springData学习（五）JpaRepository和JpaSpecificationExecutor接口学习

1.JpaRepository接口中的主要方式有：

其实很以前的方法一样，我们主要学习一下findAll（Sort sort） 方法

@Test
	public void testFindAllSort() {
		Order order = new Order(Sort.Direction.DESC, "age");
		Sort sort = new Sort(order);
		List<Student> sList = studentJpa.findAll(sort);
		sList.forEach(System.out::println);
	}

2.JpaSpecificationExecutor接口

• 不属于Repository体系，实现一组 JPA Criteria 查询相关的方法 
• 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

在上文的基础上，在继承JpaSpecificationExecutor接口。

其中path的包为：javax.persistence.criteria.Path;

public interface StudentJpa extends JpaRepository<Student, Integer>, JpaSpecificationExecutor<Student>{

}

测试类：

/**
	 * 1  分页
	 * 2  排序
	 * 3  条件查询
	 */
	@Test
	public void testQuery() {
		
		
		Sort.Order order = new Sort.Order(Sort.Direction.ASC,"id");
		Sort sort = new Sort(order);

		Pageable pageable = new PageRequest(0, 4,sort);//分页条件
		
		Specification<Student> specification = new Specification<Student>() {

			@Override
			public Predicate toPredicate(Root<Student> root, 
					                     CriteriaQuery<?> query, 
										 CriteriaBuilder cb) {
				//root中包含了Student Student包含了score
				Path path = root.get("score");
				Predicate predicate = cb.gt(path, 5);
				return predicate;
			}
		};
		Page<Student> page = studentJpa.findAll(specification, pageable);
		System.out.println("查询的总页数"+page.getTotalPages());
		System.out.println("查询的总记录数"+page.getTotalElements());
		System.out.println("查询的当前第几页"+page.getNumber()+1);
		System.out.println("查询的当前页面的集合"+page.getContent());
		System.out.println("查询的当前页面的记录数"+page.getNumberOfElements());
	}

如果我们想同时搜索多个条件时：

比如搜索年龄19岁且分数为90的人员信息

@Test
	public void testQuery() {
		
		
		Sort.Order order = new Sort.Order(Sort.Direction.ASC,"id");
		Sort sort = new Sort(order);

		Pageable pageable = new PageRequest(0, 4,sort);//分页条件
		
		Specification<Student> specification = new Specification<Student>() {

			@Override
			public Predicate toPredicate(Root<Student> root, 
					                     CriteriaQuery<?> query, 
										 CriteriaBuilder cb) {
				//root中包含了Student Student包含了score
				Path path = root.get("score");
				Path path1 = root.get("age");
				Predicate p1 = cb.equal(path, 90);
				Predicate p2 = cb.equal(path1, 18);
				return cb.and(p1, p2);
			}
		};
		Page<Student> page = studentJpa.findAll(specification, pageable);
		System.out.println("查询的总页数"+page.getTotalPages());
		System.out.println("查询的总记录数"+page.getTotalElements());
		System.out.println("查询的当前第几页"+page.getNumber()+1);
		System.out.println("查询的当前页面的集合"+page.getContent());
		System.out.println("查询的当前页面的记录数"+page.getNumberOfElements());
	}