本文共 7279 字，大约阅读时间需要 24 分钟。

hibernate使用session.createQuery(hql)查询数据的时候，有两种查询方式：

1、一种是只查询一次，将所有要查询的数据都查询出来，后面直接取数据就可以了；

      获取方式：session.createQuery(hql).list()。

      一次性加载的数据多，效率低，用于例如商品信息展示。适用于展示所有信息。

2、另一种是先查询一次，将主键查询出来，后面需要数据的时候，根据主键一条一条的取数据。

       获取方式：session.createQuery(hql).iterate()。

      用于新闻列表展示。当需要查看新闻内容时，在去根据主键查询具体内容数据。

      适用于仅仅展示某一条或几条信息。

下面用一个例子来演示一下

新建一个java项目，项目结构如下：

实体类Book代码：

package com.myeclipse.pojo;import java.util.Date;public class Book {		private int id;	private String author;	private String name;	private double price;	private Date pubDate;		public int getId() {		return id;	}	public void setId(int id) {		this.id = id;	}	public String getAuthor() {		return author;	}	public void setAuthor(String author) {		this.author = author;	}	public String getName() {		return name;	}	public void setName(String name) {		this.name = name;	}	public double getPrice() {		return price;	}	public void setPrice(double price) {		this.price = price;	}	public Date getPubDate() {		return pubDate;	}	public void setPubDate(Date pubDate) {		this.pubDate = pubDate;	}	@Override	public String toString() {		return "Book [id=" + id + ", author=" + author + ", name=" + name				+ ", price=" + price + ", pubDate=" + pubDate + "]";	}		}

Book.hbm.xml代码：

HibernateUtil代码：

package com.robert.util;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.boot.registry.StandardServiceRegistryBuilder;import org.hibernate.cfg.Configuration;/** * hibernate工具类 */public class HibernateUtil {	private static Configuration cfg = null;	private static SessionFactory factory = null;	private static Session session = null ;		static {		init();	}	/**	 * 初始化获得Configuration和SessionFacroty对象	 */	public static void init() {		cfg = new Configuration().configure();		factory = cfg.buildSessionFactory(new StandardServiceRegistryBuilder()				.applySettings(cfg.getProperties()).build());	}	/**	 * 获得Session对象	 * @return	 */	public static Session getSession() {		if (factory != null){			return session = factory.openSession();		}				init();		return session = factory.openSession();	}		/**	 * 关闭Session	 */	public static void closeSession() {		if(session!=null && session.isOpen())			session.close();	}}

hibernate.cfg.xml代码：

   
    	
     	
     
      		com.mysql.jdbc.Driver	
     	
     
      jdbc:mysql:///hibernate4
     	
     
      root
     	
     
      root
     	
     	
     
      		org.hibernate.dialect.MySQL5Dialect	
     	
     	
     
      true
     	
     	
     
      true
     	
     	
     
      update
     	
     	
     
    
   

HibernateTest测试类代码：

package com.ghibernate.test;import java.util.Date;import java.util.Iterator;import java.util.List;import org.hibernate.Query;import org.hibernate.Session;import org.hibernate.Transaction;import org.hibernate.cfg.Configuration;import org.hibernate.tool.hbm2ddl.SchemaExport;import org.junit.Test;import com.myeclipse.pojo.Book;import com.robert.util.HibernateUtil;public class HibernateTest {	@Test	public void testCreateDB() {		Configuration cfg = new Configuration().configure();		SchemaExport se = new SchemaExport(cfg);		// 第一个参数：是否生成ddl脚本		// 第二个参数：是否执行到数据库中		se.create(true, true);	}	@Test	public void testSave() {		Session session = HibernateUtil.getSession();		Transaction tx = session.beginTransaction();		Book book = new Book();		book.setName("读者");		book.setPrice(5.6);		book.setAuthor("众人");		book.setPubDate(new Date());		Book book1 = new Book();		book1.setName("傲慢与偏见");		book1.setPrice(80.0);		book1.setAuthor("简.奥斯汀");		book1.setPubDate(new Date());		Book book2 = new Book();		book2.setName("中国历史");		book2.setPrice(30.0);		book2.setAuthor("人民出版社");		book2.setPubDate(new Date());		Book book3 = new Book();		book3.setName("翩眇之旅");		book3.setPrice(70.0);		book3.setAuthor("萧鼎");		book3.setPubDate(new Date());		Book book4 = new Book();		book4.setName("蓝血人");		book4.setPrice(60.0);		book4.setAuthor("卫斯理");		book4.setPubDate(new Date());		Book book5 = new Book();		book5.setName("我的大学");		book5.setPrice(60.5);		book5.setAuthor("高尔基");		book5.setPubDate(new Date());		session.save(book);		session.save(book1);		session.save(book2);		session.save(book3);		session.save(book4);		session.save(book5);		tx.commit();		HibernateUtil.closeSession();	}	@Test	public void testIterator() {		Session session = HibernateUtil.getSession();		Transaction tx = session.beginTransaction();		List
   
     list = session.createQuery("from Book").list() ;		for(Book book : list) {			System.out.println("书名："+book.getName());		}		tx.commit();		HibernateUtil.closeSession();				System.out.println("-----------------上面是list方式-------------------------");		System.out.println("-----------------下面是iterator方式---------------------");				session = HibernateUtil.getSession();		tx = session.beginTransaction();		Iterator
    
      iter = session.createQuery("from Book").iterate() ;		for (; iter.hasNext();) {			Book book = (Book) iter.next();			System.out.println("iterator遍历的书名："+book.getName());		}		tx.commit();		HibernateUtil.closeSession();	}}
    
   

先运行testCreateDB()，重新生成数据库表；

执行testSave(),保存数据；

执行testIterator()方法，生成的sql语句如下：

Hibernate:     select        book0_.id as id1_0_,        book0_.author as author2_0_,        book0_.book_name as book_nam3_0_,        book0_.price as price4_0_,        book0_.pubDate as pubDate5_0_     from        t_book book0_书名：读者书名：傲慢与偏见书名：中国历史书名：翩眇之旅书名：蓝血人书名：我的大学-----------------上面是list方式------------------------------------------下面是iterator方式---------------------Hibernate:     select        book0_.id as col_0_0_     from        t_book book0_Hibernate:     select        book0_.id as id1_0_0_,        book0_.author as author2_0_0_,        book0_.book_name as book_nam3_0_0_,        book0_.price as price4_0_0_,        book0_.pubDate as pubDate5_0_0_     from        t_book book0_     where        book0_.id=?iterator遍历的书名：读者Hibernate:     select        book0_.id as id1_0_0_,        book0_.author as author2_0_0_,        book0_.book_name as book_nam3_0_0_,        book0_.price as price4_0_0_,        book0_.pubDate as pubDate5_0_0_     from        t_book book0_     where        book0_.id=?iterator遍历的书名：傲慢与偏见Hibernate:     select        book0_.id as id1_0_0_,        book0_.author as author2_0_0_,        book0_.book_name as book_nam3_0_0_,        book0_.price as price4_0_0_,        book0_.pubDate as pubDate5_0_0_     from        t_book book0_     where        book0_.id=?iterator遍历的书名：中国历史Hibernate:     select        book0_.id as id1_0_0_,        book0_.author as author2_0_0_,        book0_.book_name as book_nam3_0_0_,        book0_.price as price4_0_0_,        book0_.pubDate as pubDate5_0_0_     from        t_book book0_     where        book0_.id=?iterator遍历的书名：翩眇之旅Hibernate:     select        book0_.id as id1_0_0_,        book0_.author as author2_0_0_,        book0_.book_name as book_nam3_0_0_,        book0_.price as price4_0_0_,        book0_.pubDate as pubDate5_0_0_     from        t_book book0_     where        book0_.id=?iterator遍历的书名：蓝血人Hibernate:     select        book0_.id as id1_0_0_,        book0_.author as author2_0_0_,        book0_.book_name as book_nam3_0_0_,        book0_.price as price4_0_0_,        book0_.pubDate as pubDate5_0_0_     from        t_book book0_     where        book0_.id=?iterator遍历的书名：我的大学