Java Development

[Blanc]

Hi all,

Am trying to insert data in a  thread to a single table from different classes..

In the run method of the thread class am preparing the insertquery.

in generation of the insertquery am calling a static method 'getNextSurveyResponseId' of a class to generate a unique id.

as all the insert queries use 'getNextSurveyResponseId' for  unique id, am using synchronized block and getting lock on 'getNextSurveyResponseId' but the lock is holding no longer and am getting same values in the generation of unique id.

please help !!

the following is the code snippet....

String sqrid = null;
            synchronized(GenerateNextId.getNextSurveyQuestionResponseId())
            {
                sqrid = GenerateNextId.getNextSurveyQuestionResponseId();
            }


public static  String getNextSurveyQuestionResponseId()
    {
        synchronized(DatabaseFunctions._database) {
            if(GenerateNextId.SURVEY_QUESTION_RESPONSEID == null)
            {
                Tools.print("XCO: GenerateNextId: getNextSurveyQuestionResponseId: Called for the first time");
                Dictionary [][]sqrid = DatabaseFunctions.get("Select count(SurveyQuestionResponseID), (max(SurveyQuestionResponseID) +1) from OA_SURVEYQUESTIONRESPONSE");
                if(sqrid != null)
                {
                    int count = Integer.parseInt(sqrid[0][0].value.toString());
                    if(count == 0)
                    {
                        GenerateNextId.SURVEY_QUESTION_RESPONSEID = "15001";    
                    }
                    else
                    {
                        GenerateNextId.SURVEY_QUESTION_RESPONSEID = sqrid[0][1].value.toString();
                    }
                    return GenerateNextId.SURVEY_QUESTION_RESPONSEID;
                }
            }
            int temp = Integer.parseInt(GenerateNextId.SURVEY_QUESTION_RESPONSEID);
            GenerateNextId.SURVEY_QUESTION_RESPONSEID = Integer.toString(++temp);
            return GenerateNextId.SURVEY_QUESTION_RESPONSEID;
        }
    }

[simon_hain]

just to doublecheck. do you call the code from a single application instance/entry point? or do you use an autostart part?

[Blanc]

no it is not an auto start up. the app is starting from a single point of instance public static void main(String []args)

[simon_hain]

don't know why your synchronized doesn't work.

you could implement a queue with a callback maybe.

[Blanc]

now i make the getNextSurveyRespone() synchronized method and i hold a lock on the database object here even.

now am able to generate the unique ids... but everytime while inserting to database programatically it is throwing constraint failed error.

most surprising is when i copy the insert statement from debug messages and executes teh same query in the sqlite manager, the query is executing without any error...

why it is happening...?/

recap after modificcations...

getNextSurveyResponse() is a synchronized method.

am holding lock on teh datbase obj. in this mehtod.

am holding lock on the synchronized method while calling.

unique id is generating now.

but throwing constraint failed error, while inserting data.

hlp!!!!!!

[Blanc · Accepted solution]

making the method getNextSurveyResponseId as synchronized method works for me.

thanks all