Spring对事务的支持

一、事务

事务防止进行操作时，数据库里面的数据丢失。

二、Spring事务注解方式

注解方式：在配置文件中配置事务管理器，利用注解，管理事务。

实例

银行转账：一个账户向另一个账户转账。

1）先在数据库mysql中建立，账户和余额表，并对其赋值：

2）在程序中创建一个完整的javabean程序（Account类），其属性和mysql表中属性一致：

package com.bank.pajo;

public class Account {
    private String actno;
    private Double balance;

    @Override
    public String toString() {
        return "Account{" +
                "actno='" + actno + '\'' +
                ", balance=" + balance +
                '}';
    }
    public Account() {
    }

    public Account(String actno, Double balance) {
        this.actno = actno;
        this.balance = balance;
    }

    public String getActno() {
        return actno;
    }

    public void setActno(String actno) {
        this.actno = actno;
    }

    public Double getBalance() {
        return balance;
    }

    public void setBalance(Double balance) {
        this.balance = balance;
    }
}

2）引入依赖（pom.xml）：

 <packaging>jar</packaging>
<!--仓库-->
    <repositories>
        <repository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </repository>
    </repositories>
<!--依赖-->
    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>6.0.0-M2</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>6.0.0-M2</version>
        </dependency>
        <!-- mysql jar包 -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.30</version>
        </dependency>
<!--这是一个数据库连接池，在此可以配置数据源信息-->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.2.13</version>
        </dependency>
        <dependency>
            <groupId>jakarta.annotation</groupId>
            <artifactId>jakarta.annotation-api</artifactId>
            <version>2.1.1</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13.2</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

3)创建一个接口（Acount），用于存放对数据库进行操作的语句方法，查看和更新：

package com.bank.dao;
import com.bank.pajo.Account;
//只执行sql语句
public interface Acount {
    //查询账户
    Account selectBy(String actno);
    //更新
    int update(Account acc);
}

4)这个接口的实现类（AcountImp），将查看和修改的功能实现利用sql语句和JdbcTemplate：

package com.bank.dao;
import com.bank.pajo.Account;
import jakarta.annotation.Resource;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Repository;

@Repository
public class AcountImp implements Acount{
    @Resource
    private JdbcTemplate j;

    @Override
    public Account selectBy(String actno) {//查看账户
        String sql="select actno,balance from t_act where actno=?";
        Account a=j.queryForObject(sql,new BeanPropertyRowMapper<>(Account.class),actno);
        return a;
    }

    @Override
    public int update(Account acc) {//更新余额
        String sql="update t_act set balance =? where actno=?";
         int count= j.update(sql,acc.getBalance(),acc.getActno());
        return count;
    }
}

5）定义一个转账接口（AcountSer）：

package com.bank.service;
public interface AcountSer {
    void transfer(String fromActno,String toAcrno,double money);
}

6)这个接口的实现类，进行转账功能：

package com.bank.service;
import com.bank.dao.AcountImp;
import jakarta.annotation.Resource;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import com.bank.pajo.Account;
@Service
public class AccountService implements AcountSer{
    @Resource
    private AcountImp acountImp;
    //从这个账户转到另个账户
    @Transactional//事务管理器
    @Override
    public void transfer(String fromActno, String toAcrno, double money) {
        Account from= acountImp.selectBy(fromActno);//这个账户信息
        if(from.getBalance()<money){
            throw new RuntimeException("余额不足");
        }
        Account to=acountImp.selectBy(toAcrno);//另一个账户信息
        from.setBalance(from.getBalance()-money);//一个钱数加
        to.setBalance(to.getBalance()+money);//一个钱数减
        //数据库更新
       int count= acountImp.update(from);
       //模拟异常
        String s=null;
        s.toString();
       count+=acountImp.update(to);
       if(count<2){
           throw new RuntimeException("转账失败，请联系银行");
       }

    }
}

spring.xml:

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
                           http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
                           http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd">
<!--组件扫描-->
    <context:component-scan base-package="com.bank"></context:component-scan>
<!--    配置数据源-->
    <bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource">
        <property name="driverClassName" value="com.mysql.cj.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://localhost:3306/spring6"/>
        <property name="username" value="root"/>
        <property name="password" value="123456"></property>
    </bean>
<!--    配置JdbcTemplate-->
    <bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
        <property name="dataSource" ref="dataSource"></property>
    </bean>
<!--    配置事务管理器-->
    <bean id="txMange" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <property name="dataSource" ref="dataSource"></property>
    </bean>
<!--    事务注解驱动器开启,开启事务-->
    <tx:annotation-driven transaction-manager="txMange"></tx:annotation-driven>
</beans>

测试类：

public class Test {
    @org.junit.Test
    public void test(){
        ApplicationContext applicationContext=new ClassPathXmlApplicationContext("spring.xml");
       AcountSer a= applicationContext.getBean("accountService", AcountSer.class);
       try{
           a.transfer("act-001","act-002",10000);
       }catch (Exception e){
           System.out.println("转账失败");
           e.printStackTrace();
       }

    }
}