SpringBoot引入mybatis及连接Mysql数据库

Posted 2022-10-29

创建一个SpringBoot项目

其他不赘叙了，引入MyBaties、MySql依赖

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 创建mysql表

CREATE TABLE sp_users(
  `id` INT PRIMARY KEY,
  `username` VARCHAR(30),
  `age` INT
);

刚开始一直出现这个错误，弄的我怀疑人生，结果是最后一行不能加, ，物是人非。 

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INSERT INTO sp_users(id,`username`,`age`) VALUES(1,"张三",11);
INSERT INTO sp_users(id,`username`,`age`) VALUES(2,"李四",21);
INSERT INTO sp_users(id,`username`,`age`) VALUES(3,"游坦之",800);

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 编写实体类

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因为引入了Lombok，所以直接用了

package com.you.domain;

import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.ToString;

@Data
@NoArgsConstructor
@AllArgsConstructor
@ToString
public class user 
    private int id;
    private String username;
    private int age;

配置application.yaml

#datasource
spring:
  datasource:
    url: jdbc:mysql:///springboot?serverTimezone=UTC
    username: root
    password: 你的密码
    driver-class-name: com.mysql.cj.jdbc.Driver

配置Mapper

方式一，创建UserMapper接口

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package com.you.mapper;

import com.you.domain.User;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Select;
import org.springframework.stereotype.Repository;

import java.util.List;

@Mapper
@Repository
public interface UserMapper 
    @Select("select * from sp_users")
    public List<User> findAll();

配置测试类

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package com.you.boot;


import com.you.boot.domain.User;
import com.you.boot.mapper.UserMapper;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import java.util.List;

@SpringBootTest
class BootMybatis03ApplicationTests 

    @Autowired
    private UserMapper userMapper;
    @Test
    public void testFindAll()
    
        List<User> list = userMapper.findAll();
        System.out.println(list);
    

效果图

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 方法二 XML文件配置

编写xml文件，namespace一定要复制全路径，Copy/Copy Reference

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<?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.you.boot.mapper.UserXmlMapper">
    <select id="findAll" resultType="user">
        select * from sp_users
    </select>
</mapper>

 编写UserXmlMapper接口，@Repository的作用是解决在测试类内爆红，虽然爆红不影响程序的运行。

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package com.you.boot.mapper;

import com.you.boot.domain.User;
import org.apache.ibatis.annotations.Mapper;
import org.springframework.stereotype.Repository;

import java.util.List;

@Mapper
@Repository
public interface UserXmlMapper 
    public List<User> findAll();

配置yaml，*Mapper值得是所有后缀是Mapper的xml文件

mybatis:
  mapper-locations: classpath:mapper/*Mapper.xml
  type-aliases-package: com.you.boot.domain

编写测试类

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package com.you.boot;


import com.you.boot.domain.User;
import com.you.boot.mapper.UserMapper;
import com.you.boot.mapper.UserXmlMapper;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import java.util.List;

@SpringBootTest
class BootMybatis03ApplicationTests 


    @Autowired
    private UserXmlMapper userXmlMapper;
    @Test
    public void testFindAll2()
    
        List<User> list = userXmlMapper.findAll();
        System.out.println(list);
    

效果

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感叹

记得当初学MySQL的时候，编写sql语句非常的熟练，现在非常僵硬，认真写博客真的不失为一种复习的好方法。还有当初学SSM的时候，没好好学，没有扎扎实实的学，现在也挺后悔的。快速和详细真的不能兼得。别人的建议可以听听，但一定要坚守自己的内心。倚天照海花无数，流水高山心自知。