hibernate之HQL

1. 什么是hql

HQL是Hibernate Query Language的缩写

查全部

2. hql和sql区别/异同

HQL	SQL
类名/属性	表名/列名
区分大小写,关键字不区分大小写	不区分大小写
别名 : 无	别名 : as , a
?，从下标0开始计算位置(hibernate5之后不支持)	?，从顺序1开始计算位置
:命名参数	不支持:命名参数
面向对象的查询语言	面向结构查询语言

注1：QuerySyntaxException:book is not mapped

3. 处理返回的结果集

3.1 单个对象
select没有逗号

3.2 Object[]
b.bookId, b.bookName

3.3 Map
new Map(b.bookId as bid, b.bookName as bname)

3.4 new 构造方法(attr1,attr2)
new Book(b.bookId, b.price)
单个列段

4. hql中使用占位符

4.1 ?占位符
从下标0开始计算位置
hibernate5之后不再支持?占位符

4.2 :命名参数

5. 连接查询

6. 聚合函数

Sum ： 和
Avg ：平均值
Max ：最大值
Min ：最小值
Count ：总数

7. hql分页

   int page = 2; // 页码：page
   int row = 10; // 每页行数：rows
   query.setFirstResult((page - 1) * row); // 设置起始记录下标
   query.setMaxResults(row); // 设置返回的最大结果集     

a.代码演示：

Util包：

pageBean.java：

package com.qiuwenfan.five.util;

import java.util.Map;

import javax.servlet.http.HttpServletRequest;

/**
 * 分页工具类
 *
 */
public class PageBean {

	private int page = 1;// 页码

	private int rows = 5;// 页大小

	private int total = 0;// 总记录数

	private boolean pagination = true;// 是否分页
	// 获取前台向后台提交的所有参数
	private Map<String, String[]> parameterMap;
	// 获取上一次访问后台的url
	private String url;

	/**
	 * 初始化pagebean
	 * 
	 * @param req
	 */
	public void setRequest(HttpServletRequest req) {
		this.setPage(req.getParameter("page"));
		this.setRows(req.getParameter("rows"));
		// 只有jsp页面上填写pagination=false才是不分页
		this.setPagination(!"fasle".equals(req.getParameter("pagination")));
		this.setParameterMap(req.getParameterMap());
		this.setUrl(req.getRequestURL().toString());
	}

	public int getMaxPage() {
		return this.total % this.rows == 0 ? this.total / this.rows : this.total / this.rows + 1;
	}

	public int nextPage() {
		return this.page < this.getMaxPage() ? this.page + 1 : this.getMaxPage();
	}

	public int previousPage() {
		return this.page > 1 ? this.page - 1 : 1;
	}

	public PageBean() {
		super();
	}

	public int getPage() {
		return page;
	}

	public void setPage(int page) {
		this.page = page;
	}

	public void setPage(String page) {
		this.page = StringUtils.isBlank(page) ? this.page : Integer.valueOf(page);
	}

	public int getRows() {
		return rows;
	}

	public void setRows(int rows) {
		this.rows = rows;
	}

	public void setRows(String rows) {
		this.rows = StringUtils.isBlank(rows) ? this.rows : Integer.valueOf(rows);
	}

	public int getTotal() {
		return total;
	}

	public void setTotal(int total) {
		this.total = total;
	}

	public void setTotal(String total) {
		this.total = Integer.parseInt(total);
	}

	public boolean isPagination() {
		return pagination;
	}

	public void setPagination(boolean pagination) {
		this.pagination = pagination;
	}

	public Map<String, String[]> getParameterMap() {
		return parameterMap;
	}

	public void setParameterMap(Map<String, String[]> parameterMap) {
		this.parameterMap = parameterMap;
	}

	public String getUrl() {
		return url;
	}

	public void setUrl(String url) {
		this.url = url;
	}

	/**
	 * 获得起始记录的下标
	 * 
	 * @return
	 */
	public int getStartIndex() {
		return (this.page - 1) * this.rows;
	}

	@Override
	public String toString() {
		return "PageBean [page=" + page + ", rows=" + rows + ", total=" + total + ", pagination=" + pagination
				+ ", parameterMap=" + parameterMap + ", url=" + url + "]";
	}

}

StringUtils.java:

package com.qiuwenfan.five.util;

public class StringUtils {
	// 私有的构造方法，保护此类不能在外部实例化
	private StringUtils() {
	}

	/**
	 * 如果字符串等于null或去空格后等于""，则返回true，否则返回false
	 * 
	 * @param s
	 * @return
	 */
	public static boolean isBlank(String s) {
		boolean b = false;
		if (null == s || s.trim().equals("")) {
			b = true;
		}
		return b;
	}
	
	/**
	 * 如果字符串不等于null或去空格后不等于""，则返回true，否则返回false
	 * 
	 * @param s
	 * @return
	 */
	public static boolean isNotBlank(String s) {
		return !isBlank(s);
	}

}

BaseDao.java:

package com.qiuwenfan.five.util;

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

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


/**
 * 基于hql语句的通用查询工具类
 * 	1、需要给拼接的hql语句的命名参数赋值 （可以简化的）
 * 	2、分页（可以简化的）
 * 
 * 	基于sql的分页的查询做法
 * 		1、首先要查询出符合条件的总记录数
 * 		2、返回符合条件的记录
 * 
 * 	参数：sql,pagebean, Class clz
 * 		sql = select * from t_hibernate_book where bookName like "%圣墟%"
 * 	1、countSql = select count(*) from (sql) t;
 * 	2、pageSql = sql + "limit " + start + "," + rows
 * 
 * 	基于hql的分页的查询的做法
 * 		hql = from bookName like "%圣墟%"
 * 		hql = select from Book where bookName like "%圣墟%"
 * 		1、countHql = select count(*) (hql) ;
 * 
 * @author qiuwenfan
 *
 */
public class BaseDao {
	/**
	 * 
	 * @param query		里面包含了带有命名参数的hql语句，需要等待赋值
	 * 		from Book where 1 = 1 and bookName like :bookName
	 * @param paramMap
	 * 		= request.getParameterMap();
	 */
	public void setParam(Query query, Map<String, Object> paramMap) {
		if(paramMap != null && paramMap.size() > 0) {
			Set<Entry<String, Object>> entrySet = paramMap.entrySet();
			for (Entry<String, Object> entry : entrySet) {
				String key = entry.getKey();
				Object value = entry.getValue();
				if(value instanceof Object[]) {
//					value可能是数组
					query.setParameterList("bookIds", (Object[])value);
				}else if(value instanceof Collection) {
//					value可能是集合
					query.setParameterList("bookIds", (Collection)value);
				}else {
					query.setParameter(key, value);
				}
			}
		}
	}
	
	/**
	 * 拼装符合条件的做记录数
	 * @param hql
	 * @return
	 */
	public String getCountHql(String hql) {
		int fromIndex = hql.toUpperCase().indexOf("FROM");
		return "select count(*) " + hql.substring(fromIndex);
	}
	
	/**
	 * 基于hql的通用查询方法
	 * @param hql
	 * @param pageBean
	 * @param paMap
	 * @param session
	 * @return
	 */
	public List executeQuery(String hql, PageBean pageBean, Map<String, Object> paMap, Session session) {
		List list = null; 
		Query query = null;
		if(pageBean != null && pageBean.isPagination()) {
//			1、首先要查询出符合条件的总记录数
			String countHql = getCountHql(hql);
			Query countQuery = session.createQuery(countHql);
			this.setParam(countQuery, paMap);
			pageBean.setTotal(countQuery.getSingleResult().toString());
			
//			2、返回符合条件的记录
			query = session.createQuery(hql);
			this.setParam(query, paMap);
			query.setFirstResult(pageBean.getStartIndex());
			query.setMaxResults(pageBean.getRows());
			list = query.list();
			
		}else {
			query = session.createQuery(hql);
			this.setParam(query, paMap);
			list = query.list();
		}
		
		return list;
	}
	
}

test包：

HqlTes.java:

package com.qiuwenfan.five.test;

import java.util.ArrayList;
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.qiuwenfan.five.util.PageBean;
import com.qiuwenfan.four.dao.BookDao;
import com.qiuwenfan.four.entity.Book;
import com.qiuwenfan.two.util.SessionFactoryUtils;

public class HqlTest {
	private Session session;
	private Transaction transaction;
	private BookDao bookDao = new BookDao();
	
	@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当作prepareStatement
		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(5);
		query.setMaxResults(5);
		List<Book> list = query.list();
		for (Book b : list) {
			System.out.println(b);
		}
	}
	
	/**
	 * 测试list方法
	 */
	@Test
	public void testList10() {
		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);
		}
	}
	
	@Test
	public void testList11() {
		Book book = new Book();
		PageBean pageBean = new PageBean();
//		pageBean.setPagination(false); //查询全部
//		pageBean.setPage(2);           //分页查询
		book.setBookName("%圣墟%");     //模糊查询
		List<Book> list = this.bookDao.listPlus(book, pageBean);
		for (Book b : list) {
			System.out.println(b);
		}
	}
	
	
}

b.图片显示：

1、查询全部

2、分页查询

3、模糊查询：