Spring Boot jpa Service层实现代码

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);
	}

}