17-Spring声明式事务

Spring声明式事务

开启事务（所有方法都绑定在一起，要么都执行，要么都不执行）

代码理解

第一步 User类

@Data
@AllArgsConstructor
@NoArgsConstructor
public class User {
    private int id;
    private  String name;
    private String pwd;
}

第二步 UserMapper类

public interface UserMapper {

    public List<User> selectUser();

    //添加一个用户
    public int addUser(User user);
    //删除一个用户
    public int deleteUser(@Param("id") int id);
}

第三步 UserMapperImpl类

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.tian.mapper.UserMapper">
    <select id="selectUser" resultType="user">
        select * from mybatis.user;
    </select>

<insert id="addUser" parameterType="user">
    insert into user (id,name,pwd) values (#{id},#{name},#{pwd});
</insert>

    <delete id="deleteUser" parameterType="int">
        delete from user where id=#{id};
    </delete>
</mapper>

第四步配置文件

mybatis-config.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <!--      引入外置配置文件  -->
    <properties resource="db.properties"/>

    <!--起别名-->
    <typeAliases>
       <package name="com.tian.pojo"/>
    </typeAliases>


</configuration>

spring-dao.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"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/aop
        https://www.springframework.org/schema/aop/spring-aop.xsd
        http://www.springframework.org/schema/tx
        https://www.springframework.org/schema/tx/spring-tx.xsd">

    <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="com.mysql.cj.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=false&amp;characterEncoding=utf8"/>
        <property name="username" value="root"/>
        <property name="password" value="root"/>
    </bean>


    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource"/>
   		<property name="configLocation" value="classpath:mybatis-config.xml"/>
        <property name="mapperLocations"  value="classpath:com/tian/mapper/*.xml"/>
    </bean>


    <bean id="sqlSession" class="org.mybatis.spring.SqlSessionTemplate">
<!--     只能使用构造器注入sqlSessionFactory ，因为它没有set方法   -->
        <constructor-arg index="0" ref="sqlSessionFactory"/>
    </bean>

<!--配置声明式事务-->
    <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <property name="dataSource" ref="dataSource"/>
    </bean>
<!--  结合AOP实现事物的织入  -->
<!--    配置事务通知   -->
    <tx:advice id="txAdvice" transaction-manager="transactionManager">
        <tx:attributes>
<!--  给哪些方法配置事务  -->
<!--   配置事务的传播特性 new propagation （这是默认的，也可以不写）     -->
<!--    query     配置 read-only="true"  只能读不能写  -->
            <tx:method name="add" propagation="REQUIRED"/>
            <tx:method name="delete" propagation="REQUIRED"/>
            <tx:method name="update" propagation="REQUIRED"/>
            <tx:method name="query" read-only="true"/>
<!--            <tx:method name="*"/> -->
        </tx:attributes>
    </tx:advice>
<!--  配置事务切入  -->
    <aop:config>
        <aop:pointcut id="txPointCut" expression="execution(* com.kuang.mapper.*.*(..))"/>
        <aop:advisor advice-ref="txAdvice" pointcut-ref="txPointCut"/>
    </aop:config>
    
</beans>

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"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/aop
        https://www.springframework.org/schema/aop/spring-aop.xsd">

<import resource="spring-dao.xml"/>

    <bean id="userMapper" class="com.tian.mapper.UserMapperImpl">
        <property name="sqlSessionFactory" ref="sqlSessionFactory"/>
    </bean>

</beans>

第五步 UserMapperImpl类

package com.tian.mapper;

import com.tian.pojo.User;
import org.mybatis.spring.SqlSessionTemplate;
import org.mybatis.spring.support.SqlSessionDaoSupport;

import java.util.List;

public class UserMapperImpl extends SqlSessionDaoSupport implements UserMapper{


    public List<User> selectUser() {
        User user = new User(10, "小王", "465789");
        UserMapper mapper=  getSqlSession().getMapper(UserMapper.class);
        mapper.addUser(user);
        mapper.deleteUser(4);
        return  mapper.selectUser();
    }

    public int addUser(User user) {
        return getSqlSession().getMapper(UserMapper.class).addUser(user);
    }

    public int deleteUser(int id) {
        return getSqlSession().getMapper(UserMapper.class).deleteUser(3);
    }
}

第六步 测试

public class MyTest {
    @Test
    public void test() throws IOException {
        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        UserMapper userMapper = context.getBean("userMapper", UserMapper.class);
        List<User> userList = userMapper.selectUser();
        for (User user:userList){
            System.out.println(user);
        }
    }
    //假如删除语句写错，如果没有事务，那么增加语句就会执行成功，并在数据库显示
    //假如加入了事务的话，那么 他们要么都执行，要么都不执行
}

思考:
为什么需要事务?

• 如果不配置事务，可能存在数据提交不一致的情况下;
• 如果我们不在SPRING中去配置声明式事务，我们就需要在代码中手动配置事务!
• 事务在项目的开发中十分重要，设计到数据的一致性和完整性问题，不容马虎!