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MyBatis-Plus condition参数 MyBatis-Plus条件构造器之condition参数的使用

ITKaven 人气:0

首先创建一个数据库表,如下图所示:

在这里插入图片描述

然后创建一个Spring Boot项目,pom.xml和配置如下:

<?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>org.kaven</groupId>
 <artifactId>mybatis-plus</artifactId>
 <version>1.0-SNAPSHOT</version>

 <parent>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-parent</artifactId>
  <version>2.3.4.RELEASE</version>
  <relativePath/>
 </parent>

 <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-starter-test</artifactId>
  </dependency>
  <dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-webflux</artifactId>
  </dependency>
  <dependency>
   <groupId>com.baomidou</groupId>
   <artifactId>mybatis-plus-boot-starter</artifactId>
   <version>3.4.0</version>
  </dependency>
  <dependency>
   <groupId>mysql</groupId>
   <artifactId>mysql-connector-java</artifactId>
   <version>5.1.49</version>
  </dependency>
  <dependency>
   <groupId>org.projectlombok</groupId>
   <artifactId>lombok</artifactId>
  </dependency>
 </dependencies>

 <build>
  <plugins>
   <plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
   </plugin>
  </plugins>
 </build>
</project>
spring:
 application:
 name: mybatis-plus
 datasource:
 driver-class-name: com.mysql.jdbc.Driver
 username: root
 password: ITkaven@123
 url: jdbc:mysql://127.0.0.1:3306/test?characterEncoding=utf-8&useSSL=false

server:
 port: 8085

logging:
 level:
 root: warn
 com.kaven.mybatisplus.dao: trace
 pattern:
 console: '%p%m%n'

mybatis-plus:
 mapper-locations: classpath:mappers/*.xml

实体类User:

package com.kaven.mybatisplus.entity;

import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.Data;

@TableName("user")
@Data
public class User {

 @TableId
 private String id;

 @TableField("username")
 private String username;

 @TableField("password")
 private String password;

 @TableField("age")
 private Integer age;

 /**
  * 使用 @TableField(exist = false) ,表示该字段在数据库中不存在 ,所以不会插入数据库中
  * 使用 transient 、 static 修饰属性也不会插入数据库中
  */
 @TableField(exist = false)
 private String phone;
}

Mapper接口UserMapper:

package com.kaven.mybatisplus.dao;

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.kaven.mybatisplus.entity.User;
import org.springframework.stereotype.Component;


@Component
public interface UserMapper extends BaseMapper<User> {}

启动类:

package com.kaven.mybatisplus;

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

@SpringBootApplication
@MapperScan(basePackages = "com.kaven.mybatisplus.dao")
public class AppRun {
 public static void main(String[] args) {
  SpringApplication.run(AppRun.class , args);
 }
}

@MapperScan(basePackages = "com.kaven.mybatisplus.dao")这个一定要加上。

我们先在数据库中添加几行数据,方便演示。

在这里插入图片描述

我之前介绍的条件构造器都没有使用过condition参数。从AbstractWrapper<T, String, QueryWrapper<T>>的源码可以看到很多方法都有condition参数,它是一个布尔型的参数,意思就是是否将该sql语句(像in()like())加在总sql语句上,如下图所示。

在这里插入图片描述

首先我们自己来实现一个和condition参数一样功能的方法。

查询username包含字符k,并且age属于[22 , 40 , 30 ]。

package com.kaven.mybatisplus.dao;

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.kaven.mybatisplus.entity.User;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
import org.springframework.util.CollectionUtils;
import org.springframework.util.StringUtils;

import java.util.Arrays;
import java.util.List;


@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperConditionTest {

 @Autowired
 private UserMapper userMapper;

 @Test
 public void selectList(){
  String username = "k";
  List<Integer> ageList = Arrays.asList(22 , 40 , 30);
  List<User> userList = userMapper.selectList(condition(username , ageList));
  userList.forEach(System.out::println);
 }

 public QueryWrapper<User> condition(String username , List<Integer> ageList){
  QueryWrapper<User> userQueryWrapper = new QueryWrapper<>();
  if(!StringUtils.isEmpty(username)){
   userQueryWrapper.like("username" , username);
  }
  if(!CollectionUtils.isEmpty(ageList)){
   userQueryWrapper.in("age" , ageList);
  }
  return userQueryWrapper;
 }
}

结果如下:

在这里插入图片描述

结果是正确的。

我们使用condition参数来实现一下。

package com.kaven.mybatisplus.dao;

import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.kaven.mybatisplus.entity.User;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
import org.springframework.util.CollectionUtils;
import org.springframework.util.StringUtils;

import java.util.Arrays;
import java.util.List;


@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperConditionTest {

 @Autowired
 private UserMapper userMapper;

 @Test
 public void selectList(){
  String username = "k";
  List<Integer> ageList = Arrays.asList(22 , 40 , 30);
  List<User> userList = userMapper.selectList(condition(username , ageList));
  userList.forEach(System.out::println);
 }

 public QueryWrapper<User> condition(String username , List<Integer> ageList){
  QueryWrapper<User> userQueryWrapper = new QueryWrapper<>();
//  if(!StringUtils.isEmpty(username)){
//   userQueryWrapper.like("username" , username);
//  }
//  if(!CollectionUtils.isEmpty(ageList)){
//   userQueryWrapper.in("age" , ageList);
//  }
  userQueryWrapper.like(!StringUtils.isEmpty(username) , "username" , username)
      .in(!CollectionUtils.isEmpty(ageList) , "age" , ageList);
  return userQueryWrapper;
 }
}

结果如下:

在这里插入图片描述

结果也是正确的。

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