Re: [Ikvm-developers] Catching exceptions in c# from java code

[<Sha...@tr...>]

I guess I am still a bit puzzled.

In Java

public void methodCall() {

String x = null;

try {
        x.substring(3);
} catch (Exception e) {
        e.printStackTrace();
}
}


in c#

try {

        methodCall();
} catch (System.Exception x)
 ... Should I be able to catch the NullPointerException that is thrown in 
Java?
}


This doesn't seem to work for me.


Shawn Roney




Jeroen Frijters <je...@su...> 
04/30/2010 12:38 AM

To
"Sha...@tr..." <Sha...@tr...>, 
"ikv...@li..." 
<ikv...@li...>
cc

Subject
Re: [Ikvm-developers] Catching exceptions in c# from java code






Exception interop is a little bit messy. When you catch System.Exception 
you'll get all exceptions (including the Java exceptions), but when you're 
looking for a specific exception some more work is needed. Especially in 
the case of a runtime exception (i.e. an exception generated by the JVM or 
in this case the CLR).

If a Java method throws a java.lang.NullPointerException, this can surface 
on the C# side as either a System.NullPointerException or a 
java.lang.NullPointerException, depending on whether the Java code 
explicitly threw the exception or the CLR threw the exception for 
dereferencing a null reference.

In the case below, if you just want to catch the java.lang.Exception 
thrown by " throw new Exception("TriMinEx - " + output[2]);", then you can 
simply use "catch (java.lang.Exception)" in C#.

Finally, if you want the exception as Java code would see it, you can do 
this:

try { ... }
catch (System.Exception x)
{
    x = ikvm.runtime.Util.mapException(x);
    if (x is java.lang.NullPointerException) {
    ...
   } else if (x is ...) {
   }
}

Regards,
Jeroen

> -----Original Message-----
> From: Sha...@tr... [mailto:Sha...@tr...]
> Sent: Thursday, April 29, 2010 11:10 PM
> To: ikv...@li...
> Subject: [Ikvm-developers] Catching exceptions in c# from java code
> 
> 
> Hello,
> I have some Java code that I want to reuse in a c# project.  How do I 
catch the
> exceptions thrown in Java and print them out in c#?  I have tried, but 
can't
> seem to get it to work.
> 
> Here is the java method:
> 
> public String[] sendModel2(String user, String password, String xml) {
>                 String[] output = new String[4];
> 
>                 try {
> 
> 
>                         TriMinDocument triDoc = 
XMLDomUtil.returnModel2Type(xml);
>                         String docId = triDoc.getDocumentId(xml);
>                         if (docId == null || docId.trim().length() == 0) 
{
>                                 output = new String[] { "Failure", xml, 
"The document
> indentifier must be available in the XML document.", "" };
>                                 throw new Exception("TriMinEx - " + 
output[2]);
>                         }
> 
>                 // triDoc is null, so should throw a null pointer 
exception
>                 } catch (Exception e) {
> StringUtil.StringToFile("Hello","c:\\temp\\test.txt");
>                                 String errMsg = e.getMessage();
>                                 if (errMsg == null)
>                                         errMsg = "";
>                                 if (!errMsg.startsWith("TriMinEx -")) {
> 
>                                         output = new String[] { 
"Failure", xml, "Invalid XML sent
> to service", "" };
>                                 }
>                                 throw new Exception("TriMinEx - " + 
output[2]);
>                         }
> 
>         return output;
> }
> 
> 
> I cannot get an exception to print out in c#.
> 
> Thanks in advance.
> 
> Shawn
> 
> Shawn Roney
> Director, Advanced Applications
> TriMin Government Solutions
> Phone:  651-604-3653
> Cell:  651-587-3804
> http://www.triminsystems.com

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