IDEA社区版+SpringBoot+MyBatisPLus+MySQL实现数据库的保存、查询、修改操作

一、概述

　　使用IDEA社区+SpringBoot+MyBatisPlus+MySQL实现数据的保存修改与查询。主要记录一下踩坑过程。

　　注意事项：

　　1.社区版IDEA并不能直接创建SpringBoot工程，所以我采用的方式是在Spring官网上，让其帮助我创建一个，创建好后，直接下载。　

//参考案例
https://blog.csdn.net/fen_fen/article/details/123464256
//以下是官网的创建及快速开始步骤
https://start.spring.io/
https://spring.io/quickstart　

　　2.数据库安装的是5.5

　　3.maven安装的是3.8.8，安装完成后配置记得配置一下环境变量

　　4.在springboot官网下载好demo项目后，用社区版IDEA打开，打开后的配置类似下面的目录结构

 　　a.在demo上下载下来的application.properties改为application.yml。这里面用于配置应用信息，如：端口号、数据库连接配置、mybatis配置、文件上传服务配置等　　　

spring:
  #  mysql连接配置与mybaits一致
  datasource:
    # 数据库地址、端口、数据库名
    #jdbc:mysql://ip地址:端口号/数据库名称?useUnicode=true&characterEncoding=utf-8&useSSL=true&serverTimezone=GMT%2B8
    url: jdbc:mysql://127.0.0.1:3306/test?useUnicode=true&characterEncoding=utf-8&useSSL=true&serverTimezone=GMT%2B8
    username: root    #数据库账号
    password: 123456    #数据库密码
    driver-class-name: com.mysql.cj.jdbc.Driver
mybatis-plus:
  mapper-locations: mapper/*.xml #这个配置是用来连接mapper接口和mapper配置类
  configuration:
    log-impl: org.apache.ibatis.logging.stdout.StdOutImpl #运行日志
    map-underscore-to-camel-case: true #驼峰转换
  type-aliases-package: com.tony.demo.model #实体扫描包

　　b.pom.xml主要存放的是项目依赖包的信息，如果要新增或者删除依赖包，都是在这里面进行。下面是简单示例

　　c.DemoApplication是入口，如下图所示，里面有一个main函数

 　　d.在目录结构中可以看到controller、mapper以及service包。这三个包是有关联的。

 　　　　StudengController:是api请求的方法路径入口

　　　　StudentMapper:

　　　　StudentServiceImpl:

 　　model中的实体和数据库中的表做映射：

 　　总结一下controller、service、mapper：例如：用户调用登录接口api/login，首先会找到controller，controller再找到service，service再找到对应的mapper，最终用mapper的增啥改查方法，进行数据库表的操作

二、代码实现

　　代码实现不做过多解释，直接把完整代码贴出来方便作对比：

　　1.StudentController.java

@RestController
public class StudentController {
    @Autowired
    StudentService studentService;

    @RequestMapping(value = "/addStudent", method = RequestMethod.POST)
    public void addStudent(@RequestBody Student student) {
        studentService.saveStudent(student);
    }

    @RequestMapping(value = "addOrUpdateStudent",method = RequestMethod.POST)
    public void saveOrUpdateStudent(@RequestBody Student student){
        studentService.saveOrUpdate(student);
    }


    /**
     * 根据指定的id查询用户
     *
     * @param s_id 用户id
     * @return
     */
    @RequestMapping(value = "/queryStudentById/{s_id}", method = RequestMethod.GET)
    public Student queryStudentById(@PathVariable("s_id") String s_id) {
        return studentService.getStudentById(s_id);
    }

    /**
     * 根据条件查询用户列表
     *
     * @param student 指定用户
     * @return
     */
    @RequestMapping(value = "/getList", method = RequestMethod.POST)
    public List<Student> getList(@RequestBody Student student) {
        return studentService.getList(student);
    }


    /**
     * 根据用户名获取用户列表
     *
     * @param name 用户名
     * @return
     */
    @RequestMapping(value = "/getStudentsByName", method = RequestMethod.GET)
    public List<Student> getStudentsByName(@RequestParam("s_name") String name) {
        return studentService.getStudentByName(name);
    }


}

　　2.StudentServiceImpl.java、StudentService.java

@Service
public class StudentServiceImpl extends ServiceImpl<StudentMapper, Student> implements StudentService {
    @Autowired
    private StudentMapper studentMapper;

    /**
     * 添加学生
     * @param student 学生
     */
    @Transactional
    @Override
    public void saveStudent(Student student) {
//        studentMapper.addStudent(student);
        studentMapper.insert(student);
    }

    @Transactional
    @Override
    public List<Student> getList(Student student) {
        QueryWrapper<Student> wrapper = new QueryWrapper<>();
        if (student.getSId() != null) {
            wrapper.eq("s_id", student.getSId());
        }
        if (student.getSName() != null && !Objects.equals(student.getSName(), "")) {
            wrapper.like("s_name", student.getSName());
        }
        return studentMapper.selectList(wrapper);
    }

    @Transactional
    @Override
    public List<Student> getStudentByName(String s_name) {
        return studentMapper.getUserByName(s_name);
    }

    @Transactional
    @Override
    public Student getStudentById(String s_id) {
        Student student = studentMapper.getStudentById(s_id);
        if (student != null) {
            System.out.println("不为空");
        } else {
            System.out.println("为空");
        }
        return student;
    }
}

public interface StudentService extends IService<Student> {

    /**
     * 添加学生
     * @param student 学生
     */
    void saveStudent(Student student);

    /**
     * 查询条件查询
     * @param student 学生
     * @return
     */
    List<Student> getList(Student student);

    /**
     * 根据学生名称查询学生列表
     * @param s_name
     * @return
     */
    List<Student> getStudentByName(String s_name);

    /**
     * 根据学生id查询学生
     * @param s_id
     * @return
     */
    Student getStudentById(String s_id);
}

　　3.StudentMaper.java

@Mapper
public interface StudentMapper extends BaseMapper<Student> {
    //    @Select("select * from student where s_name=#{s_name}")
    List<Student> getUserByName(@Param("s_name") String s_name);

    //    @Select("select * from student where s_id=#{s_id}")
    Student getStudentById(@Param("s_id") String s_id);

    //    void addStudent(@Param("s_id,s_name,s_sex,s_age,s_description")String s_id,String s_name,String s_sex,String s_age,String s_description);
    void addStudent(@Param("student") Student student);
}

　　4.StudentMapper.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.tony.demo.mapper.StudentMapper">
    <resultMap id="studentResultMap" type="com.tony.demo.model.Student">
        <id property="sId" jdbcType="VARCHAR"  column="s_id" />
        <result property="sName" jdbcType="VARCHAR" column="s_name" />
        <result property="sAge" jdbcType="VARCHAR" column="s_age" />
        <result property="sSex" jdbcType="VARCHAR" column="s_sex" />
        <result property="sDescription" jdbcType="VARCHAR" column="s_description" />
    </resultMap>
    <insert id="addStudent" parameterType="com.tony.demo.model.Student">
        insert into student values(student.sId,student.sName,student.sSex,student.sAge,student.sDescription)
    </insert>

    <select id="getUserByName" parameterType="java.lang.String" resultType="com.tony.demo.model.Student">
        select * from student where s_name=#{s_name}
    </select>
    <select id="getStudentById" resultType="com.tony.demo.model.Student">
        select * from student where s_id=#{s_id}
    </select>

</mapper>

　　5.Student.java

@Data
@Getter
@Setter
@ToString
@TableName("student")
public class Student {
    @TableId(value = "s_id")
    private String sId= UUID.randomUUID().toString();

    @TableField(value = "s_name")
    private String sName;

    @TableField(value = "s_sex")
    private String sSex;

    @TableField(value = "s_age")
    private String sAge;

    @TableField(value = "s_description")
    private String sDescription;
}

　　6.DemoApplication

@SpringBootApplication
public class DemoApplication {

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

}