1.简介

MyBatis-Plus（简称 MP）是一个 MyBatis 的增强工具，在 MyBatis 的基础上只做增强不做改变，为简化开发、提高效率而生

官网:https://mybatis.plus/

2.搭建环境

2.1pom.xml配置

<!-- https://mvnrepository.com/artifact/com.baomidou/mybatis-plus -->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus</artifactId>
            <version>3.3.2</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>5.1.6.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-jdbc</artifactId>
            <version>5.1.6.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-orm</artifactId>
            <version>5.1.6.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.1.21</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
            <version>5.1.47</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>com.github.pagehelper</groupId>
            <artifactId>pagehelper</artifactId>
            <version>5.1.8</version>
        </dependency>

2.2spring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:tx="http://www.springframework.org/schema/tx"
       xmlns:aop="http://www.springframework.org/schema/aop"
       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/tx
        http://www.springframework.org/schema/tx/spring-tx.xsd
        http://www.springframework.org/schema/aop
        http://www.springframework.org/schema/aop/spring-aop.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd">

    <!-- dataSource -->
    <bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource">
        <property name="driverClassName" value="com.mysql.jdbc.Driver"></property>
        <property name="url" value="jdbc:mysql://localhost:3306/mybatis??characterEncoding=utf8"></property>
        <property name="username" value="root"></property>
        <property name="password" value="root"></property>
    </bean>
    <!--配置工厂  -->
    <bean id="sqlSessionFactoryBean" class="com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean">
        <property name="dataSource" ref="dataSource"></property>
        <!-- sql映射文件路径 -->
<!--        <property name="mapperLocations" value="classpath:com/qianfeng/openapi/web/master/mapper/*.xml"></property>-->
       <property name="configLocation" value="classpath:mybatis/mybatis.xml"/>
    </bean>
    <!-- 配置扫描mapper文件 -->
    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <property name="basePackage" value="com.qf.mapper"></property>
        <property name="sqlSessionFactoryBeanName" value="sqlSessionFactoryBean"/>
    </bean>
</beans>

2.3mybatis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>
    <settings>
        <!-- 打印查询语句 -->
        <setting name="logImpl" value="STDOUT_LOGGING"/>
    </settings>
    <plugins>
        <!--配置分页插件-->
        <plugin interceptor="com.github.pagehelper.PageInterceptor">
            <property name="helperDialect" value="mysql"/>
        </plugin>

    </plugins>
</configuration>

实体配置

//@TableName 注解，帮助mybatis与数据库表关联
@TableName("t_departments")
public class Department {
    @TableId(value = "id",type = IdType.AUTO)//指定自增策略
    private Integer id;
    private String name;
    private String location;
}

3.案例

3.1插入

    /**
     * 测试，mybatisplus的插入功能
     */
    @Test
    public void testInsert() {
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("bean.xml");
        DepartmentMapper departmentMapper = applicationContext.getBean("departmentMapper", DepartmentMapper.class);
        //调用mybatisplus的插入方法
        departmentMapper.insert(new Department(null, "人事部", "杭州"));
    }

3.2修改

/**
     * 根据 ID 修改
     */
    @Test
    public void testupdateById() {
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("bean.xml");
        DepartmentMapper departmentMapper = applicationContext.getBean("departmentMapper", DepartmentMapper.class);
        Department d = new Department();
        d.setId(15);
        d.setName("abc");
        d.setLocation("abc");
        departmentMapper.updateById(d);
    }

    /**
     * 根据 whereEntity 条件，更新记录
     *
     * 实体对象 (set 条件值,可以为 null)
     * 实体对象封装操作类（可以为 null,里面的 entity 用于生成 where 语句）
     */
    @Test
    public void testupdate() {
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("bean.xml");
        DepartmentMapper departmentMapper = applicationContext.getBean("departmentMapper", DepartmentMapper.class);
        Department d = new Department();
        d.setId(16);
        d.setName("123");
        d.setLocation("123");
        departmentMapper.update(d,new UpdateWrapper<Department>()
                .eq("name","abc")
                .eq("location","abc"));

    }

3.3删除

@Test
    public void testDeleteByMap(){
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("bean.xml");
        DepartmentMapper departmentMapper = applicationContext.getBean("departmentMapper", DepartmentMapper.class);
        Map map = new HashMap<>();
        map.put("id",11);
        map.put("name","人事部");
        departmentMapper.deleteByMap(map);
    }

    /**
     * 根据 entity 条件，删除记录
     *
     * 实体对象封装操作类（可以为 null）
     */
    @Test
    public void testDelete() {
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("bean.xml");
        DepartmentMapper departmentMapper = applicationContext.getBean("departmentMapper", DepartmentMapper.class);
        departmentMapper.delete(new QueryWrapper<Department>().eq("id",12));
    }

    /**
     * 删除多条数据
     * 传入参数为collection
     */
    @Test
    public void testdeleteBatchIds() {
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("bean.xml");
        DepartmentMapper departmentMapper = applicationContext.getBean("departmentMapper", DepartmentMapper.class);
        departmentMapper.deleteBatchIds(Arrays.asList(10,13,14));
    }

3.4查询

/**
     * 根据 ID 查询
     *
     * id 主键ID
     */
    @Test
    public void testselectById(){
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("bean.xml");
        DepartmentMapper departmentMapper = applicationContext.getBean("departmentMapper", DepartmentMapper.class);
        Department department = departmentMapper.selectById(1);
        System.out.println(department);
    }

    /**
     * 查询（根据ID 批量查询）
     *
     *  主键ID列表(不能为 null 以及 empty)
     */
    @Test
    public void testselectBatchIds(){
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("bean.xml");
        DepartmentMapper departmentMapper = applicationContext.getBean("departmentMapper", DepartmentMapper.class);
        List<Department> list = departmentMapper.selectBatchIds(Arrays.asList(1,2,15));
        for (Department department : list) {
            System.out.println(department);
        }
    }

    /**
     * 查询（根据 columnMap 条件）
     *
     * 表字段 map 对象
     */
    @Test
    public void testselectByMap(){
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("bean.xml");
        DepartmentMapper departmentMapper = applicationContext.getBean("departmentMapper", DepartmentMapper.class);
        Map map = new HashMap();
        map.put("name","研发部");
        map.put("location","上海");
        List<Department> list = departmentMapper.selectByMap(map);
        for (Department department : list) {
            System.out.println(department);
        }
    }

    /**
     * 根据 entity 条件，查询一条记录
     * 实体对象封装操作类（可以为 null）
     */
    @Test
    public void testselectOne(){
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("bean.xml");
        DepartmentMapper departmentMapper = applicationContext.getBean("departmentMapper", DepartmentMapper.class);
        Department department = departmentMapper.selectOne(new QueryWrapper<Department>().gt("id",10));
        System.out.println(department);
    }

    /**
     * 根据 Wrapper 条件，查询总记录数
     * 实体对象封装操作类（可以为 null）
     */
    @Test
    public void testselectCount(){
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("bean.xml");
        DepartmentMapper departmentMapper = applicationContext.getBean("departmentMapper", DepartmentMapper.class);
        int count = departmentMapper.selectCount(null);
        System.out.println(count);
    }

    /**
     * 根据 entity 条件，查询全部记录
     *
     * 实体对象封装操作类（可以为 null）
     */
    @Test
    public void testselectList(){
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("bean.xml");
        DepartmentMapper departmentMapper = applicationContext.getBean("departmentMapper", DepartmentMapper.class);
        List<Department> list = departmentMapper.selectList(null);
        for (Department department : list) {
            System.out.println(department);
        }
    }

    /**
     * 根据 Wrapper 条件，查询全部记录
     *
     *  实体对象封装操作类（可以为 null）
     */
    @Test
    public void testselectMaps(){
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("bean.xml");
        DepartmentMapper departmentMapper = applicationContext.getBean("departmentMapper", DepartmentMapper.class);
        List<Map<String,Object>> list = departmentMapper.selectMaps(new QueryWrapper<Department>().ne("id",100));
        for (Map<String, Object> stringObjectMap : list) {
            System.out.println(stringObjectMap);
        }
    }

    /**
     * 根据 Wrapper 条件，查询全部记录
     * <p>注意： 只返回第一个字段的值</p>
     *
     * 实体对象封装操作类（可以为 null）
     */
    @Test
    public void testselectObjs(){
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("bean.xml");
        DepartmentMapper departmentMapper = applicationContext.getBean("departmentMapper", DepartmentMapper.class);
        List<Object> list = departmentMapper.selectObjs(null);
        System.out.println(list);
    }

    /**
     * 分页查询
     */
    @Test
    public void testselectpage(){
        ApplicationContext applicationContext = new ClassPathXmlApplicationContext("bean.xml");
        DepartmentMapper departmentMapper = applicationContext.getBean("departmentMapper", DepartmentMapper.class);
        PageHelper.startPage(1,2);
        List<Department> list = departmentMapper.selectList(null);
        System.out.println(list);
    }