mybatis-plus快速查阅

你的名字 2022-12-24 12:57 291阅读 0赞

## 快速入门 ##

maven构建的springboot项目  
pom.xml

<?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>com.qj</groupId>
        <artifactId>mybatiesPlus</artifactId>
        <version>1.0-SNAPSHOT</version>
    
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.1.3.RELEASE</version>
            <relativePath/>
        </parent>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
            </dependency>
            <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>4.13</version>
            </dependency>
    
            <dependency>
                <groupId>com.baomidou</groupId>
                <artifactId>mybatis-plus-boot-starter</artifactId>
                <version>3.1.0</version>
            </dependency>
    
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>5.1.22</version>
            </dependency>
        </dependencies>
    </project>

application.yml

spring.datasource.driver-class-name : com.mysql.jdbc.Driver
    spring.datasource.url : jdbc:mysql://localhost:3306/bm?useUnicode=true&characterEncoding=utf8&serverTimezone=GMT
    spring.datasource.username : root
    spring.datasource.password : qianjiang

实体类：pojo

public class User implements Serializable {
        private int id;
        private String username;
        private String password;
        private String updateByLast;
        private String creatByTime;
     }

set和get方法自己补充  
然后**注意一点**：  
字段无法映射到对应的实体上，可能是需要用驼峰命名规则  
dao层：

public interface IUserMapper extends BaseMapper<User> {
    
    
    }

springboot启动类：

@SpringBootApplication
    @MapperScan("com.qj.dao")
    public class Application {
        public static void main(String[] args) {
            SpringApplication.run(Application.class,args);
        }
    }

测试类：

@RunWith(SpringRunner.class)
    @SpringBootTest
    public class SimpleTest {
    
        @Autowired(required=false)
        private IUserMapper iUserMapper;
    
        @Test
        public void select(){
            System.out.println(iUserMapper.selectList(null).stream().collect(Collectors.toList()));
    
        }
    }

查询出来出现![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDA5MzcxMQ_size_16_color_FFFFFF_t_70]

一切正常。这样查询出来的结果为：  
![在这里插入图片描述][20201128141925601.png]  
项目结构：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDA5MzcxMQ_size_16_color_FFFFFF_t_70 1]

下面可以进入学习了

## 基本使用 ##

以前ssm中，  
接口中写抽象方法–>xml或者注解写sql–>Service中调用接口–>Controller中调用service  
下面增加日志输出功能，让我们可以看到sql详细日志：  
application.yml:

新增一名用户：

//增加一名用户
        @Test
        public void insert(){
            Date date = new Date();
            SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
            String d = simpleDateFormat.format(date);
            User user = new User();
            user.setUsername("皮皮虾");
            user.setPassword("30193093");
            user.setUpdateByLast(d);
            user.setCreatByTime(d);
    
            int i = iUserMapper.insert(user);
            System.out.println("影响记录数:"+i);
        }

**如果表和我的实体类没有对应**  
注解@TableName()  
在实体上面

@TableName("t_user")
    public class User(){
    
    }

**主键id名和我表中id名不一致：**

@Tableld
    private int userId;

**表的字段名与我类的属性名不一致**

@TableField("name")
    private String realName;

**表中没有字段，我要增加一个怎么操作？**

排除 数据库非字段的三种方式（怎么增加一列）  
1、

private transient String flag;

**表中没有此字段，加上这个注解，解决在表中找不到这个字段名**

2、

private static String flag;
    
        public static void setFlag(String flag) {
            User.flag = flag;
        }
    
        public static String getFlag() {
            return flag;
        }

**表中没有此字段，加上这个注解，解决在表中找不到这个字段名**  
3、

@TableField(exist = false)
       private String flag;

**表中没有此字段，加上这个注解，解决在表中找不到这个字段名**

## 查询,通用Mapper ##

**普通查询：**  
1、根据id来查出一个用户的信息  
**selectById**  
==> Preparing: SELECT id,username,password,update\_by\_last,creat\_by\_time FROM user WHERE id=?  
==> Parameters: 12(Integer)

//根据id来查询
        @Test
        public void selectById(){
           User user =  iUserMapper.selectById(12);
            System.out.println(user);
        }

2、根据多个id查出多个用户的信息  
**selectBatchIds**  
==> Preparing: SELECT id,username,password,update\_by\_last,creat\_by\_time FROM user WHERE id IN ( ? , ? , ? )  
==> Parameters: 12(Integer), 13(Integer), 14(Integer)

//根据多个id来查询多个用户信息
        @Test
        public void selectByIds(){
            List<User> userList =iUserMapper.selectBatchIds(Arrays.asList(12,13,14));
            userList.forEach(System.out::println);
        }

3、selectByMap()  
多个条件查询  
**返回的是 List**  
==> Preparing: SELECT id,username,password,update\_by\_last,creat\_by\_time FROM user WHERE id = ? AND username = ?  
==> Parameters: 12(Integer), xia(String)

@Test
        public void selectMap(){
            //map.put("name","xia");
            //map.put("id",12);
            Map<String,Object> columnMap = new HashMap<String,Object>();/**/string存的是数据库列名，对应即可**
            //根据姓名和id 查询
            columnMap.put("username","xia");
            columnMap.put("id",12);
            List<User> userList = iUserMapper.selectByMap(columnMap);
            userList.forEach(System.out::println);
        }

**条件构造器查询**  
1、selectList()  
适用于多个条件在一起稍微比较复杂的语句  
==> Preparing: SELECT id,username,password,update\_by\_last,creat\_by\_time FROM user WHERE username LIKE ? AND password > ?  
==> Parameters: %li%(String), 123(Integer)

@Test
        public void selectByWrapper(){
           List<User> userList = iUserMapper.selectList(new QueryWrapper<User>().like("username","li").gt("password",123));
            userList.forEach(System.out::println);
        }

举例1：查询用户名字包含雨，**年龄大于等于20且小于40**，并且email不为空

iUserMapper.selectList(new QueryWrapper<User>().
                    like("name","雨").
                    between("age",20,40).
                    isNotNull("email"));

举例2：名字为王姓或者年龄大于等于25，按照年龄降序排序，年龄相同按照id升序排列  
name like ‘王%’ or age >=40 order by age desc,id asc

iUserMapper.selectList(new QueryWrapper<User>().
                    likeRight("name","王")
                    .or().gt("age",23).
                            orderByDesc("age").
                            orderByAsc("id"));

例子：函数和子查询  
创建日期为2020年11月10号并且id 名字为王姓的用户信息  
data\_format(creat\_time,’%Y-%m-%d’) and manage\_id in (select id from user where name like ‘王%’)  
==> Preparing: SELECT id,username,password,update\_by\_last,creat\_by\_time FROM user WHERE date\_format(creat\_by\_time,’%Y-%m-%d’)=? AND id IN (select id from user where username like ‘a%’)  
==> Parameters: 2020-11-10(String)

@Test
        public void selectByWrapper(){
    
           iUserMapper.selectList(new QueryWrapper<User>().
                    apply("date_format(creat_by_time,'%Y-%m-%d')={0}","2020-11-10").
                   inSql("id","select id from user where username like 'a%'")).forEach(System.out::println);
    
        }

查询名字为li并且（年龄小于40或者邮箱不为空）  
name like ‘王%’ and (age<40 or email is not null)

iUserMapper.selectList(new QueryWrapper<User>().
                   likeRight("name","王").
                   and(s->s.lt("age",23).or().isNotNull("email")));

举例：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)

iUserMapper.selectList(new QueryWrapper<User>().
                   likeRight("name","王").
                   or(s->s.lt("age",40).gt("age",20).isNotNull("email")));

举例：（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%’

iUserMapper.selectList(new QueryWrapper<User>().
    //               likeRight("name","王").
    //               and(s->s.lt("age",40).or().isNotNull("email")));
            
       iUserMapper.selectList( new QueryWrapper<User>().
               nested(g->g.lt("age",40).or().isNotNull("email").
                       likeRight("name","王")));

举例：年龄为30、31、34、35  
age in (30、31、34、35)

iUserMapper.selectList(new QueryWrapper<User>().
               in("age",Arrays.asList(30,31,34,35)));

举例：只返回满足条件的其中一条语句即可  
limit 1;  
last，只能调用一次多次以最后一次为准，有sql注入的风险

iUserMapper.selectList(new QueryWrapper<User>().
               in("age",Arrays.asList(30,31,34,35)).last("limit 1"));

**select中字段不全出现的处理方法**  
不全部查出来 只查部分指定的字段

iUserMapper.selectList(new QueryWrapper<User>().select("id","username").
                    apply("date_format(creat_by_time,'%Y-%m-%d')={0}","2020-11-10").
                   inSql("id","select id from user where username like 'a%'")).forEach(System.out::println);
    System.out.println("------------------------------------");
     iUserMapper.selectList(new QueryWrapper<User>().
                    apply("date_format(creat_by_time,'%Y-%m-%d')={0}","2020-11-10").
                   inSql("id","select id from user where username like 'a%'").
                    select(User.class,s->!s.getColumn().equals("password")&&!s.getColumn().equals("update_by_last")&&!s.getColumn().equals("creat_by_time"))).
                    forEach(System.out::println);

**condition作用：**

public void condition(String name,String email){
    //        if(StringUtils.isEmpty(name)){
    //            iUserMapper.selectList(new QueryWrapper<User>().like("name",name));
    //            
    //        }
    //        if(StringUtils.isEmpty(email)){
    //            iUserMapper.selectList(new QueryWrapper<User>().like("email",email));
    //        }
            
            iUserMapper.selectList(new QueryWrapper<User>().
                    like(StringUtils.isEmpty(name),"name",name).
                    like(StringUtils.isEmpty(email),"name",name));
            
        }

**实体作为条件构造器构造方法的参数**  
==> Preparing: SELECT id,username,password,update\_by\_last,creat\_by\_time FROM user WHERE id=? AND username LIKE CONCAT(’%’,?,’%’)  
==> Parameters: 12(Integer), xia(String)

@TableField(condition = "%s<#{%s}")
        private int id;
        @TableField(condition = SqlCondition.LIKE)
        private String username;

@Test
        public void selectByWrapperEntity(){
            User user = new User();
            user.setId(12);
            user.setUsername("xia");
    
            iUserMapper.selectList(new QueryWrapper<User>(user)).forEach(System.out::println);
        }

**allEq用法**  
==> Preparing: SELECT id,username,password,update\_by\_last,creat\_by\_time FROM user WHERE password = ? AND username = ?  
==> Parameters: 123(String), admin(String)

==> Preparing: SELECT id,username,password,update\_by\_last,creat\_by\_time FROM user WHERE password IS NULL AND username = ?  
> Parameters: admin(String)  
< Total: 0

@Test
        public void selectByWrapperAllEq(){
            Map<String,Object> map = new HashMap<>();
            map.put("username","admin");
            map.put("password",null);
            QueryWrapper queryWrapper = new QueryWrapper();
            //queryWrapper.allEq(map,false);//忽略了password
            queryWrapper.allEq((k,v)->!k.equals("admin"),map);
            iUserMapper.selectList(queryWrapper).forEach(System.out::println);
    
        }

**其他使用条件构造器的方法**  
举例：按照id分组，查询每组的平均年龄、最大年龄、最小年龄。并且只取年龄总和小于500的组  
select avg(age),min(age),max(age) from user group by id having sum(age)<500

selectMaps  
结果\{key=value,key1 = value1…\}

@Test
        public void selectByWrapperMap(){
            iUserMapper.selectMaps(new QueryWrapper<User>().
                    select("avg(age) avg_age","min(age) min_age","max(age) max_age").
                    groupBy("id").
                    having("sum(age)<{0}",500)).forEach(System.out::println);
        }

selectObject  
只返回第一个字段的值

**查询总记录数**  
==> Preparing: SELECT COUNT( 1 ) FROM user  
==> Parameters:

@Test
        public void selectByWrapperCount(){
    //       QueryWrapper<User> queryWrapper = new QueryWrapper();
    //       queryWrapper.like("username","i").lt("age",40);;
    //       Integer count = iUserMapper.selectCount(queryWrapper);
    //        System.out.println("满足条件的记录数:"+count);
    
            Integer num =iUserMapper.selectCount(null);
            System.out.println("总记录数"+num);
        }

selectOne() 根据 entity 条件，**查询一条记录**，多条报错  
实体对象封装操作类（可以为 null）

User user =  iUserMapper.selectOne(new QueryWrapper<User>().like("username","admin"));
            System.out.println(user);

**lambda条件构造器**

@Test
        public void selectLambda(){
            iUserMapper.selectList(Wrappers.<User>lambdaQuery().like(User::getUsername,"min")).forEach(System.out::println);
        }

@Test
        public void selectByWrapperObject(){
            iUserMapper.selectObjs(new QueryWrapper<User>().
                    select("password","username").
                    like("username","min").
                    gt("password",11)).forEach(System.out::println);
    
            iUserMapper.selectObjs(Wrappers.<User>lambdaQuery().
                    select(User::getPassword,User::getUsername).
                    like(User::getUsername,"min").
                    gt(User::getPassword,11)).forEach(System.out::println);
        }

**LambdaQueryChainWrapper**

@Test
        public void selectLambda1(){
           new LambdaQueryChainWrapper<User>(iUserMapper).like(User::getUsername,"min").gt(User::getPassword,"111").list().forEach(System.out::println);
        }

## 自定义sql ##

**注解形式**

public interface IUserMapper extends BaseMapper<User> {
    
     @Select(" select * from user ${ew.customSqlSegment}")
     List<User> findAll(@Param(Constants.WRAPPER) LambdaQueryWrapper<User> wrappers);
    }

测试：

@Test
        public void findAll(){
            iUserMapper.findAll(Wrappers.<User>lambdaQuery().like(User::getUsername,"min")).forEach(System.out::println);
        }

**文件配置：**  
在src/main/java下建立UserMapper.xml文件  
（在com.qj.dao.mapper下）

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE mapper
            PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
            "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
    
    
    <mapper namespace="com.qj.dao.IUserMapper">
        
        <select id="findAll" resultType="com.qj.pojo.User">
            select * from user ${ew.customSqlSegment}
        </select>
    </mapper>

可以再pom.xml中配置这段：防止上面那段文件配置读不到！

这时候dao层接口写个方法了：所谓自定义一个sql语句

import com.baomidou.mybatisplus.core.conditions.query.LambdaQueryWrapper;
    import com.baomidou.mybatisplus.core.mapper.BaseMapper;
    import com.baomidou.mybatisplus.core.toolkit.Constants;
    import com.qj.pojo.User;
    import org.apache.ibatis.annotations.Param;
    
    import java.util.List;
    
    
    public interface IUserMapper extends BaseMapper<User> {
    
     List<User> findAll(@Param(Constants.WRAPPER) LambdaQueryWrapper<User> wrappers);
    }

测试：

@Test
        public void findAll(){
            iUserMapper.findAll(Wrappers.<User>lambdaQuery().like(User::getUsername,"min")).forEach(System.out::println);
        }

主配置application.yml后面再加上一句：

mybatis-plus.mapper-locations: classpath*:com/qj/mapper/*

打印结果：

==>  Preparing: select * from user WHERE username LIKE ? 
    ==> Parameters: %min%(String)
    <==    Columns: id, username, password, usertype, update_by_user, update_by_last, creat_by_user, creat_by_time
    <==        Row: 1, admin, 123, 0, System, 2020-11-10 15:31:21.0, System, 2020-11-10 15:31:36.0
    <==      Total: 1

项目目录如下：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDA5MzcxMQ_size_16_color_FFFFFF_t_70 2]

## 分页 ##

mybatis分页介绍  
MP分页插件插件物理分页（重要）  
**如果不配置PaginationInterceptor，MP提供的分页方法是无效的**  
在建立一层包叫com.qj.configuration,我们配置它

package com.qj.configuration;
    
    import com.baomidou.mybatisplus.extension.plugins.PaginationInterceptor;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.Configuration;
    
    @Configuration
    public class MybatisPlusConfig {
    
        @Bean
        public PaginationInterceptor paginationInterceptor(){
            return new PaginationInterceptor();
        }
    }

测试：  
返回的实体数据

@Test
        public void selectPage(){
            QueryWrapper<User> queryWrapper = new QueryWrapper<>();
            queryWrapper.ge("password","11");
            Page<User> page = new Page<User>(1,2);//当前1页,每页显示两条数据
    
            IPage<User> iPage=iUserMapper.selectPage(page,queryWrapper);
    
            System.out.println("总页数"+iPage.getPages());//总页数4
            System.out.println("总记录数"+iPage.getTotal());//总记录数7
    
            iPage.getRecords().forEach(System.out::println);
    
    
        }

返回的map集合数据

IPage<Map<String,Object>> iPage= iUserMapper.selectMapsPage(page,queryWrapper);
            System.out.println("总记录数"+iPage.getTotal());
            System.out.println("总页数"+iPage.getPages());
            iPage.getRecords().forEach(System.out::println);
    
    {password=1234, update_by_last=2020-11-11 08:15:11.0, creat_by_time=2020-11-11 08:15:11.0, id=3, username=liyang}
    {password=1212, update_by_last=2020-11-11 09:00:50.0, creat_by_time=2020-11-11 09:00:50.0, id=11, username=py}

不查询总记录数和总页数（懒加载的实现）

Page<User> page = new Page<User>(2,2,false);//当前1页,每页显示两条数据

**注意：**  
mp自带的crud操作是针对单表操作的，如果操作多表，自己定义sql。  
举例：  
xml写法

<select id="mySelectList" resultType="User">     
        select u.*,r.role_name 
        from user u inner join role r 
        on u.role_id = r.role_id 
        ${ew.customSqlSegment}
    </select>

对应的mapper接口中的方法定义：

List<User> mySelectList(@Param(Constants.WRAPPER) Wrapper<User> wrapper);

返回值可以是VO。也可以是实体类，但要要记住，如果用实体类接返回值，实体中非该实体对应表的数据库字段的属性上要标注@TableField(exist = false)，如果使用了条件构造器，条件构造器的字段名别忘了带别名。

## 更新 ##

根据id更新

@Test
        public void updateById(){
            User user = new User();
            //根据id来更改
            user.setId(1);
            user.setPassword("123123");
            int row=iUserMapper.updateById(user);
            System.out.println("影响记录数:"+row);
        }
    ==>  Preparing: UPDATE user SET password=? WHERE id=? 
    ==> Parameters: 123123(String), 1(Integer)
    <==    Updates: 1
    影响记录数:1

以条件构造器作为参数的更新方法

==> Preparing: UPDATE user SET username=?, creat\_by\_time=? WHERE username = ? AND creat\_by\_user = ?  
> Parameters: xiaLi(String), 2020-11-29 01-38-39(String), xia(String), xia(String)  
< Updates: 1

@Test
        public void updateWrapper(){
            UpdateWrapper<User> userUpdateWrapper = new UpdateWrapper<>();
            userUpdateWrapper.eq("username","xia").eq("creat_by_user","xia");
            User user = new User();
            user.setUsername("xiaLi");
            String time = LocalDateTime.now().format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH-mm-ss"));
            user.setCreatByTime(time);
                int row =iUserMapper.update(user,userUpdateWrapper);
            System.out.println("影响记录数:"+row);
        }
        影响记录数:1

**简化下设置列属性值：**  
都是数据库列名  
==> Preparing: UPDATE user SET password=?,creat\_by\_time=? WHERE username = ?  
> Parameters: 938103(String), 2020-11-29 01-48-46(String), xiaLi(String)  
< Updates: 1  
影响记录数:1

@Test
        public void updateWrapper2(){
            UpdateWrapper<User> userUpdateWrapper = new UpdateWrapper<>();
            String time = LocalDateTime.now().format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH-mm-ss"));
            userUpdateWrapper.eq("username","xiaLi").set("password","938103").set("creat_by_time",time);
    
            int row =iUserMapper.update(null,userUpdateWrapper);
            System.out.println("影响记录数:"+row);
        }

条件构造器中set方法使用

@Test
        public  void updateLambada(){
            LambdaUpdateWrapper<User> lambdaUpdateWrapper = new LambdaUpdateWrapper<>();
            lambdaUpdateWrapper.eq(User::getId,"13").set(User::getUsername,"豆皮江爱喝茶");
    
            int row =iUserMapper.update(null,lambdaUpdateWrapper);
            System.out.println("影响记录数"+row);
        }

@Test
        public  void updateLambada2(){
         //LambdaUpdateChainWrapper<User> lambdaUpdateChainWrapper = new LambdaUpdateChainWrapper<User>(iUserMapper);
          // LambdaUpdateWrapper<User> lambdaUpdateWrapper = new LambdaUpdateWrapper<>();
         //LambdaUpdateWrapper<User> lambdaUpdateWrapper2=Wrappers.<User>lambdaUpdate();
    
          boolean idUpdate=  new LambdaUpdateChainWrapper<User>(iUserMapper).eq(User::getId,"14").set(User::getPassword,"0938492").update();
          if(idUpdate){
              System.out.println("更新成功");
          }else{
              System.out.println("更新失败");
          }
          
        }

## 删除 ##

根据id删除

@Test
        public void deleteById(){
           int row = iuserMapper.deleteById(1);
            System.out.println("影响记录数:"+row);
        }

批量删除

@Test
        public void deleteBatchIds(){
            int rows=iuserMapper.deleteBatchIds(Arrays.asList(1,12,13));
            System.out.println("删除记录数:"+rows);
        }

其他普通删除方法

@Test
        public void deleteByMap(){
            Map<String,Object> map = new HashMap<>();
            map.put("username","皮皮虾");
            map.put("password","0938492");
            int row =iuserMapper.deleteByMap(map);
            System.out.println("影响记录数:"+row);
        }

以条件构造器为参数的删除方法  
==> Preparing: DELETE FROM user WHERE username = ? OR password = ?  
> Parameters: py(String), 0938492(String)  
< Updates: 2  
影响记录数:2

@Test
        public void delete(){
            LambdaQueryWrapper<User> lambdaQueryWrapper =Wrappers.<User>lambdaQuery();
            lambdaQueryWrapper.eq(User::getUsername,"py").or().eq(User::getPassword,"0938492");
    
            int rows =iuserMapper.delete(lambdaQueryWrapper);
            System.out.println("影响记录数:"+rows);
    
        }

## AR模式 ##

AR即为ActiveRecord,是一种领域模型模式，一个模型类对应一个表。通过实体类对象直接进行表的CRUD操作。  
==> Preparing: INSERT INTO user ( id, username, password, update\_by\_last, creat\_by\_time ) VALUES ( ?, ?, ?, ?, ? )  
> Parameters: 0(Integer), 豆皮江(String), 731993(String), 2020-11-29 11-57-23(String), 2020-11-29 11-57-23(String)  
< Updates: 1  
true  
**此时的user类需要继承：**

Model<User>

public class User extends Model<User> implements Serializable {
    
        private int id;
        private String username;
        private String password;
        private String updateByLast;
        private String creatByTime;
    }

测试类中不需要用iUserMapper

@SpringBootTest
    @RunWith(SpringRunner.class)
    public class ARTest {
    
        @Test
        public void insert(){
            User user = new User();
            user.setUsername("豆皮江");
            user.setPassword("731993");
            String time = LocalDateTime.now().format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH-mm-ss"));
            user.setCreatByTime(time);
            user.setUpdateByLast(time);
    
            boolean idInsert=user.insert();
            System.out.println(idInsert);
        }
        @Test
        public void delete(){
            User user = new User();
            user.setId(14);
            boolean isDelete =user.deleteById();
            System.out.println(isDelete);
        }
    
        @Test
        public void update(){
            User user = new User();
            user.setId(2);
            user.setUsername("豆皮皮豆");
            Boolean isUpdate =user.updateById();
            System.out.println(isUpdate);
        }
        @Test
        public void select(){
            User user = new User();
            user.setId(2);
            User user1 =user.selectById();
            System.out.println(user1);
            System.out.println(user==user1);//false
        }
     }

增加或更新，如果存在ID就更新，没有就增加

@Test
        public void insertOrUpdate(){
            User user = new User();
    //        user.setId(2);//表中存在
    //        user.setUsername("豆豆皮皮");//修改了username的值
    
            user.setUsername("皮皮豆豆");//表中不存在,添加
            String time = LocalDateTime.now().format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH-mm-ss"));
            user.setUpdateByLast(time);//添加
            user.setCreatByTime(time);//添加
            user.setPassword("810314");//添加
            boolean isInsertOrUpdate =user.insertOrUpdate();
            System.out.println(isInsertOrUpdate);
        }

## 策略实现 ##

局部策略实现

在实体类中 ID属性加注解
    @TableId(type = IdType.AUTO) 主键自增 数据库中需要设置主键自增
    private Long id;
    @TableId(type = IdType.NONE) 默认 跟随全局策略走
    private Long id;
    @TableId(type = IdType.UUID) UUID类型主键
    private Long id;
    @TableId(type = IdType.ID_WORKER) 数值类型  数据库中也必须是数值类型 否则会报错
    private Long id;
    @TableId(type = IdType.ID_WORKER_STR) 字符串类型   数据库也要保证一样字符类型
    private Long id;
    @TableId(type = IdType.INPUT) 用户自定义了  数据类型和数据库保持一致就行
    private Long id;

@TableId(type = IdType.UUID)
        private String id;

@Test
        public void insert(){
            User user = new User();
            user.setUsername("豆皮江种子2");
            user.setPassword("2731993");
            String time = LocalDateTime.now().format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH-mm-ss"));
            user.setCreatByTime(time);
            user.setUpdateByLast(time);
    
            boolean idInsert=user.insert();
            System.out.println(idInsert);
            System.out.println(user.getId());//fc51a6f49e31ee6a11c9f709e2009b84
        }

@TableId(type = IdType.ID_WORKER_STR)
        private String id;

@Test
        public void insert(){
            User user = new User();
            user.setUsername("豆皮江种子3");
            user.setPassword("273199332");
            String time = LocalDateTime.now().format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH-mm-ss"));
            user.setCreatByTime(time);
            user.setUpdateByLast(time);
    
            boolean idInsert=user.insert();
            System.out.println(idInsert);//true
            System.out.println(user.getId());//1332908750356824066
        }

全局策略实现

mybatis-plus.mapper-locations: -com/mp/mapper/*
    global-config.db-config.id-type: uuid或者/none/或者input/或者id_worker/或者id_worker_str/或者auto

注意：**以下三种类型，只有当插入对象id为空，自动填充**  
全局唯一Id(ID\_WORKER)  
全局唯一id(UUID)  
字符串全局唯一ID\_WORKER\_STR  
**表示全局主键都采用该策略（如果全局策略和局部策略都有设置，局部策略优先级高）**

## 基本配置 ##

之前表与实体不对应，这里可以配置它的全局设置了

mybatis-plus.global-config.db-config.table-prefix: t_user

配置mybatis

mybatis-plus:
      mapper-locations: -com/mp/mapper/*
      config-location: classpath:mybatis-config.xml

在resource下建立mybatis-config.xml文件  
tyeAliasesPackage别名扫描路径。给包中的类名注册别名，注册后在mapper对应的xml文件中可以直接使用类名，而不用全限定的类名

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE mapper
            PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
            "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
    <mapper namespace="com.qj.dao.IUserMapper">
        
        <select id="findAll" resultType="User">
            select * from user ${ew.customSqlSegment}
        </select>
    </mapper>

mybatis-plus.type-aliases-package: com.qj.pojo

Maven中多模块项目的扫描路径需要已classpath\*:开头

## 通用service ##

有点类似于三层架构的思想了  
![在这里插入图片描述][20201129134555848.png]

public interface UserService extends IService<User> {
    }

@Service
    public class UserServiceImp extends ServiceImpl<IUserMapper, User> implements UserService {
    }

下面看看测试：

@RunWith(SpringRunner.class)
    @SpringBootTest
    public class ServiceTest {
        @Autowired(required = false)
        private UserService userService;
    
        @Test
        public void getOne(){
           User one = userService.getOne(Wrappers.<User>lambdaQuery().gt(User::getPassword,"121"),false);//查出多条记录会报错,该为false
            System.out.println(one);
    
        }
    
    }

批量操作  
userService.saveBatch(userList)  
插入（批量）  
@param entityList 实体对象集合

userService.saveOrUpdateBatch(userList)批量修改操作，没有就增加一条，有就修改

@Test
        public void saveOrUpdateBatch(){
            User user = new User();
            user.setUsername("admin12");
            user.setPassword("111111");
    
            User user1 = new User();
            user1.setId(22);
            user1.setUsername("豆皮江爱喝茶1");
            user1.setPassword("22222200");
    
    
            List<User> userList =Arrays.asList(user,user1);
            boolean isSaveOrUpdate=userService.saveOrUpdateBatch(userList);
            System.out.println(isSaveOrUpdate);
    
        }

链式调用：

@Test
        public void chain(){
    //        List<User> userList=userService.<User>lambdaQuery().like(User::getUsername,"皮皮").list();
    //        userList.forEach(System.out::println);
    //        boolean isUpdate=userService.<User>lambdaUpdate().eq(User::getId,"1").set(User::getPassword,"908070").update();
    //        System.out.println(isUpdate);
    
            boolean isDelete=  userService.<User>lambdaUpdate().eq(User::getId,"15").remove();
            System.out.println(isDelete);
        }

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDA5MzcxMQ_size_16_color_FFFFFF_t_70]: /images/20221120/64a7137bb7ee4e0e9102321dda4c1d16.png
[20201128141925601.png]: https://img-blog.csdnimg.cn/20201128141925601.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDA5MzcxMQ_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/20201128142004902.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80NDA5MzcxMQ==,size_16,color_FFFFFF,t_70
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[20201129134555848.png]: https://img-blog.csdnimg.cn/20201129134555848.png