mybatis-plus入门


mybatis-plus简介

快速入门

创建数据库

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#创建用户表
CREATE TABLE user (
    id BIGINT(20) PRIMARY KEY NOT NULL COMMENT '主键',
    name VARCHAR(30) DEFAULT NULL COMMENT '姓名',
    age INT(11) DEFAULT NULL COMMENT '年龄',
    email VARCHAR(50) DEFAULT NULL COMMENT '邮箱',
    manager_id BIGINT(20) DEFAULT NULL COMMENT '直属上级id',
    create_time DATETIME DEFAULT NULL COMMENT '创建时间',
    CONSTRAINT manager_fk FOREIGN KEY (manager_id)
        REFERENCES user (id)
)  ENGINE=INNODB CHARSET=UTF8;

#初始化数据：
INSERT INTO user (id, name, age, email, manager_id
    , create_time)
VALUES (1087982257332887553, '大boss', 40, '[email protected]', NULL
        , '2019-01-11 14:20:20'),
    (1088248166370832385, '王天风', 25, '[email protected]', 1087982257332887553
        , '2019-02-05 11:12:22'),
    (1088250446457389058, '李艺伟', 28, '[email protected]', 1088248166370832385
        , '2019-02-14 08:31:16'),
    (1094590409767661570, '张雨琪', 31, '[email protected]', 1088248166370832385
        , '2019-01-14 09:15:15'),
    (1094592041087729666, '刘红雨', 32, '[email protected]', 1088248166370832385
        , '2019-01-14 09:48:16');

pom.xml

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<?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>2.3.0.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.chaolong</groupId>
    <artifactId>first</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>first</name>
    <description>Demo project for Spring Boot</description>

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

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</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>

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

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

</project>

domian下的User.class

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package com.chaolong.first.domian;

import lombok.Data;

import java.util.Date;

/**
 * @author: Chaolong
 * @create: 2020/06/07
 **/
@Data
public class User {
    private Long id;
    private String name;
    private Integer age;
    private String email;
    // 上级ID
    private Long managerId;
    private Date createTime;
}

dao下的UserMapper.class

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package com.chaolong.first.dao;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.chaolong.first.domian.User;


/**
 * @author: Chaolong
 * @create: 2020/06/07
 **/
public interface UserMapper extends BaseMapper<User> {
}

配置文件 application.yml

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spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&characterEncoding=utf8&useSSL=true&serverTimezone=UTC
    username: root
    password: 123456

启动类 （application.class）

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package com.chaolong.first;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
@MapperScan("com.chaolong.first.dao") // 指定扫描Mapper接口的包路径
public class Application {

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

}

测试 ApplicationTests.class

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package com.chaolong.first;

import com.chaolong.first.dao.UserMapper;
import com.chaolong.first.domian.User;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import java.util.List;

@SpringBootTest
class ApplicationTests {

    @Autowired
    private UserMapper userMapper;
    @Test
    void select() {
        List<User> users = userMapper.selectList(null);
        //users.forEach(System.out::println);
        users.forEach((user)->{
            System.out.println(user);
        });
    }

}

插入操作

application.yml 添加开启sql语句显示

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mybatis-plus:
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl # 开启sql 语句日志显示

insertTest.class

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@SpringBootTest
class InsertTest {

    @Autowired
    private UserMapper userMapper;
    @Test
    void insert() {
        User user = new User();
        user.setName("向dong");
        user.setAge(40);
        user.setManagerId(1088248166370832385L);
        user.setCreateTime(new Date());
        userMapper.insert(user);
    }

}

@TableName @TableId @TableField

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@Data
@TableName("user_2")  // 与数据库中的哪一张表进行映射
public class User {
    @TableId("id")
    private Long id;
    @TableField("name")  // 与表中的字段进行映射
    private String name;
    private Integer age;
    private String email;
    // 上级ID
    private Long managerId;
    private Date createTime;
}

排除非表字段

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@TableField(exist =false)
private int flag;

查询操作

普通查询

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/**
 * 根据 ID 查询
 *
 * @param id 主键ID
 */
T selectById(Serializable id);

/**
 * 查询（根据ID 批量查询）
 *
 * @param idList 主键ID列表(不能为 null 以及 empty)
 */
List<T> selectBatchIds(@Param(Constants.COLLECTION) Collection<? extends Serializable> idList);

/**
 * 查询（根据 columnMap 条件）
 *
 * @param columnMap 表字段 map 对象
 */
List<T> selectByMap(@Param(Constants.COLUMN_MAP) Map<String, Object> columnMap);
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@SpringBootTest
class SelectTest {

    @Autowired
    private UserMapper userMapper;

    @Test
    void selectById() {
        User user = userMapper.selectById(1269485636327424002L);
        System.out.println(user);
        // SELECT id,name,age,email,manager_id,create_time FROM user WHERE id=?
    }

    @Test
    void selectByIds() {
        List<Long> idList = Arrays.asList(1094590409767661570L, 1088248166370832385L, 1269485636327424002L);
        List<User> users = userMapper.selectBatchIds(idList);
        users.forEach(System.out::println);
        // SELECT id,name,age,email,manager_id,create_time FROM user WHERE id IN ( ? , ? , ? )
    }

    @Test
    void selectByMap() {
        Map<String,Object> map = new HashMap<>();
        map.put("name","向南");  // key 为数据库中的字段
        map.put("age","20");
        List<User> users = userMapper.selectByMap(map);
        users.forEach(System.out::println);
        //  SELECT id,name,age,email,manager_id,create_time FROM user WHERE name = ? AND age = ?
    }


}

以条件构造器为参数的查询

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/**
 * 根据 entity 条件，查询全部记录
 *
 * @param queryWrapper 实体对象封装操作类（可以为 null）
 */
List<T> selectList(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper);
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  /**
     * 1、名字中包含雨并且年龄小于40
     * name like '%雨%' and age<40
     */
    @Test
    void select1() {
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        wrapper.like("name", "雨").lt("age", 40);
        List<User> users = userMapper.selectList(wrapper);
        users.forEach(System.out::println);
        //==>  Preparing: SELECT id,name,age,email,manager_id,create_time FROM user WHERE (name LIKE ? AND age < ?)
        //==> Parameters: %雨%(String), 40(Integer)
    }

    /**
     * 2、名字中包含雨年并且龄大于等于20且小于等于40并且email不为空
     * name like '%雨%' and age between 20 and 40 and email is not null
     */
    @Test
    void select2() {
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        wrapper.like("name", "雨").between("age", 20, 40).isNotNull("email");
        List<User> users = userMapper.selectList(wrapper);
        users.forEach(System.out::println);
        //==>  Preparing: SELECT id,name,age,email,manager_id,create_time FROM user WHERE (name LIKE ? AND age BETWEEN ? AND ? AND email IS NOT NULL)
        //==> Parameters: %雨%(String), 20(Integer), 40(Integer)
    }


    /**
     * 3、名字为王姓或者年龄大于等于25，按照年龄降序排列，年龄相同按照id升序排列
     * name like '王%' or age>=25 order by age desc,id asc
     */
    @Test
    void select3() {
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        wrapper.likeRight("name", "王").or().gt("age", 25).orderByDesc("age").orderByAsc("id");
        List<User> users = userMapper.selectList(wrapper);
        users.forEach(System.out::println);
//        ==>  Preparing: SELECT id,name,age,email,manager_id,create_time FROM user WHERE (name LIKE ? OR age > ?) ORDER BY age DESC,id ASC
//==> Parameters: 王%(String), 25(Integer)
    }


    /**
     * 4、创建日期为2019年2月14日并且直属上级为名字为王姓
     * date_format(create_time,'%Y-%m-%d')='2019-02-14' and manager_id in (select id from user where name like '王%')
     */
    @Test
    void select4() {
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        wrapper.apply("date_format(create_time,'%Y-%m-%d')={0}", "2019-02-14").inSql("manager_id", "select id from user where name like '王%'");
        List<User> users = userMapper.selectList(wrapper);
        users.forEach(System.out::println);
//==>  Preparing: SELECT id,name,age,email,manager_id,create_time FROM user WHERE (date_format(create_time,'%Y-%m-%d')=? AND manager_id IN (select id from user where name like '王%'))
//==> Parameters: 2019-02-14(String)
    }


    /**
     * 5、名字为王姓并且（年龄小于40或邮箱不为空）
     * name like '王%' and (age<40 or email is not null)
     */
    @Test
    void select5() {
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        wrapper.likeRight("name", "王").and((qw) -> {
            qw.lt("age", 40).or().isNotNull("email");
        });
        List<User> users = userMapper.selectList(wrapper);
        users.forEach(System.out::println);
//==>  Preparing: SELECT id,name,age,email,manager_id,create_time FROM user WHERE (name LIKE ? AND (age < ? OR email IS NOT NULL))
//==> Parameters: 王%(String), 40(Integer)
    }

    /**
     * 6、名字为王姓或者（年龄小于40并且年龄大于20并且邮箱不为空）
     * name like '王%' or (age<40 and age>20 and email is not null)
     */
    @Test
    void select6() {
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        wrapper.likeRight("name", "王").or((qw) -> {
            qw.between("age", 20, 40).isNotNull("email");
        });
        List<User> users = userMapper.selectList(wrapper);
        users.forEach(System.out::println);
//==>  Preparing: SELECT id,name,age,email,manager_id,create_time FROM user WHERE (name LIKE ? OR (age BETWEEN ? AND ? AND email IS NOT NULL))
//==> Parameters: 王%(String), 20(Integer), 40(Integer)
    }

    /**
     * 7、（年龄小于40或邮箱不为空）并且名字为王姓
     * (age<40 or email is not null) and name like '王%'
     */
    @Test
    void select7() {
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        wrapper.nested((qw) -> {
            qw.lt("age", 40).or().isNotNull("email");
        }).likeRight("name", "王");
        List<User> users = userMapper.selectList(wrapper);
        users.forEach(System.out::println);
//==>  Preparing: SELECT id,name,age,email,manager_id,create_time FROM user WHERE ((age < ? OR email IS NOT NULL) AND name LIKE ?)
//==> Parameters: 40(Integer), 王%(String)
    }

    /**
     * 8、年龄为30、31、34、35
     * age in (30、31、34、35)
     */
    @Test
    void select8() {
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        wrapper.in("age", Arrays.asList(31, 30, 34, 35));
        List<User> users = userMapper.selectList(wrapper);
        users.forEach(System.out::println);
//==>  Preparing: SELECT id,name,age,email,manager_id,create_time FROM user WHERE (age IN (?,?,?,?))
//==> Parameters: 31(Integer), 30(Integer), 34(Integer), 35(Integer)
    }

    /**
     * 9、只返回满足条件的其中一条语句即可
     * limit 1
     */
    @Test
    void select9() {
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        wrapper.last("limit 1"); // 有sql注入风险
        List<User> users = userMapper.selectList(wrapper);
        users.forEach(System.out::println);
//==>  Preparing: SELECT id,name,age,email,manager_id,create_time FROM user limit 1

    }

select中字段不全出现的处理方法

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    /**
     * 10、名字中包含雨并且年龄小于40(需求1加强版)
     * 第一种情况：select id,name
     * from user
     * where name like '%雨%' and age<40
     */
    @Test
    void select1Supper() {
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        wrapper.like("name", "雨").lt("age", 40).select("id", "name");
        List<User> users = userMapper.selectList(wrapper);
        users.forEach(System.out::println);
//==>  Preparing: SELECT id,name FROM user WHERE (name LIKE ? AND age < ?)
//==> Parameters: %雨%(String), 40(Integer)
    }

    /**
     * 第二种情况：select id,name,age,email
     * from user
     * where name like '%雨%' and age<40
     */
    @Test
    void select2Supper() {
        QueryWrapper<User> wrapper = new QueryWrapper<>();
        wrapper.select(User.class, (info) -> {
            return !info.getColumn().equals("create_time")&&!info.getColumn().equals("manager_id");
        }).like("name", "雨").lt("age", 40);
        List<User> users = userMapper.selectList(wrapper);
        users.forEach(System.out::println);
       
//==>  Preparing: SELECT id,name,age,email FROM user WHERE (name LIKE ? AND age < ?)
//==> Parameters: %雨%(String), 40(Integer)
    }