1.项目结构

2.添加依赖

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.5.1</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.fizzyelf</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>JPATest</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

        <!-- JPA依赖 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>

        <!-- mysql数据库驱动 -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.22</version>
        </dependency>

        <!-- lombok -->
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>

        <!-- 测试 -->
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

3.application.properties

server.port=8443

spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
spring.datasource.url=jdbc:mysql://localhost:3306/hibernatetest?serverTimezone=GMT
spring.datasource.username=root
spring.datasource.password=Good18882336322

spring.jpa.hibernate.ddl-auto=update
# 开启控制台SQL打印
spring.jpa.show_sql = true
# 开启SQL格式化
spring.jpa.properties.hibernate.format_sql = true

4.新建一个user表

5.idea连接数据库

然后在弹出框输入数据库相关信息，记得加上时区，最后点击尝试连接，连接成功后，点击确定，这样idea就和数据库连接上了。

6.编写实体类

package com.fizzyelf.demo.Entity;

import lombok.Data;

import javax.persistence.*;

@Data
@Entity
@Table(name="user")
public class User {
    @Id // 主键
    @GeneratedValue(strategy=GenerationType.IDENTITY)//主键生成策略
    @Column(name="id")//数据库字段名
    private Integer id;

    @Column(name="user_name")//数据库字段名
    private String userName;

    @Column(name="password")//数据库字段名
    private String password;
}

此时idea还解析不到数据库，我们点击“分配数据源”

将数据源选择刚刚我们添加的数据库，这样idea就可以解析到数据库中的表，和字段了。

7.repository 数据层

package com.fizzyelf.demo.Dao;

import com.fizzyelf.demo.Entity.User;
import org.springframework.data.jpa.repository.JpaRepository;


/**
 * 参数一 T :当前需要映射的实体
 * 参数二 ID :当前映射的实体中的ID的类型
 *
 */
public interface UserRepository extends JpaRepository<User,Integer> {
}

JpaRepository接口中定义了许多方法，其中就包括了基本的增删改查的方法。

8.Service业务层

接口UserService

package com.fizzyelf.demo.Service;

import com.fizzyelf.demo.Entity.User;

import java.util.List;

public interface UserService {
    /**
     * 插入一个用户
     */
    User insertUser(User user);

    /**
     * 删除用户
     */
    void deleteUser(int id);

    /**
     * 通过id查询用户
     */
    User findUserById(int id);

    /**
     * 查询所有用户
     */
    List<User> findAllUser();

    /**
     * 修改用户
     */
    User updateUser(User user);
}

实现类UserServiceImpl

package com.fizzyelf.demo.Service.impl;

import com.fizzyelf.demo.Dao.UserRepository;
import com.fizzyelf.demo.Entity.User;
import com.fizzyelf.demo.Service.UserService;
import org.springframework.stereotype.Service;

import javax.annotation.Resource;
import java.util.List;

@Service
public class UserServiceImpl implements UserService {
    @Resource
    private UserRepository userRepository;

    @Override
    public User insertUser(User user){
        return userRepository.save(user);
    }

    @Override
    public void deleteUser(int id) {
        userRepository.deleteById(id);
    }

    @Override
    public User findUserById(int id){
        return userRepository.findById(id).orElse(null);
    }

    @Override
    public List<User> findAllUser() {
        return userRepository.findAll();
    }

    @Override
    public User updateUser(User user) {
        return userRepository.save(user);
    }
}

9.Controller控制层

package com.fizzyelf.demo.Controller;


import com.fizzyelf.demo.Entity.User;
import com.fizzyelf.demo.Service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;


@RestController
@RequestMapping("/user")
public class UserController {
    @Autowired
    private UserService userService;

    /**
     * 新增用户
     */
    @PostMapping("")
    public User addUser(@RequestBody User user){
        return userService.insertUser(user);
    }

    /**
     * 根据id删除
     */
    @DeleteMapping ("/{id}")
    public void deleteUser(@PathVariable("id") int id){
        userService.deleteUser(id);
    }

    /**
     * 根据id查找
     */
    @GetMapping ("/{id}")
    public User findUser(@PathVariable("id") int id){
        return userService.findUserById(id);
    }

    /**
     * 查询所有用户
     */
    @GetMapping ("")
    public List<User> findAllUser(){
        return userService.findAllUser();
    }

    /**
     * 修改用户
     */
    @PutMapping ("")
    public User updateUser(@RequestBody User user){
        return userService.updateUser(user);
    }
}