本篇博客介绍hibernate的hql语句查询

1、什么是hql

2、hql和sql区别/异同

3、处理返回的结果集

4、hql中使用占位符

5、连接查询

6、聚合函数

7、hql分页

8、基于HQL的BaseDao的编写

1~7的相关测试代码

package com.javaxl.five.test;

import java.util.Arrays;
import java.util.List;
import java.util.Map;

import org.hibernate.Session;
import org.hibernate.Transaction;
import org.hibernate.query.Query;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import com.javaxl.four.entity.Book;
import com.javaxl.two.util.SessionFactoryUtils;

public class HqlTest {
	private Session session;
	private Transaction transaction;
	
	@Before
	public void before() {
		session = SessionFactoryUtils.openSession();
		transaction = session.beginTransaction();
	}
	
	@After
	public void after() {
		transaction.commit();
		session.close();
	}
	
	/**
	 * 返回对象（多个）
	 */
	@Test
	public void testList1() {
		Query query = session.createQuery("from Book");
		List<Book> list = query.list();
		for (Book b : list) {
			System.out.println(b);
		}
	}
	
	/**
	 * 返回单个列段，用字符串就可以接受
	 */
	@Test
	public void testList2() {
		Query query = session.createQuery("select b.bookName as ss from Book b");
		List<String> list = query.list();
		for (String b : list) {
			System.out.println(b);
		}
	}
	
	/**
	 * 查两个列段及以上，默认返回的是Object【】
	 */
	@Test
	public void testList3() {
		Query query = session.createQuery("select b.bookId,b.bookName as ss from Book b");
		List<Object[]> list = query.list();
		for (Object[] b : list) {
			System.out.println(Arrays.toString(b));
		}
	}
	
	/**
	 * 注意map是函数，所以不区分大小写，返回的是map集合
	 */
	@Test
	public void testList4() {
		Query query = session.createQuery("select new mAp(b.bookId,b.bookName) from Book b");
		List<Map> list = query.list();
		for (Map b : list) {
			System.out.println(b);
		}
	}
	
	/**
	 * 查两个列段及以上，也可返回对象，前提是有对应的构造函数
	 */
	@Test
	public void testList5() {
		Query query = session.createQuery("select new Book(b.bookId,b.bookName) from Book b");
		List<Book> list = query.list();
		for (Book b : list) {
			System.out.println(b);
		}
	}
	
	/**
	 * HQL语句支持占位符
	 */
	@Test
	public void testList6() {
//		Query query = session.createQuery("from Book where bookId = :bookId");
//		query.setParameter("bookId", 1);
//		Book b = (Book) query.getSingleResult();
//		System.out.println(b);
		
		Query query = session.createQuery("from Book where bookId in (:bookIds)");
		query.setParameterList("bookIds", new Integer[] {1,2,4});
//		List<Integer> params = new ArrayList<Integer>();
//		params.add(1);
//		params.add(2);
//		params.add(4);
//		query.setParameterList("bookIds", params);
		List<Book> list = query.list();
		for (Book b : list) {
			System.out.println(b);
		}
	}
	
	/**
	 * HQL支持连接查询
	 */
	@Test
	public void testList7() {
		Query query = session.createQuery("select o.orderNo,oi.quantity from Order o,OrderItem oi where o = oi.order");
		List<Object[]> list = query.list();
		for (Object[] b : list) {
			System.out.println(Arrays.toString(b));
		}
	}
	
	/**
	 * HQL支持聚合函数
	 */
	@Test
	public void testList8() {
		Query query = session.createQuery("select count(*) from Book");
		Long singleResult = (Long) query.getSingleResult();
		System.out.println(singleResult);
	}
	
	/**
	 * HQL分页
	 */
	@Test
	public void testList9() {
		Query query = session.createQuery("from Book");
		query.setFirstResult(2);
		query.setMaxResults(3);
		List<Book> list = query.list();
		for (Book b : list) {
			System.out.println(b);
		}
	}
}

8、基于HQL的BaseDao的编写

BookDao.java

/*
	 * hql讲解用到（需要继承BaseDao）
	 */
	/**
	 * 没有使用BaseDao之前的代码
	 * @param book
	 * @param pageBean
	 * @return
	 */
	public List<Book> list(Book book, PageBean pageBean) {
		Session session = SessionFactoryUtils.openSession();
		Transaction transaction = session.beginTransaction();
		String hql = "from Book where 1 = 1";

		if (StringUtils.isNotBlank(book.getBookName())) {
			hql += " and bookName like :bookName";
		}

		Query query = session.createQuery(hql);
		
		if (StringUtils.isNotBlank(book.getBookName())) {
			query.setParameter("bookName", book.getBookName());
		}

		if (pageBean != null && pageBean.isPagination()) {
			query.setFirstResult(pageBean.getStartIndex());
			query.setMaxResults(pageBean.getRows());
		}
		List<Book> list = query.list();
		transaction.commit();
		session.close();
		return list;

	}
	
	/**
	 * 使用BaseDao之后的代码
	 * @param book
	 * @param pageBean
	 * @return
	 */
	public List<Book> list2(Book book, PageBean pageBean) {
		Session session = SessionFactoryUtils.openSession();
		Transaction transaction = session.beginTransaction();
		String hql = "from Book where 1 = 1";
		Map<String, Object> map = new HashMap<String, Object>();

		if (StringUtils.isNotBlank(book.getBookName())) {
			hql += " and bookName like :bookName";
			map.put("bookName", book.getBookName());
		}
		List list = super.executeQuery(session, hql, map, pageBean);
		transaction.commit();
		session.close();
		return list;
	}
	
	/**
	 * 使用原生SQL
	 * @param book
	 * @param pageBean
	 * @return
	 */
	public List list3(Book book, PageBean pageBean) {
//		String sql = "select b.*,o.* from t_hibernate_book b,t_hibernate_Order o";
		String sql = "select * from t_hibernate_book";
		Session session = SessionFactoryUtils.openSession();
		Transaction transaction = session.beginTransaction();
		List list = session.createSQLQuery(sql).list();
		transaction.commit();
		session.close();
		return list;
	}

BaseDao.java

package com.javaxl.five.util;

import java.util.Collection;
import java.util.List;
import java.util.Map;

import org.hibernate.Session;
import org.hibernate.query.Query;

public class BaseDao {
	public void setParam(Query query,Map<String, Object> map) {
		if(map == null || map.size() < 1) {
			return;
		}
		Object value = null;
		for(Map.Entry<String, Object> entry:map.entrySet()) {
			value = entry.getValue();
			if(value instanceof Collection) {
				query.setParameterList(entry.getKey(), (Collection) value);
			}else if(value instanceof Object[]) {
				query.setParameterList(entry.getKey(), (Object[]) value);
			}else {
				query.setParameter(entry.getKey(), value);
			}
		}
	}
	
	public String getCountHql(String hql) {
		int index = hql.toUpperCase().indexOf("FROM");
		return "select count(*) "+hql.substring(index);
	}
	
	/**
	 * 
	 * @param hql	已经拼装好的
	 * @param map
	 * @param pageBean
	 * @return
	 */
	public List executeQuery(Session session, String hql,Map<String, Object> map,PageBean pageBean) {
		if(pageBean !=null && pageBean.isPagination()) {
			String countHql = getCountHql(hql);
			Query countQuery = session.createQuery(countHql);
			this.setParam(countQuery, map);
			pageBean.setTotal(countQuery.getSingleResult().toString());
			
			Query query = session.createQuery(hql);
			this.setParam(query, map);
			query.setFirstResult(pageBean.getStartIndex());
			query.setMaxResults(pageBean.getRows());
			List list = query.list();
			
			return list;
		}else {
			Query query = session.createQuery(hql);
			this.setParam(query, map);
			List list = query.list();
			
			return list;
		}
		
	}
}

QueryTest.java

package com.javaxl.five.test;

import java.util.Arrays;
import java.util.List;

import org.junit.Test;

import com.javaxl.five.util.PageBean;
import com.javaxl.four.dao.BookDao;
import com.javaxl.four.entity.Book;

public class QueryTest {
	private BookDao bookDao = new BookDao();
	/**
	 * 使用BaseDao前
	 */
	@Test
	public void testList1() {
		Book book = new Book();
		PageBean pageBean = new PageBean();
//		pageBean.setPage(2);
		book.setBookName("%圣墟%");
		List<Book> list = this.bookDao.list(book, pageBean);
		for (Book b : list) {
			System.out.println(b);
		}
		
	}
	
	/**
	 * 使用BaseDao后
	 */
	@Test
	public void testList2() {
		Book book = new Book();
		PageBean pageBean = new PageBean();
		pageBean.setPage(2);
//		book.setBookName("%圣墟%");
		List<Book> list = this.bookDao.list2(book, pageBean);
		for (Book b : list) {
			System.out.println(b);
		}
		
	}
	
	/**
	 * 使用原生SQL查询，不使用HQL
	 */
	@Test
	public void testList3() {
		Book book = new Book();
		PageBean pageBean = new PageBean();
		List list = this.bookDao.list3(book, pageBean);
		for (Object b : list) {
			System.out.println(Arrays.toString((Object[]) b));
		}
		
	}
	
}

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