mybatis-spring整合

整合的前提条件：事先有一个mybatis项目，这里直接提供，方便整合的说明。

项目结构

数据库

代码

UserMapper.java

package dao;

import pojo.User;

import java.util.List;

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

UserMapper.xml

<?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">

<!--configuration核心配置文件-->
<mapper namespace="dao.UserMapper">

    <select id="selectUser" resultType="user">
        select * from mybatis.user
    </select>

</mapper>

User.java

package pojo;

import lombok.Data;

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

log4j.properties

#将等级为DEBUG的日志信息输出到console和file这两个目的地，console和file的定义在下面的代码
log4j.rootLogger=DEBUG,console,file

#控制台输出的相关设置
log4j.appender.console = org.apache.log4j.ConsoleAppender
log4j.appender.console.Target = System.out
log4j.appender.console.Threshold=DEBUG
log4j.appender.console.layout = org.apache.log4j.PatternLayout
log4j.appender.console.layout.ConversionPattern=[%c]-%m%n

#文件输出的相关设置
log4j.appender.file = org.apache.log4j.RollingFileAppender
log4j.appender.file.File=./log/Log4j.log
log4j.appender.file.MaxFileSize=10mb
log4j.appender.file.Threshold=DEBUG
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=[%p][%d{yy-MM-dd}][%c]%m%n
#日志输出级别
log4j.logger.org.mybatis=DEBUG
log4j.logger.java.sql=DEBUG
log4j.logger.java.sql.Statement=DEBUG
log4j.logger.java.sql.ResultSet=DEBUG
log4j.logger.java.sq1.PreparedStatement=DEBUG

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核心配置文件-->
<configuration>
    <properties resource="db.properties"/>

    <settings>
        <setting name="logImpl" value="Log4j"/>
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>

    <typeAliases>
        <typeAlias type="pojo.User" alias="user"/>
    </typeAliases>

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="${driver}"/>
                <property name="url" value="${url}"/>
                <property name="username" value="${username}"/>
                <property name="password" value="${password}"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper resource="dao/UserMapper.xml"/>
    </mappers>

</configuration>

DemoTest.java

import dao.UserMapper;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;
import pojo.User;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class DemoTest {

    @Test
    public void test() throws IOException {

       
        //获得配置资源
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);

        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> users = mapper.selectUser();

        for (User user : users) {
            System.out.println(user);
        }
    }

}

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>Spring-Study</artifactId>
        <groupId>org.example</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>spring-mybatis</artifactId>

    <!--    导入依赖-->
    <dependencies>
        <!--junit 测试-->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
        </dependency>
        <!--  Lombok-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.10</version>
        </dependency>
        <!--  log4j 日志      -->
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.17</version>
        </dependency>
        <!--mybatis-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.4</version>
        </dependency>
        <!--mysql-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.12</version>
        </dependency>
    </dependencies>
    <!-- 静态资源导入    -->
    <build>
        <resources>
            <resource>
                <directory>src/main/java</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
            <resource>
                <directory>src/main/resources</directory>
                <includes>
                    <include>**/*.properties</include>
                    <include>**/*.xml</include>
                </includes>
                <filtering>true</filtering>
            </resource>
        </resources>
    </build>

</project>

其实mybatis-spring整合就是简化代码，不在需要new 而是通过spring的bean配置，让spring容器创建对象，整合前后，观察代码差别

方式一

添加整合需要的依赖

        <!--spring相关的-->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>5.1.10.RELEASE</version>
        </dependency>
        <!--spring-jdbc连接数据库-->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>5.3.4</version>
        </dependency>
        <!--AOP织入-->
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjweaver</artifactId>
            <version>1.9.4</version>
        </dependency>
        <!-- mybatis-spring整合-->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis-spring</artifactId>
            <version>2.0.2</version>
        </dependency>

创建spring的配置文件（ApplicationContext.xml）
1. 配置DataSource
2. 配置sqlSessionFactory
3. 配置sqlSessionTemplate

    <!--  配置数据源datasource-->
    <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=true&amp;useUnicode=true&amp;characterEncoding=UTF-8&amp;serverTimezone=UTC"/>
        <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"/>
        <!--  可以在这里直接绑定mybatis配置文件      -->
        <property name="configLocation" value="classpath:mybatis-config.xml"/>  <!--绑定mybatis-config.xml-->
        <property name="mapperLocations" value="classpath:dao/*.xml"/>
    </bean>
    <!--sqlSession-->
    <bean id="sqlSession" class="org.mybatis.spring.SqlSessionTemplate">
        <!--  只能使用构造器注入，因为它没有set方法      -->
        <constructor-arg index="0" ref="sqlSessionFactory"/>
    </bean>

写接口实现类，即UserMapper.java的实现类

UserMapperImpl.java

package dao;

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

import java.util.List;

public class UserMapperImpl implements UserMapper{

    private SqlSessionTemplate sqlSession;

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

    public List<User> selectUser() {
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        return mapper.selectUser();
    }
}

在ApplicationContext.xml配置这个实现类UserMapperImpl.java

    <bean id="userMapper" class="dao.UserMapperImpl">
        <property name="sqlSession" ref="sqlSession"/>
    </bean>

测试类

DemoTest

import dao.UserMapper;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import pojo.User;

import java.io.IOException;

public class DemoTest {

    @Test
    public void test() throws IOException {

        ApplicationContext context = new ClassPathXmlApplicationContext("ApplicationContext.xml");

        UserMapper mapper = context.getBean("userMapper", UserMapper.class);


        for (User user : mapper.selectUser()) {
            System.out.println(user);
        }

    }

}

现在我们来看看整合后和整合前的差别：

配置数据源，取代mybatis-config.xml的环境配置

配置sqlSessionFactory和sqlSession，取代工具类的sqlSession对象的获取。
多了一个接口实现类UserMapperImpl.java

多了接口实现类，当然也就多了一个配置接口实现类的bean。（在ApplicationContext.xml配置）

测试类不再需要去获取SqlSession：

相对的，mybatis-config.xml配置文件少了很多配置，工具类没有了（直接在ApplicationContext.xml中实现了工具类所获取的SqlSession）

方式二

方式二是建立在方式一的基础上进行的修改。

修改了接口实现类

UserMapperImpl2.java

package dao;

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

import java.util.List;

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

修改了注册接口实现类的bean

    <bean id="userMapper2" class="dao.UserMapperImpl2">
        <property name="sqlSessionFactory" ref="sqlSessionFactory"/>
    </bean>

如果用方式二来实现，还可以省略配置sqlSession

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

方式二是方式一的改进版，更加“偷懒”。