Spring整合MyBatis的事务管理

来源：欧得旅游网

环境

Ubuntu 22.04
IntelliJ IDEA 2022.1.3
JDK 17.0.3
Spring 5.3.21
MyBatis 3.5.10

准备

创建Maven项目 test0703 。

修改 pom.xml ，添加依赖以及设置静态资源：

    ......
    <dependencies>
        <!-- https://mvnrepository.com/artifact/junit/junit -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13.2</version>
            <scope>test</scope>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.10</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.29</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.springframework/spring-webmvc -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>5.3.21</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis-spring -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis-spring</artifactId>
            <version>2.0.7</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.springframework/spring-jdbc -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>5.3.21</version>
        </dependency>

    </dependencies>

    <build>
        <resources>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering>
            </resource>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.xml</include>
                </includes>
                <filtering>false</filtering>
            </resource>
        </resources>
    </build>
    ......

创建POJO MyObject.java ：

package pojo;

public class MyObject {
    private int c1;
    private int c2;

    public int getC1() {
        return c1;
    }

    public void setC1(int c1) {
        this.c1 = c1;
    }

    public int getC2() {
        return c2;
    }

    public void setC2(int c2) {
        this.c2 = c2;
    }

    @Override
    public String toString() {
        return "MyObject{" +
                "c1=" + c1 +
                ", c2=" + c2 +
                '}';
    }
}

创建Mapper MyMapper.java 和 MyMapper.xml ：

package dao;

import pojo.MyObject;

import java.util.List;

public interface MyMapper {
    public List<MyObject> read();

    public void add(int c1, int value);

    public void reduce(int c1, int value);
}

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="dao.MyMapper">
    <select id = "read" resultType="pojo.MyObject">
        select c1, c2 from t1
    </select>

    <update id="add">
        update t1 set c2 = c2 + #{param2} where c1 = #{param1}
    </update>

    <update id="reduce">
        update t1 set c2 = c2 - #{param2} where c1 = #{param1}
    </update>
</mapper>

创建Service MyService.java （接口）和 MyServiceImpl1.java （实现类）：

package service;

public interface MyService {
    public void show();

    public void change();
}

package service;

import dao.MyMapper;
import pojo.MyObject;

import java.util.List;

public class MyServiceImpl1 implements MyService{
    private MyMapper mapper;

    public void setMyMapper(MyMapper mapper) {
        this.mapper = mapper;
    }

    @Override
    public void show() {
        List<MyObject> list = mapper.read();
        list.forEach(System.out::println);
    }

    @Override
    public void change() {
        int value = 100;

        try {
            mapper.reduce(1, value);
            mapper.add(2, value);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

<?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">

    <!-- datasource -->
    <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://localhost:3306/repo"/>
        <property name="username" value="root"/>
        <property name="password" value="123456"/>
    </bean>

    <!-- sqlSessionFactory -->
    <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:dao/*.xml"/>
    </bean>

    <bean id="myMapper" class="org.mybatis.spring.mapper.MapperFactoryBean">
        <property name="mapperInterface" value="dao.MyMapper" />
        <property name="sqlSessionFactory" ref="sqlSessionFactory" />
    </bean>

    <bean id="myService1" class="service.MyServiceImpl1">
        <property name="myMapper" ref="myMapper"/>
    </bean>
</beans>

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import service.MyService;

import java.io.IOException;

public class MyTest {
    @Test
    public void test1() throws IOException {
        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");

        MyService service = context.getBean("myService1", MyService.class);

        System.out.println("==================== Before: ====================");
        service.show();

        service.change();

        System.out.println("==================== After: ====================");
        service.show();
    }
}

运行测试，如下：

==================== Before: ====================
MyObject{c1=1, c2=10000}
MyObject{c1=2, c2=10000}
==================== After: ====================
MyObject{c1=1, c2=9900}
MyObject{c1=2, c2=10100}

本例模拟了一个简单的转账操作， c1 账户转出100元，同时 c2 账户转入100元。

没有事务管理的问题

假定转入操作失败了。本例中，为了模拟操作失败，我们故意把SQL写错：

    ......
    <update id="add">
        updateaaa t1 set c2 = c2 + #{param2} where c1 = #{param1}
    </update>
    ......

再次运行测试：

==================== Before: ====================
MyObject{c1=1, c2=9900}
MyObject{c1=2, c2=10100}

org.springframework.jdbc.BadSqlGrammarException: 
### Error updating database.  Cause: java.sql.SQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'updateaaa t1 set c2 = c2 + 100 where c1 = 2' at line 1
### The error may exist in file [/home/ding/IdeaProjects/test0703/target/classes/dao/MyMapper.xml]
### The error may involve defaultParameterMap
### The error occurred while setting parameters
### SQL: updateaaa t1 set c2 = c2 + ? where c1 = ?
### Cause: java.sql.SQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'updateaaa t1 set c2 = c2 + 100 where c1 = 2'
......

==================== After: ====================
MyObject{c1=1, c2=9800}
MyObject{c1=2, c2=10100}

可见，这样就会出现问题， c1 账户已经转出100元，而 c2账户转入100元的操作失败了。

转账是一个典型的事务处理操作，应该使用事务管理，如果某一个操作失败，应该把整个事务回滚。

Spring的事务管理

声明式事务

Spring的声明式事务基于AOP实现，它的优点是只需修改Spring配置文件，无需修改Service组件的代码逻辑。

spring-webmvc 已经包含了对Spring AOP的依赖，但是我们还需要添加对 aspectjweaver 的依赖：

        ......
        <!-- https://mvnrepository.com/artifact/org.aspectj/aspectjweaver -->
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjweaver</artifactId>
            <version>1.9.9.1</version>
            <scope>runtime</scope>
        </dependency>
        ......

修改 applicationContext.xml 配置文件：

    ......
    <beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xmlns:aop="http://www.springframework.org/schema/aop"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/tx
        https://www.springframework.org/schema/tx/spring-tx.xsd
        http://www.springframework.org/schema/aop
        https://www.springframework.org/schema/aop/spring-aop.xsd">
    ......
    <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <constructor-arg ref="dataSource" />
    </bean>

    <tx:advice id="txAdvice" transaction-manager="transactionManager">
        <tx:attributes>
            <tx:method name="*" propagation="REQUIRED"/>
        </tx:attributes>
    </tx:advice>

    <aop:config>
        <aop:pointcut id="myPointcut" expression="execution(* service.*.*(..))"/>
        <aop:advisor advice-ref="txAdvice" pointcut-ref="myPointcut"/>
    </aop:config>
    ......

无论是声明式事务，还是编程式事务，都要添加 transactionManager ，格式是固定的，照抄就行（对于所需的 dataSource ，本例中使用的是构造器注入，如果换成属性注入也行）；
txAdvice 的格式基本也是固定的：
- 对于 method 属性，本例中使用了 name="*" ，表示所有方法都适用，可以改成比如 name="get*" ，则表示适用于 get 开头的方法；
- propagation="REQUIRED" 是默认属性，不写也可以，表示如果当前没有事务，就新建一个事务，这是最常见的选择；
- 此外，还有 read-only ， tmeout 等属性，基本上顾名思义；
myPointcut ：expression="execution(* service.*.*(..))" 表示 service 包下的所有类的所有方法，参数不限（本例中其实只有 change() 方法需要做事务管理）；

现在就可以运行测试了，但有一点需要注意，虽然说声明式事务是非侵入式的，不用修改任何代码就能直接运行，但是在本例中，service里使用了 try 块：

        ......
        try {
            mapper.reduce(1, value);
            mapper.add(2, value);
        } catch (Exception e) {
            e.printStackTrace();
        }
        ......

这会对事务失败的判断产生影响。具体说来，因为代码中捕获并处理了异常，事务管理器就不会认为事务失败并回滚事务了，就跟没有事务管理的效果一样，所以这里一定要把 try 去掉：

//        try {
            mapper.reduce(1, value);
            mapper.add(2, value);
//        } catch (Exception e) {
//            e.printStackTrace();
//        }

为了使得异常之后的代码能继续运行，可以把 try 块放到测试里：

        ......
        try {
            service.change();
        } catch (Exception e) {
            e.printStackTrace();
        }
        ......

把两条记录的 c2 值都还原为 10000 ，重新运行测试，如下：

==================== Before: ====================
MyObject{c1=1, c2=10000}
MyObject{c1=2, c2=10000}

org.springframework.jdbc.BadSqlGrammarException: 
### Error updating database.  Cause: java.sql.SQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'updateaaa t1 set c2 = c2 + 100 where c1 = 2' at line 1
### The error may exist in file [/home/ding/IdeaProjects/test0703/target/classes/dao/MyMapper.xml]
### The error may involve defaultParameterMap
### The error occurred while setting parameters
### SQL: updateaaa t1 set c2 = c2 + ? where c1 = ?
### Cause: java.sql.SQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'updateaaa t1 set c2 = c2 + 100 where c1 = 2'
......

==================== After: ====================
MyObject{c1=1, c2=10000}
MyObject{c1=2, c2=10000}

可见，出现异常后，事务回滚了。具体来说，因为转入操作失败，则之前转出的操作回滚了。

编程式事务

修改 applicationContext.xml 文件：

    ......
    <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <constructor-arg ref="dataSource" />
    </bean>
    ......

transactionManager ：和声明式事务一样，需要配置 transactionManager ；

创建 MyServiceImpl2.java ：

package service;

import dao.MyMapper;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.TransactionStatus;
import org.springframework.transaction.support.DefaultTransactionDefinition;
import pojo.MyObject;

import java.util.List;

public class MyServiceImpl2 implements MyService{
    private final PlatformTransactionManager transactionManager;

    private MyMapper mapper;

    public MyServiceImpl2(PlatformTransactionManager transactionManager) {
        this.transactionManager = transactionManager;
    }

    public void setMyMapper(MyMapper mapper) {
        this.mapper = mapper;
    }

    @Override
    public void show() {
        List<MyObject> list = mapper.read();
        list.forEach(System.out::println);
    }

    @Override
    public void change() {
        TransactionStatus txStatus =
                transactionManager.getTransaction(new DefaultTransactionDefinition());
        try {
            int value = 100;
            mapper.reduce(1, value);
            System.out.println("===================================");
            mapper.add(2, value);
        } catch (Exception e) {
            transactionManager.rollback(txStatus);
            throw e;
        }
        transactionManager.commit(txStatus);
    }
}

注：为了防止事务一开始就报错引起混淆，代码里加了一行输出，如果看到这行输出，说明转出操作已经做了。

注意：该方法需要显式 try ，捕获异常，并回滚事务。而前面介绍的声明式事务则不能捕获异常，要留给事务管理器来判断异常并回滚事务。

在 applicationContext.xml 中注册 MyServiceImpl2 ：

    ......
    <bean id="myService2" class="service.MyServiceImpl2">
        <constructor-arg ref="transactionManager"/>
        <property name="myMapper" ref="myMapper"/>
    </bean>
    ......

创建测试如下：

    @Test
    public void test2() throws IOException {
        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");

        MyService service = context.getBean("myService2", MyService.class);
        service.show();

        try {
            service.change();
        } catch (Exception e) {
            e.printStackTrace();
        }

        service.show();
    }

把SQL改成正确写法，把两条记录的 c2 值都还原为 10000 ，运行test2，如下：

MyObject{c1=1, c2=10000}
MyObject{c1=2, c2=10000}
===================================
MyObject{c1=1, c2=9900}
MyObject{c1=2, c2=10100}

把SQL改成错误写法，把两条记录的 c2 值都还原为 10000 ，运行test2，如下：

MyObject{c1=1, c2=10000}
MyObject{c1=2, c2=10000}
===================================

org.springframework.jdbc.BadSqlGrammarException: 
### Error updating database.  Cause: java.sql.SQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'updateaaa t1 set c2 = c2 + 100 where c1 = 2' at line 1
### The error may exist in file [/home/ding/IdeaProjects/test0703/target/classes/dao/MyMapper.xml]
### The error may involve defaultParameterMap
### The error occurred while setting parameters
### SQL: updateaaa t1 set c2 = c2 + ? where c1 = ?
### Cause: java.sql.SQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'updateaaa t1 set c2 = c2 + 100 where c1 = 2'
......

MyObject{c1=1, c2=10000}
MyObject{c1=2, c2=10000}

可见，转入操作失败，事务回滚了。

编程式事务有一个变种的用法：

    ......
    @Override
    public void change() {
        TransactionTemplate transactionTemplate = new TransactionTemplate(transactionManager);

        transactionTemplate.execute(txStatus -> {
            int value = 100;
            mapper.reduce(1, value);
            System.out.println("===================================");
            mapper.add(2, value);
            return null;
        });
    }
    ......

效果和前面一样，不再赘述。

注意：这里跟声明式事务类似，千万不要 try 并且捕获异常，否则事务管理器就不会认为事务失败了。

还有一点需要注意的是，在配置 SqlSessionFactory 时，不要添加如下属性：

  <property name="transactionFactory">
    <bean class="org.apache.ibatis.transaction.managed.ManagedTransactionFactory" />
  </property>

否则会报错： org.springframework.dao.TransientDataAccessResourceException: SqlSessionFactory must be using a SpringManagedTransactionFactory in order to use Spring transaction synchronization

该属性值表示由容器管理事务，而不使用Spring的事务管理。

总结

声明式事务使用AOP来管理事务，用法相对比较简单，而且是非侵入式的，推荐使用；
编程式事务需要在代码逻辑里显式管理事务，相对比较麻烦；
对于声明式事务以及编程式事务的变种写法，千万记得不要 try 并且捕获异常，否则事务管理器就不会认为事务失败了。当然，可以在外层捕获异常；

参考

http://mybatis.org/spring
http://mybatis.org/spring/zh/index.html （中文版）
https://www.bilibili.com/video/BV1WE411d7Dv?p=27&vd_source=2ec1bfab0d3afd52d760b0dd55

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