session.get(Xxx.class, id) wouldn't return null

diviner · **Joined:** Tue Sep 06, 2005 4:12 am **Posts:** 16

I find that session.get(Xxx.class, id) wouldn't return null when record not found, snippet code here:

Code:

   customer = (Customer)session.get(Customer.class, custno);
   if (customer.getAddr1() != null){
      System.out.println(customer.getCompany() + " - By get().");
   } else {
      System.out.println("Record not found");
   }

What's wrong here? Thank you very much.[/code]

diviner · **Joined:** Tue Sep 06, 2005 4:12 am **Posts:** 16

Snippet has some change, see here again:

Code:

   customer = (Customer)session.get(Customer.class, custno);
   if ([b]customer != null[/b]){
      System.out.println(customer.getCompany() + " - By get().");
   } else {
      System.out.println("Record not found");
   }

arumugam_kasi · **Posted:** Wed Sep 07, 2005 3:40 am

What is wrong with your code???

Dont you get NULL?
Or any exception?

Could you state clearly what you you need to know? get method always returns null if it cannot find the object that you are looking for in DB, whereas load throws an exception!!!

ardal · **Posted:** Wed Sep 07, 2005 4:02 am

As far as I can see, you are not querying correctly. Thee session.get() takes in an identifier as the second argument, but I don’t know if that’s what you want to use. Have you tried using Criteria.

Then it would be something like this

Code:

Criterion criterion  = Restrictions.eq(Customer.ID, customer.getId())
Criteria criteria = session.createCriteria(clazz).add(criterion);
customer = (Customer) criteria.uniqueResult();

diviner · **Joined:** Tue Sep 06, 2005 4:12 am **Posts:** 16

Sorry everybody. Let me explain more detail. I want to practice the difference record retrieving by two methods -- load() & get().

I have a sample code as following:

Code:

   private static void select8(Integer custno) {
   Session session = ConnectionBean.getCurrentSession();
   Customer customer = null;
   try {
      customer = (Customer)session.load(Customer.class, custno);
      System.out.println(customer.getCompany() + " - By load().");
   } catch (HibernateException e){
      System.out.println("Record not found - From exception by load().");
   }
      
   customer = (Customer)session.get(Customer.class, custno);
   if (customer != null){
      System.out.println(customer.getCompany() + " - By get().");
   } else {
      System.out.println("Record not found - From return null by get()");
   }
}

First to say, in Customer table, I have a record is primary key=1, but nothing record is primary key=2. Then:
After I call select8(1), it is very good for select record by both load() and get() methods. And then I call select8(2) to see how difference handling for record not found. I get the result from console:

Code:

Hibernate: select customer0_.custno as custno0_, customer0_.version as version0_0_, customer0_.company as company0_0_, customer0_.addr1 as addr4_0_0_, customer0_.addr2 as addr5_0_0_, customer0_.city as city0_0_, customer0_.state as state0_0_, customer0_.zip as zip0_0_, customer0_.country as country0_0_, customer0_.phone as phone0_0_, customer0_.fax as fax0_0_, customer0_.taxrate as taxrate0_0_, customer0_.contact as contact0_0_, customer0_.lastinvoicedate as lastinv14_0_0_ from customer customer0_ where customer0_.custno=?
16:42:56,967 INFO  DefaultLoadEventListener : Error performing load command
org.hibernate.ObjectNotFoundException: No row with the given identifier exists: [com.pkg1.hibernate.Customer#12311]
   at org.hibernate.ObjectNotFoundException.throwIfNull(ObjectNotFoundException.java:27)
   at org.hibernate.event.def.DefaultLoadEventListener.load(DefaultLoadEventListener.java:118)
   at org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:75)
   at org.hibernate.impl.SessionImpl.immediateLoad(SessionImpl.java:643)
   at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:59)
   at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:84)
   at org.hibernate.proxy.CGLIBLazyInitializer.intercept(CGLIBLazyInitializer.java:134)
   at com.pkg1.hibernate.Customer$$EnhancerByCGLIB$$1d5dd2dc.getCompany(<generated>)
   at com.pkg1.client.ConsoleDemo.select8(ConsoleDemo.java:134)
   at com.pkg1.client.ConsoleDemo.main(ConsoleDemo.java:305)
Record not found - From exception by load().
Hibernate: select customer0_.custno as custno0_, customer0_.version as version0_0_, customer0_.company as company0_0_, customer0_.addr1 as addr4_0_0_, customer0_.addr2 as addr5_0_0_, customer0_.city as city0_0_, customer0_.state as state0_0_, customer0_.zip as zip0_0_, customer0_.country as country0_0_, customer0_.phone as phone0_0_, customer0_.fax as fax0_0_, customer0_.taxrate as taxrate0_0_, customer0_.contact as contact0_0_, customer0_.lastinvoicedate as lastinv14_0_0_ from customer customer0_ where customer0_.custno=?
Hibernate: select customer0_.custno as custno0_, customer0_.version as version0_0_, customer0_.company as company0_0_, customer0_.addr1 as addr4_0_0_, customer0_.addr2 as addr5_0_0_, customer0_.city as city0_0_, customer0_.state as state0_0_, customer0_.zip as zip0_0_, customer0_.country as country0_0_, customer0_.phone as phone0_0_, customer0_.fax as fax0_0_, customer0_.taxrate as taxrate0_0_, customer0_.contact as contact0_0_, customer0_.lastinvoicedate as lastinv14_0_0_ from customer customer0_ where customer0_.custno=?
16:42:56,998 INFO  DefaultLoadEventListener : Error performing load command
org.hibernate.ObjectNotFoundException: No row with the given identifier exists: [com.pkg1.hibernate.Customer#12311]
   at org.hibernate.ObjectNotFoundException.throwIfNull(ObjectNotFoundException.java:27)
   at org.hibernate.event.def.DefaultLoadEventListener.load(DefaultLoadEventListener.java:118)
   at org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:75)
   at org.hibernate.impl.SessionImpl.immediateLoad(SessionImpl.java:643)
   at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:59)
   at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:84)
   at org.hibernate.proxy.CGLIBLazyInitializer.intercept(CGLIBLazyInitializer.java:134)
   at com.pkg1.hibernate.Customer$$EnhancerByCGLIB$$1d5dd2dc.getCompany(<generated>)
   at com.pkg1.client.ConsoleDemo.select8(ConsoleDemo.java:141)
   at com.pkg1.client.ConsoleDemo.main(ConsoleDemo.java:305)
Exception in thread "main" org.hibernate.ObjectNotFoundException: No row with the given identifier exists: [com.pkg1.hibernate.Customer#12311]
   at org.hibernate.ObjectNotFoundException.throwIfNull(ObjectNotFoundException.java:27)
   at org.hibernate.event.def.DefaultLoadEventListener.load(DefaultLoadEventListener.java:118)
   at org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:75)
   at org.hibernate.impl.SessionImpl.immediateLoad(SessionImpl.java:643)
   at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:59)
   at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:84)
   at org.hibernate.proxy.CGLIBLazyInitializer.intercept(CGLIBLazyInitializer.java:134)
   at com.pkg1.hibernate.Customer$$EnhancerByCGLIB$$1d5dd2dc.getCompany(<generated>)
   at com.pkg1.client.ConsoleDemo.select8(ConsoleDemo.java:141)
   at com.pkg1.client.ConsoleDemo.main(ConsoleDemo.java:305)

I found that the first exception is as expected ("Record not found - From exception by load().") But the subsequence exception is unexpected.

On the other hand, I try to remove a paragraph of code relation to load(), I found that if I just do try for get() only, it is ok.

Hope the information is enough to explain my problem.

Thank you very much.

ErikFK · **Posted:** Wed Sep 07, 2005 5:09 am

Hi,

Just a quick shot response before I try this out: have you tried to reverse the order of the tests (first get, then load)?

The documenation says the following about get:

Quote:

Return the persistent instance of the given entity class with the given identifier, or null if there is no such persistent instance. (If the instance, or a proxy for the instance, is already associated with the session, return that instance or proxy.)

I'm not 100% sure how to interpret this, but maybe a proxy was created by the load and is returned again in the get - which leads to unexpected behaviour.

What you are testing is certainly not a standard use case - but it is quite unexpected...

Erik

max · **Posted:** Wed Sep 07, 2005 9:12 am

and you are keeping the session opened even though an exception has occurred.

cyr2005 · **Joined:** Thu Aug 11, 2005 11:16 am **Posts:** 20

i have almost the same problem ! but me when it's return a result don't found in db , it's return something strange not a string and not nul and i can't display that because it's do a classcastexception like that :

property = BasepropertyDAO.getInstance().getpropertyByName("rouge",false);

if (property.getParam_name().toString().equals("rouge")) { <--- error here

Exception in thread "main" java.lang.ClassCastException: java.lang.String
at org.hibernate.type.IntegerType.set(IntegerType.java:39)
at org.hibernate.type.NullableType.nullSafeSet(NullableType.java:62)
at org.hibernate.type.NullableType.nullSafeSet(NullableType.java:44)
at org.hibernate.loader.Loader.bindPositionalParameters(Loader.java:1115)
at org.hibernate.loader.Loader.prepareQueryStatement(Loader.java:1177)
at org.hibernate.loader.Loader.doQuery(Loader.java:390)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:218)
at org.hibernate.loader.Loader.loadEntity(Loader.java:1345)
at org.hibernate.loader.entity.EntityLoader.load(EntityLoader.java:116)
at org.hibernate.loader.entity.EntityLoader.load(EntityLoader.java:101)
at org.hibernate.persister.entity.BasicEntityPersister.load(BasicEntityPersister.java:2471)
at org.hibernate.event.def.DefaultLoadEventListener.loadFromDatasource(DefaultLoadEventListener.java:351)
at org.hibernate.event.def.DefaultLoadEventListener.doLoad(DefaultLoadEventListener.java:332)
at org.hibernate.event.def.DefaultLoadEventListener.load(DefaultLoadEventListener.java:113)
at org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:75)
at org.hibernate.impl.SessionImpl.immediateLoad(SessionImpl.java:643)
at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:59)
at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:84)
at org.hibernate.proxy.CGLIBLazyInitializer.intercept(CGLIBLazyInitializer.java:134)
at model.AC_param$$EnhancerByCGLIB$$d94ceb45.getParam_name(<generated>)

diviner · **Joined:** Tue Sep 06, 2005 4:12 am **Posts:** 16

I have tried to do get() before invoke load(), no error is appeared. But if I do get() again after load() , that means get() --> load() --> get(), the last get() is mal-function again. It can't return null (all test is based on no record return circumstance).

diviner · **Joined:** Tue Sep 06, 2005 4:12 am **Posts:** 16

Obviously, get() method can't be invoked after load() method in a session, right?

emmanuel · **Posted:** Thu Sep 15, 2005 4:26 pm

get() will return the proxy created by load() in this case, as per the javadoc.