【Springboot】springboot中使用mybatis操作数据库

新建springboot项目的时候，选择好web，mybatis，JDBC

在application.properties或者application.yml中配置

spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/studentManagerBoot?useUnicode=true&characterEncoding=utf-8&useSSL=true&serverTimezone=UTC
    username: root
    password:

Student的实体类：

package com.hj.studentmanagerboot.user.entity;

public class Student {
    private int stuId;
    private int stuNum;
    private String stuName;
    private String stuBirthday;
    private int stuEnterYear;
    private int stiState;

    @Override
    public String toString() {
        return "Student{" +
                "stuId=" + stuId +
                ", stuNum=" + stuNum +
                ", stuName=" + stuName +
                ", stuBirthday='" + stuBirthday + '\'' +
                ", stuEnterYear=" + stuEnterYear +
                ", stiState=" + stiState +
                '}';
    }
    public String getStuName() {
        return stuName;
    }

    public void setStuName(String stuName) {
        this.stuName = stuName;
    }

    public int getStuId() {
        return stuId;
    }

    public void setStuId(int stuId) {
        this.stuId = stuId;
    }

    public int getStuNum() {
        return stuNum;
    }

    public void setStuNum(int stuNum) {
        this.stuNum = stuNum;
    }

    public String getStuBirthday() {
        return stuBirthday;
    }

    public void setStuBirthday(String stuBirthday) {
        this.stuBirthday = stuBirthday;
    }

    public int getStuEnterYear() {
        return stuEnterYear;
    }

    public void setStuEnterYear(int stuEnterYear) {
        this.stuEnterYear = stuEnterYear;
    }

    public int getStiState() {
        return stiState;
    }

    public void setStiState(int stiState) {
        this.stiState = stiState;
    }
}

写好在dao包中新建StudentMapper接口，添加getStudent(int stuId)方法

package com.hj.studentmanagerboot.user.dao;

import com.hj.studentmanagerboot.user.entity.Student;
import org.springframework.stereotype.Repository;

@Repository
public interface StudentMapper {
    Student getStudent(int stuId);
}

在service包中新建getStudentService,并自动装配StudentMapper，添加getStudentService的方法

package com.hj.studentmanagerboot.user.service;

import com.hj.studentmanagerboot.user.dao.StudentMapper;
import com.hj.studentmanagerboot.user.entity.Student;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class StudentServiceTest {
    @Autowired
    StudentMapper studentMapper;

    public Student getStudent(int stuId) {
        return studentMapper.getStudent(stuId);
    }
}

在controller中自动装配StudentService

package com.hj.studentmanagerboot.user.handler;


import com.hj.studentmanagerboot.user.service.StudentServiceTest;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("testStudent")
public class StudentHandlerTest {
    @Autowired
    private StudentServiceTest studentServiceTest;
    @RequestMapping("getUser/{id}")
    public String getUser(@PathVariable("id") int stuId) {
        return studentServiceTest.getStudent(stuId).toString();
    }

}

在SpringBoot的入口程序中增加mybatis的注解，扫描dao包（如果不使用扫描包的方式，可以在dao包中的每个Mapper接口前，加上@Mapper注解）

@MapperScan("com.hj.studentmanagerboot.user.dao")
public class ...{

}

在Resource文件下新建mapper文件夹存放Mapper.xml，并在application.yml或application.properties中增加存放mybatis的Mapper配置文件的信息：

mybatis:
  mapper-locations: classpath:mapper/*Mapper.xml
  type-aliases-package: com.hj.studentmanagerboot.user.entity
#如果不使用type-aliases-package，则在每个实体类前加上@Component即可

在StudentMapper.xml中写入配置信息

<?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.hj.studentmanagerboot.user.dao.StudentMapper">
    <select id="getStudent" resultType="com.hj.studentmanagerboot.user.entity.Student">
        select * from stuInfo where stuId = #{stuId}
    </select>
</mapper>

 最后还碰到一个这样的问题，数据中命名一般是user_name，而实体类一般是userName，如何能让查找时候，自动转化命名呢。

只需要在application.yml中加入下面的配置即可：

mybatis:
  configuration:
    map-underscore-to-camel-case: true