Exception catching, avoiding (sometimes)
hello,
i use forte for java and each time i use methods that either read or write to/from a stream without the try catch quotes, i get an error
Test_Sum.java [58:1] unreported exception java.io.IOException; must be caught or declared to be thrown
i understand that it is good convention to use the try/catch handlers and do it when writing production code but at times when one just wants to test something, this gets annoying. even some of the tutorial examples do not use these. how do i force the exception catching requirement off?
thanks in advance jiri
catch the exceptions you want, and have all methods that might throw an exception declare
throws Exception
or
put everything in a method in 1 try catch block
mymethod()
try
catch (Exception e)
Similar Messages
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How to get details about Exception catched in Exception branch of the Block
Hello Experts,
Is it possible to get details about Exception catched in Exception branch of the Block in Integration Process (BPM)?
In the Exception branch System Error is catched, but from time to time different type of System Errors are happening during sync call to WebService - Connection Timeout, Connection Refused, UnknownHost, etc.
So the task is somehow to map the type of System Error to the response. I was trying to create a mapping using as source the message which is coming from the Adapter after the sync call, but the mapping is failing with "No Source Payload" error.
Maybe the description is somewhere in Header or Dynamic configuration?
Or it is possible to access it somehow with JAVA-maping?
Thanks for your help!Hey,
the message from the exception can be utilized by using alerts(in order to mail,sms r fax). but otherwise its not possible using mappings or container.
check this link for alert configuration.
/people/michal.krawczyk2/blog/2005/09/09/xi-alerts--step-by-step -
IO or FileNotFound Exception catch does not work for getRequestDispatcher
Hi,
I am trying to catch IOException / FileNotFoundException in my servlet for the call to getRequestDispatcher().forward(request, response) and than throw user define exception from that catch. I am using JDeveloper 10.1.3. Some how the control is not going to catch block when the file does not exist to forward. But instead JDeveloper is throwing its own exception with error mesg
NOTIFICATION J2EE JSP0008 Unable to dispatch JSP Page : java.io.FileNotFoundException:
and browser shows standard 404 File Not Found error page. I would rather have want to display appropriate error page. Here is my code:
try
System.out.println("in try");
context.getRequestDispatcher("/" + currentScreen).forward(request, response);
System.out.println("after try");
catch(java.io.IOException fileNotFoundEx)
System.out.println("runtime exception");
logger.error(CLASS_OBJECT, "f n f "+RootException.getStackTraceString(fileNotFoundEx));
throw new RequestHandlerException("requestHandlerError", fileNotFoundEx);
Here is the output on console:
06/08/01 10:35:18 in try
2006-08-01 10:35:18.921 NOTIFICATION J2EE JSP0008 Unable to dispatch JSP Page : java.io.FileNotFoundException: F:\JavaProjects\WorkspaceDev\CorAssessment\web\jsp\assessment_multi_view1.jsp (The system cannot find the file specified)
at java.io.FileInputStream.open(Native Method)
at java.io.FileInputStream.<init>(FileInputStream.java:106)
at java.io.FileInputStream.<init>(FileInputStream.java:66)
at oracle.jsp.provider.JspFilesystemResource.fromStream(JspFilesystemResource.java:150)
at oracle.jsp.parse.XMLUtil.getFromStream(XMLUtil.java:228)
at oracle.jsp.runtimev2.JspPageCompiler.compilePage(JspPageCompiler.java:341)
at oracle.jsp.runtimev2.JspPageInfo.compileAndLoad(JspPageInfo.java:610)
at oracle.jsp.runtimev2.JspPageTable.compileAndServe(JspPageTable.java:634)
at oracle.jsp.runtimev2.JspPageTable.service(JspPageTable.java:370)
at oracle.jsp.runtimev2.JspServlet.internalService(JspServlet.java:478)
at oracle.jsp.runtimev2.JspServlet.service(JspServlet.java:401)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
at com.evermind.server.http.ServletRequestDispatcher.invoke(ServletRequestDispatcher.java:719)
at com.evermind.server.http.ServletRequestDispatcher.forwardInternal(ServletRequestDispatcher.java:376)
at com.evermind.server.http.ServletRequestDispatcher.unprivileged_forward(ServletRequestDispatcher.java:270)
at com.evermind.server.http.ServletRequestDispatcher.access$100(ServletRequestDispatcher.java:42)
at com.evermind.server.http.ServletRequestDispatcher$2.oc4jRun(ServletRequestDispatcher.java:204)
at oracle.oc4j.security.OC4JSecurity.doPrivileged(OC4JSecurity.java:283)
at com.evermind.server.http.ServletRequestDispatcher.forward(ServletRequestDispatcher.java:209)
at com.nexcom.cor.manager.ViewManager.forwardToNextScreen(ViewManager.java:142)
at com.nexcom.cor.controller.FrontController.doProcess(FrontController.java:85)
at com.nexcom.cor.controller.FrontController.doGet(FrontController.java:59)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:743)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
at com.evermind.server.http.ServletRequestDispatcher.invoke(ServletRequestDispatcher.java:719)
at com.evermind.server.http.ServletRequestDispatcher.forwardInternal(ServletRequestDispatcher.java:376)
at com.evermind.server.http.HttpRequestHandler.doProcessRequest(HttpRequestHandler.java:870)
at com.evermind.server.http.HttpRequestHandler.processRequest(HttpRequestHandler.java:451)
at com.evermind.server.http.HttpRequestHandler.serveOneRequest(HttpRequestHandler.java:218)
at com.evermind.server.http.HttpRequestHandler.run(HttpRequestHandler.java:119)
at com.evermind.server.http.HttpRequestHandler.run(HttpRequestHandler.java:112)
at oracle.oc4j.network.ServerSocketReadHandler$SafeRunnable.run(ServerSocketReadHandler.java:260)
at com.evermind.util.ReleasableResourcePooledExecutor$MyWorker.run(ReleasableResourcePooledExecutor.java:303)
at java.lang.Thread.run(Thread.java:534)
06/08/01 10:35:18 after try
It does not goto catch block and not printing message from System.out.You can map error codes to a specific jsp in your web.xml file, and add a parameter to the jsp that will display the message you intend to display back to the user.
Example:
<error-page>
<error-code>404</error-code>
<location>/index.html</location>
</error-page>
You can also trap specific exceptions by doing the following:
<error-page>
<exception-type> java.lang.Exception </exception-type>
<location>/ErrorPage.jsp</location>
</error-page> -
Question on exception catching
Runtime exceptions are not subject to the Catch or Specify Requirement
I came across this line in the Java tutorial at http://java.sun.com/docs/books/tutorial/essential/exceptions/catchOrDeclare.html
What did it mean?I understand some of what you write but I don't see
how a compiler does not detect it. Sorry if I am
sounding dumb. I never programmed before.Okay, more detailed explanation (which means I am in a good mood otherwise I don't like writing so much):
Consider the following code.
String s = null;
// some code in between
System.out.println(s.substring(0,1));What do you think will happen to this code? It will generate a NullPointerException when substring() is called on the String s unless something else is assigned to the s in between. Now this is something which can occur only when you execute your code.
What I mean is, is there any way for the compiler to detect whether the value of the String variable s has changed? The answer is a plain no. It is not the job of the compiler to know that. So subsequently, a compiler cannot dictate to the programmer that a possible NullPointerException (NPE) needs to be handled because there is no way a compiler could be sure about a NPE in any case (unless it is too smart). There could be several other such exceptions which could occur. So that becomes an unchecked exception which is not checked by the compiler.
Now coming to checked exception. If you are calling a method which already throws an exception as a known behaviour, the compiler is already aware. For example, a file read operation (I'm being lazy in typing code now) would throw an IOException which is defined as a part of the method signature. This makes the compiler aware of the possibility of getting an IOException. SO it checks to see if the programmer has taken care of the exception to make the code more fool-proof. This comes to be known as a checked exception.
Does this make something clear? I hope so. -
I was wondering what strategies people use to know what exceptions to try and catch? I would like to be able to know what potential exceptions may be thrown by a method or any method it calls etc.
For example I was recently working with DefaultMutableTreeNode.insertNodeInto() method, and got the following: Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 1 > 0
at java.util.Vector.insertElementAt(Vector.java:551)
at javax.swing.tree.DefaultMutableTreeNode.insert(DefaultMutableTreeNode.java:177)
at javax.swing.tree.DefaultTreeModel.insertNodeInto(DefaultTreeModel.java:218)
at CheckTree.CheckTreeModel.addNode(CheckTreeModel.java:88)
Now I can look up Vector.insertElementAt() and see what exceptions it could potentially raise. However if I look @ insertNodeInto() in the JavaDocs, it doesn't list any potential exceptions that may be raised, nor does it tell me that it uses Vector.insertElementAt().
Since A. I don't always have all the source code I need to dig through everything I call to see what may cause a problem,
and B. I don't want to have to go through 3000+ lines of source code just to go, oh look someMethod() can raise a DivideByZero exception! I better be prepared to catch it in my function 6 calls up the ladder.
So I'm guessing there is a happy medium when it comes to knowing what to look for.
I know a large part of good code it is making sure your passing sane arguments in your method calls, but when working with new API's it's not always easy to tell what will end up being sane and logical and what will be inappropriate garbage. (Especially with how lacking the JavaDocs can be).
So like I said I'm wondering what strategies work well for people?OKAY Let's take a look at a quote from the first post.
For example I was recently working with DefaultMutableTreeNode.insertNodeInto() method, and got the following: Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 1 > 0
at java.util.Vector.insertElementAt(Vector.java:551)
at javax.swing.tree.DefaultMutableTreeNode.insert(DefaultMutableTreeNode.java:177)
at javax.swing.tree.DefaultTreeModel.insertNodeInto(DefaultTreeModel.java:218)
at CheckTree.CheckTreeModel.addNode(CheckTreeModel.java:88) You all should be able to recognize a call stack printed in resoponse to an unhandled exception.
Let's take a look at the line in bold. Yes I was mistaken about the object calling insertNodeInto().
But there is a lot of useful information in the callstack, a quick inspection of the callstack reveals
A. the insertNodeInto called was a method of DefaultTreeModel.
B. The exception was raised in insertElementAt()
C. insertElementAt() is called by DefaultMutableTreeNode.insert() which is called by DefaultTreeModel.insertNodeInto().
Here is a direct copy of DefaultTreeModel,insertNodeInto() java doc:
insertNodeInto
public void insertNodeInto(MutableTreeNode newChild,
MutableTreeNode parent,
int index)Invoked this to insert newChild at location index in parents children. This will then message nodesWereInserted to create the appropriate event. This is the preferred way to add children as it will create the appropriate event.
notice a lack of mention of "ArrayIndexOutOfBoundsException" There is a very simple reason for this.
It is because the exception is raised not by insertNodeInto, but by insertElementAt().
I am not stating that the documentation for insertNodeInto() is wrong. It is merely not warning me that I may get an exception generated by a method called my a method it itself falls. For which I do not blame it, because insertNodeInto does NOT directly raise the exception.
I was simply asking what people do to handle exceptions that are generally unforseeable. -
E extends Exception Only Compiles Sometimes (possible bug)
Consider:
public interface RootedNodeAlgo<R,T,J,E extends Exception>
public R forParentNode(RootedNode<J> n, T... input) throws E;
public R forLeafNode(RootedNode<J> n, T... input) throws E;
public abstract class LeafSyntaxNodeBase extends SyntaxNodeBase implements LeafSyntaxNode
public <R, T, E extends Exception> R execute(RootedNodeAlgo<R,T,SyntaxNode,E> algo, T... input) throws E
return algo.forLeafNode(this, input); // error sometimes on this line
}When compiled as the only file being compiled, never a problem. When being compiled with a group of files I sometimes get the error:
Error: unreported exception java.lang.Exception; must be caught or declared to be thrown
This seems to an incorrect error though as we can show that E is the only checked exception that could ever be raised and we have declared E as thrown. Sometimes the compiler will generate this error and sometimes it wont for the exact same source. Compiling the files all alone never generates this error and no unusual runtime behavior has ever been observed.
Is this a compiler bug?The hierarchy is pretty big, but here is more:
Also javac = JDK 5.0_11
abstract public class SyntaxNodeBase extends VertexBridge<SyntaxNode> implements SyntaxNode
private SyntaxNode _parent;
SyntaxNodeBase()
public SyntaxNode getParent()
return _parent;
public void setParent(SyntaxNode parent)
_parent = parent;
public SyntaxNode getContents()
return this;
abstract public <R,T, E extends Exception> R execute(SyntaxNodeAlgo<R,T,E> algo, T...input) throws E;
public String toString()
return this.getClass().getName();
public <R,T, E extends Exception> R execute(AGLastNodeAlgo<R,T,E> algo, T... input) throws E
return algo.forArrayList(this, input);
public interface RootedNode<J> extends Vertex<J>
public <R,T,E extends Exception> R execute(RootedNodeAlgo<R,T,J,E> algo, T...input) throws E;
public interface LeafSyntaxNode extends SyntaxNode
// actually empty
public interface SyntaxNode extends AGLastNode<SyntaxNode>
public <R,T, E extends Exception> R execute(SyntaxNodeAlgo<R,T,E> algo, T...input) throws E;
public RootedNode<SyntaxNode> getParent();
public void setParent(SyntaxNode parent);
}Message was edited by:
DejasPerPer -
Exception catching in event processing thread
Hello!
How to catch exceptions occurring in event processing thread during repaints, mouse & keyboard event processing etc.? All uncatched exceptions displayed in screen but I need to write them in logfile.
AntonYes - push your own event processor on to the AWT event queue. See my replies at
http://forum.java.sun.com/thread.jsp?forum=57&thread=484167
and
http://forum.java.sun.com/thread.jsp?forum=57&thread=163020
Although for two completely different purposes, this technique will also allow you to put your own try/catch around super.dispatchEvent()
Hope that helps
Tom -
How to catch Exception inside the native code
Hello,
I have an error of unexpected exception during running native code,it occurrs randomly, not every time.
the error text is:
An unexpected exception has been detected in native code outside the VM.
Unexpected Signal : 11 occurred at PC=0x9535F359
Function=acy_match+0xC6
Library=/usr/lib/libNegativeMatcher.so
I don't know what exactly cause the crash inside the c code but I think it might be memory leak . What I'm concern is that this exception cause program termination.
I have few questions:
1. This exception cause the java program to end. How can I catch this exception and avoid program termination?
2. What is 0xC6 in:
Function=acy_match+0xC6
and PC=0x9535F359?
Can it help me track the problem inside the native code?
Thanks for your help.An unexpected exception has been detected in native
code outside the VM.
Unexpected Signal : 11 occurred at PC=0x9535F359
Function=acy_match+0xC6
Library=/usr/lib/libNegativeMatcher.so
I don't know what exactly cause the crash inside the
c code but I think it might be memory leak . What
I'm concern is that this exception cause program
termination.I doubt it is a memory leak (actually I am rather certain that another error would occur if it was just memory exhaustion.)
I have few questions:
1. This exception cause the java program to end. How
can I catch this exception and avoid program
termination?I suspect that would be a really bad idea. That particular signal very likely indicates that you have corrupted memory. Continuing is unlikely to work.
2. What is 0xC6 in:
As a guess it is an offset into the compiled code which indicates where the memory problem was detected.
That it unlikely to help you with a pointer/memory problem because that is where it was detected and not where it happened. By comparing the source you might be able to determine what was bad and then trace it back. -
How to catch up Exception message?
i have a question while using try{ ... }catch{ ... } clauses. for when update, delete, databse, there might be error occurred. all to often i do not deal with the message, only if to check log when serious problem i have to find it out; but i hope to learn how if i am able to display message of my own while erro occurrs. for instance, when falling into SQLException, originaly i might just utilize
}catch(SQLException e){
e.printStackTrace();
is it possible for me to catch up message inside the printStackTrace that may happen while errors appearing? (or only down to catch{} clause be the last deadline that i am able to use? because i hope i am able to capture error code like ora-1234 and tranlate it into messages that user, who doesn't know too much about pc, can understand easily while reporting bug; and not just saying "we have problem here!")
that is, if 'A' situation popping out, i hope to direct it to error page with special message shown. so does the same error page with different message specified while 'B' situation found out!
any suggestions would be appreciated~
thanks in advice,printStackTrace isn't obligatory. It's basically what you do with an exception when you don't have anything more specific to do with it.
You can certainly catch a specific exception at any level, including inside another try {} block.
Even having caught an exception you can decide that you don't want to handle it at this point in the code, and throw it again.
You might do:
try {
try {
... statment which migh cause a particular database exception
} catch(SQLException e) {
if(e.getMessage().startsWith("ORA-1232")) {
.. do somthing usefull
} else
throw e; // the particular SQL exception was unexpected so go on and crash
catch(Exception e) {
e.printStackTrace(); // unexpected program failure -
Write and read txt files and catch the exceptions
hey everyone, im in a bit of a bind. im trying to set up this try catch statement. here is what i have for code so far.
import java.util.Scanner;
import java.io.*;
public class Warning
// Reads student data (name, semester hours, quality points) from a
// text file, computes the GPA, then writes data to another file
// if the student is placed on academic warning.
public static void main (String[] args)
int creditHrs; // number of semester hours earned
double qualityPts; // number of quality points earned
double gpa; // grade point (quality point) average
String line, name, inputName = "students.dat";
String outputName = "warning.dat";
try
Scanner FileScan1 = new Scanner (new File("students.dat"));
// Set up scanner to input file
// Set up the output file stream
// Print a header to the output file
outFile.println ();
outFile.println ("Students on Academic Warning");
outFile.println ();
// Process the input file, one token at a time
while (FileScan1.hasNext())//there is another line...
{ // Get the credit hours and quality points and
// determine if the student is on warning. If so,
// write the student data to the output file.
// Close output file
catch (FileNotFoundException exception)
System.out.println ("The file " + inputName + " was not found.");
catch (IOException exception)
System.out.println (exception);
catch (NumberFormatException e)
System.out.println ("Format error in input file: " + e);
}I am pretty sure the layout is good to go, but first and foremost that try statement is hanging me up. Could someone give me some suggestions about how i should set this up.
i want to read in this students.dat file, then output another file called warning.dat.
Thanks i really appreicate the help.no, i was really hoping to just see if the way it is
set up it will be doable, that way i wouldn't be
working on code that was impossiable to sort through
properlyFair enough.
One thing I'd suggest is that if you're really basically only going to be printing the exceptions, and since that is the top-level method (main) --
I'd instead just add some "throws" clauses to main, get rid of the try/catch stuff, and just let the VM handle the exceptions for you. It will print them, just like you're doing, except that it will also print the stack traces, which you are not doing.
If you're going to handle exceptions, it's better to actually do something about them rather than just print them - otherwise you might just as well let the runtime do that for you. -
Help Me, How to catch exception thrown from ejbStore
Hi,
I am working on application running on Iplanet Application Server 4.0. Problem is the application exception thrown from the ejbStore don't reach the calling servlet, calling servlet receive TransactionRollback exception which is system exception. But there is no sign of my application exception thrown from ejbStore. Can anybody tell me how I can get my ApplicationException thrown from ejbStore in my calling servlet.
I am calling entity beans set method in servlet and in entity bean ejbStore method I am throwing Application exception.
in entity bean
public void ejbStore() throws MyException
if(true) throw new MyException();
in servlet
try {
MyEntityHome home = .......
MyEntityRemote remote = home.findBy.....
remote.setMyValue(MyValue value); //Transaction required Container managed
}catch(MyException e) {
e.printStackTrace(); // Not cahcing My Exception
}catch(Exception e) {
e.printStackTrace(); //catching TransactionRolledBackException
Thanks
ShaktiHi Ravi
Try this
try
Object retMsgs = output.get(bapiretrunmsgobject);
if(result != null )
IrecordSet rmsg = (IrecordSet) result
catch(Exception ex)
printException(ex, "Error getting function result");
Lemme know for any further questions.
Regards
Praveen -
Multiple catch for try -Exception Already caught Running smoothly..
take this code for example...
This one runs smoothly..
public class one
public static void main(String args[])
int i=27;
try
System.out.println(i/0);
catch(ArrayIndexOutOfBoundsException e)
System.out.println(e);
catch(Exception e)
System.out.println(e);
}However if i change the order it would give me a compile time error which in my sun sl-275 book is written it should run fine.
"If the Exception Catch clause is put first, then it would handle all exceptions, and the MyException or MyOtherException catch clauses would never be invoked."
which i think is wrong because the code never gets compiled...
public class one
public static void main(String args[])
int i=27;
try
System.out.println(i/0);
catch(Exception e)
System.out.println(e);
catch(ArrayIndexOutOfBoundsException e)
System.out.println(e);
}please discuss.DogsAreBarking wrote:
take this code for example...
This one runs smoothly..
public class one
public static void main(String args[])
int i=27;
try
System.out.println(i/0);
catch(ArrayIndexOutOfBoundsException e)
System.out.println(e);
catch(Exception e)
System.out.println(e);
}However if i change the order it would give me a compile time error Correct. Each exception can be caught only once, Catching an exception implicitly catches every subclass exception of the one caught.
In the first example, the code is fine, because your first catch block will catch only ArrayIndexOutOfBoundsException, and the second catch block will catch anything that was not caught previously--in other words, everything other than ArrayIndexOutOfBoundsException (and any child classes it may have).
In the second example, the first catch block handles Exception and all of its subclasses, so catching ArrayIndexOutOfBoundsException is wrong. -
Catching or Methods Throwing Exceptions
Hi,
I'm just wondering whats the difference between catching an exception and a method throwing an exception?
I'm a bit confused on their purpose dealing with exceptions.
catching an exception
void p1()
try{
p2();
}catch(IOException ex){
}method throwing an exception
void p1() throws IOException
p2();
}one more stuff i need to add is that:
When we declare a particular code within a try catch
statement it means that that particular code is very
much prone to an exception , i mean the programeer
knows that code will throw a exception and hence we
mention in try catch block.
But in other case when we suffixed that particular
method with throws clause it means the programmer is
not sure ,that code might throw an exception,hence we
put in throws clause.Not quite, the programmer always knows if a checked exception is being thrown, since the compiler requires it to be caught or having a throws clause. Unchecked (runtime) exceptions don't require a throws clause and the programmer must/can catch it if he wants to. -
How to deal exception using try{}catch{}
I don't know which is a good way from catch a exception and throw a exception,
I means that how to use exception in java,catch ? throw?Presumably you are not asking the same thing as here...
http://forum.java.sun.com/thread.jsp?thread=461313&forum=9&message=2114037
You catch an exception with code that looks like the following...
try
String s = null;
int i = s.length(); // This throws an exception
catch(NullPointerException e)
// Do something
You throw an exception with the following...
if (<some condition>)
throw new Exception("Something bad happened"); -
Hi,
Can anybody tell me why following program doesn't catch exception because of dereferencing a null pointer. Is there anything extra I have to do achieve it.
#include <stdexcept>
#include <exception>
int main ()
try
int *ptr ;
ptr = NULL;
printf("%d" , *ptr);
catch ( ... )
printf("Exception catched\n");
Thanks,This program is not throwing an exception. There is difference between UNIX signals (like NULL deref) and C++ exceptions.
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