Spring Boot jpa Service层代码实例

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);
  }

}