Cancel method in JDBC!

Has anyone ever implemented the "cancel" method on the Statement class in JDBC?
On that has anyone cancelled the Connection or the Statement object while carrying out the cancel?

Alternatively you could just close the connection from another thread.

Similar Messages

Cancel() method in "Timer" class

Hi there,
I'm just a bit wondering what's the problem with the following code. if i comment out the t.cancel() method, the program will print out "OK!". but if i don't comment it out, the program will print out nothing, although it compiles perfectly. by the way, i can't tell the difference between putting t.cancel() there and putting it within "public void run()" and after that "system.out.println("OK!");" method. I think t.cancel() can be called in any place in the program.
any comments will be very much appreciated.
Eileen2
import java.util.*;
public class Thread1
     private Timer t;
     public Thread1()
          t = new Timer();
          t.schedule(new Task(), 4000);
//          t.schedule(new Task(), 2000);
          t.cancel();
     private class Task extends TimerTask
          public void run()
               System.out.println("OK!");
     public static void main(String[] args)
          System.out.println("This program is to test how threads work...");
          new Thread1();

What you describe is exactly what I would expect that would happen. By calling cancel() on the timer, you discard any scheduled tasks, so your Task.run() will never be executed and you will not see the "OK!". Note that the call to schedule() returns immediately. It doesn't wait until the task will execute.
Your question is not very clear. What do you want to know specifically about the behaviour of your program? What did you expect it to do and what is the difference between what it really does and what you expected?
Jesper

NSURLDownload/Connection "cancel" method

Does anyone know whether sending a "cancel" message to an NSURLDownload or NSURLConnection object results in the object being released? I'm hoping so, because otherwise I have the following problem:
I implement the (NSURLRequest *)download:willSendRequest:redirectResponse: delegate method to cancel downloads that are being redirected to the wrong place. The implementation looks like this:
- (NSURLRequest *)download:(NSURLDownload *)dl willSendRequest:(NSURLRequest *)req redirectResponse:(NSURLResponse *)resp
// check new request's URL's host and see whether it's okay
if (host-is-not-okay) { [dl cancel]; }
return req;
The problem is this: if I end up canceling the download, I never receive a downloadDidFail or downloadDidFinish message from the download object, which are the usual signal to release the object. But I can't release the object at the time I cancel, because I'm in the middle of a method that returns a value to that object.
So I'm hoping that the cancel method results in the object being released. Can anyone confirm this? And if not, can anyone suggest a solution to this problem?
Thanks,
Eliza

Alternatively you could just close the connection from another thread.

Method first() JDBC

Help
i trying to put my recorset at teh firts record
i use this connection in a jsp file
<%
Class.forName("com.microsoft.jdbc.sqlserver.SQLServerDriver");
Connection Con =DriverManager.getConnection("jdbc:microsoft:sqlserver://192.168.232.35;user=x;password=x");
String Sql= "SELECT car_id.car_dsc FROM CARS"
CallableStatement Cs = Con.prepareCall(SqlT1);
ResultSet RsTabla1 =Cs.executeQuery();
%>
AND THEN WHEN I USE THIS INTRUCTION
<%RsTabla1.first();%>
THE BROWSER SEND ME THIS MESSAGE
[SQLServer 2000 Driver for JDBC]Unsupported method: ResultSet.first
help PLIS....
I use this recordset and want to go to the fisrt again...

You need to call the overloaded prepareStatement() method to get a scrollable ResultSet. If your driver does not support these, you will not be able to use the first() method. Check if you can just use the next() method in such case.

Calling setString() method in JDBC

Hello,
I have a java class which I used for database activities.
I have a method called
setStrValues(int position, String strValue) {
callablestmt.setString(position, strValue);
}Now I need to generalize this method so that I can use setStrValues method to use for preparestatement.setString(position, strValue) besides callablestmt.setString(position, strValue).
How can I acheive this? Without creating another method I need to use both for preparedstatement and callable statement.
Any help is highly appreciable.
Thanks

I'm don't follow you. I imagine you have something like this.
PreparedStatement ps = new ......
CallableStatement cs = new ......
setStrValues(ps, 2, "hello");
setStrValues(cs, 1, "world");
private void setStrValues(PreparedStatement statement, int position, String StrValue) {
statement.setString(position, strValue);
}Note: this is a highly contrived example but you should be able to do this with your code.

Statement.cancel() no longer works with WLS 8.1?

Has anyone else had a problem with the cancel() method in oracle.jdbc.OracleCallableStatement
on WLS 8.1 not doing a very good job of killing the thread in Oracle? We were
using cancel() with weblogic.jdbc.pool.CallableStatement on WLS 6.1 and it does
a very good job of killing the query on the Oracle side. But almost all of this
package has been removed and we've been told we need to use the Oracle vendor
package to get our stuff to work on 8.1. I decompiled both classes and they each
have very different implementations of the cancel() method.
I think I've managed to convert all of our DB access classes to the Oracle vendor
package successfully, with the exception of this issue. We use cancel() let users
cancel large queries and to cancel an existing query if a user tries to run a
new one. Since we implemented it we've had a huge performance boost from the lack
of runaway queries in the DB. It would be a real pain if we can't find a way to
get the Oracle version to work. Any help or tales of similar experiences would
be greatly appreciated.
thx a lot,
Matt Savino

I did a search on Oracle MetaLink. I didn't see any Oracle-confirmed
bugs related to cancel. I did see one user in the JDBC forum that
was having a problem with a remote (not on the local machine)
cancel. At this point, this case will need to be worked through
support - they will need to generate a reproducer and assuming they
do, file a tar with Oracle.
"Stephen Felts" <[email protected]> wrote in message
news:[email protected]...
Regarding the wrappers - now I remember discussing this with you in thebeta newsgroup about a month ago.
The goal was to make it transparent that everything was changed to bepassthrough in 8.1.
The good news is that you can now use the vendor interface directly andget their extensions
directly. That means that the wrapper for Oracle will be different fromthe wrapper for DB2.
Further, any new excentions in the interface will become visible to theapplication.
>
The bad news is that this only works when the vendor has a definedinterface; it doesn't work
if only a class is defined.
This is a problem for some of the Oracle data type classes that don't havedefined interfaces
and the reason why weblogic.vendor.oracle interfaces still need to be usedfor these classes.
That also applies to BEA classes and weblogic.jdbc.pool only had classesdefined, not interfaces.
>
We should have documented change.
Regarding the real problem of cancel(), the WLS JDBC code is not doinganything here
except passing the cancel call through to the thin driver. My guess isthat this is
a problem in the thin driver. I haven't had a chance to research this onthe Oracle site yet.
>
>
"Matt Savino" <[email protected]> wrote in message
news:[email protected]...
>>
Thanks a ton for your quick reply on this. On recommendation from yoursupport
team (case 426562) here is the primary line that we had to change:
[old] weblogic.jdbc.pool.CallableStatement cStat
=(weblogic.jdbc.pool.CallableStatement)connection.prepareCall(call);
>>
[new] - oracle.jdbc.OracleCallableStatement cStat
=(oracle.jdbc.OracleCallableStatement)connection.prepareCall(call);
>>
(FYI - We need this to take adavantage of some of the advanced Oraclefeatures
like returning multiple ResultSets. We'd like to avoid using the OCIclient if
possible, assuming that would even solve this.)
Further down in the code, here is the cancel() method:
public void cancelCall() {
try {
if (cStat != null) cStat.cancel();
releaseConnection();
catch (Exception e){ e.printStackTrace(); }
In both cases the cancel() call throws no error, but only on the oldversion do
we actually see the thread die promptly in Oracle.
Thanks again for your help on this,
Matt
"Stephen Felts" <[email protected]> wrote:
In versions prior to WLS 8.1, each Oracle extension had to be
individually,
explicitly wrapped
(and not all extensions were supported).
In WLS 8.1, it is a clean passthrough directly of all Oracle interfaces
using a dynamic proxy so that
all Oracle extensions show through. The only additional work that WLS
is doing to to
ensure that transactions are managed correctly (which shouldn't have
an impact here).
Note that in versions prior to WLS 8.1, you were using classes12.zip
for the client and now you are using ojdbc14.jar. There are
some big differences in this client implementation.
Maybe you should try testing this standalone without WLS in the picture
to see
if this is a driver problem. WLS doesn't have the code that isresponsible
for killing the thread in Oracle.
I'm not sure I understand what code you are changing. The goal was to
preseve the interfaces
provided in releases prior to 8.1. Code you show me an old code line
and what you are
changing it to? Thanks.
"Matt Savino" <[email protected]> wrote in message
news:[email protected]...
>>>>
Has anyone else had a problem with the cancel() method inoracle.jdbc.OracleCallableStatement
on WLS 8.1 not doing a very good job of killing the thread in Oracle?We were
using cancel() with weblogic.jdbc.pool.CallableStatement on WLS 6.1and it does
a very good job of killing the query on the Oracle side. But almostall of this
package has been removed and we've been told we need to use the
Oracle
vendor
package to get our stuff to work on 8.1. I decompiled both classesand they each
have very different implementations of the cancel() method.
I think I've managed to convert all of our DB access classes to theOracle vendor
package successfully, with the exception of this issue. We use
cancel()
let users
cancel large queries and to cancel an existing query if a user triesto run a
new one. Since we implemented it we've had a huge performance boostfrom the lack
of runaway queries in the DB. It would be a real pain if we can't
find
a way to
get the Oracle version to work. Any help or tales of similar
experiences
would
be greatly appreciated.
thx a lot,
Matt Savino

Does Oracle JDBC driver support cancel()?

In JDBC API, class Statement has a cancel method, and its support depends on the implementation of the JDBC dirver.
Does any Oracle JDBC driver support this feature? Thanks.

Does any Oracle JDBC driver support this feature? Thanks.
It is supported (but not by the server-side Thin driver); the return value will be "ORA-17015 Statement was cancelled"
cheers,
Mary

How can i cancel Fill method?

Hi!
And why your Oracle Data Provider 9.2.0.4 doesnt support IDbCommand.Cancel method?

ODP.NET does not support Cancel functionality but we will evaluate this functionality for a later release.

Jdbc/findPanel cancel button?

As mentioned a while back, there is a CallableStatement.cancel() that will abort a query if called from a separate thread.
Two questions:
1. Is there a similar critter that can be set up for RowsetInfo? There's an executeQuery() but I don't see a cancel()? ( For example, if a user specifies a FindPanel criteria that may take minutes, and wants to abort in mid-stream? )
2. If I do a cancel() for a jdbc CallableStatement, it must come from a separate thread. Does anyone have a simple code segment that shows how to set a up Swing jbutton that can cancel a jdbc call based on another Swing jbutton in the same frame? ( Or do I need to set up some sorta separate frame? ) Obviously, I'm having a problem where the CANCEL button is ignored while the query is going. ( And last but not least... how do clear the state, since I keep on getting a "java.sql.SQLException: ORA-01013: user requested cancel of current operation" after the CANCEL does kick in, on supsequent queries?
TIA
null

As mentioned a while back, there is a CallableStatement.cancel() that will abort a query if called from a separate thread.
Two questions:
1. Is there a similar critter that can be set up for RowsetInfo? There's an executeQuery() but I don't see a cancel()? ( For example, if a user specifies a FindPanel criteria that may take minutes, and wants to abort in mid-stream? )
2. If I do a cancel() for a jdbc CallableStatement, it must come from a separate thread. Does anyone have a simple code segment that shows how to set a up Swing jbutton that can cancel a jdbc call based on another Swing jbutton in the same frame? ( Or do I need to set up some sorta separate frame? ) Obviously, I'm having a problem where the CANCEL button is ignored while the query is going. ( And last but not least... how do clear the state, since I keep on getting a "java.sql.SQLException: ORA-01013: user requested cancel of current operation" after the CANCEL does kick in, on supsequent queries?
TIA
null

Statement.cancel and setQueryTimeout don't work

The method cancel() of the class Statement doesn't work always as necessary. I've had three situations while cancelling a query with this method:
1. sometimes everything's all right - SQLException "user requested cancel of current operation" occurs
2. sometimes the program hangs up
3. sometimes SQLException "Bigger type length than Maximum" occurs
We have
Oracle 7.3.4.5.0 and
Oracle8i 8.1.7 JDBC Drivers for use with JDK 1.2.x.
As far as I know setQueryTimeout() method uses cancel() method, so it won't solve the problem.
Please tell me what to do to get rid of the 2nd and 3rd situations. Thanks in advance.
null

Look at stack trace of Exception:
java.sql.SQLException: Bigger type length than Maximum
at oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:114)
at oracle.jdbc.dbaccess.DBError.throwSqlException(DBError.java:156)
at oracle.jdbc.dbaccess.DBError.check_error(DBError.java:803)
at oracle.jdbc.ttc7.MAREngine.buffer2Value(MAREngine.java:1987)
at oracle.jdbc.ttc7.MAREngine.unmarshalUB2(MAREngine.java:788)
at oracle.jdbc.ttc7.MAREngine.unmarshalSB2(MAREngine.java:763)
at oracle.jdbc.ttc7.MAREngine.processIndicator(MAREngine.java:1786)
at oracle.jdbc.ttc7.TTCItem.unmarshalIndicator(TTCItem.java:225)
at oracle.jdbc.ttc7.NonPlsqlTTCColumn.unmarshal(NonPlsqlTTCColumn.java:145)
at oracle.jdbc.ttc7.NonPlsqlTTCDataSet.unmarshalRow(NonPlsqlTTCDataSet.java:138)
at oracle.jdbc.ttc7.TTIrxd.unmarshal(TTIrxd.java:138)
at oracle.jdbc.ttc7.Oall7.receive(Oall7.java:489)
at oracle.jdbc.ttc7.TTC7Protocol.doOall7(TTC7Protocol.java:1311)
at oracle.jdbc.ttc7.TTC7Protocol.fetch(TTC7Protocol.java:797)
at oracle.jdbc.driver.OracleStatement.doExecuteQuery(OracleStatement.java:1608)
at oracle.jdbc.driver.OracleStatement.doExecute(OracleStatement.java:1758)
at oracle.jdbc.driver.OracleStatement.doExecuteWithTimeout(OracleStatement.java:1807)
at oracle.jdbc.driver.OraclePreparedStatement.executeUpdate(OraclePreparedStatement.java:332)
at oracle.jdbc.driver.OraclePreparedStatement.executeQuery(OraclePreparedStatement.java:283)
null

Problem with statement.cancel()

Hi,
I am using Oracle 10g with the 10.2.0.3 jdbc (OCI) drivers. Though my statement.quertTimeout() works fine, the statement.cancel() does not seem to do anything.
Could you please guide me as to the cause of this kind of action, since I have read that internally queryTimeout() depends on cancel() to stop qurery execution.
Thanks in advance

Hi,
I am using Oracle 10g with the 10.2.0.3 jdbc (OCI)
drivers. Though my statement.quertTimeout() works
fine, the statement.cancel() does not seem to do
anything.
Could you please guide me as to the cause of this
kind of action, since I have read that internally
queryTimeout() depends on cancel() to stop qurery
execution.
Thanks in advanceThe code I am using is:
package test;
import java.sql.*;
import oracle.jdbc.pool.OracleDataSource;
import oracle.jdbc.driver.*;
public class OracleQueryTimeout
     public static void main(String[] args)
          long timetaken; // Holds the execution time
          int numFetchedRows = 0;
          // Create a OracleDataSource instance
          OracleDataSource ods;
          try {
               ods = new OracleDataSource();
               //Sets the driver type
               ods.setDriverType("oci");
               // Sets the database server name
               ods.setServerName("<my machine name>");
               // Sets the database name
               ods.setDatabaseName("orcl");
          // Sets the port number
               ods.setPortNumber(1521);
               // Sets the user name
               ods.setUser("<username>");
               // Sets the password
               ods.setPassword("<password>");
               // Create a connection object
               Connection connection;
                    connection = ods.getConnection();
     // Sets the auto-commit property for the connection to be false.
                    connection.setAutoCommit(false);
                    Statement stmt = null;
               String query = "Select * from USER_CATEGORY,MV_SUBSCRIBER_ATTRIBS";
               stmt=connection.createStatement();
               stmt.setQueryTimeout(0);
               // Get time at start of query
               long initialTime = System.currentTimeMillis();
               // Execute the Query in query
               ResultSet rst = stmt.executeQuery(query);
               long finalTime = System.currentTimeMillis();
               timetaken = finalTime - initialTime;
               if(timetaken>0003)
                    stmt.cancel();
                    System.out.println("Statement Cancelled");
               //Populate the ResultSet object
               while ( rst.next() )
                    numFetchedRows++;
                    rst.getObject(1);
               System.out.println("Time taken for query: " + timetaken);
               System.out.println("Number of rows fetched: " + numFetchedRows);
               System.out.println(rst);
          } catch (SQLException e) {
               // TODO Auto-generated catch block
               e.printStackTrace();
The program hangs when it comes to retrieving the >resultset
The program gives the following output If I do not go through the resultset:
Statement Cancelled
Time taken for query: 50782
Number of rows fetched: 0
oracle.jdbc.driver.OracleResultSetImpl@1a85d38Here the cancel method was invoked but to no visible action.

Multithreaded clients and Oracle JDBC-drivers?

Are the thin and OCI8 drivers for Oracle multithreaded? (I know they're thread safe)
I.e. Can many threads share the same Connection object (and statement objects) to do their requests without the requests being serialized to the DB?
Sun's javadoc of package java.sql says:
We require that all operations on all the java.sql objects be multi-thread safe and able to cope correctly with having several threads simultaneously calling the same object.
Some drivers may allow more concurrent execution than others. Developers can assume fully concurrent execution; if the driver requires some form of synchronization, it will provide it. The only difference visible to the developer will be that applications will run with reduced concurrency.
For example, two Statements on the same Connection can be executed concurrently and their ResultSets can be processed concurrently (from the perspective of the developer). Some drivers will provide this full concurrency. Others may execute one statement and wait until it completes before sending the next.
One specific use of multi-threading is to cancel a long running statement. This is done by using one thread to execute the statement and another to cancel it with its Statement.cancel() method.
Restated again for Oracle; Will threads run concurrently when using the same connection and statements, or will the calls be serialized?

In the connection pool, I specified:
user
password
url
In the deployment tool (Sun Java Appl. Server 8 BE Update 1), I specified the "Resource Reference" for the EJB. This leads to the following entries in sun-ejb-jar.xml:
<res-ref-name>jdbc/pdisasdb</res-ref-name>
   <jndi-name>jdbc/pdisasdb</jndi-name>
      <default-resource-principal>
         <name>myname</name>
         <password>geheim</password>
      </default-resource-principal>
</resource-ref> The strange thing is, that now it works without this entry - but I am not gaga, yesterday it doesnt...

Polling time period for cancelled statements

I notice when I have clients cancelling statements, there is a consistent 5 minute delay before the statement is actually cancelled. Even if I use a program like TOAD in threaded mode, and click Cancel, it takes almost exactly 5 minutes before it actually breaks off. Which setting do I use and where, to adjust this polling time?

Well, in client-side code you can cancel a statement if it is blocked or running a very long operation. For example, in Java you can call a cancel() method on the Statement object after it has begun executing a SQL query (has to be done by a separate thread, of course). It should cancel it almost immediately, but for some reason there is a 5 minute delay. A friend of mine at another company can run the same code on his company's Oracle database, and the cancel is completed quickly, consistently. While my code consistently has to wait around 5 minutes.
There must be some setting to adjust this time, since we have knocked off just about ever other possible discrepency (driver/driver version, database/database version, java/JDBC/version)

Multithreaded Swing and a "Cancel Button"

I have a Swing-based app that runs some lengthy JDBC queries. Currently when the user hits the "Run Query" button a small dialog pops up to say that the process is running, please wait, etc. I'd like to add a working Cancel button to that dialog that will allow the user to stop that query before it finnishes.
From what I've been able to learn so far it seems I should use one of the SwingUtilities methods such as invokeAndWait or invokeLater. I'm not sure which one would be more appropriate for my situation though.
I'm also having trouble thinking of an elegant way (or not-so elegant if that's the only way) to have the cancel button event communicate with the DB Query thread to let it know that the process should be stopped. Detailed explanations or examples would be welcome.
Mike

You will not need to use the SwingUtilities methods. Those are when you want to update the GUI from a different thread. In your case, you want to update a class running in a non-gui thread from the GUI thread. Not a problem.
You will want to create a Runnable class that runs your query. Run that class on another thread when the query is executed. There will need to be some public 'cancel' method in that class that can be called when you want that object to cancel whatever operation it is doing. Simply call that 'cancel' method from your dialog button's action when the user hits the cancel button.
Now, how your query class handles the cancel method is the main problem. The api way of doing this would be to call the Statement.cancel() method on the statement object that is performing the query. But how (or if) that method works depends on the jdbc driver & database, hopefully yours supports it. :-)

How to cancel a Timer from inside a TimerTask ?

I have a web application with this structure:
Tomcat starts a servlet and that starts a master thread to run once every 10 minutes,
that master thread in turn starts any number of individual tasks to run until completion,
the idea being a "shoot and forget" methodology.
public class MasterTask extends TimerTask {
// run once every 10 minutes
// retrieve a list of actions to do, this is from a database, could be 10 could be 100
// for each action schedule a TimerTask
// the reason for using a new Timer each time is that any of the action tasks
// may take a long time or not, i do not want an individual task to wait
// for a previous one to finish, therefore each task is put on it's own timer
// also in order to spread resources somewhat there is an incremental delay
// so the is some time between the start of each task as there can be many
Timer timeit;
int delay = 0;
for ( ActionTask doit : taskList ) {
timeit = new Timer();
timeit(doit,delay);
delay = delay+200;
public class ActionTask extends TimerTask {
// perform whatever actions need to be done inside this individual TimerTask
// at some point the individual task has completed it's work
// how do i completely remove it from this location ?
I know that inside the TimerTask i can call cancel() but that will only prevent it from running again it does not actually remove it completely, it remains in existence and therefore uses up memory. What i need to do is call the cancel() method on the Timer in order to remove both the Timer and TimerTask.
If i do not do this then the program will just keep creating new Timers until eternity.
( or basically until i run out of memory )
How do i call the Timer.cancel() method from INSIDE the TimerTask ?
( Note that both classes are seperate classes/files and not inside the same file or class. )
thanks,
Erik
Edited by: Datapunter on Jul 27, 2009 4:06 PM

Gotcha,
the Timer does get cancelled but the TimerTask runs to completion first.
Was expecting a kill() type effect but that is not what cancel() does.
Servlet started by Tomcat
package servlet;
import java.util.*;
import javax.servlet.ServletException;
public class TestServlet extends javax.servlet.http.HttpServlet implements javax.servlet.Servlet {
    public void init() throws ServletException {
          Timer timeIt = new Timer();
          timeIt.schedule(new timertasks.testmaster(), 0, 10000); // every 10 seconds
}master task runs every 10 seconds indefinetly,
and every 10 seconds it starts (kicks off) 2 new tasks.
package timertasks;
import java.util.Timer;
import java.util.TimerTask;
public class testmaster extends TimerTask {
     public testmaster() {}
     // scheduled to run once every 10 seconds
     public void run() {
          int delay = 0;
          Timer timeit;
          for ( int count = 0; count < 2 ; count++ ) {
               timeit = new Timer();
               timeit.schedule(new ActionTask(timeit), delay, 2000);     // every 2 seconds
               delay = delay + 200;
}individual timertask, just comment out the timeit.cancel(); to see the difference in effect.
package timertasks;
import java.util.Timer;
import java.util.TimerTask;
public class ActionTask extends TimerTask {
     private Timer timeit;
     private int runcounter = 0;
     public ActionTask(Timer timeit) {
          this.timeit = timeit;
     // without cancel then values of runcounter should keep rising and more and more tasks should appear
     // with cancel each should run only once
     public void run() {
          System.out.println("before cancel, runcounter="+runcounter);
          timeit.cancel();
          System.out.println("after cancel, runcounter="+runcounter);
          runcounter++;
}thanks.

Cancel method in JDBC!

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