mybatis insert 获取主键

小咪咪 2022-05-12 14:28 161阅读 0赞

根据业务需求，我们常常需要在 insert 插入一条数据后，对刚刚插入的数据进行某种操作；这时就需要获取新添加的数据的主键，如果主键是自增的话，重新查询，比较麻烦；mybatis 提供了一种配置，可以在 insert 执行后获取到新添加数据的主键

## 配置如下 ##

<insert id="insert" useGeneratedKeys="true" keyProperty="id" parameterType="com.demo.bean.Book">
    	  insert into book(name, author)  values(#{name}, #{author}) 
    </insert>

只需在 insert 标签中添加 useGeneratedKeys="true" keyProperty="id" ，其中 keyProperty 对应的 id 为自增的主键字段

## 测试如下 ##

### 实体类 ###

package com.demo.bean;
    
    public class Book {
    	
    	private Integer id;
    	
    	private String name;
    	
    	private String author;
    
    	public Integer getId() {
    		return id;
    	}
    
    	public void setId(Integer id) {
    		this.id = id;
    	}
    
    	public String getName() {
    		return name;
    	}
    
    	public void setName(String name) {
    		this.name = name;
    	}
    
    	public String getAuthor() {
    		return author;
    	}
    
    	public void setAuthor(String author) {
    		this.author = author;
    	}
    }

### mapper层 ###

package com.demo.mapper;
    
    import org.apache.ibatis.annotations.Mapper;
    import com.demo.bean.Book;
    
    @Mapper
    public interface BookMapper {
    	
    	int insert(Book book); 
    
    }

### mapper.xml 文件 ###

<?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="com.demo.mapper.BookMapper">
    	
    	<resultMap id="BaseResultMap" type="com.demo.bean.Book">
    		<id column="id" property="id" jdbcType="VARCHAR" />
    		<result column="name" property="name" jdbcType="VARCHAR" />
    		<result column="author" property="author" jdbcType="VARCHAR" />
    	</resultMap>
    	
    	<insert id="insert" useGeneratedKeys="true" keyProperty="id" parameterType="com.demo.bean.Book">
    	  insert into book(name, author)  values(#{name}, #{author}) 
    	</insert>
    	
    </mapper>

注意： keyProperty 对应的 id ，是 resultMap 中配置的主键 id （二者字段必须对应上）

### 测试类 ###

package com.demo;
    
    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 com.demo.bean.Book;
    import com.demo.mapper.BookMapper;
    
    @RunWith(SpringRunner.class)
    @SpringBootTest
    public class SpringbootJspApplicationTests {
    	
    	@Autowired
    	private BookMapper bookMapper; 
    
    	@Test
    	public void contextLoads() {
    		Book book = new Book();
    		book.setName("西游记");
    		book.setAuthor("吴承恩");
    		bookMapper.insert(book);
    		System.out.println("返回的主键:   "+book.getId());
    	}
    
    }

### 运行测试类，控制台打印如下 ###

![70][]

### 数据库如下 ###

![70 1][]

成功获取到 主键 id = 4

[70]: /images/20220504/9fd8f93f8739405787b74ac10b569409.png
[70 1]: /images/20220504/4e36367083fc4fa88f08c0e9dff64749.png