Spring Data JPA数据操作总结. findById getOne findOne save delete 等

mybatis和Spring Data JPA基本上就是主要的数据库持久层的框架,本篇自己使用jpa的基本增删改查的方式帮助大家快速上手Spring Data JPA.
本篇使用的springboot版本为2.4.1 所依赖的jpa版本也是2.4.1不同版本会有些许差别.

  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-data-jpa</artifactId>
  <version>2.4.1</version>

1. 实体于和repository

实体要使用包装类型

package com.fierykylin.jpa.entity;

import com.fasterxml.jackson.annotation.JsonFormat;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import lombok.Data;

import javax.persistence.*;
import java.io.Serializable;
import java.time.LocalDateTime;

@Entity
@Data
@Table(name = "article")
@JsonIgnoreProperties(value = { "hibernateLazyInitializer"})
public class Article implements Serializable {
    @Id
    @GeneratedValue(strategy=GenerationType.IDENTITY)//自增
    private Integer id;
    private Integer categoryId;
    private String cover;
    private String title;
    private String introduction;
    private String contentMarkdown;
    private String content;
    private Boolean top;
    private Boolean recommend;
    private Boolean hot;
    private Integer browse;
    private Integer up;
    @JsonFormat(shape=JsonFormat.Shape.STRING, pattern="yyyy-MM-dd HH:mm:ss")
    private LocalDateTime createTime;
    @JsonFormat(shape=JsonFormat.Shape.STRING, pattern="yyyy-MM-dd HH:mm:ss")
    private LocalDateTime updateTime;
}

repository

package com.fierykylin.jpa.repository;

import com.fierykylin.jpa.entity.Article;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;

@Repository
public interface ArticleRepository extends JpaRepository<Article, Integer> {
}

2.方法基本使用

1.findById 通过id查找,没查询到就返回null

    @Test
    @Transactional
    public void testFindById(){
        Article one = articleRepository.findById(500).orElse(null);
    }

2.getOne 通过id查找 采用懒加载 使用时才真正去查库.若id为查询到会异EntityNotFoundException.

@Test
    @Transactional
    public void testGetOne(){
        Article one = articleRepository.getOne(500);
        String title = one.getTitle();
    }

id为不存在报异常

javax.persistence.EntityNotFoundException: Unable to find com.fierykylin.jpa.entity.Article with id 500

3.findOne

所查询的结果必须是只包含一条结果,否则会报如下异常

org.springframework.dao.IncorrectResultSizeDataAccessException: query did not return a unique result: 2

查询标题包含故事 并且热门的文章!

    @Test
    @Transactional
    public void testFindOne(){
        Article article = new Article();
        article.setHot(true);
        article.setTitle("故事");
        Example<Article> example = Example.of(article, ExampleMatcher.matching().withMatcher("title", ExampleMatcher.GenericPropertyMatcher::contains));
        Article one = articleRepository.findOne(example).orElse(null);
    }

4.findAllById 通过id查询多个 若未查询到则返回空集合

    @Test
    @Transactional
    public void testFindAllById(){
        List<Article> articles = articleRepository.findAllById(Arrays.asList(1,2,3));
    }

5.findAllById 通过id查询多个 若未查询到则返回空集合

查询热门并且根据top升序id倒序查询

    @Test
    @Transactional
    public void testFindAll(){
        Article article = new Article();
        article.setHot(true);
        Example<Article> example = Example.of(article);
        Sort sort = Sort.by(Sort.Order.asc("top"), Sort.Order.desc("id"));
        List<Article> articles = articleRepository.findAll(example,sort);
        YGDumper.tree(articles);
    }

简单分页使用

@Test
    @Transactional
    public void testFindAll(){
        Article article = new Article();
        Example<Article> example = Example.of(article);
        Sort sort = Sort.by(Sort.Order.asc("top"), Sort.Order.desc("id"));
        PageRequest pageRequest = PageRequest.of(0, 2,sort);
        Page<Article> articles = articleRepository.findAll(example,pageRequest);
        YGDumper.tree(articles);
    }

6.save 保存 需要配置主键自增策略 @Transactional注解要去掉不然会回滚数据添加失败!

@Test
    public void testSave(){
        Article article = new Article();
        article.setTitle("测试添加");
        Article save = articleRepository.save(article);
        YGDumper.tree(save);
    }

7.delete 删除 删除没有返回值

此种删除无效

@Test
    public void testDelete(){
        Article article = new Article();
        article.setTitle("测试添加");
        articleRepository.delete(article);
    }

实际删除需要实体中包含id即可正确删除,可以直接先查询出实体,然后删除

    @Test
    public void testDelete(){
        Article article = new Article();
        article.setId(17);
        articleRepository.delete(article);
    }
//或者
    @Test
    public void testDelete(){
        Article article = new Article();
        article.setTitle("测试添加");
        Article articleFind=articleRepository.findOne(Example.of(article)).orElse(null);
        articleRepository.delete(articleFind);
    }

7.deleteALL 删除所有数据 会执行两条sql 先查出所有id 然后根据id一条条的删除.慎用避免使用无参清空数据

@Test
    public void testDeleteAll(){
        articleRepository.deleteAll();
    }

//删除指定 同样是依据ID进行删除操作

@Test
    public void testDeleteAll1(){
        Article article1 = new Article();
        article1.setId(1);
        Article article2 = new Article();
        article2.setId(2);
        ArrayList<Article> list = new ArrayList<>();
        list.add(article1);
        list.add(article2);
        articleRepository.deleteAll(list);
    }

出输入的sql可以看到,先查询的id,然后在进行删除.

8.count 查询数量 无参的方法会返回所有的记录

@Test
    public void testCount(){
        Article article = new Article();
        article.setHot(true);
        Example<Article> example = Example.of(article);
        long count = articleRepository.count(example);
        System.out.println(count);
    }

目前就测试以上方法的基本用法,大部分方法都是都通过方法名就能轻松知道方法是怎么用的.本文只初略的总结了基本使用,更复杂的查询还待研究.