hibernate之HQL
一、hql语句基础知识
1. 什么是hql
HQL是Hibernate Query Language的缩写 hibernate查询语句
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 不支持:命名参数
面向对象的查询语言 面向结构查询语言
3. 处理返回的结果集
3.1 查单个对象 返回一个对象 用的最多
select没有逗号
3.2 查询两个列段以上 返回Object[]
b.bookId, b.bookName
3.3 Map函数，不区分大小写 返回的是map集合
new Map(b.bookId as bid, b.bookName as bname)
3.4 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
new 构造方法(attr1,attr2)
new Book(b.bookId, b.price)
3.5查询单个列段 返回String
测试类HqlTest.java
package com.jt5.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.jt2.util.SessionFactoryUtils; import com.jt4.entity.Book; 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 * sum * count * * * */ @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); } /** * sql=select * from t_hibernate_book * sql+ limit start,offset * 1 0,10 * 2 10,10 * 3 20,10 * 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); } } }
使用hql写一个分页查询
PageBean.java
package com.jt5.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.java
package com.jt5.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); } }
记下来看看dao方法首先我们要写一个BaseDao.java
package com.jt5.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; /** * hebernate的通用查询Dao层 * 思想完全借鉴于sql的BaseDao * sql=select * from t_mvc_book where bname like '%圣墟%' * countsql=select count(1) from (sql) t; * pagesql=sql limit start,offset * * hql: * hql=selct * from Book where bookName like :bookName * hql=from Book where bookName like :bookName * 思想：原生的hql语句以from关键字进行截取 * countHql=select count(*) from Book where bookName like :bookName; * pageHql不需要写：应为Hibernate已经封装了内置的分页接口 * getFirstResult * getMaxResult * @author jt * */ public class BaseDao { /** * 给hiberbate中Query对象中的命名参数列表赋值 * @param query * @param map */ public void setparam(Query query,Map<String, Object> map) { if(map!=null && map.size()>0) { Set<Entry<String,Object>> entrySet = map.entrySet(); for (Entry<String, Object> entry : entrySet) { Object 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); } } } /** * hql: * hql=select * from Book where bookName like :bookName * hql=from Book where bookName like :bookName * 思想：将原生态的hql语句以from关键字进行截取 * counthql =select count(*) from Book where bookName like :bookName; * @param hql * @return */ public String getCountHql(String hql) { return "select count(*)"+ hql.substring(hql.toUpperCase().indexOf("FROM")); } /** * 通用hql语句查询 * @param session 当前会话 * @param hql 带命名参数的hql语句 * @param map 命名参数对应的值的集合 * @param pageBean 分页实体类 * @return */ public List executeQuery(Session session,String hql,Map<String, Object> map,PageBean pageBean) { List list=null; Query query=null; if(pageBean!=null&&pageBean.isPagination()) { String countHql = getCountHql(hql); Query createQuery = session.createQuery(countHql); this.setparam(createQuery, map); pageBean.setTotal(createQuery.getSingleResult().toString()); query = session.createQuery(hql); this.setparam(query, map); query.setFirstResult(pageBean.getStartIndex()); query.setMaxResults(pageBean.getRows()); list=query.list(); }else { query = session.createQuery(hql); this.setparam(query, map); list=query.list(); } return list; } }
然后再是BookDao.java
package com.jt4.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.jt2.util.SessionFactoryUtils; import com.jt4.entity.Book; import com.jt4.entity.Category; import com.jt5.util.BaseDao; import com.jt5.util.PageBean; import com.jt5.util.StringUtils; 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(); } /**********************************************/ public List<Book> list1(Book book,PageBean pageBean) { Session session=SessionFactoryUtils.openSession(); Transaction transaction=session.beginTransaction(); //下面代码处理的是book实体类的条件查询 10*2 String bookName=book.getBookName(); //sql语句where后面可以直接写true，而hql与不能出现true String hql="from Book where 1=1"; if(StringUtils.isNotBlank(bookName)) { hql+=" and bookName like :bookName"; } Query query = session.createQuery(hql); if(StringUtils.isNotBlank(bookName)) { query.setParameter("bookName",bookName); } //处理的是分页 if(pageBean!=null&&pageBean.isPagination()) { query.setFirstResult(pageBean.getStartIndex()); query.setMaxResults(pageBean.getRows()); } List 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(); //下面代码处理的是book实体类的条件查询 10*2 String bookName=book.getBookName(); Map<String,Object> map=new HashMap<String,Object>(); //sql语句where后面可以直接写true，而hql与不能出现true String hql="from Book where 1=1"; if(StringUtils.isNotBlank(bookName)) { hql+=" and bookName like :bookName"; map.put("bookName",bookName); } List list=super.executeQuery(session, hql, map, pageBean); transaction.commit(); session.close(); return list; } }
接下来是测试类BookDaoTest.java
package com.jt4.dao; import java.util.List; import org.junit.Test; import com.jt4.entity.Book; import com.jt4.entity.Category; import com.jt5.util.PageBean; public class BookDaoTest { private BookDao bookDao = new BookDao(); @Test public void testGetBook() { Book book = new Book(); book.setBookId(8); 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 */ @Test public void test1() { Book book = new Book(); book.setBookName("jt66666666"); 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 */ @Test public void test2() { Book book = new Book(); book.setBookName("jt555555"); 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); } @Test public void testlist1() { Book book=new Book(); book.setBookName("%jt%"); PageBean pageBean=new PageBean(); //pageBean.setPage(2); List<Book> list1 = this.bookDao.list1(book, pageBean); for (Book b : list1) { System.out.println(b); } } @Test public void testList2() { Book book=new Book(); // book.setBookName("%jt%"); PageBean pageBean=new PageBean(); pageBean.setPage(2); List<Book> list2 = this.bookDao.list2(book, null); for (Book b : list2) { System.out.println(b); } } }
