本文详细介绍了Hibernate的HQL查询语言，包括HQL与SQL的区别、占位符的使用、命名参数、连接查询、聚合函数及分页操作，强调了HQL在面向对象查询上的优势。
一：HQL介绍
1. 什么是HQL
HQL是Hibernate Query Language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
?（占位符），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
支持: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：sql：select name from t_mvc_book where name like ?,?,?,?,?,?,?,?,？
hql：from Book where name like :bookName,:price,:sex::age query.setParam('bookName':圣墟)
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
avg
max
min
count
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
二：HQL语法基础
1.实体类
package com.xly.two.entity;
import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;
public class Book implements Serializable{
// book_id int primary key auto_increment,
// book_name varchar(50) not null,
// price float not null
private Integer bookId;
private String bookName;
private Float price;
private Set<Category> categories = new HashSet<Category>();
private Integer initCategories = 0;
public Integer getInitCategories() {
return initCategories;
}
public void setInitCategories(Integer initCategories) {
this.initCategories = initCategories;
}
public Integer getBookId() {
return bookId;
}
public void setBookId(Integer bookId) {
this.bookId = bookId;
}
public String getBookName() {
return bookName;
}
public void setBookName(String bookName) {
this.bookName = bookName;
}
public Float getPrice() {
return price;
}
public void setPrice(Float price) {
this.price = price;
}
public Set<Category> getCategories() {
return categories;
}
public void setCategories(Set<Category> categories) {
this.categories = categories;
}
@Override
public String toString() {
return "Book [bookId=" + bookId + ", bookName=" + bookName + ", price=" + price + "]";
}
public Book(Integer bookId, String bookName) {
super();
this.bookId = bookId;
this.bookName = bookName;
}
public Book() {
super();
}
}3. HQLTest处理返回的结果集
package com.xly.three.hql;
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.xly.two.entity.Book;
import com.xly.two.util.SessionFactoryUtil;
public class HqlTest {
private Session session;
private Transaction transaction;
@Before
public void before() {
session = SessionFactoryUtil.getSession();
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
* query对象相当于preparestament
* 传数组，也可以传集合
*/
@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");
//getSingleResult返回单行单列的数据
Long singleResult = (Long) query.getSingleResult();
System.out.println(singleResult);
}
@Test
public void testList10() {
String hql="from Book where 1 =1";
Book book=new Book();
if(book.getBookId()!=0) {
hql+=" and bookId=:bookId";
}
if(book.getBookName()!=null) {
hql+=" and bookName=:bookName";
}
Query query = session.createQuery("hql");
if(book.getBookId()!=0) {
query.setParameter("bookId", 1);
}
if(book.getBookName()!=null) {
query.setParameter("bookName", "%西%");
}
Book b = (Book) query.getSingleResult();
System.out.println(b);
}
/**
* HQL分页
* FirstResult：起始下标
* setMaxResults：偏移量，代表页大小
*/
@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);
}
}二：BaseDao
1.工具类（分页）
package com.xly.three.hql;
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 + "]";
}
}2、StringUtils
package com.xly.three.hql;
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);
}
}3、BaseDao
package com.xly.three.dao;
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;
import com.xly.three.hql.PageBean;
/**
* 1、设置参数的问题 2、分页代码重复的问题
*
* sql的通用分页的时候
*
* getCountSql(sql) select count(1) from (sql) t
*
* getCountHql(hql) hql = "from Book where bookName like :bookName" hql =
* "select * from new Book(bid,bookName) where bookName like :bookName" select
* count(1) hql
*
* @author Administrator
*
*/
public class BaseDao {
/**
* 通用的参数设值方法
*
* @param map
* 参数键值对集合
* @param query
* 预定义处理的hql对象
*/
public void setParam(Map<String, Object> map, Query query) {
if (map != null && map.size() > 0) {
Object value = null;
Set<Entry<String, Object>> entrySet = map.entrySet();
for (Entry<String, Object> entry : entrySet) {
// 例子的圣墟，但是有的时候它并不是单纯的字符串，可能是数组比如爱好，也可能是集合
value = entry.getValue();
if (value instanceof Object[]) {
query.setParameterList(entry.getKey(), (Object[]) value);
} else if (value instanceof Collection) {
query.setParameterList(entry.getKey(), (Collection) value);
} else {
query.setParameter(entry.getKey(), value);
}
}
}
}
public String getCountHql(String hql) {
// hql = "from Book where bookName like :bookName"
// * hql = "select * from new Book(bid,bookName) where bookName like :bookName"
int index = hql.toUpperCase().indexOf("FROM");
return "select count(*) " + hql.substring(index);
}
/**
* 通用查询方法
* @param session
* @param map
* @param hql
* @param pageBean
* @return
*/
public List executeQuery(Session session,Map<String, Object> map,String hql,PageBean pageBean) {
List list = null;
if(pageBean != null && pageBean.isPagination()) {
String countHql = getCountHql(hql);
Query countQuery = session.createQuery(countHql);
this.setParam(map, countQuery);
pageBean.setTotal(countQuery.getSingleResult().toString());
Query query = session.createQuery(hql);
// 给预定义hql语句执行对象中的参数赋值，有多少赋值多少
this.setParam(map, query);
query.setFirstResult(pageBean.getStartIndex());
query.setMaxResults(pageBean.getRows());
list = query.list();
}else {
Query query = session.createQuery(hql);
// 给预定义hql语句执行对象中的参数赋值，有多少赋值多少
this.setParam(map, query);
list = query.list();
}
return list;
}
}4、BookDao extends BaseDao
package com.xly.two.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.xly.three.dao.BaseDao;
import com.xly.three.hql.PageBean;
import com.xly.three.hql.StringUtils;
import com.xly.two.entity.Book;
import com.xly.two.entity.Category;
import com.xly.two.util.SessionFactoryUtil;
public class BookDao extends BaseDao{
public Integer addBook(Book book) {
Session session = SessionFactoryUtil.getSession();
Transaction transaction = session.beginTransaction();
Integer bid = (Integer) session.save(book);
transaction.commit();
session.close();
return bid;
}
public Integer addCategory(Category category) {
Session session = SessionFactoryUtil.getSession();
Transaction transaction = session.beginTransaction();
Integer cid = (Integer) session.save(category);
transaction.commit();
session.close();
return cid;
}
public Category getCategory(Category category) {
Session session = SessionFactoryUtil.getSession();
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 = SessionFactoryUtil.getSession();
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 = SessionFactoryUtil.getSession();
Transaction transaction = session.beginTransaction();
session.delete(book);
transaction.commit();
session.close();
}
public void delCategory(Category category) {
Session session = SessionFactoryUtil.getSession();
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();
}
/*
* hql讲解用到（需要继承BaseDao）
*/
/**
* 没有使用BaseDao之前的代码
* @param book
* @param pageBean
* @return
*/
public List<Book> list(Book book, PageBean pageBean) {
Session session = SessionFactoryUtil.getSession();
Transaction transaction = session.beginTransaction();
String hql = "from Book where 1 = 1";
if (StringUtils.isNotBlank(book.getBookName())) {
hql += " and bookName like :bookName";
}
Query query = session.createQuery(hql);
if (StringUtils.isNotBlank(book.getBookName())) {
query.setParameter("bookName", book.getBookName());
}
if (pageBean != null && pageBean.isPagination()) {
query.setFirstResult(pageBean.getStartIndex());
query.setMaxResults(pageBean.getRows());
}
List<Book> list = query.list();
transaction.commit();
session.close();
return list;
}
/**
* 使用BaseDao之后的代码
* @param book
* @param pageBean
* @return
*/
public List<Book> list2(Book book, PageBean pageBean) {
Session session = SessionFactoryUtil.getSession();
Transaction transaction = session.beginTransaction();
String hql = "from Book where 1 = 1";
Map<String, Object> map = new HashMap<String, Object>();
if (StringUtils.isNotBlank(book.getBookName())) {
hql += " and bookName like :bookName";
map.put("bookName", book.getBookName());
}
List list = super.executeQuery(session, map, hql, pageBean);
transaction.commit();
session.close();
return list;
}
/**
* 使用原生SQL
* @param book
* @param pageBean
* @return
*/
public List list3(Book book, PageBean pageBean) {
//String sql = "select b.*,o.* from t_hibernate_book b,t_hibernate_Order o";
String sql = "select * from t_hibernate_book";
Session session = SessionFactoryUtil.getSession();
Transaction transaction = session.beginTransaction();
List list = session.createSQLQuery(sql).list();
transaction.commit();
session.close();
return list;
}
}
@Test
public void testList2() {
PageBean pageBean=new PageBean();
pageBean.setRows(3);
Book book=new Book();
book.setBookName("%圣墟%");
List<Book> list = this.bookDao.list2(book, pageBean);
for (Book b : list) {
System.out.println(b);
}
// c.getBooks().add(book);
} 
@Test
public void testList3() {
PageBean pageBean=new PageBean();
pageBean.setRows(3);
Book book=new Book();
book.setBookName("%圣墟%");
List<Object[]> list = this.bookDao.list3(book, pageBean);
for (Object[] o : list) {
System.out.println(Arrays.toString(o));
}
// c.getBooks().add(book);
}
扫一扫
1910
被折叠的 条评论
为什么被折叠?
到【灌水乐园】发言
