). 基本配置
2). 配置TransactionManager 进行事务操作的通知类
3). 配置事务模板对象
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spring的ioc -->
<bean id="accountService" class="com.itheima.service.impl.AccountServiceImpl">
<property name="accountDao" ref="accountDao"></property>
<property name="transactionTemplate" ref="transactionTemplate"></property>
</bean>
<bean id="accountDao" class="com.itheima.dao.impl.AccountDaoImpl">
<property name="queryRunner" ref="queryRunner"></property>
</bean>
<bean id="queryRunner" class="org.apache.commons.dbutils.QueryRunner">
<constructor-arg name="ds" ref="dataSource"></constructor-arg>
</bean>
<!-- 配置数据源 -->
<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
<property name="driverClass" value="com.mysql.jdbc.Driver"></property>
<property name="jdbcUrl" value="jdbc:mysql:///spring_01"></property>
<property name="user" value="root"></property>
<property name="password" value="abc123"></property>
</bean>
<!-- 配置TransactionManager 进行事务操作的通知类 -->
<bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
<property name="dataSource" ref="dataSource"></property>
</bean>
<!-- 配置事务模板对象 -->
<bean id="transactionTemplate" class="org.springframework.transaction.support.TransactionTemplate">
<property name="transactionManager" ref="transactionManager"></property>
</bean>
</beans>
4). 在需要事务的地方，使用TransactionTemplate将业务逻辑“包裹”起来
底层就是在被“包裹”的代码前后开启 嵌套事务，进行过程增强，比如取消自动提交事务、开启事务、提交事务、回滚事务，释放资源等！
package com.itheima.service.impl;
import com.itheima.dao.AccountDao;
import com.itheima.domain.Account;
import com.itheima.service.AccountService;
import org.springframework.transaction.TransactionStatus;
import org.springframework.transaction.support.TransactionCallback;
import org.springframework.transaction.support.TransactionTemplate;
import java.sql.SQLException;
public class AccountServiceImpl implements AccountService {
private AccountDao accountDao;
private TransactionTemplate transactionTemplate;
public void setAccountDao(AccountDao accountDao) {
this.accountDao = accountDao;
}
public void setTransactionTemplate(TransactionTemplate transactionTemplate) {
this.transactionTemplate = transactionTemplate;
}
/** @事务
* 转账业务 */
@Override
public boolean transfer(Integer fromId, Integer toId, Float money) throws Exception {
// 编程式声明事务控制
return (boolean) transactionTemplate.execute(new TransactionCallback<Object>() {
@Override
public Object doInTransaction(TransactionStatus transactionStatus) {
// 1. 查询原账户余额
Account fromMoney = null;
try {
fromMoney = accountDao.queryMoney(fromId);
} catch (SQLException e) {
throw new RuntimeException(e);
}
if (fromMoney.getMoney() < money) {
throw new RuntimeException("账户余额不足，无法完成转账");
}
// 2. 查询被转入账户的余额
Account toMoney = null;
try {
toMoney = accountDao.queryMoney(toId);
} catch (SQLException e) {
throw new RuntimeException(e);
}
// 3. 扣除原账户的money
try {
accountDao.updateMoney(fromId, fromMoney.getMoney() - money);
} catch (SQLException e) {
throw new RuntimeException(e);
}
// 显示抛出一个异常。
int a = 8 / 0;
// 4. 添加被转入账户的余额
try {
accountDao.updateMoney(toId, toMoney.getMoney() + money);
} catch (SQLException e) {
throw new RuntimeException(e);
}
return true;
}
});
}
}
二、完整的项目代码
1). 项目结构
spring基于编程式的事务控制项目结构.png
2). domain
public class Account {
private Integer id;
private String name;
private Float money;
... get/set/toString...
3). dao持久层
import com.itheima.domain.Account;
import java.sql.SQLException;
public interface AccountDao {
/** 根据id查询账户的余额 */
public Account queryMoney(Integer id) throws SQLException;
/** 根据id更新账户的余额 */
public int updateMoney(Integer id, Float money) throws SQLException;
}
import com.itheima.dao.AccountDao;
import com.itheima.domain.Account;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import java.sql.SQLException;
public class AccountDaoImpl implements AccountDao {
private QueryRunner queryRunner;
public void setQueryRunner(QueryRunner queryRunner) {
this.queryRunner = queryRunner;
}
/** @事务
* 根据id查询账户的余额，将异常显示抛出 */
@Override
public Account queryMoney(Integer id) throws SQLException {
return queryRunner.query("select money from account where id = ?",
new BeanHandler<Account>(Account.class), id);
}
/** @事务
* 根据id更新账户的余额, 将异常显示抛出 */
@Override
public int updateMoney(Integer id, Float money) throws SQLException {
return queryRunner.update("update account set money = ? where id = ?", money, id);
}
}
4). service业务层
public interface AccountService {
/** 转账业务 */
public boolean transfer(Integer fromId, Integer toId, Float money) throws Exception;
}
实现类代码详见
4). 在需要事务的地方，使用TransactionTemplate将业务逻辑“包裹”起来
