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