hibernate之HQL

了解什么是hql

HQL是Hibernate Query Language的缩写

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

接下来运用HQL实现分页等功能并解决代码重复等问题

工具类

BaseDao

package com.y.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;


/**
 * 1、设置参数的问题
 * 2、分页代码重复的问题
 * @author 17936
 *
 *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
 *
 */
public class BaseDao {
	/**
	 *  通用的参数设置方法
	 * @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) {
			
			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 createQuery = session.createQuery(countHql);
				this.setParam(map, createQuery);
				pageBean.setTotal(createQuery.getSingleResult().toString());
				
				Query query = session.createQuery(hql);
//				给预定义hql语句执行对象中参数，有多少复制多少
				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语句执行对象中参数，有多少复制多少
				this.setParam(map, query);
				list = query.list();
			}
			
			return list;
		}
}

pageBean

package com.y.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 + "]";
	}

}

package com.y.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);
	}

}

dao方法

继承BaseDao

package com.n.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.h.util.SessionFactoryUtils;
import com.n.entity.Book;
import com.n.entity.Category;
import com.y.util.BaseDao;
import com.y.util.PageBean;
import com.y.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();
	}
	
	/**
	 * 需求：
	 * 		写一个带查询条件的并且能分页方法
	 * @param book
	 * @param pageBean
	 * @return
	 */
	public List<Book> list1(Book  book,PageBean pageBean) {
		Session session = SessionFactoryUtils.openSession();
		Transaction transaction = session.beginTransaction();

		String bookName = book.getBookName();
		String hql = "from Book where 1=1";
		if (StringUtils.isNotBlank(bookName)) {
			hql +=" and bookName like :bookName";
		}
//		query相当于sql所用的prepare Statement
		Query query = session.createQuery(hql);
		
		if (StringUtils.isNotBlank(bookName)) {
			query.setParameter("bookName", bookName);
		}
//		通过写上述代码会发现，同样的if判断写了两次
		
//		下面这个代码每个实体类分页都得写
		if (pageBean !=null && pageBean.isPagination()) {
			query.setFirstResult(pageBean.getStartIndex());
			query.setMaxResults(pageBean.getRows());
		}
		List<Book> 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();

		String bookName = book.getBookName();
		Map<String, Object> map = new HashMap<>();
		String hql = "from Book where 1=1";
		if (StringUtils.isNotBlank(bookName)) {
			hql +=" and bookName like :bookName";
			map.put("bookName", bookName);
		}
		List<Book> list = super.executeQuery(session, map, hql, pageBean);
		
		transaction.commit();
		session.close();
		return list;
	}
	
	
	
}

测试

用JUnit进行测试

package com.n.dao;

import java.util.List;

import org.junit.Test;

import com.n.entity.Book;
import com.n.entity.Category;
import com.y.util.PageBean;


public class BookDaoTest {
	private BookDao bookDao = new BookDao();

	@Test
	public void testGetBook() {
		Book book = new Book();
		book.setBookId(3);
		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("丹麦");
		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=true
	 * 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("玻璃");
		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();
		PageBean pageBean = new PageBean();
//		pageBean.setPage(2);
//		book.setBookName("%玻璃%");
		pageBean.setPagination(false);
		List<Book> list = this.bookDao.list1(book, pageBean);
		for (Book b : list) {
			System.out.println(b);
		}
	}
	
	
	@Test
	public void testList2() {
		Book book = new Book();
		PageBean pageBean = new PageBean();
//		pageBean.setPage(2);
//		book.setBookName("%玻璃%");
		pageBean.setPagination(false);
		List<Book> list = this.bookDao.list2(book, pageBean);
		for (Book b : list) {
			System.out.println(b);
		}
	}
	
	
}

结果