How to re-issue an SQL query in java code in deadlock situation ?

Question

Hi all..
I have a java application (in Struts) which is running on JBoss 4.0.1 server. The database is MySql 6.0. It is an
application made to be used among multiusers. The background operating system is Windows Vista.
Now a days i am facing a peculiar problem due to which the further things go wrong. I am getting following error :
com.mysql.jdbc.exceptions.MySQLTransactionRollbackException: Deadlock found when trying to get lock; try restarting transaction
I searched over forums and i got response as restart the transaction in deadlock.
In my java code it is a delete query where i get such exception when multiple users are accessing the application. What i tried for time being is as follows :
Statement stmt = null;
String temp = null;
Connection conn = null;
String sUserID =(String) session.getAttribute("username")
try
conn = DBConnection.getJndiConnection();
stmt = conn.createStatement();
temp = "Delete FROM temptable where Login ='"+sUserID+"'";
System.out.println("QUERY:"+temp);
int rowCount = stmt.executeUpdate(temp);
System.out.println("Rows affected in try ="+rowCount+" for user :"+sUserID);
// in catch i re-issue the delete query in deadlock..
catch (com.mysql.jdbc.exceptions.MySQLTransactionRollbackException ne)
System.out.println("Error ....Deadlock occured for user: "+sUserID);
ne.printStackTrace();
try
int rowCount = s.executeUpdate(temp);
System.out.println("Rows affected in catch ="+rowCount+" for user :"+sUserID);
catch (Exception e)
System.out.println("Exception again after restarting transaction..with user :"+sUserID);
e.printStackTrace();
(all necessary imports are present in code)
Here i am properly establishing the database connection with the help of other class DBConnection. As most of the forum insisted to re-issue the transaction, i have tried upto one level with above code. But still the problem is just partially solved.
How can i write my code so that every time if there is MySQLTransactionRollbackException , then the delete query should be re-issued again and again untill the transaction is complete.
Can i use GOTO statement ? or is it bad programming practice?
What are the other possible ways ??
Can someone please help in this regard ??
Thanks in advance..
Regards
Prasad

Answer 1

Hi all
i am new for these kind of databae transaction operation i am getting following error
/resetattendancedata.dqlMessage: Deadlock found when trying to get lock; Try restarting transaction, message from server: "Lock wait timeout exceeded; try restarting transaction" Cause: null Error Message: Deadlock found when trying to get lock; Try restarting transaction, message from server: "Lock wait timeout exceeded; try restarting transaction" Cause: null Error code: 1205 Error state: 41000 java.sql.SQLException: Deadlock found when trying to get lock; Try restarting transaction, message from server: "Lock wait timeout exceeded; try restarting transaction"
Here is my code i have written
if(movements.equalsIgnoreCase("ON"))
System.out.println("Movement");
if(submovements.equalsIgnoreCase("statusonly"))
query="";
query="UPDATE TRNMOVEMENT SET PROCESSED='N',STATUSPUT='N',ATTDATE=NULL,TIMEDIFF='' "
+"WHERE ATTDATE BETWEEN '"datefrom1"' AND '"dateto"' AND EMPID IN "
+"(SELECT SYSEMPID "
+"FROM (((MSTPERSONALDETAILS PD LEFT JOIN MSTCATEGORY CAT ON PD.CATEGCODE=CAT.SYSCATEGCODE)"
+"LEFT JOIN MSTUNITDETAILS U ON PD.UNITCODE=U.SYSUNITCODE) "
+"LEFT JOIN MSTDESIGNATION DES ON PD.DESIGCODE=DES.SYSDESIGCODE) "
+"LEFT JOIN MSTDEPARTMENT DEP ON PD.DEPTCODE=DEP.SYSDEPTCODE "strFltrString" ) ";
leaveStmt.executeUpdate(query);
leaveStmt.executeUpdate("commit");
else if(submovements.equalsIgnoreCase("flagstatus"))
query="";
query="UPDATE TRNMOVEMENT SET PROCESSED='N',STATUSPUT='N',ATTDATE=NULL,FLAG='',TIMEDIFF='',BREAK='N'WHERE ATTDATE BETWEEN '"datefrom1"' AND '"dateto"' AND EMPID IN (SELECT SYSEMPID FROM(((MSTPERSONALDETAILS PD LEFT JOIN MSTCATEGORY CAT ON PD.CATEGCODE=CAT.SYSCATEGCODE) LEFT JOIN MSTUNITDETAILS U ON PD.UNITCODE=U.SYSUNITCODE) LEFT JOIN MSTDESIGNATION DES ON PD.DESIGCODE=DES.SYSDESIGCODE) LEFT JOIN MSTDEPARTMENT DEP ON PD.DEPTCODE=DEP.SYSDEPTCODE WHERE EMPID IS NOT NULL "strFltrString" ) ";
leaveStmt.executeUpdate(query);
synchronized(leaveStmt)
//leaveStmt1.executeUpdate("set TRANSACTION ISOLATION LEVEL REPEATABLE READ"); // setting transaction level using SQL
// leaveStmt1.executeUpdate("start transaction"); // Starting a transaction using SQL     
query1="DELETE FROM TRNDAILYATTENDANCE WHERE ATTDATE BETWEEN '"datefrom1"' AND '"dateto"' AND EMPID IN (SELECT SYSEMPID FROM (((MSTPERSONALDETAILS PD "
+"LEFT JOIN MSTCATEGORY CAT ON PD.CATEGCODE=CAT.SYSCATEGCODE) LEFT JOIN MSTUNITDETAILS U ON PD.UNITCODE=U.SYSUNITCODE) LEFT JOIN MSTDESIGNATION DES ON PD.DESIGCODE = DES.SYSDESIGCODE )LEFT JOIN MSTDEPARTMENT DEP ON PD.DEPTCODE=DEP.SYSDEPTCODE WHERE EMPID IS NOT NULL "strFltrString" )";
//leaveStmt.addBatch(query1);
leaveStmt.executeUpdate(query1);
synchronized(leaveStmt)
query2="UPDATE TRNLEAVEAPPLICATION SET TAKENTOATT='N' WHERE '"datefrom1"' BETWEEN FROMDATE AND "
+"TODATE AND '"dateto"' BETWEEN FROMDATE AND TODATE AND EMPID IN (SELECT SYSEMPID FROM (((MSTPERSONALDETAILS PD LEFT JOIN MSTCATEGORY CAT ON "
+"PD.CATEGCODE=CAT.SYSCATEGCODE) LEFT JOIN MSTUNITDETAILS U ON PD.UNITCODE=U.SYSUNITCODE) LEFT JOIN "
+"MSTDESIGNATION DES ON PD.DESIGCODE=DES.SYSDESIGCODE) LEFT JOIN MSTDEPARTMENT DEP ON PD.DEPTCODE=DEP.SYSDEPTCODE WHERE EMPID IS NOT NULL "+strFltrString +") ";
//leaveStmt.addBatch(query2);
//leaveStmt.executeBatch();
leaveStmt.executeUpdate(query2);
//} // end of for loop
else
leaveStmt.executeUpdate("commit");
Please Solve my problem for this error thanks in advance........