hql语句基础
1.什么是hql
HQL是Hibernate Query Language（Hibernate 查询语言）的缩写
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 as a
?，从下标0开始计算位置 ?，从顺序1开始计算位置
(hibernate5之后不支持，因为问号占位符存在sql注入，sql攻击)
: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
注意：QuerySyntaxException:book is not mapped
3. 处理返回的结果集
- 单个对象
select没有逗号 - Object[]
b.bookId, b.bookName - Map
new Map(b.bookId as bid, b.bookName as bname) - new 构造方法(attr1,attr2)
new Book(b.bookId, b.price)
单个列段
代码演示
结合hibernate关联多对多代码的Book实体类
PageBean
package com.myy.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
package com.myy.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);
}
}
HqlTest
package com.myy.five.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.myy.four.entity.Book;
import com.myy.two.util.SessionFactoryUtils;
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
*/
@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);
}
/**
* 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);
}
}
}
测试
testList1方法运行结果：
返回对象（多个）
testList2方法运行结果：
返回单个列段，用字符串就可以接受
testList3方法运行结果：
查两个列段及以上，默认返回的是Object[ ]
testList4方法运行结果：
map是函数，函数不区分大小写，返回map集合
相比testList3的好处：不用去数下标。（但是基本上不会用）
testList5方法运行结果：
有构造函数返回对象
没有构造函数时，会报没有构造函数的错误：
no appropriate constructor in class: com.myy.four.entity.Book
4. hql中使用占位符
-
?占位符
从下标0开始计算位置
hibernate5之后不再支持?占位符 -
:命名参数
testList6方法运行结果：
hql支持占位符
传数组
传集合调的方法是同一个,修改一下代码：
/**
* 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);
}
}
运行结果：
5. 连接查询
testList7运行结果：
查出了所有的映射关系
6. 聚合函数
sum
avg
max
min
count
testList8方法运行结果：
和sql没有什么太大的区别
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
查第二页数据，五条。(2-1)*5,5
以前sql语句：select * from t_hibernate_book limit 5,5
hql语句：
Query当作prepareStatement，自动封装了接口。
/**
* HQL分页
*/
@Test
public void testList9() {
Query query = session.createQuery("from Book");
query.setFirstResult(5);//自动设置了起始下标
query.setMaxResults(5);//偏移量
List<Book> list = query.list();
for (Book b : list) {
System.out.println(b);
}
}
运行结果：
结合hibernate关联多对多代码的BookDao
版本一：
基于hql语句
BookDao
/**
* 书籍的分页查询
* 1.动态的拼接hql语句
* 2.需要给拼接的hql语句的命名参数赋值（可以简化的）
* 3.分页
* @param book
* @param pageBean
* @return
*/
public List<Book> list(Book book,PageBean pageBean){
Session session = SessionFactoryUtils.openSession();
// Transaction transaction = session.beginTransaction();
String hql = "from Book where 1=1";
String bname = book.getBookName();
// 传参
if(StringUtils.isNotBlank(bname)) {
hql += " and bookName like :bookName";
}
Query query= session.createQuery(hql);
// 赋值
if(StringUtils.isNotBlank(bname)) {
query.setParameter("bookName", bname);
}
// 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;
}
HqlTest
@Test
public void testList10() {
Book book = new Book();
PageBean pageBean = new PageBean();
// 设置页码
// pageBean.setPage(2);
// 带条件查询
// book.setBookName("%圣墟%");
List<Book> list = this.bookDao.list(book, pageBean);
for (Book b : list) {
System.out.println(b);
}
}
运行结果:
设置页码：
带条件查询：
升级：版本二
BaseDao
package com.myy.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 Book where bookName like "%圣墟%"
*hql = select * from Book where bookName like "%圣墟%"
*1.countHql = select count(*) hql;
*
* @author myy
*
*/
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 paMap
* = request.getParameterMap();
*/
public void setParam(Query query,Map<String, Object> paMap) {
if(paMap != null && paMap.size() > 0) {
Set<Entry<String,Object>> entrySet = paMap.entrySet();
for (Entry<String, Object> entry : entrySet) {
// 命名参数
String key = entry.getKey();
// 赋值
Object value = entry.getValue();
if(value instanceof Object[]) {
// value可能是数组
query.setParameterList(key, (Object [])value);
}else if(value instanceof Collection) {
// value可能是集合
query.setParameterList(key, (Collection)value);
}
else {
query.setParameter(key, value);
}
}
}
}
/**
* 拼装符合条件的总记录数
* @param hql
* @return
*/
public String getCountHql(String hql) {
// 把hql全变成大写，得到fromIndex关键字下标
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 pMap
* @param session
* @return
*/
public List executeQuery(String hql,PageBean pageBean,Map<String, Object> pMap,Session session) {
List list = null;
Query query = null;
if(pageBean != null && pageBean.isPagination()) {
// 1.首先要查询符合条件的总记录数
String countHql = getCountHql(hql);
Query countQuery = session.createQuery(countHql);
this.setParam(countQuery, pMap);
pageBean.setTotal(countQuery.getSingleResult().toString());
// 2.返回符合条件的记录
query = session.createQuery(hql);
this.setParam(query, pMap);
query.setFirstResult(pageBean.getStartIndex());
query.setMaxResults(pageBean.getRows());
list = query.list();
}else {
query = session.createQuery(hql);
this.setParam(query, pMap);
list = query.list();
}
return list;
}
}
BookDao继承BaseDao
package com.myy.four.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.myy.five.util.BaseDao;
import com.myy.five.util.PageBean;
import com.myy.five.util.StringUtils;
import com.myy.four.entity.Book;
import com.myy.four.entity.Category;
import com.myy.two.util.SessionFactoryUtils;
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();
}
/**
* 书籍的分页查询
* 1.动态的拼接hql语句
* 2.需要给拼接的hql语句的命名参数赋值（可以简化的）
* 3.分页
* @param book
* @param pageBean
* @return
*/
public List<Book> list(Book book,PageBean pageBean){
Session session = SessionFactoryUtils.openSession();
// Transaction transaction = session.beginTransaction();
String hql = "from Book where 1=1";
String bname = book.getBookName();
// 传参
if(StringUtils.isNotBlank(bname)) {
hql += " and bookName like :bookName";
}
Query query= session.createQuery(hql);
// 赋值
if(StringUtils.isNotBlank(bname)) {
query.setParameter("bookName", bname);
}
// 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;
}
/**
* 基于hql的plus版本
* @param book
* @param pageBean
* @return
*/
public List<Book> listPlus(Book book,PageBean pageBean){
Session session = SessionFactoryUtils.openSession();
// Transaction transaction = session.beginTransaction();
String hql = "from Book where 1=1";
String bname = book.getBookName();
// 这个是jsp自动传递过来的，不需要手写
Map<String, Object> map = new HashMap<String, Object>();
if(StringUtils.isNotBlank(bname)) {
hql +=" and bookName like :bookName";
map.put("bookName", bname);
}
Query query= session.createQuery(hql);
List list = super.executeQuery(hql, pageBean, map, session);
// transaction.commit();
session.close();
return list;
}
}
HqlTest测试
package com.myy.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.myy.five.util.PageBean;
import com.myy.four.dao.BookDao;
import com.myy.four.entity.Book;
import com.myy.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);
}
}
@Test
public void testList10() {
Book book = new Book();
PageBean pageBean = new PageBean();
// 设置页码
pageBean.setPage(2);
// 带条件查询
// 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();
// 设置页码
// pageBean.setPage(2);
// 带条件查询
// book.setBookName("%圣墟%");
List<Book> list = this.bookDao.listPlus(book, pageBean);
for (Book b : list) {
System.out.println(b);
}
}
}
testList11方法运行结果：
