Java Exception Handling

Hello everyone,
I'm searching for a design pattern / framework to manage exception handling. I'm currently working on a distributed document management system for PC / AS/400, which consists of Commandline clients, a Socket Server and a windows NT daemon in java, which accepts network requests from the Socket Server. Communication is done via serialized Objects.
My Problem is, that exceptions can be thrown either on the server or on the client side and have to be transferred to the user. Error Messages should be read from the database. Exception handling should prefferably take place in a central piece of code, such as the two endpoints of network connections, the SocketServer as service under win32 and another SocketServer as Application on another box, currently with UNIX OS.
thanks in advance for any answers
regards

You should look into Bridge [GOF:151] and Memento [GOF:273].
Bridge allows you to decouple your mechanism from the implementation memento on how to propergate the decoupled exception information.

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Java Exception handling framework

Please suggest some frameworks for Java Exception handling

http://java.sun.com/docs/books/tutorial/essential/exceptions/
http://forum.java.sun.com/thread.jsp?forum=31&thread=173005
http://www.tfh-berlin.de/~knabe/java/multex/
http://www.impetus.com/comp_jeh.htm
http://www.softwaresummit.com/1998/1998/speakers/haggar.htm

Java Exception handling incorrect ?

Check this program out:
I tried it on 3 different machines but the result is the same
class TestEx extends Exception
class Excp
void test() throws Exception
throw new TestEx();
public static void main(String args[])
     Excp e = new Excp();
     try
     e.test();
     catch(Throwable ee)
          System.out.println("Exception caught");
Compile it and then delete TestEx.class. What should happen ? In all of the 3 machines the NoClassDeffoundError (thrown on TestEx.class) was not caught at the 'catch (Throwable ee)' although to me it seems it should be.
Martin.

I am clear about the loading and linking phases.
So this statement "...It is pretty clear that when a class is first loaded and linked, all classes that it refers to are loaded (but not necessarily linked)..."
it not necessarily true.
When a class is loaded, all superclasses/interfaces are loaded. The time of linking is not really specified. It could be early linking or late linking, specifically the resolving part of the linking phase, since that is the issue here (not the verification or preparation). A VM should always make sure it looks like late resolving since a statement that could create error might never be executed.
In most cases, the VM does not try and should not to load all classes in constant pool when it does the linking phase. It should do so when that class is resolved (on the many bytecodes that do so).
So the case above. Yes, when Excp is loaded and linked it could preload TestEx, but this is not really relevant here. Next, when the 'new' bytecode is executed in test() on TestEx, it knows the TestEx is missing and at this point it must create NoClassDefFoundError instance and throw it. Up to here the behavior is clear.
What happens after the new is executed and now we know we have NoClassDefFoundError, what happens now is the question. The user might still want to handle this exception. Of course it is quite rare, but should be possible.
thx,
Martin.

JAVA BEANSHELL EXCEPTION HANDLING

Hi
still new to ODI
I have created a java beanshell script in ODI which calls a simple java class, cars, then sets the no of seats to a value designed to raise an exception. Exception raised but procedure works OK,
How can I register the fact that it has failed through exception handling? (It is possible that my java exception handling isn't quite right)
The no of seats has no effect on the success/failure of the ODI procedure, but the log shows that the exception is caught !
any assistance gratefully received.
Regards
Terry
cars class: (added to agent start)
====================
public class cars {
private int seats;
public void setSeats (int seats) throws tooManySeatsException {
if (seats) < 100) {
this .seats = seats;
} else {
throw new tooManySeatsException("Too many seats");
public int getSeats () {
return this.seats;
class tooManySeatsException extends Exception {
public tooManySeatsException (String msg){
super();
Java beanshell procedure in ODI
====================
import cars;
public class carsTest {
public carsTest(){
public void init(){
cars c = new cars();
c.setSeats(20);
//c.setseats(200);
try {
carsTest ct = new carsTest();
ct.init();
} catch (Exception e) {
throw Error (e);
}

Your code throws exception when you set value >100 but you are setting 20 thus it would not throw exception.
In the procedure step you can uncheck "Ignore error" flag to let execution failed on throwing any exception from your code. If you check that flag then the execution would not fail rather lease the task in warning state.

Advantage of Java Exceptions over C error handling.

I understand the advantages of Java Exception handling(as against C) when it comes to the ability to define exclusive Exception types or reuse exceptions, documentation benefits of the throws clause, advantages due to OO etc. But some people say that using exceptions in Java it is possible to recover from an exceptional condition and that's an advantage over how errors are dealt in C.
Is that really an advantage? (I mean is that true?)AFAIK in C errors can be handled using perror or errno.h. For every error code generated there seems to be a description. And by checking the return values from functions we could see if there had been an exceptional condition and if there really had been one take appropriate action and recover from the error. So how is it that Java can recover from exceptions while in C it is not possible to recover from errors?
Thank you very much.

I'm waiting in my cold cell when the bell begins to chime
Reflecting on my past life and it doesn't have much time
Cos at 5 o'clock they take me to the Gallows Pole
The sands of time for me are running low
When the priest comes to read me the last rites
I take a look through the bars at the last sights
Of a world that has gone very wrong for me
Can it be there's some sort of error
Hard to stop the surmounting terror
Is it really the end not some crazy dream
Somebody please tell me that I'm dreaming
It's not so easy to stop from screaming
But words escape me when I try to speak
Tears they flow but why am I crying
After all I am not afraid of dying
Don't believe that there is never an end
As the guards march me out to the courtyard
Someone calls from a cell "God be with you"
If there's a God then why has he let me die?
As I walk all my life drifts before me
And though the end is near I'm not sorry
Catch my soul cos it's willing to fly away
Mark my words please believe my soul lives on
Please don't worry now that I have gone
I've gone beyond to see the truth
When you know that your time is close at hand
maybe then you'll begin to understand
Life down there is just a strange illusion.
Yeah, yeah, yeah, Hallowed be thy name
Yeah, yeah, yeah, Hallowed be thy name

Good exception handling policy for Java web application

I'm looking for a good exception handling policy for Java web application. First I found this Java exception handling best practices - How To Do In Java which says that you should never catch the Trowable class nor use e.printStackTrace();
Then I found this Oracle page The Message-Driven Bean Class - The Java EE 6 Tutorial, which does just that. So now I'm confused. Is there a good page online for an exception handling policy for Java EE Web applications? I have a hard time finding one. I've read that you should not catch the Exception class. I've been catching it previously to make sure that some unknown exception doesn't slip through early in the loop and stops all other customers from executing later on in the loop. We have a loop which runs once a minute implemented using the Quartz framework. Is it OK if you just change the implementation to catch the RuntimeException class instead of the Exception class? We're using Java 7 and the Jetty Servlet Container.

I'm looking for a good exception handling policy for Java web application.
If you have not done so I suggest you start by reviewing the several trails in The Java Tutorials.
Those trails cover both HOW to use exceptions and WHEN to use them.
This trail discusses the 'controversy' you mention regarding 'Unchecked Exceptions'
http://docs.oracle.com/javase/tutorial/essential/exceptions/runtime.html
Unchecked Exceptions — The Controversy
Because the Java programming language does not require methods to catch or to specify unchecked exceptions (RuntimeException, Error, and their subclasses), programmers may be tempted to write code that throws only unchecked exceptions or to make all their exception subclasses inherit from RuntimeException. Both of these shortcuts allow programmers to write code without bothering with compiler errors and without bothering to specify or to catch any exceptions. Although this may seem convenient to the programmer, it sidesteps the intent of the catch or specify requirement and can cause problems for others using your classes.
Why did the designers decide to force a method to specify all uncaught checked exceptions that can be thrown within its scope? Any Exception that can be thrown by a method is part of the method's public programming interface. Those who call a method must know about the exceptions that a method can throw so that they can decide what to do about them. These exceptions are as much a part of that method's programming interface as its parameters and return value.
The next question might be: "If it's so good to document a method's API, including the exceptions it can throw, why not specify runtime exceptions too?" Runtime exceptions represent problems that are the result of a programming problem, and as such, the API client code cannot reasonably be expected to recover from them or to handle them in any way. Such problems include arithmetic exceptions, such as dividing by zero; pointer exceptions, such as trying to access an object through a null reference; and indexing exceptions, such as attempting to access an array element through an index that is too large or too small.
Generally don't catch an exception unless you plan to HANDLE the exception. Logging, by itself is NOT handliing.
First I found this Java exception handling best practices - How To Do In Java which says that you should never catch the Trowable class nor use e.printStackTrace();
That article, like many, has some good advice and some poor or even bad advice. You get what you pay for!
I've read that you should not catch the Exception class.
Ok - but all that does is indicate that a problem of some sort happened somewhere. Not very useful info. Java goes to a lot of trouble to provide specific exceptions for specific problems.
I've been catching it previously to make sure that some unknown exception doesn't slip through early in the loop and stops all other customers from executing later on in the loop.
If the exception is 'unknown' then maybe it NEEDS to 'stop all other customers from executing later on in the loop'.
That is EXACTLY why you don't want to do that. You need to identify which exceptions should NOT stop processing and which ones should.
Some 'unknown' exceptions can NOT be recovered and indicate a serious problem, perhaps with the JVM itself. You can NOT just blindly keep executing and ignore them without risking data corruption and/or the integrity of the entire system Java is running on.
Is it OK if you just change the implementation to catch the RuntimeException class instead of the Exception class? We're using Java 7 and the Jetty Servlet Container.
No - not if you want a well-behaved system.
Don't catch exceptions unless you HANDLE/resolve them. There are times when it makes sense to log the exception (which does NOT handle it) and then raise it again so that it gets handled properly later. Yes - I know that is contrary to the advice given in that article but, IMHO, that article is wrong about that point.
If you have ever had to maintain/fix/support someone else's Java code you should already understand how difficult it can be to find WHERE a problem occurs and WHAT the exact problem is when exceptions are not handled properly.

Exception handling - general concepts

ok, well i skipped the chapter on exception handling :=)
Correct me if im wrong, but lets say im writing some code and im not sure how to handle some of the exceptions that might get thrown or what exceptions will get thrown for that matter. How does one go about handling every possible exception that is "required".
I guess what im trying to ask is that if a certain block of code is calling methods that throw specific exceptions, then you will need to handle those exceptions. So that means you need to be aware of, or know to go lookup the possible exceptions that those methods can throw.
Im skipping around in Beginning Java 2, from wronx press jdk 1.4 edition

This is quite a hard one to be specific on as I think most of us learned this with a bit of trial and error.
1. IO always requires the method to be thrown ie
public void writeContents() throws IOException {
// methods
2. The compiler will tell you when you need a try /catch block
3. I often code this with;-
try {
// my methods here;
catch (Exception ignore) {}
and have empty braces with a general catch all Exception on the first run
4. Then if there are problems such as the code won't work I fill in the blanks ie;-
catch (Exception e) {System.out.println(e);}
// or e.getMessage() );
// or printStackTrace();
depending on what the first message is
5. Correct the exception now that you know what it is. Really this is a form of 'divide and conquer' as you eliminate the problems as they occur through javas exception handling abilities.
6. With a bit more practice you will implement things like finally and know when to put the handler back to 'catch (Exception ignore) {}' and when to leave it in.
7. Exception handling can also be used to instruct the client in useful ways too eg;-
try {
myTextfield.setText("Enter Your Age");
myInt = parse ...(myTextfield.getText(etc ...
catch (NumberFormatException nfe) {
myTextfield.setText("Enter Number Values Only");
// or something like
catch (NullPointerException nfe) {
myTextfield.setText("Oops you forgot to enter a value");
This has been my experience anyway + I trust I have assisted

Integration Process exception handling & alerts, Java

Hello,
I would like to enhance my basic scenarios fool proof and with as much Java as possible.
I have set up several asynchronous and synchronous File to SOAP transfers between systems A and B
using PI70 including my own Java mapping classes and PI's AF_Modules beans. They work just fine.
I have not designed my own Integration Processes yet, so execution is based on channel settings and availability timing.
I have learned this aproach may be exposed to general faults resulting manual monitoring and repairing.
For example server problems at receiver side can result data losses as sender channel just keeps removing source
files like normally, as the process would be better to just stop right there and alert or something.
My question is, is the "Enterprise services Builders" Integration Process & Graphical definition screen the one and only tool to
customize whole process exception handling and alerts in PI, and Java is not an option?
Appreciate your advice on this.
Kind regards m

Hi m,
Strange Name
>>I have learned this aproach may be exposed to general faults resulting manual monitoring and repairing. For example server problems at receiver side can result data losses as sender channel just keeps removing source files like normally, as the process would be better to just stop right there and alert or something.
If you are looking to handle this particular scenario, then we have the alert mechanism and CCMS monitoring. There you will come to know whether the end system down or not.
Also in addition to this you can write your own java (in message mapping, as modules, java mapping) /abap code (as abap mapping, user exit in standard functions etc) for providing more details in error scenarios. But you need to validate whether the maintenance/development cost for the code is justified in your scenarios
Regards
Suraj

Exception Handling in Java .. Help

Hi folks I needed some help in exception handling ...
I know that I could go like this
public class MyClass
     public static void main(String args[])
          try
          System.out.println(1/0);
          catch(java.lang.Exception e)
               e.printStackTrace();
Now what if i want to throw an error for example in C++ we would go like
try
throw 1;
throw 0;
throw 'A';
catch (int i) //If exception is of integer type ... you may overload it
cout << "Integer value thrown and caught \n";
catch (...) //Unexpected error
cout << "Some other unexpected exception \n";
How could i impliment a code such as the above in Java using throw...
Thanks again folks...

1. When you post code, use code tags to make it readable. Copy/paste from your original source in your editor (NOT from your earlier post here), highlight the code, and click the CODE button. Use the Preview tab to see how your post will work.
2. [http://download.oracle.com/javase/tutorial/essential/exceptions/]

Is there a way to handle custom java exception in OSB?

For example, i created a exception that extends RuntimeException.
My exception has a new field called "code".
I want to handle this exception in Oracle Service Bus process and retrieve this code to throws another exception with a XML structure that includes the code.
Is there a way to do that ?
<con:fault xmlns:con="http://www.bea.com/wli/sb/context">
     <con:errorCode>BEA-382515</con:errorCode>
     <con:reason>Callout to java method "public static org.apache.xmlbeans.XmlObject ...</con:reason>
     <con:java-exception xmlns:con="http://www.bea.com/wli/sb/context">
         <con:java-content ref="jcid:33a6c126:14006f3df18:-7fd9"/>
     </con:java-exception>
     <con:location xmlns:con="http://www.bea.com/wli/sb/context">
         <con:node>optmusPipeline</con:node>
         <con:pipeline>optmusPipeline_request</con:pipeline>
         <con:stage>processStage</con:stage>
         <con:path>request-pipeline</con:path>
     </con:location>
</con:fault>
it is not enough to recover the information i needed.

Hi Sandro,
I've got the same situation. I agree that returning xml from function is not a best choice as you have to manually check if return status is an error or not. Processing exception in error handler is better and this is how I do it:
I am doing a java callout to a function that can throw exception. Then I add ErrorHandler to stage containing this callout (all the exception are caught here).
In the error handler I check if $fault/ctx:java-exception is not null. If not then I pass thrown exception to my utility function that converts it to xml similar to yours:
import org.apache.xmlbeans.XmlException;
import org.apache.xmlbeans.XmlObject;
public static XmlObject exceptionToXML(Throwable exception)
throws XmlException {
String xmlString = exceptionToString(exception);
return XmlObject.Factory.parse(xmlString);
public static String exceptionToString(Throwable exception) {
String cause = "";
if (exception.getCause() != null) {
cause = exceptionToString(exception.getCause());
return String
.format("<exception><name>%s</name><description>%s</description>%s</exception>",
exception.getClass().getName(), exception.getMessage(),
cause);
Calling exceptionToXML with $fault/ctx:java-exception/ctx:java-content returns:
<exception>
     <name>pl.app.MyException</name>
     <description>Exception message</description>
</exception>
Then you can check the exception class (IF action: $exception/name/text() = "pl.app.MyException") and handle it accordingly.
Good luck,
Krzysiek

Is Exception Handling in every Java code?

Hi there,
just curious, is including exception handling the "norm" for any Java code?

Java divide the exception handling in two kinds :
- exceptions which need to be programatically handled
- exceptions which are automatically handled by Java such as ArrayIndexOutOfBounds, DivisionByZero, and lot of subclasses of RuntimeException.
It's not because they are automatically handled that you can't handle them programatically, but programming will be too difficult and long if they wasn't handled automatically.
Exception mechanism is very powerfull but a little bit long when an exception is thrown.
Denis

Study security related exception handling in Java

Hi all,
I am required to do an indepth study on security-related exception handling in Java, their Pluses and minuses... Can ppl suggest me places where I can get a kick start? Any resource that u know can help me out?
I appreciate ur help in this regard...FYI, I am a grad student and I am doing this as a part of my course-work...I am writing up a report on this...
Thanx a bunch, in advance for ur help ppl..

Take a look at the JAAS API and docs.
- Saish

Generic Exception handler in java

We have developed a client java application with our own exception hierarchy derived from java.lang.exception. We raise our own exception in case of error scenarios. But there is one additional thing which we want to do:
1. When ever any exception is raised in our exception we want to do some generic exception handling (like kicking of some module which collects the log files and send it to the administrator.
2. We want the above activity to happen also when any runtime exception is raised. We are not catching any runtime exception and we have no handle for this.
How should we go about this. Can we write a very low-level generic exception handler?
We do not want to have done at every catch block we have in our code. I mean we want to have some hook at a very generic place.
Let me know if some body can be help me on this.

As far as I know, for exceptions that are caught, you must make a call to a generic handler in the catch block, or you may rethrow the exception as a RuntimeException, and let it propagate.
For RuntimeExceptions and Errors in threads that you create, the easiest way to solve this is to subclass ThreadGroup, override uncaughtException with the appropriate code, and create all your threads in this group. For a thread like main, have the first thing in the thread be the creation of a new thread in the new group, then pass control to that thread. For fixed threads, like the event queue, someone had a suggestion already. Note that uncaughtException is only called just before the thread ends, so an exception that shouldn't end the thread should be handled seperately.

Handling/passing Java exceptions to JavaFX

My Java class has a try/catch statement indicating a communication error to MySQL server. I want to add a user-friendly dialog box in my JavaFX application in the event my java class cannot access the database.
What's the best way of handling Java exceptions within JavaFX?
Cheers!

Rethrow an exception and catch it in the call in JavaFX code?

Handling apllication java.Exceptions

I've developed an Weblogic WebService Application with several webservices inside.
They are working fine but when a WebService throws a java Exception this exception is putted inside a SoapFaultException.
After some research I figured that I should create my own Exceptions that inherits from SoapFaultException to best format the exception message
my clients will receive, ok it is done and it's working. Now I need to handle all java Exceptions (witch were not throw by me) to put it in my own Exceptions witch inherits from soapFaultException. Does anybody know if I can implement an Exception handler that will capture all java Exceptions unhandled by my applicatio.
I'm using WLS 9.2.

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