前言

上篇咱们学到如何用链接数据库，但是我们对数据的操作都是写死在代码里面，本篇主要学习mapper，entity，以及mybatis的使用

安装依赖

pom.xml新增mybatis依赖

+++
<dependency>
    <groupId>org.mybatis.spring.boot</groupId>
    <artifactId>mybatis-spring-boot-starter</artifactId>
    <version>2.1.0</version>
</dependency>
+++

修改配置文件

+++
#SpringBoot整合Mybatis配置
mybatis.type-aliases-package=com.semyin.blog
mybatis.mapper-locations=classpath:mapper/*.xml
mybatis.configuration.map-underscore-to-camel-case=true
+++

entity 类

实体类，一般用作与相关数据库表或者查询条件做映射，便于更好的操作数据库
在src/main/java/com/semyin/blog/下新建包entity，并在entity中新建Article实体类

package com.semyin.blog.entity;

import java.util.Date;

public class Article {

    private Integer id;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public String getDetail() {
        return detail;
    }

    public void setDetail(String detail) {
        this.detail = detail;
    }

    public Integer getStatus() {
        return status;
    }

    public void setStatus(Integer status) {
        this.status = status;
    }

    public Date getCreateTime() {
        return createTime;
    }

    public void setCreateTime(Date createTime) {
        this.createTime = createTime;
    }

    public Date getUpdateTime() {
        return updateTime;
    }

    public void setUpdateTime(Date updateTime) {
        this.updateTime = updateTime;
    }

    private String title;

    private String detail;

    private Integer status;

    private Date createTime;

    private Date updateTime;
}

mapper

在src/main/java/com/semyin/blog/下新建包mapper，并在mapper中新建ArticleMapper接口

package com.semyin.blog.mapper;

import com.semyin.blog.entity.Article;

import java.util.List;

public interface ArticleMapper {
    List<Article> getArticles();
}

在src/main/resources新建mapper文件夹，并新建ArticleMapper.xml

<?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.semyin.blog.mapper.ArticleMapper">
    <select id="getArticles" resultType="Article">
        select * from article
    </select>
</mapper>

修改controller，调用mapper

+++
@Resource
private ArticleMapper articleMapper;
+++

/// 省略代码

@GetMapping("/articles")
public Object getArticles() {
+++
    return articleMapper.getArticles();
+++
}

修改主程序入口支持扫描mapper

package com.semyin.blog;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
+++
@MapperScan("com.semyin.blog.mapper")
+++
public class BlogApplication {

    public static void main(String[] args) {
        SpringApplication.run(BlogApplication.class, args);
    }

}

打开postman请求，发现数据已经帮我们返回好了

结语

本篇主要是配置mybatis，mapper，然后把数据库里面字段映射到entity中，便于我们自定义操作