MyBatis-Plus实现数据库CRUD

• MyBatis-Plus是一个MyBatis的增强工具
• 自动实现Mapper CRUD操作，极致提高数据库开发效率
• MyBatis-Plus在MyBatis的基础上制作增强不做改变
• 官方文档

一、整合步骤

1. 引入mybatis-plus依赖

pom.xml

<dependencies>
    <!-- 1.引入mybatis-plus依赖 -->
    <dependency>
        <groupId>com.baomidou</groupId>
        <artifactId>mybatis-plus</artifactId>
        <version>3.3.2</version>
    </dependency>
</dependencies>

2. Spring XML更改配置SqlSessionFactory实现类

applicationContext.xml

<beans ... >
    <!--
        原生Mybatis与Spring整合
        <bean id="sessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
    -->
    <!-- 2.更改配置SqlSessionFactory实现类 -->
    <bean id="sessionFactory" class="com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean">
        <property name="driverClassName" value="com.mysql.cj.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://localhost:3306/databasename?useSSL=false&useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai"/>
        <property name="username" value="root"/>
        <property name="password" value="password"/>
        <property name="initialSize" value="5"/>
        <property name="maxActive" value="20"/>
    </bean>
</beans>

3. mybatis-config.xml增加MyBatis-plus分页插件

mybatis-config.xml

<configuration>
    <plugins>
        <!-- 3.配置Mybatis-plus分页插件 -->
        <plugin interceptor="com.baomidou.mybatisplus.extension.plugins.PaginationInterceptor"></plugin>
    </plugins>
</configuration>

二、开发步骤

1. 创建实体类，使用@TableName、@TableId、@TableField注解实现与表字段的映射

核心注解

• @TableName 将实体类与表名映射

• @TableId 说明对应属性是表的主键

• @TableField 设置属性与列名的对应关系

..entity.Test

@TableName("test") // 说明实体对应哪一张表
public class Test {
    @TableId(type = IdType.AUTO) // 主键
    @TableField("id") // 说明属性对应哪个字段
    private Integer id;
    // 如果字段名与属性名相同或符合驼峰命名转换规则，则可以省略TableField
    // @TableField("content")
    private String content;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }
}

2. 创建Mapper接口继承BaseMapper，创建Mapper XML

..mapper.TestMapper

public interface TestMapper extends BaseMapper<Test> {
    public void insertSample();//自定义insert方法
}

..mappers/test.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="..mapper.TestMapper">
    <!-- 自定义insert方法SQL语句 -->
    <insert id="insertSample">
        insert into test(content) values ('测试内容')
    </insert>
</mapper>

3. 开发时注入Mapper对象，通过内置API实现CRUD操作

核心API

测试用例

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = {"classpath:applicationContext.xml"})
public class MyBatisPlusTest {
    @Resource
    private TestMapper testMapper;

    @org.junit.Test
    public void testInsert (){
        Test test = new Test();
        test.setContent("MyBatis Plus测试内容");
        testMapper.insert(test);
    }

    @org.junit.Test
    public void testUpdate (){
        Test test = testMapper.selectById(16);
        test.setContent("新的MyBatis Plus测试内容");
        testMapper.updateById(test);
    }

    @org.junit.Test
    public void testDelete (){
        testMapper.deleteById(16);
    }

    @org.junit.Test
    public void testSelect (){
        QueryWrapper<Test> queryWrapper = new QueryWrapper<Test>();
        //QueryWrapper条件生成器：.eq()等于 .gt()大于
        queryWrapper.eq("id", 20);
        //queryWrapper.gt("id", 20);
        List<Test> list = testMapper.selectList(queryWrapper);
        System.out.println(list.get(0));
    }
}