ConcurrentModificationException on ActionErrors
I have a Struts action that is trying to show all of the errors that might occur from
either or both of two subordinate methods. The
code looks like:
...
ActionErrors errors = new ActionErrors();
ActionErrors errors1 = null;
ActionErrors errors2 = null;
Obj1 obj1 = new Obj1();
Obj2 obj2 = new Obj2();
obj1.method1();
errors1 = obj1.getErrors();
if (!errors1.isEmpty()) {
errors.add(errors1);
}
obj2.method2();
errors2 = obj2.getErrors();
if (!errors2.isEmpty()) {
errors.add(errors1);
}
...
Problem is I get the ConcurrentModificationException when I try and do either of the
errors.add methods above. Methods
method1/method2 are pretty vanilla, just doing some database work and accumulating any
errors in an associated ActionErrors.
I've searched the archives but only found one or two references to
ConcurrentModificationException and they did not involve
ActionErrors. Any ideas or help is appreciated.
- Richard
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Re: ConcurrentModificationException on ActionErrors
I don't know what is causing the exact error from your code snippet, but a
ConcurrentModificationException is thrown when you try to modify a list on which you
have an iterator.
See here:
http://java.sun.com/j2se/1.4.1/docs/api/java/util/ConcurrentModificationException.html
Paul
Global Equity Derivatives Technology
Deutsche Bank [/]
Office +44 (0)20 754 55458
Mobile +44 (0)7736 299483
Fax +44 (0)20 7547 2752
Richard Mixon
(qwest) To: Struts Users Mailing List
[EMAIL PROTECTED]
[EMAIL PROTECTED]cc:
iz Subject:
ConcurrentModificationException on ActionErrors
31/12/2003 15:36
Please respond to
Struts Users
Mailing List
I have a Struts action that is trying to show all of the errors that might occur from
either or both of two subordinate methods. The
code looks like:
...
ActionErrors errors = new ActionErrors();
ActionErrors errors1 = null;
ActionErrors errors2 = null;
Obj1 obj1 = new Obj1();
Obj2 obj2 = new Obj2();
obj1.method1();
errors1 = obj1.getErrors();
if (!errors1.isEmpty()) {
errors.add(errors1);
}
obj2.method2();
errors2 = obj2.getErrors();
if (!errors2.isEmpty()) {
errors.add(errors1);
}
...
Problem is I get the ConcurrentModificationException when I try and do either of the
errors.add methods above. Methods
method1/method2 are pretty vanilla, just doing some database work and accumulating any
errors in an associated ActionErrors.
I've searched the archives but only found one or two references to
ConcurrentModificationException and they did not involve
ActionErrors. Any ideas or help is appreciated.
- Richard
-
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RE: ConcurrentModificationException on ActionErrors
Paul,
Thanks I had seen the exception javadoc. An in one of my subordinate methods I do have
a logging snippet that uses an Iterator to
display ALL of the contents of the ActionErrors. And I imagine that my subsequent use
of the ActionErrors.add(ActionErrors) method
also uses an Iterator to enumerate the ActionError objects. Is there anyway to close
the first Iterator so that it does not cause
this conflict?
Thanks again - Richard
-Original Message-
From: Paul-J Woodward [mailto:[EMAIL PROTECTED]
Sent: Wednesday, December 31, 2003 8:51 AM
To: Struts Users Mailing List
Subject: Re: ConcurrentModificationException on ActionErrors
I don't know what is causing the exact error from your code snippet, but a
ConcurrentModificationException is thrown when you try to
modify a list on which you have an iterator.
See here:
http://java.sun.com/j2se/1.4.1/docs/api/java/util/ConcurrentModificationException.html
Paul
Global Equity Derivatives Technology
Deutsche Bank [/]
Office +44 (0)20 754 55458
Mobile +44 (0)7736 299483
Fax +44 (0)20 7547 2752
Richard Mixon
(qwest) To: Struts Users Mailing List
[EMAIL PROTECTED]
[EMAIL PROTECTED]cc:
iz Subject:
ConcurrentModificationException on ActionErrors
31/12/2003 15:36
Please respond to
Struts Users
Mailing List
I have a Struts action that is trying to show all of the errors that might occur from
either or both of two subordinate methods. The
code looks like:
...
ActionErrors errors = new ActionErrors();
ActionErrors errors1 = null;
ActionErrors errors2 = null;
Obj1 obj1 = new Obj1();
Obj2 obj2 = new Obj2();
obj1.method1();
errors1 = obj1.getErrors();
if (!errors1.isEmpty()) {
errors.add(errors1);
}
obj2.method2();
errors2 = obj2.getErrors();
if (!errors2.isEmpty()) {
errors.add(errors1);
}
...
Problem is I get the ConcurrentModificationException when I try and do either of the
errors.add methods above. Methods
method1/method2 are pretty vanilla, just doing some database work and accumulating any
errors in an associated ActionErrors.
I've searched the archives but only found one or two references to
ConcurrentModificationException and they did not involve
ActionErrors. Any ideas or help is appreciated.
- Richard
-
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For additional commands, e-mail: [EMAIL PROTECTED]
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Re: ConcurrentModificationException on ActionErrors
It almost sounds like your code isn't handling errors1 and/or errors2 in a
thread-safe manner. ConcurrentModificationException will be thrown if one thread
is in the proces of iterating over a collection and another thread modifies that
collection. ActionMessages.add(ActionMessages) will iterate over both the arg's
properties and the messages for each property, so there's certainly the
potential for the error you're seeing. Can you provide some more detail on how
your code is organized?
BTW, not sure if it's a c/p error, but you've got:
if (!errors2.isEmpty()) {
errors.add(errors1); // shouldn't that be errors2?
}
Quoting Richard Mixon (qwest) [EMAIL PROTECTED]:
I have a Struts action that is trying to show all of the errors that might
occur from either or both of two subordinate methods. The
code looks like:
...
ActionErrors errors = new ActionErrors();
ActionErrors errors1 = null;
ActionErrors errors2 = null;
Obj1 obj1 = new Obj1();
Obj2 obj2 = new Obj2();
obj1.method1();
errors1 = obj1.getErrors();
if (!errors1.isEmpty()) {
errors.add(errors1);
}
obj2.method2();
errors2 = obj2.getErrors();
if (!errors2.isEmpty()) {
errors.add(errors1);
}
...
Problem is I get the ConcurrentModificationException when I try and do either
of the errors.add methods above. Methods
method1/method2 are pretty vanilla, just doing some database work and
accumulating any errors in an associated ActionErrors.
I've searched the archives but only found one or two references to
ConcurrentModificationException and they did not involve
ActionErrors. Any ideas or help is appreciated.
- Richard
--
Kris Schneider mailto:[EMAIL PROTECTED]
D.O.Tech http://www.dotech.com/
-
To unsubscribe, e-mail: [EMAIL PROTECTED]
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Re: ConcurrentModificationException on ActionErrors
Could you show the implementation(s) of your ObjX.getErrors() methods. I'm
guessing there's probably a better way to do what you're trying to do.
It probably has something to do with the implementation of:
http://jakarta.apache.org/struts/api/org/apache/struts/action/ActionMessages.html#add(org.apache.struts.action.ActionMessages)
which calls:
http://jakarta.apache.org/struts/api/org/apache/struts/action/ActionMessages.html#properties()
which returns an Iterator, which, as described below probably throws your
exception.
It sounds like the ActionErrors instance you're adding may be the same one
you're trying to add it to.
-Ben
From: Paul-J Woodward [EMAIL PROTECTED]
Reply-To: Struts Users Mailing List [EMAIL PROTECTED]
To: Struts Users Mailing List [EMAIL PROTECTED]
Subject: Re: ConcurrentModificationException on ActionErrors
Date: Wed, 31 Dec 2003 15:51:01 +
I don't know what is causing the exact error from your code snippet, but a
ConcurrentModificationException is thrown when you try to modify a list on
which you have an iterator.
See here:
http://java.sun.com/j2se/1.4.1/docs/api/java/util/ConcurrentModificationException.html
Paul
Global Equity Derivatives Technology
Deutsche Bank [/]
Office +44 (0)20 754 55458
Mobile +44 (0)7736 299483
Fax +44 (0)20 7547 2752
Richard Mixon
(qwest) To: Struts Users
Mailing List [EMAIL PROTECTED]
[EMAIL PROTECTED]cc:
iz Subject:
ConcurrentModificationException on ActionErrors
31/12/2003 15:36
Please respond to
Struts Users
Mailing List
I have a Struts action that is trying to show all of the errors that might
occur from either or both of two subordinate methods. The
code looks like:
...
ActionErrors errors = new ActionErrors();
ActionErrors errors1 = null;
ActionErrors errors2 = null;
Obj1 obj1 = new Obj1();
Obj2 obj2 = new Obj2();
obj1.method1();
errors1 = obj1.getErrors();
if (!errors1.isEmpty()) {
errors.add(errors1);
}
obj2.method2();
errors2 = obj2.getErrors();
if (!errors2.isEmpty()) {
errors.add(errors1);
}
...
Problem is I get the ConcurrentModificationException when I try and do
either of the errors.add methods above. Methods
method1/method2 are pretty vanilla, just doing some database work and
accumulating any errors in an associated ActionErrors.
I've searched the archives but only found one or two references to
ConcurrentModificationException and they did not involve
ActionErrors. Any ideas or help is appreciated.
- Richard
-
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
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RE: ConcurrentModificationException on ActionErrors
Ben,
The implementation is a pretty simple getter. The ActionErrors object is built by
the call to obj1.method1().
/**
* Get ActionErrors object
*/
public ActionErrors getErrors() {
return errors;
}
The actual code for obj1 is very large (1900 lines) and of course 99% is not relevant
to the issue (but which 1% is :) ) so I
hesitate to attach it.
The obj1 and obj2 objects (not their actual names) are actually DAO objects that take
as input a Struts form bean and update and
add/chg/delete the corresponding database object. All of the edit, error and mapping
code is included (generated by XDoclet) so its
huge (actually compiles small, but being generated its quite verbose).
If I cannot figure this out, I will go back to a simpler strategy. I had weanted to
let the user see all errors at once, rather than
showing them some, having them correct them and then showing them more.
Thanks again - Richard
-Original Message-
From: Ben Anderson [mailto:[EMAIL PROTECTED]
Sent: Wednesday, December 31, 2003 9:04 AM
To: [EMAIL PROTECTED]
Subject: Re: ConcurrentModificationException on ActionErrors
Could you show the implementation(s) of your ObjX.getErrors() methods. I'm
guessing there's probably a better way to do what you're trying to do.
It probably has something to do with the implementation of:
http://jakarta.apache.org/struts/api/org/apache/struts/action/ActionMessages.html#add(org.apache.struts.action.ActionMessages)
which calls:
http://jakarta.apache.org/struts/api/org/apache/struts/action/ActionMessages.html#properties()
which returns an Iterator, which, as described below probably throws your
exception.
It sounds like the ActionErrors instance you're adding may be the same one
you're trying to add it to.
-Ben
From: Paul-J Woodward [EMAIL PROTECTED]
Reply-To: Struts Users Mailing List [EMAIL PROTECTED]
To: Struts Users Mailing List [EMAIL PROTECTED]
Subject: Re: ConcurrentModificationException on ActionErrors
Date: Wed, 31 Dec 2003 15:51:01 +
I don't know what is causing the exact error from your code snippet, but a
ConcurrentModificationException is thrown when you try to modify a list on
which you have an iterator.
See here:
http://java.sun.com/j2se/1.4.1/docs/api/java/util/ConcurrentModificationException.html
Paul
Global Equity Derivatives Technology
Deutsche Bank [/]
Office +44 (0)20 754 55458
Mobile +44 (0)7736 299483
Fax +44 (0)20 7547 2752
Richard Mixon
(qwest) To: Struts Users
Mailing List [EMAIL PROTECTED]
[EMAIL PROTECTED]cc:
iz Subject:
ConcurrentModificationException on ActionErrors
31/12/2003 15:36
Please respond to
Struts Users
Mailing List
I have a Struts action that is trying to show all of the errors that might
occur from either or both of two subordinate methods. The
code looks like:
...
ActionErrors errors = new ActionErrors();
ActionErrors errors1 = null;
ActionErrors errors2 = null;
Obj1 obj1 = new Obj1();
Obj2 obj2 = new Obj2();
obj1.method1();
errors1 = obj1.getErrors();
if (!errors1.isEmpty()) {
errors.add(errors1);
}
obj2.method2();
errors2 = obj2.getErrors();
if (!errors2.isEmpty()) {
errors.add(errors1);
}
...
Problem is I get the ConcurrentModificationException when I try and do
either of the errors.add methods above. Methods
method1/method2 are pretty vanilla, just doing some database work and
accumulating any errors in an associated ActionErrors.
I've searched the archives but only found one or two references to
ConcurrentModificationException and they did not involve
ActionErrors. Any ideas or help is appreciated.
- Richard
-
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
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are not the intended recipient (or have received this e-mail in error)
please notify the sender immediately and destroy this e-mail. Any
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For additional
RE: ConcurrentModificationException on ActionErrors
Kris,
Thanks - I do not think I have multiple threads involved, but certaily multiple
Iterators may be hanging around that are not GC'd
yet.
And yes that was a typo. Because the real code is so huge, I created a simple example
to paste in and obviously did not compile it
:)
- Richard
-Original Message-
From: Kris Schneider [mailto:[EMAIL PROTECTED]
Sent: Wednesday, December 31, 2003 9:01 AM
To: Struts Users Mailing List
Subject: Re: ConcurrentModificationException on ActionErrors
It almost sounds like your code isn't handling errors1 and/or errors2 in a
thread-safe manner. ConcurrentModificationException will be thrown if one thread
is in the proces of iterating over a collection and another thread modifies that
collection. ActionMessages.add(ActionMessages) will iterate over both the arg's
properties and the messages for each property, so there's certainly the
potential for the error you're seeing. Can you provide some more detail on how
your code is organized?
BTW, not sure if it's a c/p error, but you've got:
if (!errors2.isEmpty()) {
errors.add(errors1); // shouldn't that be errors2?
}
Quoting Richard Mixon (qwest) [EMAIL PROTECTED]:
I have a Struts action that is trying to show all of the errors that might
occur from either or both of two subordinate methods. The
code looks like:
...
ActionErrors errors = new ActionErrors();
ActionErrors errors1 = null;
ActionErrors errors2 = null;
Obj1 obj1 = new Obj1();
Obj2 obj2 = new Obj2();
obj1.method1();
errors1 = obj1.getErrors();
if (!errors1.isEmpty()) {
errors.add(errors1);
}
obj2.method2();
errors2 = obj2.getErrors();
if (!errors2.isEmpty()) {
errors.add(errors1);
}
...
Problem is I get the ConcurrentModificationException when I try and do either
of the errors.add methods above. Methods
method1/method2 are pretty vanilla, just doing some database work and
accumulating any errors in an associated ActionErrors.
I've searched the archives but only found one or two references to
ConcurrentModificationException and they did not involve
ActionErrors. Any ideas or help is appreciated.
- Richard
--
Kris Schneider mailto:[EMAIL PROTECTED]
D.O.Tech http://www.dotech.com/
-
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
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To unsubscribe, e-mail: [EMAIL PROTECTED]
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RE: ConcurrentModificationException on ActionErrors
Although it's possible to generate that exception from within the same thread,
it's usually triggered by multiple threads accessing the same collection. In
general, if you grab an iterator, then modify the underlying collection, and
then call iter.next(), you'll see that exception. Having multiple iterators
shouldn't be an issue - you don't explicitly close an iterator like a database
connection. It will be GC-ed just like any other object. The problem really
boils down to modifying the backing collection while iteration is in progress.
By in progress, I mean doing something like calling iter.next(), not that
there's just an iterator instance lying around.
Quoting Richard Mixon (qwest) [EMAIL PROTECTED]:
Kris,
Thanks - I do not think I have multiple threads involved, but certaily
multiple Iterators may be hanging around that are not GC'd
yet.
And yes that was a typo. Because the real code is so huge, I created a simple
example to paste in and obviously did not compile it
:)
- Richard
-Original Message-
From: Kris Schneider [mailto:[EMAIL PROTECTED]
Sent: Wednesday, December 31, 2003 9:01 AM
To: Struts Users Mailing List
Subject: Re: ConcurrentModificationException on ActionErrors
It almost sounds like your code isn't handling errors1 and/or errors2 in a
thread-safe manner. ConcurrentModificationException will be thrown if one
thread
is in the proces of iterating over a collection and another thread modifies
that
collection. ActionMessages.add(ActionMessages) will iterate over both the
arg's
properties and the messages for each property, so there's certainly the
potential for the error you're seeing. Can you provide some more detail on
how
your code is organized?
BTW, not sure if it's a c/p error, but you've got:
if (!errors2.isEmpty()) {
errors.add(errors1); // shouldn't that be errors2?
}
Quoting Richard Mixon (qwest) [EMAIL PROTECTED]:
I have a Struts action that is trying to show all of the errors that
might
occur from either or both of two subordinate methods. The
code looks like:
...
ActionErrors errors = new ActionErrors();
ActionErrors errors1 = null;
ActionErrors errors2 = null;
Obj1 obj1 = new Obj1();
Obj2 obj2 = new Obj2();
obj1.method1();
errors1 = obj1.getErrors();
if (!errors1.isEmpty()) {
errors.add(errors1);
}
obj2.method2();
errors2 = obj2.getErrors();
if (!errors2.isEmpty()) {
errors.add(errors1);
}
...
Problem is I get the ConcurrentModificationException when I try and do
either
of the errors.add methods above. Methods
method1/method2 are pretty vanilla, just doing some database work and
accumulating any errors in an associated ActionErrors.
I've searched the archives but only found one or two references to
ConcurrentModificationException and they did not involve
ActionErrors. Any ideas or help is appreciated.
- Richard
--
Kris Schneider mailto:[EMAIL PROTECTED]
D.O.Tech http://www.dotech.com/
--
Kris Schneider mailto:[EMAIL PROTECTED]
D.O.Tech http://www.dotech.com/
-
To unsubscribe, e-mail: [EMAIL PROTECTED]
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