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org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing:

2 comments January 14th, 2008

ORA-01747: invalid user.table.column, table.column, or column specification

Today I got this error.

ORA-01747: invalid user.table.column, table.column, or column specification.

There could be many reasons why you can get this error. But the basic reason is the query which is finally getting executed to your database is wrong in some way. In my case, I had a column with column name as DESC. I got rid of this problem by simply dropping the table and creating a new one with column name DESCRIPTION instead of DESC. You may not be able to do that if the table is already existing with many records in it.
Other reason could be that, if you are using named query your named query is not syntactically right.

No matter how the you get this error or for that matter any DB error in Hibernate, the best approach is to enable the show_sql variable in hibernate configuration and get the final query which hibernate is firing against the database.

Get this query and try running it directly in your database client. You can easily find out the culprit part of the query from there. Once you find out root cause of the problem you can think of workarounds or solution for this problem.

And yes, don’t forget to turn off the show_sql parameter after you are done with it. It will unnecessarily clutter your logs.

6 comments January 9th, 2008

org.hibernate.QueryParameterException: could not locate named parameter

When you query the database in Hibernate using NamedQuery you may run into this error

org.hibernate.QueryParameterException: could not locate named parameter [parm1]

Chances are that you are either trying to set a parmeter to the query which infact doesn’t exist in your query. For example

you are trying to do

query.setParameter(”parm1″, new Long(parm1Value));

whereas, in query there is no parameter like parm1

i.e. query might be just “from Item item”

Or you might be committing some spelling mistake in your code

Eg. query.setParameter(”pram1″, new Long(parm1Value));

and query is “from Item item item.desc like :parm1″

Do note that your parameter name in Java Class is misspelt as pram1 instead of parm1.

Add comment January 8th, 2008

synchronization in DWR

AJAX(Asynchronous JavaScript + XML) got its name because of its ability to interact asynchronously. This makes Ajax famous for the Rich Internet Applications aka RIAs.

But sometimes you purposefully need synchronization in your code. I needed it once. I was calling the same business method consecutively from my ajax code for two different fields. Even after synchronizing the business method and making it thread safe,I was not able to guarantee that the first method was fully finished before the second starts. Sometimes the first DWR call was processing the returned values and in the meantime second DWR call will return and mess with the original returned values. I had to synchronize the calls to make sure that both the calls get fired and completed in a proper order.

Starting from DWR1.1 you can synchronize your method calls at various levels.

I synchronized at the method level. My normal ajax code looked like myBusinessManagerImpl.getValues(’param1′, setValuesInDWR);

Where

myBusinessManagerImpl - business layer class

getValues - the method called by Ajax

param1 - the parameter passed to the business method

setValuesInDWR - the function variable, which was defined somewhere in the code like

var setValuesInDWR = function(data){
//….DWR Code…..
};

To make the method calls synchronized I modified the method call like this

myBusinessManagerImpl.getValues(’param1′, {callback:setValuesInDWR, async:false});

This way I was able to make two consecutive calls to the same method synchronously.

1 comment December 28th, 2007

addOptions problem in DWR

Have you ever wondered why the addOptions is not working in DWR even after reading the specs carefully. It happened to me recently. First, of all, the API or specs or documentation for DWR(addOptions Documentation) are not detailed and sufficient. Especially, for the new and impatient learners like me, who don’t want to go through each and every page of the spec before using the technology. Second, if you are impatient and new learner then probably you might have missed some of the part. Problem: I was trying to populate the Select box from a list of Objects using the addOptions method of DWR. I have followed the documentation fully but my drop down was not being populated. (It was my second day with DWR so I didn’t know some of the complexities which ultimately solved the problem)

Solution:- I will take one example to explain this Let your select field something like this



<select id=”statesList” />



And the class whose list of Objects you are trying to add is something like this



package testPackage.dwr;
public class State{
private String stateId;
private String stateName;
…………
//getter and setter methods
…………
}



and you want to populate this using DWR after some user action. Make sure that your callback function looks like this



var setValuesInDWR = function(data){
var fieldId = ’statesList’;
var valueText = ’stateId’;
var nameText = ’stateName’;
dwr.util.removeAllOptions(fieldId);// step 1
dwr.util.addOptions(fieldId, data, valueText, nameText);//step 2
};


All the above steps are important

Step 1 - Actually removes the already existing values from your select list. If you don’t do this. the addOptions method will simply append the list.

Step 2 - This will actually add the values to the drop-down list.

I forgot/missed/didn’t know that you have to add the following line in dwr.xml

<convert converter=”bean” match=”testPackage.dwr.State”/>

Reason is, unless you don’t explicitly specify in your dwr.xml the user defined beans will not be converted in DWR. If your bean consists of supported datatypes which DWR can automatically convert then you can just add this declaration. After following all these steps carefully the problem of Dropdown not getting populated in DWR should be solved.

3 comments December 21st, 2007

JRun Error - Exception parsing the TLD null : The tag function on line 14 is not a valid TLD element

Problem - Last week we had hard time with this problem. Our Web App was running all fine on Tomcat 5. But when we deployed our application on JRun we got

Exception parsing the TLD null : The tag function on line 14 is not a valid TLD element

Solution: - Carefully look into the Jars you are using in the classpath. In the most probability some of the Jars have some tlds which are incompatible with the JRun expects. Try removing all the Jars and carefully add only the required Jars checking the compatibility of the Jars one by one. See the explanation section below for the more details.

Explanation:- The error itself says that there is some TLD parsing error. The tag which JRun is trying to parse is having a different TLD than Jrun expects. If you look into Jrun.jar you will find a file called JSP.tld. It says tld version as 1.2. In our case we were having standard-1.1.2.jar in our classpath. That was the root cause of the problem. In fact this jar was not required at all. It was just sitting there in one of the common Jar repository. This solved our problem. You can think of looking into the struts.jar, servelet-api jars and Spring jars to check the compatibility with your JRun jars

Add comment May 17th, 2007

Hibernate Error - Identifier of an instance altered from 1 to 1

Problem:-Getting the error ” identifier of an instance of com.sample.db.Sample altered from 1 to 1″

Solution:- Check whether the java type of the identifier field in the Data Object, the type of the field in the hibernate xml file and the type of the column in the database are compatible types or not.

Explanation:- I had faced this strange problem today. I am using struts, hibernate and spring.

I found out that the problem roots from

public void

checkId(Object object, EntityPersister persister, Serializable id, EntityMode entityMode) method of DefaultFlushEntityEventListener class.

I solved this problem by changing the type of the id field in the class and the hbm.xml file.

We made some mistakes in declaring getter and setter methods and id field for this object. (therefore it is advisable to use Hibernate tools or other reverse engineer tools to generate your data object and hbm files)

The sample class was as follows

class Sample{

integer sampleId;

String sampleName;

public int getSampleId(){

….

}

public void setSampleId(int i){

…..

}

}

And this was the hbm file declaration

<id
name=”sampleId”
type=”integer”
column=”sample_id”
unsaved-value=”0″>
<generator class=”identity” />
</id>

<property
name=”sampleName”
type=”string”
column=”sample_name”
length=”50″
not-null=”true”
unique=”true”
/>

The problem was that in the database the type of the field was smallint which corresponds to the short data type in Java. Therefore somewhere in the org.hibernate.type.Type class hierarchy the

public boolean isEqual(Object x, Object y, EntityMode entityMode) method was failing.

What I did is I modified the Data Object and the hbm file like this

class Sample{

integer sampleId;

String sampleName;

public int getSampleId(){

public short getSampleId(){

….

}

public void setSampleId(int i){

public void setSampleId(short s){

…..

}

}

<id
name=”sampleId”
type=”integer”

type=”short”

column=”sample_id”
unsaved-value=”0″>
<generator class=”identity” />
</id>

7 comments May 16th, 2007

/hibernate.cfg.xml not found

Problem: Many a times we get a problem in hibernate saying /hibernate.cfg.xml not found

Solution: As per Java Persistence with Hibernate book, you should keep the hibernate configuration file directly in the source directory of your project outside any package. In Rational Application Developer, I have solved this problem by placing it directly src folder.

2 comments March 18th, 2007

Struts showing blank page

Problem: When you submit a JSP page in struts sometimes you get a blank page.

Solution: One of the solution I found is to check whether the action class class execute method is properly overridden or not. If it is not properly overridden, some other execute method of base Action class’ will be called.

There are two execute method in org.apache.struts.action.Action class

1)
ActionForward execute(ActionMapping mapping, ActionForm form, javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response)

2)
ActionForward execute(ActionMapping mapping, ActionForm form, javax.servlet.ServletRequest request, javax.servlet.ServletResponse response)

For HTTP request struts calls the first execute method. If the signature of your execute method inadvertently says ServletRequest and ServletResponse as parameters then you will get a blank page because parent’s execute method with HttpServletRequest and HttpServletResponse is called and it returns null.

Add comment March 18th, 2007