l jpql simple query

JPQL全称Java Persistence Query Language

 

 

package com.ytkj.test;

com.ytk.utils.JpaUtils amount;
import org.junit.Test;

import javax.persistence.EntityManager;
import javax.persistence.EntityTransaction;
import javax.persistence.Query;
import java.util.List;

/**
 * Jpql test
 */
public class JpqlTest {
    /**
     * All inquiries
     */
    @Test
    public void findAll(){
        EntityManager entityManager = JpaUtils.getEntityManager();
        // open affairs
        EntityTransaction transaction = entityManager.getTransaction();
        transaction.begin();

        // Create a query object manipulation entity classes instead of directly taking operation database
        String jpql="from Customer";
        Query query = entityManager.createQuery(jpql);

        //Inquire
        List list = query.getResultList();
        for (Object o : list) {
            System.out.println(o);
        }

        // 5. commit the transaction
        transaction.commit();
        // 6 Release resources
        entityManager.close();
    }

    /**
     * Sorting Query
     */
    @Test
    public void findAllOrderBy(){
        EntityManager entityManager = JpaUtils.getEntityManager();
        // open affairs
        EntityTransaction transaction = entityManager.getTransaction();
        transaction.begin();

        // Create a query object manipulation entity classes instead of directly taking operation database
        String jpql="from Customer order by custId desc";
        Query query = entityManager.createQuery(jpql);

        //Inquire
        List list = query.getResultList();
        for (Object o : list) {
            System.out.println(o);
        }

        // 5. commit the transaction
        transaction.commit();
        // 6 Release resources
        entityManager.close();
    }

    /**
     * The total number of queries
     */
    @Test
    public void getCount(){
        EntityManager entityManager = JpaUtils.getEntityManager();
        // open affairs
        EntityTransaction transaction = entityManager.getTransaction();
        transaction.begin();

        // Create a query object manipulation entity classes instead of directly taking operation database
        String jpql="select count(custId) from Customer ";
        Query query = entityManager.createQuery(jpql);
        //Inquire
        Object result = query.getSingleResult();
        System.out.println(result);
        // 5. commit the transaction
        transaction.commit();
        // 6 Release resources
        entityManager.close();
    }

    /**
     * Paging query
     */
    @Test
    public void getByPage(){
        EntityManager entityManager = JpaUtils.getEntityManager();
        // open affairs
        EntityTransaction transaction = entityManager.getTransaction();
        transaction.begin();

        // Create a query object manipulation entity classes instead of directly taking operation database
        pageno int = 0;
        int pageSize=2;
        String jpql=" from Customer";
        Query query = entityManager.createQuery(jpql);
        // paging parameter assignment
        query.setFirstResult (pageno);
        query.setMaxResults(pageSize);
        //Inquire
        List list = query.getResultList();
        for (Object o : list) {
            System.out.println(o);
        }
        // 5. commit the transaction
        transaction.commit();
        // 6 Release resources
        entityManager.close();
    }


    /**
     * Conditions inquiry
     */
    @Test
    public void getByCondition(){
        EntityManager entityManager = JpaUtils.getEntityManager();
        // open affairs
        EntityTransaction transaction = entityManager.getTransaction();
        transaction.begin();

        // Create a query object manipulation entity classes instead of directly taking operation database
        String jpql=" from Customer where custName like ?";
        Query query = entityManager.createQuery(jpql);
        // placeholders for parameter assignment
        query.setParameter(1,"zhe%");
        //Inquire
        List list = query.getResultList();
        for (Object o : list) {
            System.out.println(o);
        }
        // 5. commit the transaction
        transaction.commit();
        // 6 Release resources
        entityManager.close();
    }


}