Spring boot JPA service layer code example

This article mainly introduces the spring boot JPA service layer code examples, which are introduced in great detail through the example code, which has a certain reference value for everyone's study or work. Friends in need can refer to it

package com.fei.service.impl;

import java.util.ArrayList;
import java.util.List;

import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Predicate;
import javax.persistence.criteria.Root;

import org.springframework.beans.BeanUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.Pageable;
import org.springframework.data.jpa.domain.Specification;
import org.springframework.stereotype.Service;

import com.fei.NotFoundException;
import com.fei.po.Blog;
import com.fei.po.Type;
import com.fei.repository.BlogRepository;
import com.fei.service.BlogService;

/**
 * Created by zxf on 2019年10月3日
 */
@Service
public class BlogServiceImpl implements BlogService {

  @Autowired
  private BlogRepository blogRepository;

  /**
   * 根据id查询一条博客
   *
   * @param id
   * @return
   */
  @Override
  public Blog getBlog(Long id) {
    return blogRepository.findById(id).get();
  }

  /**
   * 多条件动态查询博客列表
   *
   * @param pageable
   * @param blog
   * @return
   */
  @Override
  public Page<Blog> listBlog(Pageable pageable,Blog blog) {
    return blogRepository.findAll(new Specification<Blog>() {

      @Override
      public Predicate toPredicate(Root<Blog> root,CriteriaQuery<?> cq,CriteriaBuilder cb) {
        List<Predicate> predicates = new ArrayList<>();

        String title = blog.getTitle();
        if (!"".equals(title) && title != null) {
          predicates.add(cb.like(root.<String>get("title"),"%" + title + "%"));
        }

        Long id = blog.getType().getId();
        if (id != null) {
          predicates.add(cb.equal(root.<Type>get("type").get("id"),id));
        }

        boolean isRecommend = blog.isRecommend();
        if (isRecommend) {
          predicates.add(cb.equal(root.<Boolean>get("recommend"),isRecommend));
        }

        cq.where(predicates.toArray(new Predicate[predicates.size()]));
        return null;
      }
    },pageable);
  }

  /**
   * 保存一条博客
   *
   * @param blog
   * @return
   */
  @Override
  public Blog saveBlog(Blog blog) {
    return blogRepository.save(blog);
  }

  /**
   * 更新一条博客，先根据id查出结果回显
   *
   * @param id
   * @param blog
   * @return
   */
  @Override
  public Blog updateBlog(Long id,Blog blog) {
    Blog b = blogRepository.findById(id).get();
    if (b == null) {
      throw new NotFoundException("你要更新的博客不存在！");
    }

    BeanUtils.copyProperties(b,blog);
    return blogRepository.save(blog);
  }

  /**
   * 根据id删除一条博客
   *
   * @param id
   */
  @Override
  public void deleteBlog(Long id) {
    blogRepository.deleteById(id);
  }

}

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