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：
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。
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。
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：
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：
结果也是正确的。
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