MyBatis Demo

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本文介绍MyBatis在项目中的具体应用，包括数据库连接配置、Mapper文件使用、实体类创建，以及通过MyBatis Generator自动生成代码的过程。

一、mybatis demo

1、建表

CREATE TABLE `users` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(20) DEFAULT NULL,
  `sex` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`)
)

插入两条数据

2、pom文件添加依赖

        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>1.3.2</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.9-rc</version>
        </dependency>

3、添加配置

<?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>
    <!-- 配置数据库连接信息 -->
    <environments default="Local">
        <environment id="Local">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/myDataBase"/>
                <property name="username" value="root"/>
                <property name="password" value="12345678"/>
            </dataSource>
        </environment>
    </environments>
    <!-- 注册mapper.xml文件 -->
    <mappers>
        <mapper resource="com/sunshine/shine/mapper/UserMapper.xml"/>
    </mappers>
</configuration>

4、UserMapper.xml、User

User

package com.sunshine.shine.dao.model;

import lombok.Data;

@Data
public class User {
    private Integer id;
    private String name;
    private Integer sex;
}

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="com.sunshine.shine.mapper.UserMapper">
    <select id="selectOneUser" parameterType="int" resultType="com.sunshine.shine.dao.model.User">
        select * from users where id = #{id}
    </select>
</mapper>

5、测试

package com.sunshine.shine.Test;

import com.sunshine.shine.dao.model.User;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;

import java.io.InputStream;

public class MybatisTest {
    @Test
    public  void testMybatis(){
        String resource="mybatis-config.xml";
        InputStream resourceAsStream = MybatisTest.class.getClassLoader().getResourceAsStream(resource);
        SqlSessionFactory sqlSessionFactory=new SqlSessionFactoryBuilder().build(resourceAsStream);
        SqlSession session = sqlSessionFactory.openSession();
        String statement ="com.sunshine.shine.mapper.UserMapper.selectOneUser";
        User o = session.selectOne(statement,2);
        System.out.println(o.getId()+" name="+o.getName()+" sex="+o.getSex());
    }
}

输出：

15:14:43.930 [main] DEBUG com.sunshine.shine.mapper.UserMapper.selectOneUser - ==>  Preparing: select * from users where id = ? 
15:14:43.971 [main] DEBUG com.sunshine.shine.mapper.UserMapper.selectOneUser - ==> Parameters: 2(Integer)
15:14:44.008 [main] DEBUG com.sunshine.shine.mapper.UserMapper.selectOneUser - <==      Total: 1
2 name=sunshineGirl sex=0

二、实际应用

1、application.properties 中配置（或对应的环境中自定义配置文件中配置）

#配置数据库连接信息
spring.datasource.url = jdbc:mysql://127.0.0.1:3306/myDataBase?useSSL=false
spring.datasource.driver-class-name = com.mysql.cj.jdbc.Driver
  ##com.mysql.jdbc.Driver
spring.datasource.username = root
spring.datasource.password = 12345678
#配置扫描mapper.xml文件路径
mybatis.mapper-locations = com/sunshine/shine/mapper/*.xml

2、UserMapper.xml 、UserMapper、UserController

<?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.sunshine.shine.dao.UserMapper">
    <select id="selectOneUser" parameterType="java.lang.Integer" resultType="com.sunshine.shine.dao.model.User">
        select * from users where id = #{id,jdbcType=INTEGER}
    </select>
</mapper>

package com.sunshine.shine.dao;

import com.sunshine.shine.dao.model.User;

public interface UserMapper {
    User selectOneUser(Integer id);
}

package com.sunshine.shine.controller;

import com.sunshine.shine.Util.JsonData;
import com.sunshine.shine.config.ConfigBean;
import com.sunshine.shine.dao.model.User;
import com.sunshine.shine.dao.UserMapper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.annotation.Resource;

@RestController
public class UserController {
    private static final Logger LOGGER =LoggerFactory.getLogger(UserController.class);

    @Autowired
    private UserMapper userMapper;

   @GetMapping("/testMybatis")
    public User testMybatis(Integer id){
        if(id==null){
            id=1;
        }
        User user = userMapper.selectOneUser(id);
        return user;
    }
}

3、在main方法的类上加上扫描mapper.xml映射接口的注解

@MapperScan("com.sunshine.shine.dao")

4、运行程序请求 /testMybatis

返回数据:

三、使用MyBatis Generator自动生成

1、pom文件添加mbg插件

            <plugin>
                <groupId>org.mybatis.generator</groupId>
                <artifactId>mybatis-generator-maven-plugin</artifactId>
                <version>1.3.7</version>
                <dependencies>
                    <dependency>
                        <groupId>mysql</groupId>
                        <artifactId>mysql-connector-java</artifactId>
                        <version>8.0.9-rc</version>
                    </dependency>
                    <dependency>
                        <groupId>org.mybatis.generator</groupId>
                        <artifactId>mybatis-generator-core</artifactId>
                        <version>1.3.7</version>
                    </dependency>
                </dependencies>
                <configuration>
                    <!-- 配置文件位置 -->
                    <configurationFile>${basedir}/src/main/resources/mbgConfig.xml</configurationFile>
                    <overwrite>true</overwrite>
                    <verbose>true</verbose>
                </configuration>
            </plugin>

2、添加配置文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE generatorConfiguration
        PUBLIC "-//mybatis.org//DTD MyBatis Generator Configuration 1.0//EN"
        "http://mybatis.org/dtd/mybatis-generator-config_1_0.dtd">
<generatorConfiguration>
    <context id="local"    targetRuntime="MyBatis3">
    <commentGenerator>
        <property name="suppressDate" value="true"/>
        <property name="suppressAllComments" value="true"/>
    </commentGenerator>
    <!--数据库链接地址账号密码-->
    <jdbcConnection driverClass="com.mysql.cj.jdbc.Driver"
                    connectionURL="jdbc:mysql://127.0.0.1:3306/myDataBase?useSSL=false"
                    userId="root"
                    password="12345678">
    </jdbcConnection>

    <!-- 类型转换 -->
    <javaTypeResolver>
        <property name="forceBigDecimals" value="false"/>
    </javaTypeResolver>
    
    <!--targetProject与targetPackage配置生成文件的保存路径 -->
    <!--生成实体类 -->
    <javaModelGenerator targetPackage="com.sunshine.shine.dao.model"
                        targetProject="src/main/java">
    </javaModelGenerator>
    <!--生成SQLMAP文件-->
    <sqlMapGenerator targetPackage="com.sunshine.shine.mapper"
                     targetProject="src/main/java">
    </sqlMapGenerator>
    <!--生成Dao文件-->
    <javaClientGenerator type="XMLMAPPER" targetPackage="com.sunshine.shine.dao"
                         targetProject="src/main/java">
    </javaClientGenerator>

    <!--生成对应表及类名-->
        <table tableName="books" domainObjectName="books" enableCountByExample="false" enableUpdateByExample="false" enableDeleteByExample="false" enableSelectByExample="false" selectByExampleQueryId="false"></table>

    </context>

</generatorConfiguration>

3、直接点击右侧Maven Project->项目->Plugins->mybatis-generator->mybatis-generator:generate