mybatis-plus学习（一）

java后端指南

发布于 2021-05-13 14:22:13

2760

发布于 2021-05-13 14:22:13

文章被收录于专栏：java后端java后端

今日主题:mybatis-plus

简介

mybatis-plus是mybatis的增强款，封装很多常见的CRUD等其他方法，非常好用，我知道他的原因是因为公司后端持久层就是在他的基础上进行封装的，所以我就学习了一下，还是非常不错的，分多期来写吧

环境

IDEA
springboot
maven3
mysql5.7

开始

1.首先需要准备一张表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)
);

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');

2.创建一个springboot初始化工程

根据需要选择

完整pom.xml:(大家可以根据需要添加坐标)

<?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 https://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>2.3.4.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.king</groupId>
    <artifactId>mybatis_plus</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>mybatis_plus</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
     <dependency>
     <groupId>com.baomidou</groupId>
     <artifactId>mybatis-plus-boot-starter</artifactId>
      <version>3.3.1.tmp</version>
  </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
    </dependencies>

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

</project>

3.在application.yml中配置mysql数据源

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    username: root
    password: 123456
    url: jdbc:mysql://localhost:3306/mybatis?useUnicode=true&characterEncoding=utf8&serverTimezone=UTC

4.编写表对应的实体类User

@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {
    private Long Id;
    private String name;
    private Integer age;
    private String email;
}

5.编写操作实体类的 Mapper 类，直接继承 BaseMapper，这是 mybatis-plus 封装好的类。

6.先得在启动类里扫描 Mapper 类，即添加 @MapperScan 注解

@SpringBootApplication
//mapper类所在的目录路径
@MapperScan("com.king.mybatis_plus.mapper")
public class MybatisPlusApplication {

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

}

7.编写测试类

@SpringBootTest
class MybatisPlusApplicationTests {
    @Autowired(required = false)
    private UserMapper userMapper;

    /**
     * 查询
     */
    @Test
    public void testSelect(){
        /*查询所有的数据UserMapper
        中的 selectList() 方法的参数为 MP 内置的条件封装器 Wrapper，
        所以不填写就是无任何条件*/
        List<User> list=userMapper.selectList(null);
        for (User user:list){
            System.out.println(user);
        }

        //根据主键查询
        System.out.println("记录：");
        System.out.println(userMapper.selectById(1));
    }

    /**
     * 添加
     */
    @Test
    public void testInsert(){
        //主键会自动生成
        User user=new User();
        user.setName("king");
        user.setAge(20);
        user.setEmail("123456@qq.com");
        System.out.println("插入结果："+userMapper.insert(user));
    }
    /**
     * 删除
     */
    @Test
    public void testDelete(){
        System.out.println("删除结果："+userMapper.deleteById(1));
    }

    /**
     * 修改
     */
    @Test
    public void testUpdate(){
        User user=new User();
        user.setId(2L);
        user.setName("ting");
        user.setAge(30);
        user.setEmail("2345@qq.com");
        System.out.println("修改结果："+userMapper.updateById(user));
    }
}

好的，到这里简单的CRUD就好了,咋们下期再见。

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原始发表：2020-10-31，如有侵权请联系 cloudcommunity@tencent.com 删除

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