SpringBoot学习笔记(四)——Spring Data JPA的使用

本文链接：https://blog.youkuaiyun.com/javaEE_zero/article/details/124392962

JPA即Java Persistence API，它的查询语言是面向对象而非面向数据库，可以看作是Hibernate hql的等价物。这一节记录Springboot整合JPA反向创建数据库表并实现增删改查功能。

1、创建springboot项目，如下：

添加web、JPA、mysql数据库驱动依赖

2、完成JPA和数据源配置

# 开发环境
server.port=8082
# 自动生成数据库表
spring.jpa.hibernate.ddl-auto=update
# 数据源
spring.datasource.url=jdbc:mysql://localhost:3306/login?useUnicode=true&characterEncoding=utf-8&useSSL=false
spring.datasource.username=root
spring.datasource.password=root123
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver
# jpa配置
# 在控制台显示SQL
spring.jpa.show-sql=true
spring.thymeleaf.cache=false

3、创建层级结构

3.1、创建层级结构目录

3.2 创建Book实体类，用于映射生成book数据库表

package com.galago.demo_jpa.entity;

import org.springframework.format.annotation.DateTimeFormat;

import javax.persistence.*;
import java.util.Date;

@Entity
public class Book {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    @Column(unique = true)
    private String bookName;

    @Column(nullable = true)
    private String author;

    @DateTimeFormat(pattern = "yyyy-MM-dd")
    private Date publishTime;

    public Integer getId() {
        return id;
    }

    public String getBookName() {
        return bookName;
    }

    public String getAuthor() {
        return author;
    }

    public Date getPublishTime() {
        return publishTime;
    }

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

    public void setBookName(String bookName) {
        this.bookName = bookName;
    }

    public void setAuthor(String author) {
        this.author = author;
    }

    public void setPublishTime(Date publishTime) {
        this.publishTime = publishTime;
    }

    public Book(Integer id, String bookName, String author, Date publishTime) {
        this.id = id;
        this.bookName = bookName;
        this.author = author;
        this.publishTime = publishTime;
    }

    public Book(String bookName, String author, Date publishTime) {
        this.bookName = bookName;
        this.author = author;
        this.publishTime = publishTime;
    }

    public Book() {
    }
}

启动项目生成book数据库表，运行结果如下：

3.3 编写BookRepo接口类，并extends JpaRepository接口

package com.galago.demo_jpa.repo;

import com.galago.demo_jpa.entity.Book;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

import java.util.List;

@Repository
public interface BookRepo extends JpaRepository<Book, Integer> {
   // 该接口类包含增删改查等功能接口，减少了很多编写代码
}

查看JpaRepository接口源码，其内置了增删改查等功能，如下

3.4 编写BookController类

package com.galago.demo_jpa.controller;

import com.galago.demo_jpa.entity.Book;
import com.galago.demo_jpa.repo.BookRepo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;

import java.util.List;

@RequestMapping("/book")
@Controller
public class UserController {

    @Autowired
    private BookRepo bookRepo;

    @RequestMapping("/getbook")
    @ResponseBody
    public List<Book> getbook() {
        return bookRepo.findAll();
    }

    @PostMapping("/add")
    @ResponseBody
    public Book addBook(Book book) {
        return bookRepo.save(book);
    }

    @RequestMapping("/del")
    @ResponseBody
    public void deleteById(Integer id) {
        System.out.println(id);
        bookRepo.deleteById(id);
    }

}