整合Spring Data JPA操作数据及排序分页

一、 Sping Data JPA 简介

Spring Data JPA 是 Spring 基于 ORM 框架、JPA 规范的基础上封装的一套 JPA 应用框架，底层使用了 Hibernate 的 JPA 技术实现，可使开发者用极简的代码即可实现对数据的访问和操作。它提供了包括增删改查等在内的常用功能接口，且易于扩展！学习并使用 Spring Data JPA 可以极大提高开发效率！
由于微服务系统的广泛应用，服务粒度逐渐细化，多表关联查询的场景一定程度减少。单表查询和单表的数据操作正是JPA的优势。

二、 将Spring Data JPA集成到Spring Boot

第一步：引入maven依赖包，包括Spring Data JPA和Mysql的驱动
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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>SpringBootComplete</artifactId>
    <version>1.0-SNAPSHOT</version>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.0.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <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.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>io.projectreactor</groupId>
            <artifactId>reactor-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
    </dependencies>

</project>

第二步：修改application.yml，配置好数据库连接和jpa的相关配置

server:
  port: 8089
spring:
  #通用的数据源配置
  datasource:
    driverClassName: com.mysql.jdbc.Driver
    url: jdbc:mysql://123.57.87.54:3306/ssm?useSSL=false&useUnicode=true&characterEncoding=utf8
    username: bms
    password: bms@2018
  jpa:
    #这个参数是在建表的时候，将默认的存储引擎切换为 InnoDB 用的
    database-platform: org.hibernate.dialect.MySQL5InnoDBDialect
    #配置在日志中打印出执行的 SQL 语句信息。
    show-sql: true
    hibernate:
      #配置指明在程序启动的时候要删除并且创建实体类对应的表
      ddl-auto: validate

三、 基础核心用法

实体Model类

@Data
@Entity
@Table(name = "tt_user")
public class User {
    public User(){
    }
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;
    private String user_name;
//    @JsonFormat(shape=JsonFormat.Shape.STRING, pattern="yyyy-MM-dd HH:mm:ss")
    private Date birthday;
    private String sex;
    private String address;
}

实现DAO层,数据操作接口

@Repository
public interface UserRepository extends JpaRepository<User, Integer> {
}

service层接口

public interface UserService {
//    查询所有
    public  List<User> findall();
    /** 删除 */
    public void delete(int id);
    /** 增加*/
    public void insert(User user);
    /** 更新*/
    public int update(User user);
    /** 查询单个*/
    public User selectById(int id);
    /** 查询全部列表*/
    public Iterator<User> selectAll(int pageNum, int pageSize);
}

service层接口实现

package com.dj.lunch.service;

import com.dj.lunch.dao.UserRepository;
import com.dj.lunch.model.User;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Pageable;
import org.springframework.data.domain.Sort;
import org.springframework.stereotype.Service;

import java.util.Iterator;
import java.util.List;
import java.util.Optional;

@Slf4j
@Service
public class UserServiceImpl implements UserService {

    @Autowired
    private UserRepository userRepository;

    /**
     * 删除
     *
     * @param id
     */
    @Override
    public void delete(int id) {
        userRepository.deleteById(id);
    }

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

    /**
     * 增加
     *
     * @param user
     */
    @Override
    public void insert(User user) {
        userRepository.save(user);
    }

    /**
     * 更新
     *
     * @param user
     */
    @Override
    public int update(User user) {
        userRepository.save(user);
        return 1;
    }

    /**
     * 查询单个
     *
     * @param id
     */
    @Override
    public User selectById(int id) {
        Optional<User> optional = userRepository.findById(id);
        User user = optional.get();
        return user;
    }

//    @Override
//    public Iterator<User> selectAll(int pageNum, int pageSize) {
//        return null;
//    }

    /**
     * 查询全部列表,并做分页
     *  @param pageNum 开始页数
     * @param pageSize 每页显示的数据条数
     */
    @Override
    public Iterator<User> selectAll(int pageNum, int pageSize) {
        //将参数传给这个方法就可以实现物理分页了，非常简单。

//        Sort sort = new Sort.by(Sort.Direction.DESC, "id");
//        Pageable pageable = new PageRequest(pageNum, pageSize, sort);
        //2.2以上不适合此方法
        Sort sort = Sort.by(Sort.Direction.DESC,"id");
        PageRequest Page = PageRequest.of(pageNum,pageSize,sort);
        Page<User> users = userRepository.findAll(Page);
        Iterator<User> userIterator =  users.iterator();
        return  userIterator;

    }


}

实现Controller

@RestController
@RequestMapping("/user")
public class UserController {

    @Autowired
    private UserService userService;

    @RequestMapping(method = RequestMethod.GET,value = "/delete/{id}")
    public void delete(@PathVariable("id")int id){
        userService.delete(id);
    }

    @RequestMapping(method = RequestMethod.GET,value = "/findall")
    public  List<User> findall(){
        List<User> u =   userService.findall();
        return u;
    }
    @RequestMapping(method = RequestMethod.POST,value = "/insert")
    public void insert(@RequestBody User user){

        userService.insert(user);
    }
    @RequestMapping(method = RequestMethod.POST,value = "/update/{id}")
    public void update(@RequestBody User user){
        userService.update(user);
    }

    @RequestMapping(method = RequestMethod.GET,value = "/{id}/select")
    public User select(@PathVariable("id")int id){
        return userService.selectById(id);
    }

    @RequestMapping(method = RequestMethod.GET,value = "/selectAll/{pageNum}/{pageSize}")
    public List<User> selectAll(@PathVariable("pageNum") int pageNum, @PathVariable("pageSize") int pageSize){
        Iterator<User> userIterator = userService.selectAll(pageNum, pageSize);
        List<User> list = new ArrayList<>();
        while(userIterator.hasNext()){
            list.add(userIterator.next());
        }
        return list;
    }

}

源码地址
参考链接：
https://www.jianshu.com/p/3b31270a44b1
https://www.kancloud.cn/hanxt/springboot2/1177605