list方法返回的是结果集的list集合，iterate返回的是iterator迭代器。
list方法查询所有记录只发送一条sql语句，select * from 表名
iterate方法查询所有记录的话，先查询到满足条件的所有记录id，并不立即查询所有结果，当我们有用到某个记录的话，他才查询。如果显示所有记录的话需要n+1条sql语句。第一条查id，接下去根据id，一条一条查询，所以是n+1条。
list方法缓存中有记录了，他还是会发生sql语句到数据库中查询。
iterate方法缓存中有记录了，他只发送一条查符合条件的id的sql语句。
先看看list方法。
Session session =DBUtil.getSession();
String hql ="from Deptment" ;
Query query = session.createQuery(hql);
System.out.println("第一次查询");
List list1 = query.list();
Iterator iter1 = list1.iterator();
while(iter1.hasNext())
{
System.out.println( iter1.next());
}
System.out.println("第二次查询");
List list2 = query.list();
Iterator iter2 = list2.iterator();
while(iter2.hasNext())
{
System.out.println( iter2.next());
}
session.close();
结果：
第一次查询
Hibernate: select deptment0_.DEPTID as DEPTID0_, deptment0_.DEPTNAME as DEPTNAME0_ from SCOTT.DEPTMENT deptment0_
Deptment [deptid=2, deptname=sdsdzz]
Deptment [deptid=3, deptname=sdsdzz]
Deptment [deptid=4, deptname=sdsdzz]
Deptment [deptid=1, deptname=a]
第二次查询
Hibernate: select deptment0_.DEPTID as DEPTID0_, deptment0_.DEPTNAME as DEPTNAME0_ from SCOTT.DEPTMENT deptment0_
Deptment [deptid=2, deptname=sdsdzz]
Deptment [deptid=3, deptname=sdsdzz]
Deptment [deptid=4, deptname=sdsdzz]
Deptment [deptid=1, deptname=a]
iterate（）方法
Session session =DBUtil.getSession();
String hql ="from Deptment" ;
Query query = session.createQuery(hql);
System.out.println("第一次查询");
Iterator iter1 = query.iterate();
while(iter1.hasNext())
{
System.out.println( iter1.next());
}
System.out.println("第二次查询");
Iterator iter2 = query.iterate();
while(iter2.hasNext())
{
System.out.println( iter2.next());
}
session.close();
结果：
第一次查询
Hibernate: select deptment0_.DEPTID as col_0_0_ from SCOTT.DEPTMENT deptment0_
Hibernate: select deptment0_.DEPTID as DEPTID0_0_, deptment0_.DEPTNAME as DEPTNAME0_0_ from SCOTT.DEPTMENT deptment0_ where deptment0_.DEPTID=?
Deptment [deptid=1, deptname=a]
Hibernate: select deptment0_.DEPTID as DEPTID0_0_, deptment0_.DEPTNAME as DEPTNAME0_0_ from SCOTT.DEPTMENT deptment0_ where deptment0_.DEPTID=?
Deptment [deptid=2, deptname=sdsdzz]
Hibernate: select deptment0_.DEPTID as DEPTID0_0_, deptment0_.DEPTNAME as DEPTNAME0_0_ from SCOTT.DEPTMENT deptment0_ where deptment0_.DEPTID=?
Deptment [deptid=3, deptname=sdsdzz]
Hibernate: select deptment0_.DEPTID as DEPTID0_0_, deptment0_.DEPTNAME as DEPTNAME0_0_ from SCOTT.DEPTMENT deptment0_ where deptment0_.DEPTID=?
Deptment [deptid=4, deptname=sdsdzz]
第二次查询
Hibernate: select deptment0_.DEPTID as col_0_0_ from SCOTT.DEPTMENT deptment0_
Deptment [deptid=1, deptname=a]
Deptment [deptid=2, deptname=sdsdzz]
Deptment [deptid=3, deptname=sdsdzz]
Deptment [deptid=4, deptname=sdsdzz]
query.list()和query.iterate()区别,布布扣,bubuko.com