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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。
引入依赖
<? 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 https://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>2.7.3</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.wyh</groupId>
<artifactId>SpringBootMybatisPlus01</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>SpringBootMybatisPlus01</name>
<description>SpringBootMybatisPlus01</description>
<properties>
<java.version>1.8</java.version>
</properties>
<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>8.0.28</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
编写application.properties
spring.application.name = itcast-mp-springboot
spring.datasource.driver-class-name=com.mysql.cj.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
编写实体和mapper
package com.wyh.entity;
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 com.wyh.mapper;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.wyh.entity.User;
import org.apache.ibatis.annotations.Mapper;
/**
* @description :
* @author : 魏一鹤
* @createDate : 2022-08-25 22:01
**/
public interface UserMapper extends BaseMapper<User> {
}
编写启动类并扫描到mapper
package com.wyh.springbootmybatisplus01;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
@MapperScan( "com.wyh.mapper" )
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
编写测试用例
package com.wyh.test;
import com.wyh.entity.User;
import com.wyh.mapper.UserMapper;
import com.wyh.springbootmybatisplus01.Application;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import javax.annotation.Resource;
import java.util.List;
/**
* @description : 测试MP整合SpringBoot
* @author : 魏一鹤
* @createDate : 2022-08-25 22:03
**/
@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest(classes= Application.class)
public class TestMybatisPlusSpringBoot {
@Resource
UserMapper userMapper;
@Test
public void queryUser(){
List<User> userList = userMapper.selectList(null);
for (User user : userList) {
System.out.println(user);
}
}
}
-
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
-
int insert(T entity); //插入一条数据 参数就是实体 -
测试用例
-
package com.wyh.test; import com.wyh.entity.User; import com.wyh.mapper.UserMapper; import com.wyh.springbootmybatisplus01.Application; import org.junit.Test; import org.junit.runner.RunWith; import org.springframework.boot.test.context.SpringBootTest; import org.springframework.test.context.junit4.SpringJUnit4ClassRunner; import javax.annotation.Resource; import java.util.List; /** * @description : 测试MP整合SpringBoot * @author : 魏一鹤 * @createDate : 2022-08-25 22:03 **/ @RunWith(SpringJUnit4ClassRunner.class) @SpringBootTest(classes= Application.class) public class TestMybatisPlusSpringBoot { @Resource UserMapper userMapper; /** * 测试MybatisPlus的新增操作 **/ @Test public void addUser(){ User user=new User(); user.setAge(19); user.setName( "caocao" ); user.setUserName( "曹操" ); user.setPassword( "123456" ); user.setEmail( "caocao@qq.com" ); // 受影响行数 int count = userMapper.insert(user); System.out.println( "受影响行数 = " + count); // 获取自增后的ID的值,自增长后的ID值会自动回填到User对象中 Long id = user.getId(); System.out.println( "id=" +id); } }
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。
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
* <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),
如何设置id的生成策略呢？
设置ID生成策略
MP默认的生成策略是NONE 我们需要手动改为Auto,也就是自动自增
//指定ID生成策略 AUTO=自增 默认是NONE
@TableId(type=IdType.AUTO)
设置完之后 需要吧数据库那条ID不对的数据删掉 同时修改表当前自动自增为5,因为目前只有四条,id最大为4
然后再次重启
这次终于没问题啦
