hibernate之HQL语句

矫情吗；* 2021-10-25 12:18 356阅读 0赞

## 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

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

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

## 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

## 代码演示如下： ##

工具类：

PageBean

package com.hxc.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 = 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.hxc.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);
        }
    
    }

hql语句的测试类 HqlTest

package com.hxc.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.hxc.four.entity.Book;
    import com.hxc.three.id.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);
            }
        }
    }

BaseDao：

package com.hxc.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;
    
    /**
     * 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 cout(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：将原生的hql语句以from关键字进行截取
     *  countHql=select count(*) from Book where bookName like : bookName:
     *  pageeHql不需要写，因为hibernate已经封装了内置分页接口 getFirstResult getMaxResult
     * 
     * @author 旧城
     *
     */
    public class BaseDao {
    
        /**
         * 给hibernate中的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.setParameter(entry.getKey(), (Collection)value);
                    }else if(value instanceof Object[]){
                        query.setParameter(entry.getKey(), (Object[])value);
                    }else {
                        query.setParameter(entry.getKey(), value);
                    }
                }
            }
        }
        /**
         * hql= select * from Book where bookName like :bookName
         *      hql=from book where bookName like :bookName
         *     思想：将原生的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;
        }
    }

BookDao

package com.hxc.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.hxc.five.util.BaseDao;
    import com.hxc.five.util.PageBean;
    import com.hxc.five.util.StringUtils;
    import com.hxc.four.entity.Book;
    import com.hxc.four.entity.Category;
    import com.hxc.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();
        }
    
        /********************** 通用查询 **************************/
        public List<Book> list1(Book book, PageBean pageBean) {
            Session session = SessionFactoryUtils.openSession();
            Transaction transaction = session.beginTransaction();
    
            // 下面代码处理的是book实体类的条件查询
            String bookName = book.getBookName();
    
            // sql语句where后面可以直接写true，而hql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);
            }
    
            // 处理的是分页
            if (pageBean != null && pageBean.isPagination()) {
                query.setFirstResult(pageBean.getStartIndex());
                query.setMaxResults(pageBean.getRows());
            }
            List list = query.list();
    
            transaction.commit();
            session.close();
            return list;
    
        }
    
        
        public List<Book> list2(Book book, PageBean pageBean) {
             Session session=SessionFactoryUtils.openSession();
                Transaction transaction=session.beginTransaction();
                //下面代码处理的是book实体类的条件查询 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 list;
            }
    }

BookDaoTest

package com.hxc.four.dao;
    
    import java.util.List;
    
    import org.junit.Test;
    
    import com.hxc.five.util.PageBean;
    import com.hxc.four.entity.Book;
    import com.hxc.four.entity.Category;
    
    public class BookDaoTest {
        private BookDao bookDao = new BookDao();
    
        @Test
        public void testGetBook() {
            Book book = new Book();
            book.setBookId(8);
            book.setInitCategories(1);
            Book b = this.bookDao.getBook(book );
            System.out.println(b.getBookName());
            System.out.println(b.getCategories());
        }
        
        /**
         * book.hbm.xml    inverse=fasle
         * category.hbm.xml inverse=true
         * 数据添加正常
         * 书籍表、桥接表各新增一条数据
         */
        @Test
        public void test1() {
            Book book = new Book();
            book.setBookName("旧城");
            book.setPrice(10f);
            Category category = new Category();
            category.setCategoryId(5);
    //        直接将category对象加入到新建的book中是错误的，因为此时的category是临时态的，hibernate是不会管理的
    //        book.getCategories().add(category);
            Category c = this.bookDao.getCategory(category);
            
    //        c.getBooks().add(book);
            book.getCategories().add(c);
            this.bookDao.addBook(book);
        }
    
        /**
         * book.hbm.xml    inverse=false
         * category.hbm.xml inverse=true
         * 只增加书籍表数据
         * 桥接表不加数据
         * 原因：双方都没有去维护关系
         */
        @Test
        public void test2() {
            Book book = new Book();
            book.setBookName("c");
            book.setPrice(10f);
            Category category = new Category();
            category.setCategoryId(5);
            Category c = this.bookDao.getCategory(category);
            
            book.getCategories().add(c);
            this.bookDao.addBook(book);
    //        c.getBooks().add(book);
        }
        
        
        @Test
        public void testList1() {
            Book book=new Book();
    //        book.setBookName("%旧城%");
            PageBean pageBean=new PageBean();
            pageBean.setPage(2);
            List<Book> list1=this.bookDao.list1(book, pageBean);
            for (Book b : list1) {
                System.out.println(b);
            }
            
        }
        
        
        @Test
        public void testList2() {
            Book book=new Book();
    //        book.setBookName("%旧城%");
            PageBean pageBean=new PageBean();
            pageBean.setPage(2);
            List<Book> list1=this.bookDao.list2(book, pageBean);
            for (Book b : list1) {
                System.out.println(b);
            }
        }    
        
    }

testList1运行结果：

![1691488-20190808232402251-708438897.png][]

转载于:https://www.cnblogs.com/huxiaocong/p/11324519.html

[1691488-20190808232402251-708438897.png]: /images/20211025/e92e3d51e4eb41b095525c153df2bd71.png