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
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