HQL 即Hibernate Query Language的缩写
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
例:
多个对象:
/** * 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:
单个对象:
/** * 返回单个列段,用字符串就可以接收 */ @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); } }
object:
/** * 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.price,b.bookName as ss from Book b"); List<Object[]> list = query.list(); for (Object[] b : list) { System.out.println(Arrays.toString(b)); } }
map 函数:
/** * 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); } }
有构造方法:
/** * 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); } }
占位符:
/** * 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); } }
连接查询
/** * 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)); } }
聚合函数:
/** * 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); } }
按名字分页查询对应书籍信息
BookDao(继承BaseDao):
package com.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;
/**
* hibernate的通用查询Dao层
*
* @author xyls
*
*/
public class BaseDao {
/** * * * @param category */ public List<Book> list1(Book book, PageBean pageBean) { Session session = SessionFactoryUtils.openSession(); Transaction transaction = session.beginTransaction(); // 处理book实体类的条件查询 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); if (StringUtils.isNotBlank(bookName)) { query.setParameter("bookName", bookName); } // 处理分页 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(); // 处理book实体类的条件查询 String bookName = book.getBookName(); Map<String, Object> map=new HashMap<String,Object>(); // 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; }
BaseDao:
package com.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; /** * hibernate的通用查询Dao层 * * @author xyls * */ public class BaseDao { /** * 给hibernate中的query对象中的参数列表赋值 * * @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.setParameter(entry.getKey(), (Collection) value); else if (value instanceof Object[]) query.setParameter(entry.getKey(), (Object[]) value); else query.setParameter(entry.getKey(), value); } } } /** * * @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 * @param hql * @param map * @param pageBean * @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 countQuery = session.createQuery(counthql); this.setParam(countQuery, map); pageBean.setTotal(countQuery.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; } }
PageBean:
package com.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 + "]"; } }
测试:
package com.dao; import java.util.List; import org.junit.Test; import com.entity.Book; import com.entity.Category; import com.util.PageBean; public class BookDaoTest { private BookDao bookDao = new BookDao(); @Test public void testList1() { Book book = new Book(); // book.setBookName("%0030%"); PageBean pageBean = new PageBean(); pageBean.setPage(2); List<Book> list1 = this.bookDao.list1(book, pageBean); for (Book book2 : list1) { System.out.println(book2); } } @Test public void testList2() { Book book = new Book(); book.setBookName("%0030%"); PageBean pageBean = new PageBean(); // pageBean.setPage(2); List<Book> list1 = this.bookDao.list2(book, pageBean); for (Book book2 : list1) { System.out.println(book2); } } }
testList1:
testList2:
hql实现不了的功能,可以考虑使用原生sql
多表(5+)联查
未配置映射文件中关系