Mybatis-Plus入门

了解Mybatis-Plus

Mybatis-Plus介绍

MyBatis-Plus(简称 MP)是一个 MyBatis 的增强工具,在 MyBatis 的基础上只做增强不做改变,为简化开发、提高效率而生。

官网:https://mybatis.plus/https://mp.baomidou.com/

愿景
我们的愿景是成为 MyBatis 最好的搭档,就像 魂斗罗 中的 1P、2P,基友搭配,效率翻倍。

代码以及文档

文档地址:https://mybatis.plus/guide/
源码地址:https://github.com/baomidou/mybatis-plus

特性

  • 无侵入:只做增强不做改变,引入它不会对现有工程产生影响,如丝般顺滑
  • 损耗小:启动即会自动注入基本 CURD,性能基本无损耗,直接面向对象操作
  • 强大的 CRUD 操作:内置通用 Mapper、通用 Service,仅仅通过少量配置即可实现单表大部分 CRUD 操作,更有强大的条件构造器,满足各类使用需求
  • 支持 Lambda 形式调用:通过 Lambda 表达式,方便的编写各类查询条件,无需再担心字段写错
  • 支持多种数据库:支持 MySQL、MariaDB、Oracle、DB2、H2、HSQL、SQLite、Postgre、
    SQLServer2005、SQLServer 等多种数据库
  • 支持主键自动生成:支持多达 4 种主键策略(内含分布式唯一 ID 生成器 - Sequence),可自由配置,完美解决主键问题
  • 支持 XML 热加载:Mapper 对应的 XML 支持热加载,对于简单的 CRUD 操作,甚至可以无 XML 启动
  • 支持 ActiveRecord 模式:支持 ActiveRecord 形式调用,实体类只需继承 Model 类即可进行强大的 CRUD 操作
  • 支持自定义全局通用操作:支持全局通用方法注入( Write once, use anywhere )
  • 支持关键词自动转义:支持数据库关键词(order、key……)自动转义,还可自定义关键词
  • 内置代码生成器:采用代码或者 Maven 插件可快速生成 Mapper 、 Model 、 Service 、 Controller 层代码,支持模板引擎,更有超多自定义配置等您来使用
  • 内置分页插件:基于 MyBatis 物理分页,开发者无需关心具体操作,配置好插件之后,写分页等同于普通 List查询
  • 内置性能分析插件:可输出 Sql 语句以及其执行时间,建议开发测试时启用该功能,能快速揪出慢查询
  • 内置全局拦截插件:提供全表 delete 、 update 操作智能分析阻断,也可自定义拦截规则,预防误操作
  • 内置 Sql 注入剥离器:支持 Sql 注入剥离,有效预防 Sql 注入攻击

架构

作者

Mybatis-Plus是由baomidou(苞米豆)组织开发并且开源的,目前该组织大概有30人左右。
码云地址:https://gitee.com/organizations/baomidou

快速开始

对于Mybatis整合MP有常常有三种用法,分别是Mybatis+MP、Spring+Mybatis+MP、Spring Boot+Mybatis+MP。

创建数据库以及表

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-- 创建测试表
CREATE TABLE `tb_user` (
`id` bigint(20) NOT NULL AUTO_INCREMENT COMMENT '主键ID',
`user_name` varchar(20) NOT NULL COMMENT '用户名',
`password` varchar(20) NOT NULL COMMENT '密码',
`name` varchar(30) DEFAULT NULL COMMENT '姓名',
`age` int(11) DEFAULT NULL COMMENT '年龄',
`email` varchar(50) DEFAULT NULL COMMENT '邮箱',
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;
-- 插入测试数据
INSERT INTO `tb_user` (`id`, `user_name`, `password`, `name`, `age`, `email`) VALUES
('1', 'zhangsan', '123456', '张三', '18', 'test1@itcast.cn');
INSERT INTO `tb_user` (`id`, `user_name`, `password`, `name`, `age`, `email`) VALUES
('2', 'lisi', '123456', '李四', '20', 'test2@itcast.cn');
INSERT INTO `tb_user` (`id`, `user_name`, `password`, `name`, `age`, `email`) VALUES
('3', 'wangwu', '123456', '王五', '28', 'test3@itcast.cn');
INSERT INTO `tb_user` (`id`, `user_name`, `password`, `name`, `age`, `email`) VALUES
('4', 'zhaoliu', '123456', '赵六', '21', 'test4@itcast.cn');
INSERT INTO `tb_user` (`id`, `user_name`, `password`, `name`, `age`, `email`) VALUES
('5', 'sunqi', '123456', '孙七', '24', 'test5@itcast.cn');

创建工程

导入依赖:

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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
http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>cn.itcast.mp</groupId>
<artifactId>itcast-mybatis-plus</artifactId>
<version>1.0-SNAPSHOT</version>
<modules>
<module>itcast-mybatis-plus-simple</module>
</modules>
<packaging>pom</packaging>
<dependencies>
<!-- mybatis-plus插件依赖 -->
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus</artifactId>
<version>3.1.1</version>
</dependency>
<!-- MySql -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.47</version>
</dependency>
<!-- 连接池 -->
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>druid</artifactId>
<version>1.0.11</version>
</dependency>
<!--简化bean代码的工具包-->
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
<version>1.18.4</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>1.6.4</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
</plugins>
</build>
</project>

Mybatis + MP

下面演示,通过纯Mybatis与Mybatis-Plus整合。

创建子Module

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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
http://maven.apache.org/xsd/maven-4.0.0.xsd">
<parent>
<artifactId>itcast-mybatis-plus</artifactId>
<groupId>cn.itcast.mp</groupId>
<version>1.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<packaging>jar</packaging>
<artifactId>itcast-mybatis-plus-simple</artifactId>
</project>

log4j.properties:

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log4j.rootLogger=DEBUG,A1

log4j.appender.A1=org.apache.log4j.ConsoleAppender
log4j.appender.A1.layout=org.apache.log4j.PatternLayout
log4j.appender.A1.layout.ConversionPattern=[%t] [%c]-[%p] %m%n

Mybatis实现查询User

第一步,编写mybatis-config.xml文件:

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<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql://127.0.0.1:3306/mp?
useUnicode=true&amp;characterEncoding=utf8&amp;autoReconnect=true&amp;allowMultiQuerie
s=true&amp;useSSL=false"/>
<property name="username" value="root"/>
<property name="password" value="root"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="UserMapper.xml"/>
</mappers>
</configuration>

第二步,编写User实体对象:(这里使用lombok进行了进化bean操作)

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package cn.itcast.mp.simple.pojo;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {
private Long id;
private String userName;
private String password;
private String name;
private Integer age;
private String email;
}

第三步,编写UserMapper接口:

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package cn.itcast.mp.simple.mapper;
import cn.itcast.mp.simple.pojo.User;
import java.util.List;
public interface UserMapper {
List<User> findAll();
}

第四步,编写UserMapper.xml文件:

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<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="cn.itcast.mp.simple.mapper.UserMapper">
<select id="findAll" resultType="cn.itcast.mp.simple.pojo.User">
select * from tb_user
</select>
</mapper>

第五步,编写TestMybatis测试用例:

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package cn.itcast.mp.simple;
import cn.itcast.mp.simple.mapper.UserMapper;
import cn.itcast.mp.simple.pojo.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;
import java.io.InputStream;
import java.util.List;
public class TestMybatis {
@Test
public void testUserList() throws Exception{
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new
SqlSessionFactoryBuilder().build(inputStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
List<User> list = userMapper.findAll();
for (User user : list) {
System.out.println(user);
}
}
}

测试结果:

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[main] [cn.itcast.mp.simple.mapper.UserMapper.findAll]-[DEBUG] ==> Parameters:
[main] [cn.itcast.mp.simple.mapper.UserMapper.findAll]-[DEBUG] <== Total: 5
User(id=1, userName=null, password=123456, name=张三, age=18, email=test1@itcast.cn)
User(id=2, userName=null, password=123456, name=李四, age=20, email=test2@itcast.cn)
User(id=3, userName=null, password=123456, name=王五, age=28, email=test3@itcast.cn)
User(id=4, userName=null, password=123456, name=赵六, age=21, email=test4@itcast.cn)
User(id=5, userName=null, password=123456, name=孙七, age=24, email=test5@itcast.cn)

Mybatis+MP实现查询User

第一步,将UserMapper继承BaseMapper,将拥有了BaseMapper中的所有方法:

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package cn.itcast.mp.simple.mapper;
import cn.itcast.mp.simple.pojo.User;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import java.util.List;
public interface UserMapper extends BaseMapper<User> {
List<User> findAll();
}

第二步,使用MP中的MybatisSqlSessionFactoryBuilder进程构建:

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package cn.itcast.mp.simple;
import cn.itcast.mp.simple.mapper.UserMapper;
import cn.itcast.mp.simple.pojo.User;
import com.baomidou.mybatisplus.core.MybatisSqlSessionFactoryBuilder;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;
import java.io.InputStream;
import java.util.List;
public class TestMybatisPlus {
@Test
public void testUserList() throws Exception {
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
//这里使用的是MP中的MybatisSqlSessionFactoryBuilder
SqlSessionFactory sqlSessionFactory = new
MybatisSqlSessionFactoryBuilder().build(inputStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
// 可以调用BaseMapper中定义的方法
List<User> list = userMapper.selectList(null);
for (User user : list) {
System.out.println(user);
}
}
}

运行报错:

解决:在User对象中添加@TableName,指定数据库表名

测试:

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[main] [cn.itcast.mp.simple.mapper.UserMapper.selectList]-[DEBUG] ==> Preparing:
SELECT id,user_name,password,name,age,email FROM tb_user
[main] [cn.itcast.mp.simple.mapper.UserMapper.selectList]-[DEBUG] ==> Parameters:
[main] [cn.itcast.mp.simple.mapper.UserMapper.selectList]-[DEBUG] <== Total: 5
User(id=1, userName=zhangsan, password=123456, name=张三, age=18, email=test1@itcast.cn)
User(id=2, userName=lisi, password=123456, name=李四, age=20, email=test2@itcast.cn)
User(id=3, userName=wangwu, password=123456, name=王五, age=28, email=test3@itcast.cn)
User(id=4, userName=zhaoliu, password=123456, name=赵六, age=21, email=test4@itcast.cn)
User(id=5, userName=sunqi, password=123456, name=孙七, age=24, email=test5@itcast.cn)

简单说明:

  • 由于使用了MybatisSqlSessionFactoryBuilder进行了构建,继承的BaseMapper中的方法就载入到了
    SqlSession中,所以就可以直接使用相关的方法;

Spring + Mybatis + MP

引入了Spring框架,数据源、构建等工作就交给了Spring管理。

创建子Module

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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
http://maven.apache.org/xsd/maven-4.0.0.xsd">
<parent>
<artifactId>itcast-mybatis-plus</artifactId>
<groupId>cn.itcast.mp</groupId>
<version>1.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>itcast-mybatis-plus-spring</artifactId>
<properties>
<spring.version>5.1.6.RELEASE</spring.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-jdbc</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-test</artifactId>
<version>${spring.version}</version>
</dependency>
</dependencies>
</project>

实现查询User

第一步,编写jdbc.properties

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jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://127.0.0.1:3306/mp?
useUnicode=true&characterEncoding=utf8&autoReconnect=true&allowMultiQueries=true&useSSL
=false
jdbc.username=root
jdbc.password=root

第二步,编写applicationContext.xml

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<?xml version="1.0" encoding="UTF-8"?>
<beans
xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd">
<context:property-placeholder location="classpath:*.properties"/>
<!-- 定义数据源 -->
<bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource"
destroy-method="close">
<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
<property name="driverClassName" value="${jdbc.driver}"/>
<property name="maxActive" value="10"/>
<property name="minIdle" value="5"/>
</bean>
<!--这里使用MP提供的sqlSessionFactory,完成了Spring与MP的整合-->
<bean id="sqlSessionFactory"
class="com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean">
<property name="dataSource" ref="dataSource"/>
</bean>
<!--扫描mapper接口,使用的依然是Mybatis原生的扫描器-->
<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
<property name="basePackage" value="cn.itcast.mp.simple.mapper"/>
</bean>
</beans>

第三步,编写User对象以及UserMapper接口:

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package cn.itcast.mp.simple.pojo;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
@Data
@NoArgsConstructor
@AllArgsConstructor
@TableName("tb_user")
public class User {
private Long id;
private String userName;
private String password;
private String name;
private Integer age;
private String email;
}
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package cn.itcast.mp.simple.mapper;
import cn.itcast.mp.simple.pojo.User;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
public interface UserMapper extends BaseMapper<User> {
}

第四步,编写测试用例:

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package cn.itcast.mp.simple;
import cn.itcast.mp.simple.mapper.UserMapper;
import cn.itcast.mp.simple.pojo.User;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import java.util.List;
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath:applicationContext.xml")
public class TestSpringMP {
@Autowired
private UserMapper userMapper;
@Test
public void testSelectList(){
List<User> users = this.userMapper.selectList(null);
for (User user : users) {
System.out.println(user);
}
}
}

测试:

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[main] [cn.itcast.mp.simple.mapper.UserMapper.selectList]-[DEBUG] ==> Preparing:
SELECT id,user_name,password,name,age,email FROM tb_user
[main] [cn.itcast.mp.simple.mapper.UserMapper.selectList]-[DEBUG] ==> Parameters:
[main] [cn.itcast.mp.simple.mapper.UserMapper.selectList]-[DEBUG] <== Total: 5
[main] [org.mybatis.spring.SqlSessionUtils]-[DEBUG] Closing non transactional
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@74287ea3]
User(id=1, userName=zhangsan, password=123456, name=张三, age=18,
email=test1@itcast.cn)
User(id=2, userName=lisi, password=123456, name=李四, age=20, email=test2@itcast.cn)
User(id=3, userName=wangwu, password=123456, name=王五, age=28, email=test3@itcast.cn)
User(id=4, userName=zhaoliu, password=123456, name=赵六, age=21, email=test4@itcast.cn)
User(id=5, userName=sunqi, password=123456, name=孙七, age=24, email=test5@itcast.cn)

SpringBoot + Mybatis + MP

使用SpringBoot将进一步的简化MP的整合,需要注意的是,由于使用SpringBoot需要继承parent,所以需要重新创建工程,并不是创建子Module。

创建工程

导入依赖

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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
http://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>2.1.4.RELEASE</version>
</parent>
<groupId>cn.itcast.mp</groupId>
<artifactId>itcast-mp-springboot</artifactId>
<version>1.0-SNAPSHOT</version>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter</artifactId>
<exclusions>
<exclusion>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-logging</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<!--简化代码的工具包-->
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<optional>true</optional>
</dependency>
<!--mybatis-plus的springboot支持-->
<dependency>
<groupId>com.baomidou</groupId>
<artifactId>mybatis-plus-boot-starter</artifactId>
<version>3.1.1</version>
</dependency>
<!--mysql驱动-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.47</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>

log4j.properties:

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log4j.rootLogger=DEBUG,A1

log4j.appender.A1=org.apache.log4j.ConsoleAppender
log4j.appender.A1.layout=org.apache.log4j.PatternLayout
log4j.appender.A1.layout.ConversionPattern=[%t] [%c]-[%p] %m%n

编写application.properties

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spring.application.name = itcast-mp-springboot
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
spring.datasource.url=jdbc:mysql://127.0.0.1:3306/mp?
useUnicode=true&characterEncoding=utf8&autoReconnect=true&allowMultiQueries=true&useSSL
=false
spring.datasource.username=root
spring.datasource.password=root

编写pojo

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package cn.itcast.mp.pojo;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
@Data
@NoArgsConstructor
@AllArgsConstructor
@TableName("tb_user")
public class User {
private Long id;
private String userName;
private String password;
private String name;
private Integer age;
private String email;
}

编写mapper

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package cn.itcast.mp.mapper;
import cn.itcast.mp.pojo.User;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;

public interface UserMapper extends BaseMapper<User> {
}

编写启动类

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package cn.itcast.mp;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.WebApplicationType;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
@MapperScan("cn.itcast.mp.mapper") //设置mapper接口的扫描包
@SpringBootApplication
public class MyApplication {
public static void main(String[] args) {
SpringApplication.run(MyApplication.class, args);
}
}

编写测试用例

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package cn.itcast.mp;
import cn.itcast.mp.mapper.UserMapper;
import cn.itcast.mp.pojo.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 java.util.List;
@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {
@Autowired
private UserMapper userMapper;
@Test
public void testSelect() {
List<User> userList = userMapper.selectList(null);
for (User user : userList) {
System.out.println(user);
}
}
}

测试:

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[main] [cn.itcast.mp.mapper.UserMapper.selectList]-[DEBUG] ==> Preparing: SELECT
id,user_name,password,name,age,email FROM tb_user
[main] [cn.itcast.mp.mapper.UserMapper.selectList]-[DEBUG] ==> Parameters:
[main] [cn.itcast.mp.mapper.UserMapper.selectList]-[DEBUG] <== Total: 5
[main] [org.mybatis.spring.SqlSessionUtils]-[DEBUG] Closing non transactional
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@14faa38c]
User(id=1, userName=zhangsan, password=123456, name=张三, age=18, email=test1@itcast.cn)
User(id=2, userName=lisi, password=123456, name=李四, age=20, email=test2@itcast.cn)
User(id=3, userName=wangwu, password=123456, name=王五, age=28, email=test3@itcast.cn)
User(id=4, userName=zhaoliu, password=123456, name=赵六, age=21, email=test4@itcast.cn)
User(id=5, userName=sunqi, password=123456, name=孙七, age=24, email=test5@itcast.cn)

通用CRUD

通过前面的学习,我们了解到通过继承BaseMapper就可以获取到各种各样的单表操作,接下来我们将详细讲解这些操作。

插入操作

方法定义

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/**
* 插入一条记录
*
* @param entity 实体对象
*/
int insert(T entity);

测试用例

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package cn.itcast.mp;
import cn.itcast.mp.mapper.UserMapper;
import cn.itcast.mp.pojo.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 java.util.List;
@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {
@Autowired
private UserMapper userMapper;
@Test
public void testInsert(){
User user = new User();
user.setAge(20);
user.setEmail("test@itcast.cn");
user.setName("曹操");
user.setUserName("caocao");
user.setPassword("123456");
int result = this.userMapper.insert(user); //返回的result是受影响的行数,并不是自增
后的id
System.out.println("result = " + result);
System.out.println(user.getId()); //自增后的id会回填到对象中
}
}

测试

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[main] [cn.itcast.mp.mapper.UserMapper.insert]-[DEBUG] ==> Preparing: INSERT INTO
tb_user ( id, user_name, password, name, age, email ) VALUES ( ?, ?, ?, ?, ?, ? )
[main] [cn.itcast.mp.mapper.UserMapper.insert]-[DEBUG] ==> Parameters:
1122045867793072130(Long), caocao(String), 123456(String), 曹操(String), 20(Integer),
test@itcast.cn(String)
[main] [cn.itcast.mp.mapper.UserMapper.insert]-[DEBUG] <== Updates: 1
[main] [org.mybatis.spring.SqlSessionUtils]-[DEBUG] Closing non transactional
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@411291e5]
result = 1
1122045867793072130

可以看到,数据已经写入到了数据库,但是,id的值不正确,我们期望的是数据库自增长,实际是MP生成了id的值写入到了数据库。
如何设置id的生成策略呢?

MP支持的id策略:

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package com.baomidou.mybatisplus.annotation;
import lombok.Getter;
/**
* 生成ID类型枚举类
*
* @author hubin
* @since 2015-11-10
*/
@Getter
public enum IdType {
/**
* 数据库ID自增
*/
AUTO(0),
/**
* 该类型为未设置主键类型
*/
NONE(1),
/**
* 用户输入ID
* <p>该类型可以通过自己注册自动填充插件进行填充</p>
*/
INPUT(2),
/* 以下3种类型、只有当插入对象ID 为空,才自动填充。 */
/**
* 全局唯一ID (idWorker)
*/
ID_WORKER(3),
/**
* 全局唯一ID (UUID)
*/
UUID(4),
/**
* 字符串全局唯一ID (idWorker 的字符串表示)
*/
ID_WORKER_STR(5);
private final int key;
IdType(int key) {
this.key = key;
}
}

修改User对象:

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package cn.itcast.mp.pojo;
import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
@Data
@NoArgsConstructor
@AllArgsConstructor
@TableName("tb_user")
public class User {
@TableId(type = IdType.AUTO) //指定id类型为自增长
private Long id;
private String userName;
private String password;
private String name;
private Integer age;
private String email;
}

数据插入成功:

@TableField

在MP中通过@TableField注解可以指定字段的一些属性,常常解决的问题有2个:
1、对象中的属性名和字段名不一致的问题(非驼峰)
2、对象中的属性字段在表中不存在的问题
使用:

其他用法,如大字段不加入查询字段:

效果:

更新操作

在MP中,更新操作有2种,一种是根据id更新,另一种是根据条件更新。

根据id更新

方法定义:

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/**
* 根据 ID 修改
*
* @param entity 实体对象
*/
int updateById(@Param(Constants.ENTITY) T entity);

测试:

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@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {
@Autowired
private UserMapper userMapper;
@Test
public void testUpdateById() {
User user = new User();
user.setId(6L); //主键
user.setAge(21); //更新的字段
//根据id更新,更新不为null的字段
this.userMapper.updateById(user);
}
}

结果:

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[main] [cn.itcast.mp.mapper.UserMapper.updateById]-[DEBUG] ==> Preparing: UPDATE
tb_user SET age=? WHERE id=?
[main] [cn.itcast.mp.mapper.UserMapper.updateById]-[DEBUG] ==> Parameters: 21(Integer),
6(Long)
[main] [cn.itcast.mp.mapper.UserMapper.updateById]-[DEBUG] <== Updates: 1

根据条件更新

方法定义:

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/**
* 根据 whereEntity 条件,更新记录
*
* @param entity 实体对象 (set 条件值,可以为 null)
* @param updateWrapper 实体对象封装操作类(可以为 null,里面的 entity 用于生成 where 语句)
*/
int update(@Param(Constants.ENTITY) T entity, @Param(Constants.WRAPPER) Wrapper<T>
updateWrapper);

测试用例:

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package cn.itcast.mp;
import cn.itcast.mp.mapper.UserMapper;
import cn.itcast.mp.pojo.User;
import com.baomidou.mybatisplus.core.conditions.Wrapper;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.core.conditions.update.UpdateWrapper;
import net.minidev.json.writer.UpdaterMapper;
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 java.util.List;
@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {
@Autowired
private UserMapper userMapper;
@Test
public void testUpdate() {
User user = new User();
user.setAge(22); //更新的字段
//更新的条件
QueryWrapper<User> wrapper = new QueryWrapper<>();
wrapper.eq("id", 6);
//执行更新操作
int result = this.userMapper.update(user, wrapper);
System.out.println("result = " + result);
}
}

或者,通过UpdateWrapper进行更新:

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@Test
public void testUpdate() {
//更新的条件以及字段
UpdateWrapper<User> wrapper = new UpdateWrapper<>();
wrapper.eq("id", 6).set("age", 23);
//执行更新操作
int result = this.userMapper.update(null, wrapper);
System.out.println("result = " + result);
}

测试结果:

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[main] [cn.itcast.mp.mapper.UserMapper.update]-[DEBUG] ==> Preparing: UPDATE tb_user
SET age=? WHERE id = ?
[main] [cn.itcast.mp.mapper.UserMapper.update]-[DEBUG] ==> Parameters: 23(Integer),
6(Integer)
[main] [cn.itcast.mp.mapper.UserMapper.update]-[DEBUG] <== Updates: 1

均可达到更新的效果。
关于wrapper更多的用法后面会详细讲解。

删除操作

deleteById

方法定义:

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/**
* 根据 ID 删除
*
* @param id 主键ID
*/
int deleteById(Serializable id);

测试用例:

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package cn.itcast.mp;
import cn.itcast.mp.mapper.UserMapper;
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;
@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {
@Autowired
private UserMapper userMapper;
@Test
public void testDeleteById() {
//执行删除操作
int result = this.userMapper.deleteById(6L);
System.out.println("result = " + result);
}
}

结果:

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[main] [cn.itcast.mp.mapper.UserMapper.deleteById]-[DEBUG] ==> Preparing: DELETE FROM
tb_user WHERE id=?
[main] [cn.itcast.mp.mapper.UserMapper.deleteById]-[DEBUG] ==> Parameters: 6(Long)
[main] [cn.itcast.mp.mapper.UserMapper.deleteById]-[DEBUG] <== Updates: 1


数据被删除。

deleteByMap

方法定义:

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/**
* 根据 columnMap 条件,删除记录
*
* @param columnMap 表字段 map 对象
*/
int deleteByMap(@Param(Constants.COLUMN_MAP) Map<String, Object> columnMap);

测试用例:

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package cn.itcast.mp;
import cn.itcast.mp.mapper.UserMapper;
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 java.util.HashMap;
import java.util.Map;
@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {
@Autowired
private UserMapper userMapper;
@Test
public void testDeleteByMap() {
Map<String, Object> columnMap = new HashMap<>();
columnMap.put("age",20);
columnMap.put("name","张三");
//将columnMap中的元素设置为删除的条件,多个之间为and关系
int result = this.userMapper.deleteByMap(columnMap);
System.out.println("result = " + result);
}
}

结果:

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[main] [cn.itcast.mp.mapper.UserMapper.deleteByMap]-[DEBUG] ==> Preparing: DELETE FROM
tb_user WHERE name = ? AND age = ?
[main] [cn.itcast.mp.mapper.UserMapper.deleteByMap]-[DEBUG] ==> Parameters: 张三
(String), 20(Integer)
[main] [cn.itcast.mp.mapper.UserMapper.deleteByMap]-[DEBUG] <== Updates: 0

delete

方法定义:

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/**
* 根据 entity 条件,删除记录
*
* @param wrapper 实体对象封装操作类(可以为 null)
*/
int delete(@Param(Constants.WRAPPER) Wrapper<T> wrapper);

测试用例:

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package cn.itcast.mp;
import cn.itcast.mp.mapper.UserMapper;
import cn.itcast.mp.pojo.User;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
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 java.util.HashMap;
import java.util.Map;
@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {
@Autowired
private UserMapper userMapper;
@Test
public void testDeleteByMap() {
User user = new User();
user.setAge(20);
user.setName("张三");
//将实体对象进行包装,包装为操作条件
QueryWrapper<User> wrapper = new QueryWrapper<>(user);
int result = this.userMapper.delete(wrapper);
System.out.println("result = " + result);
}
}

结果:

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[main] [cn.itcast.mp.mapper.UserMapper.delete]-[DEBUG] ==> Preparing: DELETE FROM
tb_user WHERE name=? AND age=?
[main] [cn.itcast.mp.mapper.UserMapper.delete]-[DEBUG] ==> Parameters: 张三(String),
20(Integer)
[main] [cn.itcast.mp.mapper.UserMapper.delete]-[DEBUG] <== Updates: 0

deleteBatchIds

方法定义:

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/**
* 删除(根据ID 批量删除)
*
* @param idList 主键ID列表(不能为 null 以及 empty)
*/
int deleteBatchIds(@Param(Constants.COLLECTION) Collection<? extends Serializable>
idList);

测试用例:

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package cn.itcast.mp;
import cn.itcast.mp.mapper.UserMapper;
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 java.util.Arrays;
@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {
@Autowired
private UserMapper userMapper;
@Test
public void testDeleteByMap() {
//根据id集合批量删除
int result = this.userMapper.deleteBatchIds(Arrays.asList(1L,10L,20L));
System.out.println("result = " + result);
}
}

结果:

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[main] [cn.itcast.mp.mapper.UserMapper.deleteBatchIds]-[DEBUG] ==> Preparing: DELETE
FROM tb_user WHERE id IN ( ? , ? , ? )
[main] [cn.itcast.mp.mapper.UserMapper.deleteBatchIds]-[DEBUG] ==> Parameters: 1(Long),
10(Long), 20(Long)
[main] [cn.itcast.mp.mapper.UserMapper.deleteBatchIds]-[DEBUG] <== Updates: 1

查询操作

MP提供了多种查询操作,包括根据id查询、批量查询、查询单条数据、查询列表、分页查询等操作。

selectById

方法定义:

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

测试用例:

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package cn.itcast.mp;
import cn.itcast.mp.mapper.UserMapper;
import cn.itcast.mp.pojo.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;
@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {
@Autowired
private UserMapper userMapper;
@Test
public void testSelectById() {
//根据id查询数据
User user = this.userMapper.selectById(2L);
System.out.println("result = " + user);
}
}

结果:

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[main] [cn.itcast.mp.mapper.UserMapper.selectById]-[DEBUG] ==> Preparing: SELECT
id,user_name,password,name,age,email FROM tb_user WHERE id=?
[main] [cn.itcast.mp.mapper.UserMapper.selectById]-[DEBUG] ==> Parameters: 2(Long)
[main] [cn.itcast.mp.mapper.UserMapper.selectById]-[DEBUG] <== Total: 1
result = User(id=2, userName=lisi, password=123456, name=李四, age=20,
email=test2@itcast.cn, address=null)

selectBatchIds

方法定义:

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/**
* 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);

测试用例:

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package cn.itcast.mp;
import cn.itcast.mp.mapper.UserMapper;
import cn.itcast.mp.pojo.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 java.util.Arrays;
import java.util.List;
@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {
@Autowired
private UserMapper userMapper;
@Test
public void testSelectBatchIds() {
//根据id集合批量查询
List<User> users = this.userMapper.selectBatchIds(Arrays.asList(2L, 3L, 10L));
for (User user : users) {
System.out.println(user);
}
}
}

结果:

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[main] [cn.itcast.mp.mapper.UserMapper.selectBatchIds]-[DEBUG] ==> Preparing: SELECT
id,user_name,password,name,age,email FROM tb_user WHERE id IN ( ? , ? , ? )
[main] [cn.itcast.mp.mapper.UserMapper.selectBatchIds]-[DEBUG] ==> Parameters: 2(Long),
3(Long), 10(Long)
[main] [cn.itcast.mp.mapper.UserMapper.selectBatchIds]-[DEBUG] <== Total: 2
User(id=2, userName=lisi, password=123456, name=李四, age=20, email=test2@itcast.cn,
address=null)
User(id=3, userName=wangwu, password=123456, name=王五, age=28, email=test3@itcast.cn,
address=null)

selectOne

方法定义:

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/**
* 根据 entity 条件,查询一条记录
*
* @param queryWrapper 实体对象封装操作类(可以为 null)
*/
T selectOne(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper);

测试用例:

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package cn.itcast.mp;
import cn.itcast.mp.mapper.UserMapper;
import cn.itcast.mp.pojo.User;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
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;
@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {
@Autowired
private UserMapper userMapper;
@Test
public void testSelectOne() {
QueryWrapper<User> wrapper = new QueryWrapper<User>();
wrapper.eq("name", "李四");
//根据条件查询一条数据,如果结果超过一条会报错
User user = this.userMapper.selectOne(wrapper);
System.out.println(user);
}
}

结果:

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[main] [cn.itcast.mp.mapper.UserMapper.selectOne]-[DEBUG] ==> Preparing: SELECT
id,user_name,password,name,age,email FROM tb_user WHERE name = ?
[main] [cn.itcast.mp.mapper.UserMapper.selectOne]-[DEBUG] ==> Parameters: 李四(String)
[main] [cn.itcast.mp.mapper.UserMapper.selectOne]-[DEBUG] <== Total: 1
User(id=2, userName=lisi, password=123456, name=李四, age=20, email=test2@itcast.cn,
address=null)

selectCount

方法定义:

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/**
* 根据 Wrapper 条件,查询总记录数
*
* @param queryWrapper 实体对象封装操作类(可以为 null)
*/
Integer selectCount(@Param(Constants.WRAPPER) Wrapper<T> queryWrapper);

测试用例:

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package cn.itcast.mp;
import cn.itcast.mp.mapper.UserMapper;
import cn.itcast.mp.pojo.User;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
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;
@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {
@Autowired
private UserMapper userMapper;
@Test
public void testSelectCount() {
QueryWrapper<User> wrapper = new QueryWrapper<User>();
wrapper.gt("age", 23); //年龄大于23岁
//根据条件查询数据条数
Integer count = this.userMapper.selectCount(wrapper);
System.out.println("count = " + count);
}
}

结果:

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[main] [cn.itcast.mp.mapper.UserMapper.selectCount]-[DEBUG] ==> Preparing: SELECT
COUNT( 1 ) FROM tb_user WHERE age > ?
[main] [cn.itcast.mp.mapper.UserMapper.selectCount]-[DEBUG] ==> Parameters: 23(Integer)
[main] [cn.itcast.mp.mapper.UserMapper.selectCount]-[DEBUG] <== Total: 1
count = 2

selectList

方法定义:

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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);

测试用例:

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package cn.itcast.mp;
import cn.itcast.mp.mapper.UserMapper;
import cn.itcast.mp.pojo.User;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
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 java.util.List;
@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {
@Autowired
private UserMapper userMapper;
@Test
public void testSelectList() {
QueryWrapper<User> wrapper = new QueryWrapper<User>();
wrapper.gt("age", 23); //年龄大于23岁
//根据条件查询数据
List<User> users = this.userMapper.selectList(wrapper);
for (User user : users) {
System.out.println("user = " + user);
}
}
}

结果:

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[main] [cn.itcast.mp.mapper.UserMapper.selectList]-[DEBUG] ==> Preparing: SELECT
id,user_name,password,name,age,email FROM tb_user WHERE age > ?
[main] [cn.itcast.mp.mapper.UserMapper.selectList]-[DEBUG] ==> Parameters: 23(Integer)
[main] [cn.itcast.mp.mapper.UserMapper.selectList]-[DEBUG] <== Total: 2
user = User(id=3, userName=wangwu, password=123456, name=王五, age=28,
email=test3@itcast.cn, address=null)
user = User(id=5, userName=sunqi, password=123456, name=孙七, age=24,
email=test5@itcast.cn, address=null)

selectPage

方法定义:

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/**
* 根据 entity 条件,查询全部记录(并翻页)
*
* @param page 分页查询条件(可以为 RowBounds.DEFAULT)
* @param queryWrapper 实体对象封装操作类(可以为 null)
*/
IPage<T> selectPage(IPage<T> page, @Param(Constants.WRAPPER) Wrapper<T> queryWrapper);

配置分页插件:

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import com.baomidou.mybatisplus.annotation.DbType;
import com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor;
import com.baomidou.mybatisplus.extension.plugins.pagination.optimize.JsqlParserCountOptimize;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

//Spring boot方式
@Configuration
@MapperScan("com.kaoxb.kaoxb.mapper")
public class MybatisPlusConfig {

// 最新版
@Bean
public MybatisPlusInterceptor mybatisPlusInterceptor() {
MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
interceptor.addInnerInterceptor(new PaginationInnerInterceptor(DbType.H2));
return interceptor;
}

}

测试用例:

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package cn.itcast.mp;
import cn.itcast.mp.mapper.UserMapper;
import cn.itcast.mp.pojo.User;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
import com.baomidou.mybatisplus.core.metadata.IPage;
import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
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 java.util.List;
@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {
@Autowired
private UserMapper userMapper;
@Test
public void testSelectPage() {
QueryWrapper<User> wrapper = new QueryWrapper<User>();
wrapper.gt("age", 20); //年龄大于20岁
Page<User> page = new Page<>(1,1);
//根据条件查询数据
IPage<User> iPage = this.userMapper.selectPage(page, wrapper);
System.out.println("数据总条数:" + iPage.getTotal());
System.out.println("总页数:" + iPage.getPages());
List<User> users = iPage.getRecords();
for (User user : users) {
System.out.println("user = " + user);
}
}
}

结果:

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[main] [cn.itcast.mp.mapper.UserMapper.selectPage]-[DEBUG] ==> Preparing: SELECT
COUNT(1) FROM tb_user WHERE age > ?
[main] [cn.itcast.mp.mapper.UserMapper.selectPage]-[DEBUG] ==> Parameters: 20(Integer)
[main] [cn.itcast.mp.mapper.UserMapper.selectPage]-[DEBUG] ==> Preparing: SELECT
id,user_name,password,name,age,email FROM tb_user WHERE age > ? LIMIT ?,?
[main] [cn.itcast.mp.mapper.UserMapper.selectPage]-[DEBUG] ==> Parameters: 20(Integer),
0(Long), 1(Long)
[main] [cn.itcast.mp.mapper.UserMapper.selectPage]-[DEBUG] <== Total: 1
[main] [org.mybatis.spring.SqlSessionUtils]-[DEBUG] Closing non transactional
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@6ecd665]
数据总条数:3
总页数:3
user = User(id=3, userName=wangwu, password=123456, name=王五, age=28,
email=test3@itcast.cn, address=null)

SQL注入的原理

前面我们已经知道,MP在启动后会将BaseMapper中的一系列的方法注册到meppedStatements中,那么究竟是如何注入的呢?流程又是怎么样的?下面我们将一起来分析下。

在MP中,ISqlInjector负责SQL的注入工作,它是一个接口,AbstractSqlInjector是它的实现类,实现关系如下:

在AbstractSqlInjector中,主要是由inspectInject()方法进行注入的,如下:

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@Override
public void inspectInject(MapperBuilderAssistant builderAssistant, Class<?>
mapperClass) {
Class<?> modelClass = extractModelClass(mapperClass);
if (modelClass != null) {
String className = mapperClass.toString();
Set<String> mapperRegistryCache = GlobalConfigUtils.getMapperRegistryCache(builderAssistant.getConfiguration());
if (!mapperRegistryCache.contains(className)) {
List<AbstractMethod> methodList = this.getMethodList();
if (CollectionUtils.isNotEmpty(methodList)) {
TableInfo tableInfo = TableInfoHelper.initTableInfo(builderAssistant,modelClass);
// 循环注入自定义方法
methodList.forEach(m -> m.inject(builderAssistant, mapperClass,
modelClass, tableInfo));
} else {
logger.debug(mapperClass.toString() + ", No effective injection method was found.");
}
mapperRegistryCache.add(className);
}
}
}

在实现方法中, methodList.forEach(m -> m.inject(builderAssistant, mapperClass, modelClass, tableInfo)); 是关键,循环遍历方法,进行注入。

最终调用抽象方法injectMappedStatement进行真正的注入:

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/**
* 注入自定义 MappedStatement
*
* @param mapperClass mapper 接口
* @param modelClass mapper 泛型
* @param tableInfo 数据库表反射信息
* @return MappedStatement
*/
public abstract MappedStatement injectMappedStatement(Class<?> mapperClass, Class<?
> modelClass, TableInfo tableInfo);

查看该方法的实现:

以SelectById为例查看:

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public class SelectById extends AbstractMethod {
@Override
public MappedStatement injectMappedStatement(Class<?> mapperClass, Class<?>
modelClass, TableInfo tableInfo) {
SqlMethod sqlMethod = SqlMethod.LOGIC_SELECT_BY_ID;
SqlSource sqlSource = new RawSqlSource(configuration,
String.format(sqlMethod.getSql(),
sqlSelectColumns(tableInfo, false),
tableInfo.getTableName(), tableInfo.getKeyColumn(),
tableInfo.getKeyProperty(),
tableInfo.getLogicDeleteSql(true, false)), Object.class);
return this.addSelectMappedStatement(mapperClass, sqlMethod.getMethod(),
sqlSource, modelClass, tableInfo);
}
}

可以看到,生成了SqlSource对象,再将SQL通过addSelectMappedStatement方法添加到meppedStatements中。

配置

在MP中有大量的配置,其中有一部分是Mybatis原生的配置,另一部分是MP的配置,详情:https://mybatis.plus/config/

下面我们对常用的配置做讲解。

基本配置

configLocation

MyBatis 配置文件位置,如果您有单独的 MyBatis 配置,请将其路径配置到 configLocation 中。 MyBatis Configuration 的具体内容请参考MyBatis 官方文档

Spring Boot:

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Spring MVC:

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<bean id="sqlSessionFactory"
class="com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean">
<property name="configLocation" value="classpath:mybatis-config.xml"/>
</bean>

mapperLocations

MyBatis Mapper 所对应的 XML 文件位置,如果您在 Mapper 中有自定义方法(XML 中有自定义实现),需要进行该配置,告诉 Mapper 所对应的 XML 文件位置。

Spring Boot:

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Spring MVC:

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<bean id="sqlSessionFactory"
class="com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean">
<property name="mapperLocations" value="classpath*:mybatis/*.xml"/>
</bean>

Maven 多模块项目的扫描路径需以 classpath*: 开头 (即加载多个 jar 包下的 XML 文件)

测试:

UserMapper.xml:

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<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="cn.itcast.mp.mapper.UserMapper">
<select id="findById" resultType="cn.itcast.mp.pojo.User">
select * from tb_user where id = #{id}
</select>
</mapper>
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package cn.itcast.mp.mapper;
import cn.itcast.mp.pojo.User;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
public interface UserMapper extends BaseMapper<User> {
User findById(Long id);
}

测试用例:

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package cn.itcast.mp;
import cn.itcast.mp.mapper.UserMapper;
import cn.itcast.mp.pojo.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;
@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {
@Autowired
private UserMapper userMapper;

@Test
public void testSelectPage() {
User user = this.userMapper.findById(2L);
System.out.println(user);
}
}

运行结果:

typeAliasesPackage

MyBaits 别名包扫描路径,通过该属性可以给包中的类注册别名,注册后在 Mapper 对应的 XML 文件中可以直接使用类名,而不用使用全限定的类名(即 XML 中调用的时候不用包含包名)。

Spring Boot:

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Spring MVC:

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<bean id="sqlSessionFactory"
class="com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean">
<property name="typeAliasesPackage"
value="com.baomidou.mybatisplus.samples.quickstart.entity"/>
</bean>

进阶配置

本部分(Configuration)的配置大都为 MyBatis 原生支持的配置,这意味着您可以通过 MyBatis XML 配置文件的形式进行配置。

mapUnderscoreToCamelCase

  • 类型: boolean
  • 默认值: true

是否开启自动驼峰命名规则(camel case)映射,即从经典数据库列名 A_COLUMN(下划线命名) 到经典 Java 属性名 aColumn(驼峰命名) 的类似映射。

注意:
此属性在 MyBatis 中原默认值为 false,在 MyBatis-Plus 中,此属性也将用于生成最终的 SQL 的 select body

如果您的数据库命名符合规则无需使用 @TableField 注解指定数据库字段名

示例(SpringBoot):

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#关闭自动驼峰映射,该参数不能和mybatis-plus.config-location同时存在
mybatis-plus.configuration.map-underscore-to-camel-case=false

cacheEnabled

  • 类型: boolean
  • 默认值: true

全局地开启或关闭配置文件中的所有映射器已经配置的任何缓存,默认为 true。
示例:

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mybatis-plus.configuration.cache-enabled=false

DB 策略配置

idType

  • 类型: com.baomidou.mybatisplus.annotation.IdType
  • 默认值: ID_WORKER

全局默认主键类型,设置后,即可省略实体对象中的@TableId(type = IdType.AUTO)配置。

示例:
SpringBoot:

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SpringMVC:

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<!--这里使用MP提供的sqlSessionFactory,完成了Spring与MP的整合-->
<bean id="sqlSessionFactory"
class="com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean">
<property name="dataSource" ref="dataSource"/>
<property name="globalConfig">
<bean class="com.baomidou.mybatisplus.core.config.GlobalConfig">
<property name="dbConfig">
<bean
class="com.baomidou.mybatisplus.core.config.GlobalConfig$DbConfig">
<property name="idType" value="AUTO"/>
</bean>
</property>
</bean>
</property>
</bean>

tablePrefix

  • 类型: String
  • 默认值:null

表名前缀,全局配置后可省略@TableName()配置。
SpringBoot:

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SpringMVC:

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<bean id="sqlSessionFactory"
class="com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean">
<property name="dataSource" ref="dataSource"/>
<property name="globalConfig">
<bean class="com.baomidou.mybatisplus.core.config.GlobalConfig">
<property name="dbConfig">
<bean
class="com.baomidou.mybatisplus.core.config.GlobalConfig$DbConfig">
<property name="idType" value="AUTO"/>
<property name="tablePrefix" value="tb_"/>
</bean>
</property>
</bean>
</property>
</bean>

条件构造器

在MP中,Wrapper接口的实现类关系如下:

可以看到,AbstractWrapper和AbstractChainWrapper是重点实现,接下来我们重点学习AbstractWrapper以及其子类。

说明:
QueryWrapper(LambdaQueryWrapper) 和 UpdateWrapper(LambdaUpdateWrapper) 的父类 用于生成 sql的 where 条件, entity 属性也用于生成 sql 的 where 条件 注意: entity 生成的 where 条件与 使用各个 api 生成的 where 条件没有任何关联行为

官网文档地址:https://mybatis.plus/guide/wrapper.html

allEq

说明

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allEq(Map<R, V> params)
allEq(Map<R, V> params, boolean null2IsNull)
allEq(boolean condition, Map<R, V> params, boolean null2IsNull)

全部eq(或个别isNull)

个别参数说明: params : key 为数据库字段名, value 为字段值 null2IsNull : 为 true 则在 map 的 value 为null 时调用 isNull 方法,为 false 时则忽略 value 为 null 的

  • 例1: allEq({id:1,name:"老王",age:null}) —> id = 1 and name = '老王' and age is null
  • 例2: allEq({id:1,name:"老王",age:null}, false) —>id = 1 and name = '老王'
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allEq(BiPredicate<R, V> filter, Map<R, V> params)
allEq(BiPredicate<R, V> filter, Map<R, V> params, boolean null2IsNull)
allEq(boolean condition, BiPredicate<R, V> filter, Map<R, V> params, boolean
null2IsNull)

个别参数说明: filter : 过滤函数,是否允许字段传入比对条件中 params 与 null2IsNull : 同上
例1: allEq((k,v) -> k.indexOf("a") > 0, {id:1,name:"老王",age:null}) —>name = '老王' and age is null
例2: allEq((k,v) -> k.indexOf("a") > 0, {id:1,name:"老王",age:null}, false) —> name = '老王'

测试用例

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package cn.itcast.mp;
import cn.itcast.mp.mapper.UserMapper;
import cn.itcast.mp.pojo.User;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
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 java.util.HashMap;
import java.util.List;
import java.util.Map;
@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {
@Autowired
private UserMapper userMapper;
@Test
public void testWrapper() {
QueryWrapper<User> wrapper = new QueryWrapper<>();

//设置条件
Map<String,Object> params = new HashMap<>();
params.put("name", "曹操");
params.put("age", "20");
params.put("password", null);
// wrapper.allEq(params);//SELECT * FROM tb_user WHERE password IS NULL AND name = ? AND age = ?
// wrapper.allEq(params,false); //SELECT * FROM tb_user WHERE name = ? AND age = ?
// wrapper.allEq((k, v) -> (k.equals("name") || k.equals("age")) ,params);//SELECT * FROM tb_user WHERE name = ? AND age = ?

List<User> users = this.userMapper.selectList(wrapper);
for (User user : users) {
System.out.println(user);
}
}
}

基本比较操作

  • eq
    • 等于 =
  • ne
    • 不等于 <>
  • gt
    • 大于 >
  • ge
    • 大于等于 >=
  • lt
    • 小于 <
  • le
    • 小于等于 <=
  • between
    • BETWEEN 值1 AND 值2
  • notBetween
    • NOT BETWEEN 值1 AND 值2
  • in
    • 字段 IN (value.get(0), value.get(1), …)
  • notIn
    • 字段 NOT IN (v0, v1, …)

测试用例:

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package cn.itcast.mp;
import cn.itcast.mp.mapper.UserMapper;
import cn.itcast.mp.pojo.User;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
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 java.util.List;
@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {
@Autowired
private UserMapper userMapper;
@Test
public void testEq() {
QueryWrapper<User> wrapper = new QueryWrapper<>();
//SELECT id,user_name,password,name,age,email FROM tb_user WHERE password = ? AND age >= ? AND name IN (?,?,?)
wrapper.eq("password", "123456")
.ge("age", 20)
.in("name", "李四", "王五", "赵六");
List<User> users = this.userMapper.selectList(wrapper);
for (User user : users) {
System.out.println(user);
}
}
}

模糊查询

  • like
    • LIKE ‘%值%’
    • 例: like("name", "王") ---> name like '%王%'
  • notLike
    • NOT LIKE '%值%'
    • 例: notLike("name", "王") ---> name not like '%王%'
  • likeLeft
    • LIKE '%值'
    • 例: likeLeft("name", "王") ---> name like '%王'
  • likeRight
    • LIKE '值%'
    • 例: likeRight("name", "王") ---> name like '王%'

测试用例:

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package cn.itcast.mp;
import cn.itcast.mp.mapper.UserMapper;
import cn.itcast.mp.pojo.User;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
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 java.util.List;
@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {
@Autowired
private UserMapper userMapper;
@Test
public void testWrapper() {
QueryWrapper<User> wrapper = new QueryWrapper<>();
//SELECT id,user_name,password,name,age,email FROM tb_user WHERE name LIKE ?
//Parameters: %曹%(String)
wrapper.like("name", "曹");
List<User> users = this.userMapper.selectList(wrapper);
for (User user : users) {
System.out.println(user);
}
}
}

排序

  • orderBy
    • 排序:ORDER BY 字段, …
    • 例: orderBy(true, true, "id", "name") ---> order by id ASC,name ASC
  • orderByAsc
    • 排序:ORDER BY 字段, … ASC
    • 例: orderByAsc("id", "name") ---> order by id ASC,name ASC
  • orderByDesc
    • 排序:ORDER BY 字段, … DESC
    • 例: orderByDesc("id", "name") ---> order by id DESC,name DESC

测试用例:

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package cn.itcast.mp;
import cn.itcast.mp.mapper.UserMapper;
import cn.itcast.mp.pojo.User;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
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 java.util.List;
@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {
@Autowired
private UserMapper userMapper;
@Test
public void testWrapper() {
QueryWrapper<User> wrapper = new QueryWrapper<>();
//SELECT id,user_name,password,name,age,email FROM tb_user ORDER BY age DESC
wrapper.orderByDesc("age");
List<User> users = this.userMapper.selectList(wrapper);
for (User user : users) {
System.out.println(user);
}
}
}

逻辑查询

  • or
    • 拼接 OR
    • 主动调用 or 表示紧接着下一个方法不是用 and 连接!(不调用 or 则默认为使用 and 连接)
  • and
    • AND 嵌套
    • 例: and(i -> i.eq("name", "李白").ne("status", "活着")) ---> and (name = '李白' and status <> '活着')
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package cn.itcast.mp;
import cn.itcast.mp.mapper.UserMapper;
import cn.itcast.mp.pojo.User;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
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 java.util.List;
@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {
@Autowired
private UserMapper userMapper;
@Test
public void testWrapper() {
QueryWrapper<User> wrapper = new QueryWrapper<>();
//SELECT id,user_name,password,name,age,email FROM tb_user WHERE name = ? OR age = ?
wrapper.eq("name","李四").or().eq("age", 24);
List<User> users = this.userMapper.selectList(wrapper);
for (User user : users) {
System.out.println(user);
}
}
}

select

在MP查询中,默认查询所有的字段,如果有需要也可以通过select方法进行指定字段。

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package cn.itcast.mp;
import cn.itcast.mp.mapper.UserMapper;
import cn.itcast.mp.pojo.User;
import com.baomidou.mybatisplus.core.conditions.query.QueryWrapper;
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 java.util.List;
@RunWith(SpringRunner.class)
@SpringBootTest
public class UserMapperTest {
@Autowired
private UserMapper userMapper;
@Test
public void testWrapper() {
QueryWrapper<User> wrapper = new QueryWrapper<>();
//SELECT id,name,age FROM tb_user WHERE name = ? OR age = ?
wrapper.eq("name", "李四")
.or()
.eq("age", 24)
.select("id", "name", "age");
List<User> users = this.userMapper.selectList(wrapper);
for (User user : users) {
System.out.println(user);
}
}
}

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