1 添加依赖

在pom.xml中添加SpringBoot JPA使用必须的相关依赖（主要依赖为：spring-boot-starter-data-jpa、spring-boot-starter-web、mysql-connector-java、lombok）。

在初始化SpringBoot项目时勾选，即可自动添加。

<?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>2.2.4.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>springboot</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>springboot</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-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>**
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
    </dependencies>

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

</project>

2 配置JPA连接数据库相关信息

在application.yml中配置数据库相关信息。

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/library?useUnicode=true&characterEncoding=UTF-8&serverTimezone=UTC
    username: root
    password: root
    driver-class-name: com.mysql.cj.jdbc.Driver
  jpa:
    show-sql: true
    properties:
      hibernate:
        format_sql: true

3 根据数据库表信息设计entity类

数据库表信息：

在entity包中创建出相应的类：

package com.example.entity;

import lombok.Data;

import javax.persistence.Entity;
import javax.persistence.Id;

@Entity
@Data
public class Book {
    @Id
    private Integer id;

    private String name;

    private String author;
}

4 根据entity.Book类创建数据库访问接口

package com.example.repository;

import com.example.entity.Book;
import org.springframework.data.jpa.repository.JpaRepository;

public interface BookRepository extends JpaRepository<Book, Integer> {
}

5 测试

在BookRepository上右键，创建相应测试类。

点击OK后，会在相应的目录中创建测试类：

在该类中编写相应的测试方法，运行进行测试：

package com.example.repository;

import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

import javax.persistence.Temporal;

import static org.junit.jupiter.api.Assertions.*;
@SpringBootTest
class BookRepositoryTest {
    @Autowired
    private BookRepository bookRepository;

    @Test
    void findAll() {
        System.out.println(bookRepository.findAll());
    }
}

6 创建controller类，为前端提供数据接口

package com.example.controller;

import com.example.entity.Book;
import com.example.repository.BookRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

@RestController
@RequestMapping("/book")
public class BookHandler {
    @Autowired
    BookRepository bookRepository;

    @GetMapping("findAll")
    public List<Book> findAll() {
        return bookRepository.findAll();
    }
}

至此，一个前端 —> SpringBoot —> 数据库的工作流程编写完毕。