Mybatis-Plus使用指南
1、了解Mybatis-Plus
1.1、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/ 或 https://mp.baomidou.com/
1.2、代码以及文档
文档地址：https://mybatis.plus/guide/
源码地址：https://github.com/baomidou/mybatis-plus
1.3、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
1.4、架构
1.5、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
2、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。
2.1、创建数据库以及表
-- 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', '[email protected]');
INSERT INTO `tb_user` (`id`, `user_name`, `password`, `name`, `age`, `email`) VALUES ('2', 'lisi', '123456', '李四', '20', '[email protected]');
INSERT INTO `tb_user` (`id`, `user_name`, `password`, `name`, `age`, `email`) VALUES ('3', 'wangwu', '123456', '王五', '28', '[email protected]');
INSERT INTO `tb_user` (`id`, `user_name`, `password`, `name`, `age`, `email`) VALUES ('4', 'zhaoliu', '123456', '赵六', '21', '[email protected]');
INSERT INTO `tb_user` (`id`, `user_name`, `password`, `name`, `age`, `email`) VALUES ('5', 'sunqi', '123456', '孙七', '24', '[email protected]');
2.2、创建工程
导入依赖：
<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>4.0.0modelVersion>
<groupId>cn.itcast.mpgroupId>
<artifactId>itcast-mybatis-plusartifactId>
<version>1.0-SNAPSHOTversion>
<modules>
<module>itcast-mybatis-plus-simplemodule>
modules>
<packaging>pompackaging>
<dependencies>
<dependency>
<groupId>com.baomidougroupId>
<artifactId>mybatis-plusartifactId>
<version>3.1.1version>
dependency>
<dependency>
<groupId>mysqlgroupId>
<artifactId>mysql-connector-javaartifactId>
<version>5.1.47version>
dependency>
<dependency>
<groupId>com.alibabagroupId>
<artifactId>druidartifactId>
<version>1.0.11version>
dependency>
<dependency>
<groupId>org.projectlombokgroupId>
<artifactId>lombokartifactId>
<optional>trueoptional>
<version>1.18.4version>
dependency>
<dependency>
<groupId>junitgroupId>
<artifactId>junitartifactId>
<version>4.12version>
dependency>
<dependency>
<groupId>org.slf4jgroupId>
<artifactId>slf4j-log4j12artifactId>
<version>1.6.4version>
dependency>
dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.pluginsgroupId>
<artifactId>maven-compiler-pluginartifactId>
<configuration>
<source>1.8source>
<target>1.8target>
configuration>
plugin>
plugins>
build>
project>
2.3、Mybatis + MP
下面演示，通过纯Mybatis与Mybatis-Plus整合。
2.3.1、创建子Module
<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-plusartifactId>
<groupId>cn.itcast.mpgroupId>
<version>1.0-SNAPSHOTversion>
parent>
<modelVersion>4.0.0modelVersion>
<packaging>jarpackaging>
<artifactId>itcast-mybatis-plus-simpleartifactId>
project>
log4j.properties：
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
2.3.2、Mybatis实现查询User
第一步，编写mybatis-config.xml文件：
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&characterEncoding=utf8&autoReconnect=true&allowMultiQueries=true&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）
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：
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：
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：
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：
[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=[email protected])
User(id=2, userName=null, password=123456, name=李四, age=20, email=[email protected])
User(id=3, userName=null, password=123456, name=王五, age=28, email=[email protected])
User(id=4, userName=null, password=123456, name=赵六, age=21, email=[email protected])
User(id=5, userName=null, password=123456, name=孙七, age=24, email=[email protected])
2.3.3、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：
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：
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：
[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=[email protected])
User(id=2, userName=lisi, password=123456, name=李四, age=20, email=[email protected])
User(id=3, userName=wangwu, password=123456, name=王五, age=28, email=[email protected])
User(id=4, userName=zhaoliu, password=123456, name=赵六, age=21, email=[email protected])
User(id=5, userName=sunqi, password=123456, name=孙七, age=24, email=[email protected])
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；
- 如图：
2.4、Spring + Mybatis + MP
引入了Spring框架，数据源、构建等工作就交给了Spring管理。
2.4.1、创建子Module
<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-plusartifactId>
<groupId>cn.itcast.mpgroupId>
<version>1.0-SNAPSHOTversion>
parent>
<modelVersion>4.0.0modelVersion>
<artifactId>itcast-mybatis-plus-springartifactId>
<properties>
<spring.version>5.1.6.RELEASEspring.version>
properties>
<dependencies>
<dependency>
<groupId>org.springframeworkgroupId>
<artifactId>spring-webmvcartifactId>
<version>${spring.version}version>
dependency>
<dependency>
<groupId>org.springframeworkgroupId>
<artifactId>spring-jdbcartifactId>
<version>${spring.version}version>
dependency>
<dependency>
<groupId>org.springframeworkgroupId>
<artifactId>spring-testartifactId>
<version>${spring.version}version>
dependency>
dependencies>
project>
2.4.2、实现查询User
第一步，编写jdbc.properties
jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://127.0.0.1:3306/mp?useUnicode=true&characterEncoding=utf8&autoReconnect=true&allowMultiQueries=true&useSSL=false
jdbc.username=root
jdbc.password=root
第二步，编写applicationContext.xml
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context.xsd">
<context:property-placeholder location="classpath:*.properties"/>
<bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource"
destroy-method="close">
<property name="url" value="${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>
<bean id="sqlSessionFactory" class="com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean">
<property name="dataSource" ref="dataSource"/>
bean>
<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：
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;
}
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：
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：
[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=[email protected])
User(id=2, userName=lisi, password=123456, name=李四, age=20, email=[email protected])
User(id=3, userName=wangwu, password=123456, name=王五, age=28, email=[email protected])
User(id=4, userName=zhaoliu, password=123456, name=赵六, age=21, email=[email protected])
User(id=5, userName=sunqi, password=123456, name=孙七, age=24, email=[email protected])
2.5、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。
2.5.1、创建工程
2.5.2、导入依赖
<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>4.0.0modelVersion>
<parent>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-parentartifactId>
<version>2.1.4.RELEASEversion>
parent>
<groupId>cn.itcast.mpgroupId>
<artifactId>itcast-mp-springbootartifactId>
<version>1.0-SNAPSHOTversion>
<dependencies>
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starterartifactId>
<exclusions>
<exclusion>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-loggingartifactId>
exclusion>
exclusions>
dependency>
<dependency>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-starter-testartifactId>
<scope>testscope>
dependency>
<dependency>
<groupId>org.projectlombokgroupId>
<artifactId>lombokartifactId>
<optional>trueoptional>
dependency>
<dependency>
<groupId>com.baomidougroupId>
<artifactId>mybatis-plus-boot-starterartifactId>
<version>3.1.1version>
dependency>
<dependency>
<groupId>mysqlgroupId>
<artifactId>mysql-connector-javaartifactId>
<version>5.1.47version>
dependency>
<dependency>
<groupId>org.slf4jgroupId>
<artifactId>slf4j-log4j12artifactId>
dependency>
dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.bootgroupId>
<artifactId>spring-boot-maven-pluginartifactId>
plugin>
plugins>
build>
project>
log4j.properties：
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
2.5.3、编写application.properties
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
2.5.4、编写pojo
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;
}
2.5.5、编写mapper
package cn.itcast.mp.mapper;
import cn.itcast.mp.pojo.User;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
public interface UserMapper extends BaseMapper<User> {
}
2.5.6、编写启动类
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);
}
}
2.5.7、编写测试用例
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：
[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=[email protected])
User(id=2, userName=lisi, password=123456, name=李四, age=20, email=[email protected])
User(id=3, userName=wangwu, password=123456, name=王五, age=28, email=[email protected])
User(id=4, userName=zhaoliu, password=123456, name=赵六, age=21, email=[email protected])
User(id=5, userName=sunqi, password=123456, name=孙七, age=24, email=[email protected])
3、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。
3.1、插入操作
3.1.1、方法定义
/**
* 插入一条记录
*
* @param entity 实体对象
*/
int insert(T entity);
3.1.2、测试用例
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("[email protected]");
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
}
}
3.1.3、测试
[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), [email protected](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：
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
* 该类型可以通过自己注册自动填充插件进行填充
*/
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：
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：
3.1.4、@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：
3.2、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。
3.2.1、根据id更新
方法定义：
/**
* 根据 ID 修改
*
* @param entity 实体对象
*/
int updateById(@Param(Constants.ENTITY) T entity);
测试：
@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：
[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
3.2.2、根据条件更新
方法定义：
/**
* 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：
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：
@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：
[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。
3.3、删除操作
3.3.1、deleteById
方法定义：
/**
* 根据 ID 删除
*
* @param id 主键ID
*/
int deleteById(Serializable id);
测试用例：
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：
[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。
3.3.2、deleteByMap
方法定义：
/**
* 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：
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：
[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
3.3.3、delete
方法定义：
/**
* 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：
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：
[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
3.3.4、deleteBatchIds
方法定义：
/**
* 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：
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：
[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
3.4、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。
3.4.1、selectById
方法定义：
/**
* 根据 ID 查询
*
* @param id 主键ID
*/
T selectById(Serializable id);
测试用例：
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：
[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=[email protected], address=null)
3.4.2、selectBatchIds
方法定义：
/**
* 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：
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：
[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=[email protected], address=null)
User(id=3, userName=wangwu, password=123456, name=王五, age=28, email=[email protected], address=null)
3.4.3、selectOne
方法定义：
/**
* 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：
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：
[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=[email protected], address=null)
3.4.4、selectCount
方法定义：
/**
* 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：
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：
[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
3.4.5、selectList
方法定义：
/**
* 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：
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：
[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=[email protected], address=null)
user = User(id=5, userName=sunqi, password=123456, name=孙七, age=24, email=[email protected], address=null)
3.4.6、selectPage
方法定义：
/**
* 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：
package cn.itcast.mp;
import com.baomidou.mybatisplus.extension.plugins.PaginationInterceptor;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
@Configuration
@MapperScan("cn.itcast.mp.mapper") //设置mapper接口的扫描包
public class MybatisPlusConfig {
/**
* 分页插件
*/
@Bean
public PaginationInterceptor paginationInterceptor() {
return new PaginationInterceptor();
}
}
测试用例：
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：
[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=[email protected], address=null)
3.5、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：
@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：
/**
* 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：
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。
4、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。
4.1、基本配置
4.1.1、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：
mybatis-plus.config-location = classpath:mybatis-config.xml
Spring MVC：
<bean id="sqlSessionFactory" class="com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean">
<property name="configLocation" value="classpath:mybatis-config.xml"/>
bean>
4.1.2、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：
mybatis-plus.mapper-locations = classpath*:mybatis/*.xml
Spring MVC：
<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：
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>
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：
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：
4.1.3、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：
mybatis-plus.type-aliases-package = cn.itcast.mp.pojo
Spring MVC：
<bean id="sqlSessionFactory" class="com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean">
<property name="typeAliasesPackage" value="com.baomidou.mybatisplus.samples.quickstart.entity"/>
bean>
4.2、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。
4.2.1、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）：
#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
4.2.2、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：
mybatis-plus.configuration.cache-enabled=false
4.3、DB 策略配置
4.3.1、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：
mybatis-plus.global-config.db-config.id-type=auto
SpringMVC：
<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>
4.3.2、tablePrefix
- 类型：
String - 默认值：
null
表名前缀，全局配置后可省略@TableName()配置。
SpringBoot：
mybatis-plus.global-config.db-config.table-prefix=tb_
SpringMVC：
<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>
5、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
5.1、allEq
5.1.1、说明
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'
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'
5.1.2、测试用例
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);
}
}
}
5.2、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：
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);
}
}
}
5.3、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：
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);
}
}
}
5.4、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：
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);
}
}
}
5.5、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')
测试用例：
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);
}
}
}
5.6、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。
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);
}
}
}
m.out.println(user);
}
}
}
### 5.5、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')`
测试用例：
```java
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 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 users = this.userMapper.selectList(wrapper);
for (User user : users) {
System.out.println(user);
}
}
}
```
### 5.6、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。
```java
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 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 users = this.userMapper.selectList(wrapper);
for (User user : users) {
System.out.println(user);
}
}
}
```