hibernate之HQL
1. 什么是hql
HQL是Hibernate Query Language的缩写
查全部
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 : 无 | 别名 : as , a |
| ?，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 |
注1：QuerySyntaxException:book is not mapped
3. 处理返回的结果集
3.1 单个对象
select没有逗号
3.2 Object[]
b.bookId, b.bookName
3.3 Map
new Map(b.bookId as bid, b.bookName as bname)
3.4 new 构造方法(attr1,attr2)
new Book(b.bookId, b.price)
单个列段
4. hql中使用占位符
4.1 ?占位符
从下标0开始计算位置
hibernate5之后不再支持?占位符
4.2 :命名参数
5. 连接查询
6. 聚合函数
Sum ： 和
Avg ：平均值
Max ：最大值
Min ：最小值
Count ：总数
7. hql分页
int page = 2; // 页码：page
int row = 10; // 每页行数：rows
query.setFirstResult((page - 1) * row); // 设置起始记录下标
query.setMaxResults(row); // 设置返回的最大结果集
a.代码演示：
Util包：
pageBean.java：
package com.qiuwenfan.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 = 5;// 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.qiuwenfan.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);
}
}
BaseDao.java:
package com.qiuwenfan.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;
/**
* 基于hql语句的通用查询工具类
* 1、需要给拼接的hql语句的命名参数赋值 （可以简化的）
* 2、分页（可以简化的）
*
* 基于sql的分页的查询做法
* 1、首先要查询出符合条件的总记录数
* 2、返回符合条件的记录
*
* 参数：sql,pagebean, Class clz
* sql = select * from t_hibernate_book where bookName like "%圣墟%"
* 1、countSql = select count(*) from (sql) t;
* 2、pageSql = sql + "limit " + start + "," + rows
*
* 基于hql的分页的查询的做法
* hql = from bookName like "%圣墟%"
* hql = select from Book where bookName like "%圣墟%"
* 1、countHql = select count(*) (hql) ;
*
* @author qiuwenfan
*
*/
public class BaseDao {
/**
*
* @param query 里面包含了带有命名参数的hql语句，需要等待赋值
* from Book where 1 = 1 and bookName like :bookName
* @param paramMap
* = request.getParameterMap();
*/
public void setParam(Query query, Map<String, Object> paramMap) {
if(paramMap != null && paramMap.size() > 0) {
Set<Entry<String, Object>> entrySet = paramMap.entrySet();
for (Entry<String, Object> entry : entrySet) {
String key = entry.getKey();
Object value = entry.getValue();
if(value instanceof Object[]) {
// value可能是数组
query.setParameterList("bookIds", (Object[])value);
}else if(value instanceof Collection) {
// value可能是集合
query.setParameterList("bookIds", (Collection)value);
}else {
query.setParameter(key, value);
}
}
}
}
/**
* 拼装符合条件的做记录数
* @param hql
* @return
*/
public String getCountHql(String hql) {
int fromIndex = hql.toUpperCase().indexOf("FROM");
return "select count(*) " + hql.substring(fromIndex);
}
/**
* 基于hql的通用查询方法
* @param hql
* @param pageBean
* @param paMap
* @param session
* @return
*/
public List executeQuery(String hql, PageBean pageBean, Map<String, Object> paMap, Session session) {
List list = null;
Query query = null;
if(pageBean != null && pageBean.isPagination()) {
// 1、首先要查询出符合条件的总记录数
String countHql = getCountHql(hql);
Query countQuery = session.createQuery(countHql);
this.setParam(countQuery, paMap);
pageBean.setTotal(countQuery.getSingleResult().toString());
// 2、返回符合条件的记录
query = session.createQuery(hql);
this.setParam(query, paMap);
query.setFirstResult(pageBean.getStartIndex());
query.setMaxResults(pageBean.getRows());
list = query.list();
}else {
query = session.createQuery(hql);
this.setParam(query, paMap);
list = query.list();
}
return list;
}
}
test包：
HqlTes.java:
package com.qiuwenfan.five.test;
import java.util.ArrayList;
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.qiuwenfan.five.util.PageBean;
import com.qiuwenfan.four.dao.BookDao;
import com.qiuwenfan.four.entity.Book;
import com.qiuwenfan.two.util.SessionFactoryUtils;
public class HqlTest {
private Session session;
private Transaction transaction;
private BookDao bookDao = new BookDao();
@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当作prepareStatement
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);
}
/**
* HQL分页
*/
@Test
public void testList9() {
Query query = session.createQuery("from Book");
query.setFirstResult(5);
query.setMaxResults(5);
List<Book> list = query.list();
for (Book b : list) {
System.out.println(b);
}
}
/**
* 测试list方法
*/
@Test
public void testList10() {
Book book = new Book();
PageBean pageBean = new PageBean();
// pageBean.setPage(2);
book.setBookName("%圣墟%");
List<Book> list = this.bookDao.list(book, pageBean);
for (Book b : list) {
System.out.println(b);
}
}
@Test
public void testList11() {
Book book = new Book();
PageBean pageBean = new PageBean();
// pageBean.setPagination(false); //查询全部
// pageBean.setPage(2); //分页查询
book.setBookName("%圣墟%"); //模糊查询
List<Book> list = this.bookDao.listPlus(book, pageBean);
for (Book b : list) {
System.out.println(b);
}
}
}
b.图片显示：
1、查询全部
2、分页查询
3、模糊查询：
