Java-Mybatis-Spring · YASINBlog

概念

什么是 MyBatis-Spring？
- MyBatis-Spring会帮助你将MyBatis代码无缝地整合到Spring中。它将允许MyBatis参与到Spring的事务管理之中，创建映射器mapper和SqlSession并注入到bean中，以及将Mybatis的异常转换为Spring的DataAccessException。最终，可以做到应用代码不依赖于MyBatis，Spring或MyBatis-Spring。

核心原理

跟单独使用mybatis的区别
- 跟单独使用Mybatis类似，只是在此基础上让将Mybatis在Spring的配置中注册为bean，然后让Spring接管了Mybatis的一些配置项（甚至可以让Spring全部接管Mybatis配置，并删除原来的mybatis-config.xml核心配置文件）。
- 最终Mybatis在Spring中呈现为一个实现类为SqlSessionTemplate的bean（习惯上命名为：sqlSession），供程序在任意地方调用。
- Spring接管Mybatis以后多了一个实现类，在该类中定义一个sqlSession属性，并增加setter，然后在Spring注册bean并注入sqlSession属性即可。
- 新版本中还用另一种方式，让这个实现类继承SqlSessionDaoSupport，调用getSqlSession()方法你会得到一个SqlSessionTemplate。==注意：这种方式需要在bean中注入sqlSessionFactory属性，而不是sqlSession。==
其中两个核心bean
- sqlSessionFactory（SqlSessionFactoryBean）
- sqlSession（SqlSessionTemplate）

具体实现核心代码

目录机构
- module
  - main
    - java
      - mapper
        
        UserMapper.java
        
        UserMapper.xml
        
        UserMapperImpl.java
        
        UserMapperImpl2.java
      - pojo
        
        User.java
    - resources
      - applicationContext.xml
      - jdbc.properties
      - mybatis-config.xml
      - spring-dao.xml
  - test
    - java
      - UserMapperTest.java
- pom.xml

配置文件（resources）

pom.xml

<!-- https://mvnrepository.com/artifact/org.mybatis/mybatis-spring -->
<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis-spring</artifactId>
    <version>2.0.6</version>
</dependency>

jdbc.properties

jdbc.driverClassName=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/jdbc_test?useSSL=false&characterEncoding=utf8&serverTimezone=Asia/Shanghai
jdbc.username=root
jdbc.password=root

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>
    <settings>
        <setting name="logImpl" value="STDOUT_LOGGING"/>
    </settings>
    <typeAliases>
        <package name="cn.cnyasin.pojo"/>
    </typeAliases>
    <mappers>
        <mapper resource="cn/cnyasin/mapper/UserMapper.xml"/>
    </mappers>
</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:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="
       http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
       http://www.springframework.org/schema/context https://www.springframework.org/schema/context/spring-context.xsd
">
    <!-- 读取jdbc配置文件 -->
    <context:property-placeholder location="jdbc.properties"/>
    <!-- 定义DataSource：c3p0 dbcp druid -->
    <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="${jdbc.driverClassName}"/>
        <property name="url" value="${jdbc.url}"/>
        <property name="username" value="${jdbc.username}"/>
        <property name="password" value="${jdbc.password}"/>
    </bean>
    <!-- 注册sqlSessionFactory -->
    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource"/>
        <!-- 绑定mybatis配置文件 -->
        <property name="configLocation" value="classpath:mybatis-config.xml"/>
        <!--<property name="mapperLocations" value="classpath:cn/cnyasin/mapper/UserMapper.xml"/>-->
    </bean>
    <!-- 注册sqlSession -->
    <bean id="sqlSession" class="org.mybatis.spring.SqlSessionTemplate">
        <!-- 注入SQLSessionFactory：只能通过构造器，因为他无set方法 -->
        <constructor-arg index="0" ref="sqlSessionFactory"/>
    </bean>
</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"
       xsi:schemaLocation="
       http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
">
    <!-- 导入其他配置文件 -->
    <import resource="spring-dao.xml"/>
    <!-- mapper -->
    <!-- 方式一 -->
    <bean id="userMapper" class="cn.cnyasin.mapper.UserMapperImpl">
        <property name="sqlSession" ref="sqlSession"/>
    </bean>
    <!-- 方式二 -->
    <bean id="userMapper2" class="cn.cnyasin.mapper.UserMapperImpl2">
        <property name="sqlSessionFactory" ref="sqlSessionFactory"/>
    </bean>
</beans>

java代码

UserMapper.java

public interface UserMapper {
    public List<User> getAll();
}

UserMapper.xml

<?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="cn.cnyasin.mapper.UserMapper">
    <resultMap id="userList" type="user">
        <result property="createdAt" column="created_at"/>
    </resultMap>
    <select id="getAll" resultMap="userList">
        select * from user
    </select>
</mapper>

UserMapperImpl.java

public class UserMapperImpl implements UserMapper {
    private SqlSessionTemplate sqlSession;
    public void setSqlSession(SqlSessionTemplate sqlSession) {
        this.sqlSession = sqlSession;
    }
    public List<User> getAll() {
        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        return userMapper.getAll();
    }
}

UserMapperImpl2.java

public class UserMapperImpl2 extends SqlSessionDaoSupport implements UserMapper{
    public List<User> getAll() {
        return getSqlSession().getMapper(UserMapper.class).getAll();
    }
}

User.java

@NoArgsConstructor
@AllArgsConstructor
@Data
public class User {
    private int id;
    private String username;
    private String email;
    private String password;
    private long balance;
    private long createdAt;
}

UserMapperTest.java

public class UserMapperTest {
    @Test
    public void getAllTest() {
        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        UserMapper userMapper = context.getBean("userMapper", UserMapper.class);
        System.out.println(userMapper.getAll());
    }
    @Test
    public void getAllTest2() {
        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        UserMapper userMapper = context.getBean("userMapper2", UserMapper.class);
        System.out.println(userMapper.getAll());
    }
}

Mybatis配合Spring开启事务

如何理解？
- 不要被这个标题误导哦，Mybatis的事务非常笨重，而MybatisSpring中Mybatis默认关闭了事务，你可以直接使用Spring的事务。
  - XML方式（配置事务通知、事务切入点）
  - AOP方式（Spring开启注解、使用注解开启事务）
注意：最终实例化bean的时候，约束类必须是接口而不是接口的实现类，否则报错：org.springframework.beans.factory.BeanNotOfRequiredTypeException: Bean named 'userMapper' is expected to be of type......
- 错误用法：UserMapperImpl userMapper = context.getBean("userMapper", UserMapperImpl.class);
- 正确用法：UserMapper userMapper = context.getBean("userMapper", UserMapper.class);

关于作者 · AdminI am Yasin, let's talk about these first!

概念

核心原理

具体实现核心代码

Mybatis配合Spring开启事务

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