Hibernate之HQL

目录:

一,hql的定义

二,hql与sql的对比

三,hql的使用

四,Basedao

一、HQL的定义

          1、定义:HQL是Hibernate Query Language的缩写Hibernate语言查询,它是完全面向对象的查询语句,查询功能非常强。

二、HQL与SQL的对比

        HQL(面向对象)                                   SQL(面向结构)

         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

        从下标0开始计算位置                                从顺序1开始计算位置

        支持命名参数                                               不支持命名参数

三、HQL的使用:

首先将相关的实体类和dao方法导入进去:

package com.lsy.three.hql;

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.lsy.two.entity.Book;
import com.lsy.two.util.SessionFactoryUtil;

public class HqlTest {
	private Session session;
	private Transaction transaction;
	
	@Before
	public void before() {
		session = SessionFactoryUtil.getSession();
		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
	 * sql是否支持连接查询,BaseDao,Vo
	 * 
	 */
	@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);//起始下标
		query.setMaxResults(3);//偏移量
		List<Book> list = query.list();
		for (Book b : list) {
			System.out.println(b);
		}
	}
	
	public void testList10() {
		String hql="from Book where 1=1";
		Book book=new Book();
		if(book.getBookId()!=0) {
			hql+=" and bookId=:bookId";
		}
		if(book.getBookName()!=null) {
			hql+=" and bookName=:bookName";
		}
		Query query = session.createQuery(hql);
		if(book.getBookId()!=0) {
			query.setParameter("bookId", 1);
		}
		if(book.getBookName()!=null) {
			query.setParameter("bookName", "%圣墟%");
		}
		query.setParameter("bookId", 1);
		Book b = (Book) query.getSingleResult();
		System.out.println(b);
	
	
	}
	
}

PageBean

package com.lsy.three.hql;

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 = 3;// 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

package com.lsy.three.hql;

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);
	}

}

 一 、HQL查询:一共有以下几种情况:

              1、返回对象(多个):

代码:

/**
	 * 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);
		}
	}

结果

Hibernate之HQLHibernate之HQL

 

/**
	 * 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);
		}
	}

 Hibernate之HQL

 

/**
	 * 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));
		}
	}

Hibernate之HQL

 

/**
	 * 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);
		}
	}

 Hibernate之HQL

 

/**
	 * 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);
		}
	}

Hibernate之HQL

 

HQL支持占位符、支持连接查询、支持聚合函数、支持分页:

              1、支持占位符:

                    一共有三种情况:

                                              1、第一种是根据对象来命名参数 

                                              2、第二种是根据数组来命名参数 

                                              3、第三种是根据集合来命名参数 

/**
	 * 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);
}

Hibernate之HQL

 

/**
	 * HQL支持连接查询
	 * sql是否支持连接查询,BaseDao,Vo
	 * 
	 */
	@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));
		}
	}

Hibernate之HQL

 

/**
	 * 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);
	}

Hibernate之HQL

/**
	 * HQL分页
	 */
	@Test
	public void testList9() {
		Query query = session.createQuery("from Book");
		query.setFirstResult(2);//起始下标
		query.setMaxResults(3);//偏移量
		List<Book> list = query.list();
		for (Book b : list) {
			System.out.println(b);
		}
	}

 Hibernate之HQL

 

四、BaseDao:
basedao是一个基础的dao包,在自定义mvc中也写了一个公用的dao方法,在设计dao层的时候,也涉及了设计的思路:

思路:

        1、完成一个基础的查询方法

        2、分析共同之处:

              1、都有非空判断

              2、都有query对象执行

              3、都有通用分页

              4、都有具体的对象/map
 

代码

package com.lsy.three.dao;

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;

import com.lsy.three.hql.PageBean;

/**
 * 1、设置参数的问题 2、分页代码重复的问题
 * 
 * sql的通用分页的时候
 * 
 * getCountSql(sql) select count(1) from (sql) t
 * 
 * getCountHql(hql) hql = "from Book where bookName like :bookName" hql =
 * "select * from new Book(bid,bookName) where bookName like :bookName" select
 * count(1) hql
 * 
 * @author Administrator
 *
 */
public class BaseDao {

	/**
	 * 通用的参数设值方法
	 * 
	 * @param map
	 *            参数键值对集合
	 * @param query
	 *            预定义处理的hql对象
	 */
	public void setParam(Map<String, Object> map, Query query) {
		if (map != null && map.size() > 0) {
			Object value = null;
			Set<Entry<String, Object>> entrySet = map.entrySet();
			for (Entry<String, Object> entry : entrySet) {
				// 例子的圣墟,但是有的时候它并不是单纯的字符串,可能是数组比如爱好,也可能是集合
				value = entry.getValue();
				if (value instanceof Object[]) {
					query.setParameterList(entry.getKey(), (Object[]) value);
				} else if (value instanceof Collection) {
					query.setParameterList(entry.getKey(), (Collection) value);
				} else {
					query.setParameter(entry.getKey(), value);
				}
			}
		}
	}

	public String getCountHql(String hql) {
		// hql = "from Book where bookName like :bookName"
		// * hql = "select * from new Book(bid,bookName) where bookName like :bookName"
		int index = hql.toUpperCase().indexOf("FROM");
		return "select count(*) " + hql.substring(index);
	}
	
	/**
	 * 通用查询方法
	 * @param session
	 * @param map
	 * @param hql
	 * @param pageBean
	 * @return
	 */
	public List executeQuery(Session session,Map<String, Object> map,String hql,PageBean pageBean) {
		List list = null;
		if(pageBean != null && pageBean.isPagination()) {
			String countHql = getCountHql(hql);
			Query countQuery = session.createQuery(countHql);
			this.setParam(map, countQuery);
			pageBean.setTotal(countQuery.getSingleResult().toString());
			
			Query query = session.createQuery(hql);
//			给预定义hql语句执行对象中的参数赋值,有多少赋值多少
			this.setParam(map, query);
			query.setFirstResult(pageBean.getStartIndex());
			query.setMaxResults(pageBean.getRows());
			list = query.list();
		}else {
			Query query = session.createQuery(hql);
//			给预定义hql语句执行对象中的参数赋值,有多少赋值多少
			this.setParam(map, query);
			list = query.list();
		}
		return list;
	}

}

bye~

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