spring data jap操作

package com.example.demo;

import com.example.entity.UserJ;
import com.example.respository.UserJRespository;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Sort;
import org.springframework.data.jpa.domain.Specification;
import org.springframework.test.context.junit4.SpringRunner;

import javax.persistence.EntityManager;
import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Predicate;
import javax.persistence.criteria.Root;
import java.util.ArrayList;
import java.util.List;

@RunWith(SpringRunner.class)
@SpringBootTest
public class TestJpaCurd {
    @Autowired
    private UserJRespository userJRespository;

    @Autowired
    private EntityManager entityManager;

    /**
     * 插入或者是更新一条数据
     */
    @Test
    public void insertAndUpdate() {
        UserJ userJ = new UserJ();
        userJ.setUsername("alex222");
        userJ.setEmail("wangzhilei@jd.com");
        userJ.setId(1);
        userJRespository.save(userJ);
    }

    /**
     * 删除一条数据
     */
    @Test
    public void delete() {
        userJRespository.deleteById(1);
    }

    /**
     * 获取所有的数据
     *
     * @return
     */
    @Test
    public void getAll() {
        List<UserJ> all = userJRespository.findAll();
        for (UserJ userJ : all) {
            System.out.println(userJ);
        }
    }

    /**
     * 查询所有并+分页+排序
     * <p>
     * 从0页开始
     * 用最新的PageRequest.of来分页
     */
    @Test
    public void getOneData() {
        Sort sort = new Sort(Sort.Direction.DESC, "id");
        PageRequest pageRequest = PageRequest.of(0, 1, sort);
        /**
         * 使用匿名内部类
         * 构建查询条件
         * root 代表查询的对象
         * criteriaBuilder 条件封闭器，如and or like 等
         *  criteriaQuery 查询的条件
         */
        Specification<UserJ> specification = new Specification<UserJ>() {
            @Override
            public Predicate toPredicate(Root<UserJ> root, CriteriaQuery<?> criteriaQuery, CriteriaBuilder cb) {
                // 单个条件查询
//                Predicate predicate = cb.equal(root.get("email"), "sqyinchao@jd.com");
                /**
                 * 多条件查询
                 */
                List<Predicate> list = new ArrayList<>();
                list.add(cb.equal(root.get("email"), "sqyinchao@jd.com"));
                list.add(cb.equal(root.get("email"), "wangzhilei@jd.com"));
                // 这里面放的是可变参数，则可以放一个数组进去，然后给拆分 相当于js中的...符号
                Predicate[] predicates = new Predicate[list.size()];
                return cb.or(list.toArray(predicates));
            }
        };
        Page<UserJ> all = userJRespository.findAll(specification, pageRequest);
        for (UserJ userJ : all) {
            System.out.println(userJ);
        }
    }
}