Mybatis-Plus快速入门：Mybatis+MPSpring+Mybatis+MPSpring Boot+Mybatis+MP

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Mybatis-Plus⼊⻔

1、安装

全新的 MyBatis-Plus 3.0 版本基于 JDK8，提供了 lambda 形式的调⽤，所以安装集成 MP3.0 要求如下：

  • JDK8+
  • Maven or Gradle

1.1、Spring Boot

Maven：

<dependency>
	<groupId>com.baomidou</groupId>
	<artifactId>mybatis-plus-boot-starter</artifactId>
	<version>3.4.0</version>
</dependency>

1.2、Spring MVC

Maven:

<dependency>
	<groupId>com.baomidou</groupId>
	<artifactId>mybatis-plus</artifactId>
	<version>3.4.0</version>
</dependency>

注意

引入 MyBatis-Plus 之后请不要再次引入 MyBatis 以及 MyBatis-Spring，以避免因版本差异导致的问题。

对于Mybatis整合MP有常常有三种⽤法，分别是Mybatis+MP、Spring+Mybatis+MP、Spring Boot+Mybatis+MP。

2、创建数据库以及表

创建User表，其表结构如下：

idnameageemail
1Jone18test1@baomidou.com
2Jack20test2@baomidou.com
3Tom28test3@baomidou.com
4Sandy21test4@baomidou.com
5Billie24test5@baomidou.com
-- 创建测试表
DROP TABLE IF EXISTS user;

CREATE TABLE user
(
    id BIGINT(20) NOT NULL COMMENT '主键ID',
    name VARCHAR(30) NULL DEFAULT NULL COMMENT '姓名',
    age INT(11) NULL DEFAULT NULL COMMENT '年龄',
    email VARCHAR(50) NULL DEFAULT NULL COMMENT '邮箱',
    PRIMARY KEY (id)
);

-- 插⼊测试数据
DELETE FROM user;

INSERT INTO user (id, name, age, email) VALUES
(1, 'Jone', 18, 'test1@baomidou.com'),
(2, 'Jack', 20, 'test2@baomidou.com'),
(3, 'Tom', 28, 'test3@baomidou.com'),
(4, 'Sandy', 21, 'test4@baomidou.com'),
(5, 'Billie', 24, 'test5@baomidou.com');

3、创建工程

导⼊依赖：

<dependencies>
     <!-- mybatis-plus插件依赖 -->
     <dependency>
         <groupId>com.baomidou</groupId>
         <artifactId>mybatis-plus</artifactId>
         <version>3.1.1</version>
     </dependency>
     <!--mysql-->
     <dependency>
         <groupId>mysql</groupId>
         <artifactId>mysql-connector-java</artifactId>
         <version>5.1.47</version>
     </dependency>
     <!--连接池-->
     <dependency>
         <groupId>com.alibaba</groupId>
         <artifactId>druid</artifactId>
         <version>1.0.11</version>
     </dependency>
     <!--简化bean代码的⼯具包-->
     <dependency>
         <groupId>org.projectlombok</groupId>
         <artifactId>lombok</artifactId>
         <version>1.18.4</version>
     </dependency>
     <dependency>
         <groupId>junit</groupId>
         <artifactId>junit</artifactId>
         <version>4.12</version>
     </dependency>
     <dependency>
         <groupId>org.slf4j</groupId>
         <artifactId>slf4j-log4j12</artifactId>
         <version>1.6.4</version>
     </dependency>
 </dependencies>
 <build>
     <plugins>
         <plugin>
             <groupId>org.apache.maven.plugins</groupId>
             <artifactId>maven-compiler-plugin</artifactId>
             <configuration>
                 <source>1.8</source>
                 <target>1.8</target>
             </configuration>
         </plugin>
     </plugins>
 </build>

4、 Mybatis + MP

下⾯演示，通过纯Mybatis与Mybatis-Plus整合。

4.1、创建⼦Module

<?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>mybatis-plus-test</artifactId>
        <groupId>com.tao</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>mybatis-plus-simple</artifactId>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>

</project>

log4j.properties：

log4j.rootLogger=DEBUG,A1
log4j.appender.A1=org.apache.log4j.ConsoleAppender
log4j.appender.A1.layout=org.apache.log4j.PatternLayout
log4j.appender.A1.layout.ConversionPattern=[%t] [%c]-[%p] %m%n

4.2、Mybatis实现查询User

第⼀步，编写sqlMapConfig.xml⽂件：

<?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>
    <properties resource="jdbc.properties"></properties>
    <!--environments: 运⾏环境-->
    <environments default="development">
        <environment id="development">
            <!--当前的事务事务管理器是JDBC-->
            <transactionManager type="JDBC"></transactionManager>
            <!--数据源信息 POOLED：使⽤mybatis的连接池-->
            <dataSource type="POOLED">
                <property name="driver" value="$jdbc.driver"/>
                <property name="url" value="$jdbc.url"/>
                <property name="username" value="$jdbc.username"/>
                <property name="password" value="$jdbc.password"/>
            </dataSource>
        </environment>
    </environments>
    <!--引⼊映射配置⽂件-->
    <mappers>
        <package name="com.tao.mapper" />
    </mappers>
</configuration>

第⼆步，编写User实体对象：（这⾥使⽤lombok进⾏了进化bean操作）

@Data
@NoArgsConstructor
@AllArgsConstructor
public class User 
    private Long id;
    private String name;
    private String age;
    private String email;

第三步，编写UserMapper接⼝：

public interface UserMapper 

    /*
        查询所有用户
     */
    public List<User> findAll();

第四步，编写UserMapper.xml⽂件：

<?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.tao.mapper.UserMapper">
    <!--查询所有用户-->
    <select id="findAll" resultType="com.tao.pojo.User">
        select * from user
    </select>
</mapper>

第五步，编写mybatisTest测试⽤例：

@Test
public void mybatisTest() throws IOException 
    InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
    SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
    SqlSession sqlSession = sqlSessionFactory.openSession();
    UserMapper mapper = sqlSession.getMapper(UserMapper.class);
    List<User> all = mapper.findAll();
    for (User user : all) 
        System.out.println(user);

测试结果：

User(id=1, name=Jone, age=18, email=test1@baomidou.com)
User(id=2, name=Jack, age=20, email=test2@baomidou.com)
User(id=3, name=Tom, age=28, email=test3@baomidou.com)
User(id=4, name=Sandy, age=21, email=test4@baomidou.com)
User(id=5, name=Billie, age=24, email=test5@baomidou.com)

注：如果实体类名称和表名称不⼀致，可以在实体类上添加注解@TableName(“指定数据库表名”)

4.3、Mybatis+MP实现查询User

第⼀步，将UserMapper继承BaseMapper，将拥有了BaseMapper中的所有⽅法：

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.tao.pojo.User;

public interface UserMapper extends BaseMapper<User>

第⼆步，使⽤MP中的MybatisSqlSessionFactoryBuilder进程构建：

@Test
public void mybatisPlusTest() throws IOException 
    InputStream resourceAsStream = Resources.getResourceAsStream("sqlMapConfig.xml");
    SqlSessionFactory sqlSessionFactory = new MybatisSqlSessionFactoryBuilder().build(resourceAsStream);
    SqlSession sqlSession = sqlSessionFactory.openSession();
    UserMapper mapper = sqlSession.getMapper(UserMapper.class);
    List<User> users = mapper.selectList(null);
    for (User user : users) 
        System.out.println(user);

测试结果：

User(id=1, name=Jone, age=18, email=test1@baomidou.com)
User(id=2, name=Jack, age=20, email=test2@baomidou.com)
User(id=3, name=Tom, age=28, email=test3@baomidou.com)
User(id=4, name=Sandy, age=21, email=test4@baomidou.com)
User(id=5, name=Billie, age=24, email=test5@baomidou.com)

注：如果实体类名称和表名称不⼀致，可以在实体类上添加注解@TableName(“指定数据库表名”)

简单说明：

  • 由于使⽤了 MybatisSqlSessionFactoryBuilder 进⾏了构建，继承的BaseMapper中的⽅法就载⼊到了 SqlSession 中，所以就可以直接使⽤相关的⽅法；

  • 如图所示

5、Spring + Mybatis + MP

引⼊了Spring框架，数据源、构建等⼯作就交给了Spring管理。

5.1、创建⼦Module

<?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>mybatis-plus-test</artifactId>
        <groupId>com.tao</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>mybatis-plus-spring</artifactId>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <spring.version>5.1.6.RELEASE</spring.version>
    </properties>


    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>$spring.version</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>$spring.version</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test</artifactId>
            <version>$spring.version</version>
        </dependency>
    </dependencies>

</project>

5.2、实现查询User

第⼀步，编写jdbc.properties

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://127.0.0.1:3306/mp?characterEncoding=utf-8&useSSL=false&serverTimezone=UTC
jdbc.username=root
jdbc.password=数据库密码

第⼆步，编写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"
       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
 http://www.springframework.org/schema/context/spring-context.xsd">

    <!--引入properties文件-->
    <context:property-placeholder location="classpath:jdbc.properties"></context:property-placeholder>

    <!--数据源-->
    <bean id="datasource" class="com.alibaba.druid.pool.DruidDataSource">
        <property name="driverClassName" value="$jdbc.driver" />
        <property name="url" value="$jdbc.url" />
        <property name="username" value="$jdbc.username" />
        <property name="password" value="$jdbc.password" />
    </bean>

    <!--1. 将sqlSessionFactory对象的创建交给spring-->
    <bean id="sqlSessionFactory" class="com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean">
        <property name="dataSource" ref="datasource"></property>
    </bean>

    <!--2. mapper映射扫描-->
    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
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