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 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
hqlTest
package com.zl5.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.zl2.util.SessionFactoryUtils;
import com.zl4.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
* query对象相当于preparestatement
*/
@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、
*
* select * from t_hibernate_order o,t_hibernate_order_item oi where o.orderid =oi.oid and o.orderid=2
*/
@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
* count
* sum
* avg
*/
@Test
public void testList8() {
Query query = session.createQuery("select count(*) from Book");
//getsingleresult，查询返回单行单列得数据
Long singleResult = (Long) query.getSingleResult();
System.out.println(singleResult);
}
/**
* sql=|select * from t_tibernate_book
* sql+limt start,offset
* 1 0,10
* 2 10,10
* 3 20,10
*
* firetResult:代表起始下标 start
* MaxResults:代表页大小offset
* 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);
}
}
}
PageBean
package com.zl5.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
package com.zl5.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
package com.zl5.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
*
* 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=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;
* pagehql不需要写：因为hibernate已经封装了内置的分页接口
* getFirstResult
* getMaxResult
* @author 2018111801
*
*/
public class BaseDao {
/**
* 给hibernate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;
}
}
接着BookDao继承 BaseDao
package com.zl4.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.zl2.util.SessionFactoryUtils;
import com.zl4.entity.Book;
import com.zl4.entity.Category;
import com.zl5.util.BaseDao;
import com.zl5.util.PageBean;
import com.zl5.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();
}
/*********************通用查询*************************/
public List<Book> list1(Book book,PageBean pageBean) {
Session session = SessionFactoryUtils.openSession();
Transaction transaction = session.beginTransaction();
//下面代码处理得是book实体类得条件查询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);
}
//处理得是分页
if(pageBean!=null&&pageBean.isPagination()) {
query.setFirstResult(pageBean.getStartIndex());
query.setMaxResults(pageBean.getRows());
}
List list=query.list();
transaction.commit();
session.close();
return null;
}
public List<Book> list2(Book book,PageBean pageBean) {
Session session = SessionFactoryUtils.openSession();
Transaction transaction = session.beginTransaction();
//下面代码处理得是book实体类得条件查询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 null;
}
}
在BookDaoTest测试
