SpringBoot JPA简单使用

引自B站楠哥：https://www.bilibili.com/video/BV137411B7vB

一、新建Springboot项目

​ pom.xml文件

<?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>2.2.2.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.southwind</groupId>
    <artifactId>springboottest</artifactId>
    <version>1.0.0-SNAPSHOT</version>
    <name>springboottest</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
        <skipTests>true</skipTests>
    </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>

application.yml文件

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/db20201107_demo?useUnicode=true&characterEncoding=UTF-8&serverTimezone=Asia/Shanghai
    username: root
    password: 123456
    driver-class-name: com.mysql.cj.jdbc.Driver
  jpa:
    show-sql: true
    properties:
      hibernate:
        format_sql: true
server:
  port: 8088

启动类：

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class SpringboottestApplication {

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

}

实体类Book

import lombok.Data;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Entity
@Data
public class Book {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;
    private String name;
    private String author;
}

二、在数据库中创建对应的book表

create table `book` (
	`id` int (10),
	`name` varchar (60),
	`author` varchar (60),
	`publish` varchar (60),
	`pages` int (10),
	`price` float ,
	`bookcaseid` int (10),
	`abled` int (10)
); 
insert into `book` (`id`, `name`, `author`, `publish`, `pages`, `price`, `bookcaseid`, `abled`) values('1','解忧杂货店','东野圭吾','电子工业出版社','102','27.30','9','1');
insert into `book` (`id`, `name`, `author`, `publish`, `pages`, `price`, `bookcaseid`, `abled`) values('2','追风筝的人','卡勒德·胡赛尼','中信出版社','330','26.00','1','1');
insert into `book` (`id`, `name`, `author`, `publish`, `pages`, `price`, `bookcaseid`, `abled`) values('3','人间失格','太宰治','作家出版社','150','17.30','1','1');
insert into `book` (`id`, `name`, `author`, `publish`, `pages`, `price`, `bookcaseid`, `abled`) values('4','这就是二十四节气','高春香','电子工业出版社','220','59.00','3','1');
insert into `book` (`id`, `name`, `author`, `publish`, `pages`, `price`, `bookcaseid`, `abled`) values('5','白夜行','东野圭吾','南海出版公司','300','27.30','4','1');
insert into `book` (`id`, `name`, `author`, `publish`, `pages`, `price`, `bookcaseid`, `abled`) values('6','摆渡人','克莱儿·麦克福尔','百花洲文艺出版社','225','22.80','1','1');
insert into `book` (`id`, `name`, `author`, `publish`, `pages`, `price`, `bookcaseid`, `abled`) values('7','暖暖心绘本','米拦弗特毕','湖南少儿出版社','168','131.60','5','1');
insert into `book` (`id`, `name`, `author`, `publish`, `pages`, `price`, `bookcaseid`, `abled`) values('8','天才在左疯子在右','高铭','北京联合出版公司','330','27.50','6','1');
insert into `book` (`id`, `name`, `author`, `publish`, `pages`, `price`, `bookcaseid`, `abled`) values('9','我们仨','杨绛','生活.读书.新知三联书店','89','17.20','7','1');
insert into `book` (`id`, `name`, `author`, `publish`, `pages`, `price`, `bookcaseid`, `abled`) values('10','活着','余华','作家出版社','100','100.00','6','1');
insert into `book` (`id`, `name`, `author`, `publish`, `pages`, `price`, `bookcaseid`, `abled`) values('11','水浒传','施耐庵','三联出版社','300','50.00','1','1');
insert into `book` (`id`, `name`, `author`, `publish`, `pages`, `price`, `bookcaseid`, `abled`) values('12','三国演义','罗贯中','三联出版社','300','50.00','2','1');
insert into `book` (`id`, `name`, `author`, `publish`, `pages`, `price`, `bookcaseid`, `abled`) values('13','红楼梦','曹雪芹','三联出版社','300','50.00','5','1');
insert into `book` (`id`, `name`, `author`, `publish`, `pages`, `price`, `bookcaseid`, `abled`) values('14','西游记','吴承恩','三联出版社','300','60.00','3','1');

三、项目分层

3.1 BookRepository

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

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

3.2 BookController

import com.southwind.springboottest.entity.Book;
import com.southwind.springboottest.repository.BookRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;
import org.springframework.web.bind.annotation.*;

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

    @GetMapping("/findAll/{page}/{size}") 
    public Page<Book> findAll(@PathVariable("page") Integer page, @PathVariable("size") Integer size){
        PageRequest request = PageRequest.of(page-1,size);//此处第一个参数是从0开始计数，所以用page-1
        System.out.println("request="+request.toString());
        return bookRepository.findAll(request);
    }

    @PostMapping("/save")
    public String save(@RequestBody Book book){
        Book result = bookRepository.save(book);
        if(result != null){
            return "success";
        }else{
            return "error";
        }
    }

    @GetMapping("/findById/{id}")
    public Book findById(@PathVariable("id") Integer id){
        return bookRepository.findById(id).get();
    }

    @PutMapping("/update")
    public String update(@RequestBody Book book){
        Book result = bookRepository.save(book);
        if(result != null){
            return "success";
        }else{
            return "error";
        }
    }

    @DeleteMapping("/deleteById/{id}")
    public void deleteById(@PathVariable("id") Integer id){
        bookRepository.deleteById(id);
    }
}