第一个搭建SpringBoot项目（连接mysql）

首先新建项目找到Spring Initializr 我使用的URL是https://start.spring.io这里最低的JDK版本是17，而且当网速不好的时候可能会显示超时，这里可以选用阿里云的镜像https://start.aliyun.com可以更快一些但是里面还是有一些区别的

我们这里选择Java语言，Maven框架

在这里我们选择一些我们需要用到的

这个版本可以选低一点更加稳定

进来之后我们需要先等pom文件加载，我们可以选择刷新Maven

加载完之后由于我们加载了MySQL所以还不能运行可以先注释掉，然后刷新maven

后面就可以运行了，但是它默认的是8080端口，有可能会有被占用的我们可以更改端口

后面既可以运行了

运行结果就是这样的后面没有了，刚开始由于我学习的时候和别人运行的不一样，还以为是卡住了，调试了好久好久，结果发现这就已经是运行了

下面我们就可以去页面看看结果了

用阿里云镜像的输出会有点不一样但是没有问题。

下面我们就可以创建一个测试类

新建一个TestController

@RestController
public class TestController {
    @GetMapping("/hello")
    public String hello(){
        return "hello word!";
    }
}

再去页面观察

rest api规范

路径

路径又称"终点"(endpoint)，表示API的具体网址。在RESTfuI架构中，每个网址代表一种资源(resource)，所以网址中不能有动词，只能有名词，而且所用的名词往往与数据库的表格名对应。

Http 动词

GET(SELECT):从服务器取出资源(一项或多项)。

POST(CREATE):在服务器新建一个资源。

PUT(UPDATE):在服务器更新资源(客户端提供改变后的完整资源)。。PATCH(UPDATE):在服务器更新资源(客户端提供改变的属性)

DELETE(DELETE):从服务器删除资源。

新建一个数据库，创建表student

使用mysql语句是这样的

创建

在这里我遇到的问题是JpaRepository我继承不了，然后不断的查找问题是更改pom文件里面的内容

加入

org.springframework.data

spring-data-jpa

然后刷新一下maven就好了

创建Student

Student

package com.example.mysqldemo3.dao;

import jakarta.persistence.*;

import static jakarta.persistence.GenerationType.IDENTITY;

@Entity
@Table(name = "student")
public class Student {
    @Id
    @Column(name = "id")
    @GeneratedValue(strategy = IDENTITY)
    private long id;
    @Column(name = "name")
    private String name;
    @Column(name = "email")
    private String email;
    @Column(name = "age")
    private int age;

    public long getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
}

返回到接口补全代码

package com.example.mysqldemo3.dao;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

@Repository
public interface StudentRepository extends JpaRepository<Student,Long> {

}

Service层

StudentService

package com.example.mysqldemo3.service;

import com.example.mysqldemo3.dao.Student;

public interface StudentService {
    Student getStudentById(long id);

}

StudentServiceImpl

package com.example.mysqldemo3.service;

import com.example.mysqldemo3.dao.Student;
import com.example.mysqldemo3.dao.StudentRepository;
import jakarta.persistence.Id;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class StudentServiceImpl implements StudentService{
    @Autowired
    private StudentRepository StudentRepository;
    @Override
    public Student getStudentById(long id) {
        return StudentRepository.findById(id).orElseThrow(RuntimeException::new) ;
    }
}

controller层

package com.example.mysqldemo3.controller;

import com.example.mysqldemo3.dao.Student;
import com.example.mysqldemo3.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class StudentController {
    @Autowired
    private StudentService studentService;
    @GetMapping("/student/{id}")
    public Student getStudentById(@PathVariable long id){
        return studentService.getStudentById(id);
    }
}

连接数据库这些配置写在application里面

数据库

spring.application.name=mysql-demo3
server.port=8085
spring.datasource.url=jdbc:mysql://localhost:3306/数据库名字?characterEncoding=utf-8
spring.datasource.username=root
spring.datasource.password=sgz250hhh

在数据库中填入数据

后面就可以去网页测试了

再往后我们需要做一些信息的隐藏，不想去展示这莫多的数据

创建

StudentDTO进行封装

package com.example.mysqldemo3.dto;

public class StudentDTO {
    private long id;
    private String name;
    private String email;

    public long getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }
}

新建converter将student的数据进行转换成DTO

StudentConverter

package com.example.mysqldemo3.converter;

import com.example.mysqldemo3.dao.Student;
import com.example.mysqldemo3.dto.StudentDTO;

public class StudentConverter {
    public static StudentDTO converStudent(Student student){
        //student转换成DTO对象
        StudentDTO studentDTO = new StudentDTO();
        studentDTO.setId(student.getId());
        studentDTO.setName(student.getName());
        studentDTO.setEmail(student.getEmail());
        return studentDTO;
    }
}

新建

判断是否查询成功

Response

package com.example.mysqldemo3;

public class Response <T>{
    //返回后端的一些格式
    private T data;
    private boolean success;
    private String errorMsg;

    public static <K> Response<K> newSuccess(K data){
        //返回成功
        Response<K> response = new Response<>();
        response.setData(data);
        response.setSuccess(true);
        return response;
    }
    public static  Response<Void> newFail(String errorMsg){
        //返回失败
        Response<Void> response = new Response<>();
        response.setErrorMsg(errorMsg);
        response.setSuccess(false);
        return response;
    }
    public T getData() {
        return data;
    }

    public void setData(T data) {
        this.data = data;
    }

    public boolean isSuccess() {
        return success;
    }

    public void setSuccess(boolean success) {
        this.success = success;
    }

    public String getErrorMsg() {
        return errorMsg;
    }

    public void setErrorMsg(String errorMsg) {
        this.errorMsg = errorMsg;
    }
}

StudentService

package com.example.mysqldemo3.service;

import com.example.mysqldemo3.dao.Student;
import com.example.mysqldemo3.dto.StudentDTO;

public interface StudentService {
    StudentDTO getStudentById(long id);

}

StudentServiceImpl

package com.example.mysqldemo3.service;

import com.example.mysqldemo3.converter.StudentConverter;
import com.example.mysqldemo3.dao.Student;
import com.example.mysqldemo3.dao.StudentRepository;
import com.example.mysqldemo3.dto.StudentDTO;
import jakarta.persistence.Id;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class StudentServiceImpl implements StudentService{
    @Autowired
    private StudentRepository StudentRepository;
    @Override
    public StudentDTO getStudentById(long id) {
        Student student = StudentRepository.findById(id).orElseThrow(RuntimeException::new);
        return StudentConverter.converStudent(student);
    }
}

StudentController

package com.example.mysqldemo3.controller;

import com.example.mysqldemo3.Response;
import com.example.mysqldemo3.dao.Student;
import com.example.mysqldemo3.dto.StudentDTO;
import com.example.mysqldemo3.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class StudentController {
    @Autowired
    private StudentService studentService;
    @GetMapping("/student/{id}")
    public Response<StudentDTO> getStudentById(@PathVariable long id){
        return Response.newSuccess(studentService.getStudentById(id));
    }
}

刷新页面

就可以看见age被隐藏起来了

后面的就是增加删除和修改的操作可以使用Postman进行接口测试，可以直接官网下载

StudentServiceImpl

package com.example.mysqldemo3.service;

import com.example.mysqldemo3.converter.StudentConverter;
import com.example.mysqldemo3.dao.Student;
import com.example.mysqldemo3.dao.StudentRepository;
import com.example.mysqldemo3.dto.StudentDTO;
import jakarta.persistence.Id;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.util.CollectionUtils;
import org.springframework.util.StringUtils;

import java.util.List;

@Service
public class StudentServiceImpl implements StudentService{
    @Autowired
    private StudentRepository StudentRepository;
    @Override
    public StudentDTO getStudentById(long id) {
        Student student = StudentRepository.findById(id).orElseThrow(RuntimeException::new);
        return StudentConverter.converStudent(student);
    }

    @Override
    public Long addNewStudent(StudentDTO studentDTO) {
        List<Student> studentList = StudentRepository.findByEmail(studentDTO.getEmail());
        if (!CollectionUtils.isEmpty(studentList)){
            throw new IllegalStateException("email:"+studentDTO.getEmail()+"has been taken");
        }
        Student student = StudentRepository.save(StudentConverter.converStudent(studentDTO));
        return student.getId();
    }

    @Override
    public void deleteStudentById(long id) {
        StudentRepository.findById(id).orElseThrow(()->new IllegalArgumentException("id"+id+"doesn`s exist!"));
        StudentRepository.deleteById(id);
    }

    @Override
    public StudentDTO updateStudentById(long id, String name, String email) {
        Student studentDB = StudentRepository.findById(id).orElseThrow(()->new IllegalArgumentException("id"+id+"doesn`s exist!"));
        if (StringUtils.hasLength(name) && !studentDB.getName().equals(name)){
            studentDB.setName(name);
        }
        if(StringUtils.hasLength(email) && !studentDB.getEmail().equals(email)){
            studentDB.setEmail(email);
        }
        Student student = StudentRepository.save(studentDB);
        return StudentConverter.converStudent(student);
    }

}

StudentService

package com.example.mysqldemo3.service;

import com.example.mysqldemo3.dao.Student;
import com.example.mysqldemo3.dto.StudentDTO;

public interface StudentService {
    StudentDTO getStudentById(long id);

    Long addNewStudent(StudentDTO studentDTO);

    void deleteStudentById(long id);

    StudentDTO updateStudentById(long id, String name, String email);
}

StudentRepository

package com.example.mysqldemo3.dao;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

import java.util.List;

@Repository
public interface StudentRepository extends JpaRepository<Student,Long> {
    List<Student> findByEmail(String emile);

}

StudentConverter

package com.example.mysqldemo3.converter;

import com.example.mysqldemo3.dao.Student;
import com.example.mysqldemo3.dto.StudentDTO;

public class StudentConverter {
    public static StudentDTO converStudent(Student student){
        //student转换成DTO对象
        StudentDTO studentDTO = new StudentDTO();
        studentDTO.setId(student.getId());
        studentDTO.setName(student.getName());
        studentDTO.setEmail(student.getEmail());
        return studentDTO;
    }
    public static Student converStudent(StudentDTO StudentDTO){
        //student转换成DTO对象
        Student student = new Student();
        student.setName(StudentDTO.getName());
        student.setEmail(StudentDTO.getEmail());
        return student;
    }
}

StudentController

package com.example.mysqldemo3.controller;

import com.example.mysqldemo3.Response;
import com.example.mysqldemo3.dao.Student;
import com.example.mysqldemo3.dto.StudentDTO;
import com.example.mysqldemo3.service.StudentService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

@RestController
public class StudentController {
    @Autowired
    private StudentService studentService;
    @GetMapping("/student/{id}")
    public Response<StudentDTO> getStudentById(@PathVariable long id){
        return Response.newSuccess(studentService.getStudentById(id));
    }
    @PostMapping("/student")
    public Response<Long> addNewStudent(@RequestBody StudentDTO studentDTO){
        return Response.newSuccess(studentService.addNewStudent(studentDTO));
    }
    @DeleteMapping("/student/{id}")
    public void deleteStudentById(@PathVariable long id){
        studentService.deleteStudentById(id);
    }
    @PutMapping("/student/{id}")
    public Response<StudentDTO> updateStudentById(@PathVariable long id,@RequestParam(required = false) String name,@RequestParam(required = false) String email){
        return Response.newSuccess(studentService.updateStudentById(id,name,email));
    }
}

最后就可以使用maven对文件进行打包了

标签： spring boot mysql 后端

本文转载自: https://blog.csdn.net/qq_63126439/article/details/141979018
版权归原作者 重生之苦练代码养女友 所有，如有侵权，请联系我们删除。

第一个搭建SpringBoot项目（连接mysql）

Service层

controller层

数据库

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