Spring Boot (3) Jap使用

在url后加?useUnicode=true&characterEncoding=utf-8 解决中文乱码问题。

JpaSpecificationExecutor<T> 接口 ：

1.不属于Repository体系，实现一组 JPA Criteria 查询相关的方法 。
2.Specification：封装 JPA Criteria 查询条件。通常使用匿名内部类的方式来创建该接口的对象。

nativeQuery：是否开启本地查询，默认false

package com.java1234.dao;

import java.util.List;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
import org.springframework.data.jpa.repository.Query;

import com.java1234.Books;

public interface Bookdao extends JpaRepository<Books, Integer>,JpaSpecificationExecutor<Books>  {
	@Query("select b from Books b where b.name like %?1% ")
	public List<Books> findByname(String name);
	/*本地查询*/
	@Query(value="select * from book order by RAND() limit ?1",nativeQuery=true)
	public List<Books> randomList(Integer n);
}

CriteriaBuilder是一个工厂对象

	@RequestMapping("/list1")
	public ModelAndView list1(Books book) {
		ModelAndView mav = new ModelAndView();
		System.out.println("book::"+book.getName());
		mav.addObject("bookslist", bookdao.findAll(new Specification<Books>() {
			
			@Override
			public Predicate toPredicate(Root<Books> arg0, CriteriaQuery<?> arg1, CriteriaBuilder cd) {
				Predicate	 predicate=cd.conjunction();
				if(book!=null) {
					if(book.getName()!=null&&!"".equals(book.getName())) {
						predicate.getExpressions().add(cd.like(arg0.get("name"),"%"+book.getName()+"%"));
					}
					if(book.getAuthor()!=null&&!"".equals(book.getAuthor())) {
						predicate.getExpressions().add(cd.like(arg0.get("author"),"%"+book.getAuthor()+"%"));
					}
				}
				return predicate;
			}
		}));
		mav.setViewName("booklist");
		return mav;	
	}