Hibernate的HQL查询语句

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
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
支持 :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

首先我们来编写一个HqlTest的测试类，来进行Hql查询语句的简单应用

package com.wyy.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.wyy.four.entity.Book;
import com.wyy.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 params = new ArrayList();
//		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() {
		//select * from t_hibernate_order o,t_hibernate_order_item oi where o.order_id=oi.oid
		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
	 * 
	 * hql=from Book
	 * 
	 * 同样可以自动根据方言生成分页语句
	 * 		setFirstResult:设置起始下标
	 * 		setMaxResults:设置偏移量
	 */
	@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);
		}
	}
}

我先给大家看一下测试7方法的效果与测试九方法的效果（其他方法都是正确的，效果就不一一展示啦）
测试七

测试九

接下来我们来写HQL通用分页的查询方法
一、导入相对应的工具类PageBean、StringUtils
PageBean

package com.wyy.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 = 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.wyy.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);
	}

}

二、我们开始编写BaseDao

package com.wyy.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;

/**
 * 1、设置参数的问题
 * 2、分页代码重复问题
 * 
 * 
 * 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 20190614
 *
 */
public class BaseDao {
	
	/**
	 * 通过的参数设置方法
	 * @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) {
				value = entry.getValue();//相当于例子中的hh，但是有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
				if(value instanceof Object[]) {
					query.setParameter(entry.getKey(), (Object[])value);
				}
				else if(value instanceof Collection) {
					query.setParameter(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("FORM");
		
		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 createQuery = session.createQuery(countHql);
			this.setParam(map, createQuery);
			pageBean.setTotal(createQuery.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;
	}
}

最后我们开始编写测试方法
一、所写的BookDao需要继承上面所写的BaseDao
BookDao

package com.wyy.four.dao;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

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

import com.wyy.five.util.BaseDao;
import com.wyy.five.util.PageBean;
import com.wyy.five.util.StringUtils;
import com.wyy.four.entity.Book;
import com.wyy.four.entity.Category;
import com.wyy.two.util.SessionFactoryUtils;



public class BookDao extends BaseDao{

	/**
	 * 需求：
	 * 		写一个带查询条件并且能分页的方法
	 * @param book
	 * @param pageBean
	 * @return
	 */
	public List<Book> list1(Book book, PageBean pageBean) {
		Session session = SessionFactoryUtils.openSession();
		Transaction transaction = session.beginTransaction();
		String bookName = book.getBookName();
		String hql="from Book where 1=1";
		if(StringUtils.isNotBlank(bookName)) {
			hql +=" and bookName like :bookName";
		}
		Query query = session.createQuery(hql );
		//query相当于前面sql所学的prepareStatement
		if(StringUtils.isNotBlank(bookName)) {
			query.setParameter("bookName", bookName);
		}
		//通过上述代码会发现，同样的if判断写了两次
		
		//下面这个代码每个实体类分页都得写
		if(pageBean != null&& pageBean.isPagination()) {
			query.setFirstResult(pageBean.getStartIndex());
			query.setMaxResults(pageBean.getRows());
			
		}
		List<Book> list=query.list();
		transaction.commit();
		session.close();
		return list;
	}
	
	public List<Book> list2(Book book, PageBean pageBean) {
		Session session = SessionFactoryUtils.openSession();
		Transaction transaction = session.beginTransaction();
		String bookName = book.getBookName();
		Map<String, Object> map = new HashMap<>();  
		String hql="from Book where 1=1";
		if(StringUtils.isNotBlank(bookName)) {
			hql +=" and bookName like :bookName";
		}
		List<Book> list=super.executeQuery(session, map, hql, pageBean);
		transaction.commit();
		session.close();
		return list;
	}
}

二、开始调用方法
BookDaoTest

package com.wyy.four.dao;

import java.util.List;

import org.junit.Test;

import com.wyy.five.util.PageBean;
import com.wyy.four.entity.Book;
import com.wyy.four.entity.Category;

public class BookDaoTest {
	private BookDao bookDao = new BookDao();

	/**
	 * five测试
	 */
	@Test
	public void testList1() {
		Book book = new Book();
		PageBean pageBean = new PageBean();
//		pageBean.setPage(2);//查询第二页
		book.setBookName("%hh%");
		List<Book> list = this.bookDao.list1(book, pageBean);
		for (Book b : list) {
			System.out.println(b);
		}
	}
	
	@Test
	public void testList2() {
		Book book = new Book();
		PageBean pageBean = new PageBean();
//		pageBean.setPage(2);//查询第二页
		pageBean.setPagination(false);
//		book.setBookName("%hh%");
		List<Book> list = this.bookDao.list1(book, pageBean);
		for (Book b : list) {
			System.out.println(b);
		}
	}
}

效果
testList1

testList2