1.什么是hql

HQL是Hibernate Query Language的缩写

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	别名
?，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	面向结构查询语言
面向对象的查询语言	面向结构查询语言

3.案例

首先写一个测试类，来进行查询
HqlTest

package com.yinyi.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.yinyi.four.entity.Book;
import com.yinyi.two.util.SessionFactoryUtils;public class HqlTest {private Session session;private Transaction transaction;@Beforepublic void before() {session = SessionFactoryUtils.openSession();transaction = session.beginTransaction();}@Afterpublic void after() {transaction.commit();session.close();}/*** 返回对象（多个）*/@Testpublic 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*/@Testpublic 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【】*/@Testpublic 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*/@Testpublic 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*/@Testpublic 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*/@Testpublic 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[] {1,2,7});
//      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*/@Testpublic void testList7() {//select * from t_hibernate_order o,t_hibernate_orider_item oi where o.order_id=oi.oidQuery 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*/@Testpublic void testList8() {Query query = session.createQuery("select count(*) from Book");//getSingResult是用来获取单条记录的Long singleResult = (Long) query.getSingleResult();System.out.println(singleResult);}/*** HQL分页* * sql* * sql limit 5 ，5* * hql=select * from Book* *        同样的可以根据方言生成分页语句*            setFirstResult：设置其实下标*           setMaxResults：设置偏移量* * mysql：hql limit 5,5* hql limit 2 ，3* oracle* select *from （select tb.*, rownum rn hql t where t,rn>5）  t1  where  t1.rn<10* */@Testpublic 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);}}
}

BaseDao

package com.yinyi.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;}
}

PageBean

package com.yinyi.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urlprivate 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;}@Overridepublic String toString() {return "PageBean [page=" + page + ", rows=" + rows + ", total=" + total + ", pagination=" + pagination+ ", parameterMap=" + parameterMap + ", url=" + url + "]";}}

StringUitls

package com.yinyi.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);}}

现在写dao方法

package com.yinyi.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;}
}

BookDao

package com.yinyi.four.dao;import java.util.List;import org.hibernate.Hibernate;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.hibernate.query.Query;import com.yinyi.five.util.PageBean;
import com.yinyi.five.util.StringUtils;
import com.yinyi.four.entity.Book;
import com.yinyi.four.entity.Category;
import com.yinyi.two.util.SessionFactoryUtils;public class BookDao  extends BaseDao{public Integer addBook(Book book) {Session session = SessionFactoryUtils.openSession();Transaction transaction = session.beginTransaction();Integer bid = (Integer) session.save(book);transaction.commit();session.close();return bid;}public Integer addCategory(Category category) {Session session = SessionFactoryUtils.openSession();Transaction transaction = session.beginTransaction();Integer cid = (Integer) session.save(category);transaction.commit();session.close();return cid;}public Category getCategory(Category category) {Session session = SessionFactoryUtils.openSession();Transaction transaction = session.beginTransaction();Category c = session.get(Category.class, category.getCategoryId());transaction.commit();session.close();return c;}public Book getBook(Book book) {Session session = SessionFactoryUtils.openSession();Transaction transaction = session.beginTransaction();Book b = session.get(Book.class, book.getBookId());if (b != null && new Integer(1).equals(book.getInitCategories())) {Hibernate.initialize(b.getCategories());}transaction.commit();session.close();return b;}public void delBook(Book book) {Session session = SessionFactoryUtils.openSession();Transaction transaction = session.beginTransaction();session.delete(book);transaction.commit();session.close();}public void delCategory(Category category) {Session session = SessionFactoryUtils.openSession();Transaction transaction = session.beginTransaction();Category c = session.get(Category.class, category.getCategoryId());if(c!=null) {for (Book b : c.getBooks()) {//              通过在被控方通过主控方来解除关联关系，最后被控方再做删除b.getCategories().remove(c);}}session.delete(c);transaction.commit();session.close();}/*** 需求：*       写一个带查询条件并且能分页方法* @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:相当于前面sql所用的prepareStatementQuery query = session.createQuery(hql);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();System.out.println(list.size());transaction.commit();session.close();return list;}}

BookDaoTest开始调用

package com.yinyi.four.dao;import java.util.List;import org.junit.Test;import com.yinyi.five.util.PageBean;
import com.yinyi.four.entity.Book;
import com.yinyi.four.entity.Category;public class BookDaoTest {private BookDao bookDao = new BookDao();@Testpublic void testGetBook() {Book book = new Book();book.setBookId(1);book.setInitCategories(1);Book b = this.bookDao.getBook(book);System.out.println(b.getBookName());System.out.println(b.getCategories());}/*** book.hbm.xml inverse=fasle* category.hbm.xml inverse=true* 数据添加正常* 书籍表、桥接表各新增一条数据*/@Testpublic void test1() {Book book = new Book();book.setBookName("斗气化马");book.setPrice(10f);Category category = new Category();category.setCategoryId(5);
//      直接将category对象加入到新建的book中是错误的，因为此时的category是临时态的，hibernate是不会管理的
//      book.getCategories().add(category);Category c = this.bookDao.getCategory(category);//      c.getBooks().add(book);book.getCategories().add(c);this.bookDao.addBook(book);}/*** book.hbm.xml    inverse=false* category.hbm.xml inverse=true* 只增加书籍表数据* 桥接表不加数据* 原因：双方都没有去维护关系*/@Testpublic void test2() {Book book = new Book();book.setBookName("斗宗强者，恐怖如斯");book.setPrice(10f);Category category = new Category();category.setCategoryId(5);Category c = this.bookDao.getCategory(category);book.getCategories().add(c);this.bookDao.addBook(book);
//      c.getBooks().add(book);}/*** 测试*/@Testpublic 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);}}@Testpublic void testList2() {Book book = new Book();PageBean pageBean = new PageBean();
//      pageBean.setPage(2);//查询第二页pageBean.setPagination(false);
//      book.setBookName("%aa%");List<Book> list = this.bookDao.list1(book, pageBean);for (Book b : list) {System.out.println(b);}}}

本次的分享就到此結束了，感謝您的觀看。

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目录

1.什么是hql

2.hql和sql区别/异同

3.案例

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