Spring笔记：整合MyBtis 山上下了雪

Spring中通常有两种方式整合MyBtis，一种是通过在xml中配置SqlSession，另一种是定义一个继承SqlSessionDaoSupport的类。

会用到的maven依赖：

<dependencies>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>8.0.26</version>
    </dependency>
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.5.7</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-webmvc</artifactId>
        <version>5.3.12</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-jdbc</artifactId>
        <version>5.3.12</version>
    </dependency>
    <dependency>
        <groupId>org.aspectj</groupId>
        <artifactId>aspectjweaver</artifactId>
        <version>1.9.7</version>
    </dependency>
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis-spring</artifactId>
        <version>2.0.6</version>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <version>1.18.20</version>
    </dependency>
</dependencies>

1. 整合方式一：在xml中配置SqlSession

直接贴示例，详细解释请看注释。

MyBtis部分代码

实体类：

package com.yun.pojo;

import lombok.Data;

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

mapper接口：

package com.yun.mapper;

import com.yun.pojo.User;

import java.util.List;

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

mapper对应的xml配置：

<?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="com.yun.mapper.UserMapper">
    <select id="selectUser" resultType="user">
        select * from mybatis.user;
    </select>
</mapper>

MyBtis的xml配置：

<?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>
    <typeAliases>
        <package name="com.yun.pojo"/>
    </typeAliases>

    <!-- 以下配置已经在Spring的xml中配置，就不用重复配置了 -->
    <!--
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url"
                          value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&amp;useUnicode=true&amp;characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="123456"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper class="com.yun.mapper.UserMapper"/>
    </mappers>
     -->
</configuration>

Spring整合MyBtis代码

Spring的xml配置：

<?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
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/aop
        https://www.springframework.org/schema/aop/spring-aop.xsd">

    <!-- 使用Spring的数据源替换MyBatis的配置，这里使用Spring提供的JDBC，
     这样就不用在MyBatis的xml中来配置数据源了-->
    <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/mybatis?useSSL=true&amp;useUnicode=true&amp;characterEncoding=UTF-8"/>
        <property name="username" value="root"/>
        <property name="password" value="123456"/>
    </bean>

    <!-- 使用Spring配置来创建sqlSessionFactory，不再单独写一个公共方法来创建sqlSessionFactory了 -->
    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource"/>
        <!-- 绑定MyBatis相关配置，这里需要注意classpath:后面没有空格 -->
        <property name="configLocation" value="classpath:mybatis-config.xml"/>
        <property name="mapperLocations" value="classpath:com/yun/mapper/*.xml"/>
    </bean>

    <!-- Spring的SqlSessionTemplate就相当于MyBatis中的SqlSession对象，
    并且由于SqlSessionTemplate没有对应的set方法，所以只能使用构造器进行注入 -->
    <bean id="sqlSession" class="org.mybatis.spring.SqlSessionTemplate">
        <constructor-arg index="0" ref="sqlSessionFactory"/>
    </bean>

    <bean id="userMapper" class="com.yun.mapper.UserMapperImpl">
        <property name="sqlSession" ref="sqlSession"/>
    </bean>
</beans>

Spring实现类：

package com.yun.mapper;

import com.yun.pojo.User;
import org.mybatis.spring.SqlSessionTemplate;

import java.util.List;

public class UserMapperImpl implements UserMapper{
    private SqlSessionTemplate sqlSession;

    public void setSqlSession(SqlSessionTemplate sqlSession) {
        this.sqlSession = sqlSession;
    }

    // 将该类通过Spring注入之后，直接使用此方法即可获得数据库查询结果
    public List<User> selectUser() {
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        return mapper.selectUser();
    }

}

测试：

import com.yun.mapper.UserMapper;
import com.yun.pojo.User;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;


public class MyTest {
    @Test
    public void test(){
        ApplicationContext context = new ClassPathXmlApplicationContext("spring-dao.xml");
        UserMapper userMapper = context.getBean("userMapper", UserMapper.class);
        for (User user : userMapper.selectUser()) {
            System.out.println(user);
        }
    }
}

输出：

User(id=1, name=ZhangSan, pwd=123456)
User(id=2, name=lisi, pwd=123456)
User(id=3, name=wangwu, pwd=123456)
User(id=4, name=zhaoliu, pwd=123456)

2. 整合方式二：自定义类，并继承SqlSessionDaoSupport类

这种方式其实就是第一种方式的简化版，下面只贴一些差异点。

实现类：

package com.yun.mapper;

import com.yun.pojo.User;
import org.mybatis.spring.support.SqlSessionDaoSupport;

import java.util.List;

// 需要继承SqlSessionDaoSupport类，并实现对应的mapper接口
public class UserMapperImpl2 extends SqlSessionDaoSupport implements UserMapper {
    public List<User> selectUser() {
        // 通过getSqlSession()就可以直接拿到SqlSession对象，不需要再用set方法进行注入
        return getSqlSession().getMapper(UserMapper.class).selectUser();
    }
}

Spring中xml配置：

<!-- 与第一种方式相比，不需要再配置sqlSession，直接在实现类的bean中配置sqlSessionFactory即可 -->
<bean id="userMapper2" class="com.yun.mapper.UserMapperImpl2">
    <property name="sqlSessionFactory" ref="sqlSessionFactory"/>
</bean>