CreateQuery and Createsqlquery in Hibernate

This article: http://stta04.javaeye.com/blog/377633CreateQuery and Createsqlquery in Hibernate

Last night to help colleagues see the code to 2 o'clock in the morning, this morning 6 o'clock woke up to find that he sent a message saying null pointer error, really can't sleep, up his own test, console also really reported:

2009-4-25 8:12:34 Org.apache.catalina.core.ApplicationContext Log
Info: java.lang.ClassCastException: [Ljava.lang.Object; cannot is cast to Com.miracle.dm.doc.catalog.model.DocCatalogInfo

The original query statement:

String sql = "Select a.* from Tb_doc_catalog a where a.cat_code like '" +catcode+ "% '";
Session session = This.getsession ();
try {
List catnamelist = session.createsqlquery (SQL). List ();
return catnamelist;
} finally {
Releasesession (session); Release session
}

Analysis: Fields that were originally queried are not automatically converted to bean objects.

Solution one (using HQL query):

String sql = "Select a from Doccataloginfo a where a.catcode like '" +catcode+ "% '";
List catnamelist =gethibernatetemplate (). find (SQL);
return catnamelist;
OK, test to find no problem, it seems still because of the original SQL query reason, search online: Createsqlquery returned to the object, saw an article only to realize:

Solution two (with native SQL query):

String sql = "Select a.* from Tb_doc_catalog a where a.cat_code like '" +catcode+ "% '";
Session session = This.getsession ();
try {
List catnamelist = session.createsqlquery (sql). Addentity (Doccataloginfo.class). List ();
return catnamelist;
} finally {
Releasesession (session); Release session
}

It's OK again.

This article is also posted:

The difference between CreateQuery and Createsqlquery in Hibernate is:
The former uses the HQL statement to query, the latter can use the SQL statement query
The formerHibernate-generated bean for object Mount list return
The latter is stored as an array of objects
So using createsqlquery sometimes also wants toHibernate-generated beans are not convenient for loading a list of objects.
Suddenly discovered that Createsqlquery had a way to convert objects directly
Query query = session.createsqlquery (SQL). addentity (Xxxxxxx.class);
XXXXXXX represents the object of the bean generated by hibernate, which is the bean that the data table maps out.
Hehe after more attention, or from time to time to see the use of various methods hibernate object.

There is another minor detail that should be noted:
For example, there is such a PO
PO:User.class
Properties:userid,username
Ddl:create table Tuser (userid varchar), username varchar (20));
When executing:
Session.createquery ("From User U"). The SQL generated when list ():
Select Userid,username from Tuser;
When executing:

SQL generated by Session.createquery ("from User U"). Iterator ():
　　
Select UserID from Tuser;
　　
You can see that list () reads data from the database at once and fills it directly into the list
　　
Iterator () reads the primary key of the data from the database and adds execution when the iterator is looped:
　　
Select Userid,username from user where userid=?; read out the data.
Different methods are used in different application areas and should be noted in hibernate applications.

CreateQuery and Createsqlquery in Hibernate