万隆的笔记
2022-12-10
目录

MyBaits Plus快速入门

# MyBatis Plus快速入门

参考：快速开始 (opens new window) & 安装 (opens new window)

# 安装

MyBatis-Plus 3.x 版本基于JDK8，提供了lambda形式的调⽤，安装集成要求：

  • JDK 8+
  • Maven or Gradle

# Release版本

# Spring Boot

Maven：

<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>最新版本</version>
</dependency>

Gradle：

compile group: 'com.baomidou', name: 'mybatis-plus-boot-starter', version: '最新版本'

# Spring

Maven:

<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus</artifactId>
    <version>最新版本</version>
</dependency>

Gradle：

compile group: 'com.baomidou', name: 'mybatis-plus', version: '最新版本'

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。

# 创建数据库以及表

使用MySQL，创建数据库mybatis_plus & 创建User表：

create database mybatis_plus;

use mybatis_plus;

-- 创建测试表
CREATE TABLE IF NOT EXISTS 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
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');

# 快速开始

MyBatis整合MP常常有三种⽤法，分别是MyBatis+MP、Spring+Mybatis+MP、SpringBoot+Mybatis+MP。

这里的Demo工程，MP版本选择较新的v3.4.3 (opens new window)为例，创建Maven的POM工程 hello-mybatis-plus ，引入Maven依赖管理：

<?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">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>hello-mybatis-plus</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>pom</packaging>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <!--MyBatis-Plus-Springboot-->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.4.3</version>
        </dependency>
        <!--MySQL-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.28</version>
        </dependency>
        <!--连接池-->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.0.11</version>
        </dependency>
        <!--Lombok-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.4</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13.1</version>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-reload4j</artifactId>
            <version>2.0.7</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>

</project>

# MyBatis + MP

通过纯Mybatis与Mybatis-Plus整合：

  1. 创建⼦工程Module：mybatis-plus-simple
<?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">
    <modelVersion>4.0.0</modelVersion>

    <parent>
        <groupId>org.example</groupId>
        <artifactId>hello-mybatis-plus</artifactId>
        <version>1.0-SNAPSHOT</version>
    </parent>

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

</project>

父工程定义模块：

<modules>
    <module>mybatis-plus-simple</module>
</modules>

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
  1. MyBatis实现查询User

Step1：编写 mybatis-config.xml⽂件&jdbc.properties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"/>
    <!--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"/>
            <!-- 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>
        <mapper resource="mapper/UserMapper.xml"/>
    </mappers>
</configuration>

jdbc.properties⽂件：

jdbc.driver=com.mysql.cj.jdbc.Driver
#jdbc.driver=com.mysql.jdbc.Driver 5.x 驱动
jdbc.url=jdbc:mysql://127.0.0.1:3306/mybatis_plus?characterEncoding=utf-8
jdbc.username=root
jdbc.password=123456

Step2：编写实体User（lombok简化）

@Data
public class User {

    private Long id;
    private String name;
    private Integer age;
    private String email;

}

Step3：编写 UserMapper接⼝

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

Step4：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="org.example.hello.mp.mapper.UserMapper">
    <select id="findAll" resultType="org.example.hello.mp.entity.User">
        select * from user
    </select>
</mapper>

Step5：编写 UserMapperTest测试⽤例：

public class UserMapperTest {

    @Test
    public void testFindAll() throws IOException {
        InputStream resourceAsStream = Resources.getResourceAsStream("mybatis-config.xml");
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> all = mapper.findAll();
        all.forEach(System.out::println);
    }

}
// 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)
  1. Mybatis+MP实现查询User

Step1：在引入了MP后，只需要将UserMapper继承 BaseMapper，就可以拥有MP封装好的CURD方法：

package org.example.hello.mp.mapper;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import org.example.hello.mp.entity.User;
import java.util.List;

public interface UserMapper extends BaseMapper<User> {
    List<User> findAll();
}

Step2：使⽤MP中的 MybatisSqlSessionFactoryBuilder构建SqlSessionFactory`：

@Test
public void testFindAllByMP() throws IOException {
    InputStream resourceAsStream = Resources.getResourceAsStream("mybatis-config.xml");
    // 使⽤的是MP的MybatisSqlSessionFactoryBuilder
    SqlSessionFactory sqlSessionFactory = new MybatisSqlSessionFactoryBuilder().build(resourceAsStream);
    SqlSession sqlSession = sqlSessionFactory.openSession();
    UserMapper mapper = sqlSession.getMapper(UserMapper.class);
    // BaseMapper中定义的⽅法
    List<User> all = mapper.selectList(null);
    all.forEach(System.out::println);
}

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")

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的 mappedStatements中，所以就可以直接使⽤相关的⽅法。

# Spring + MyBatis + MP

引⼊Spring框架，就可以将数据源、构建等⼯作就交给Spring管理。

  1. 创建⼦工程Module，mybatis-plus-spring

    <?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">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.example</groupId>
        <artifactId>hello-mybatis-plus</artifactId>
        <version>1.0-SNAPSHOT</version>
    </parent>

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

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <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>
            <scope>test</scope>
            <version>${spring.version}</version>
        </dependency>
    </dependencies>


</project>

  2. Spring + Mybatis + MP 实现查询User

Step1：编写 jdbc.properties⽂件和 log4j.properties文件（略）

Step2：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-->
    <context:property-placeholder location="classpath:jdbc.properties"/>
    <!--DBSource-->
    <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>
    <!--使⽤MP提供的sqlSessionFactory,完成spring与mp的整合-->
    <bean id="sqlSessionFactory" class="com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource"/>
    </bean>
    <!--扫描mapper接⼝，使⽤的依然是mybatis原⽣的扫描器-->
    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <property name="basePackage" value="org.example.hello.mp.mapper"/>
    </bean>

</beans>

Step3：编写User对象以及UserMapper接⼝（略）

Step4：编写测试⽤例

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath:applicationContext.xml")
public class UserMapperSpringTest {

    @Autowired
    private UserMapper userMapper;

    @Test
    public void testFindAllByMP() throws IOException {
        List<User> users = this.userMapper.selectList(null);
        for (User user : users) {
            System.out.println(user);
        }
    }

}

# SpringBoot + MyBatis + MP

使⽤SpringBoot将进⼀步的简化MP的整合，需要注意的是，由于使⽤SpringBoot需要继承Parent，所以需要重新创建⼯程，并不是创建⼦Module。

  1. 创建工程：mybatis-plus-springboot，引入依赖：
<?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">
    <modelVersion>4.0.0</modelVersion>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.5.6</version>
        <relativePath/>
    </parent>

    <groupId>org.example</groupId>
    <artifactId>mybatis-plus-springboot</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
            <exclusions>
                <exclusion>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-starter-logging</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

        <!--MyBatis-Plus-Springboot-->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.4.3</version>
        </dependency>
        <!--MySQL-->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.28</version>
        </dependency>
        <!--Lombok-->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.4</version>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-reload4j</artifactId>
            <version>2.0.7</version>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-slf4j2-impl</artifactId>
            <version>2.20.0</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>
  1. SpringBoot + Mybatis + MP 实现查询User

Step1：编写 log4j.properties（略）

Step2：编写 application.properties：

spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.url=jdbc:mysql://127.0.0.1:3306/mybatis_plus?characterEncoding=utf-8
spring.datasource.username=root
spring.datasource.password=123456

Step2：编写User对象以及UserMapper接⼝（略）

Step3：编写启动类

@MapperScan("org.example.hello.mp.mapper")
@SpringBootApplication
public class MyApplication {

    public static void main(String[] args) {
        SpringApplication.run(MyApplication.class, args);
    }

}

Step4：编写测试⽤例

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath:applicationContext.xml")
public class UserMapperSpringTest {

    @Autowired
    private UserMapper userMapper;

    @Test
    public void testFindAllByMP() throws IOException {
        List<User> users = this.userMapper.selectList(null);
        for (User user : users) {
            System.out.println(user);
        }
    }

}
上次更新: 5/30/2023, 11:23:39 PM
MyBaits Plus CURD

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