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From "Denys Rtveliashvili (Jira)" <j...@apache.org>
Subject [jira] [Commented] (THRIFT-5333) Exceptions defined in IDL to extend Exception rather than TException
Date Wed, 06 Jan 2021 13:18:01 GMT

    [ https://issues.apache.org/jira/browse/THRIFT-5333?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17259703#comment-17259703
] 

Denys Rtveliashvili commented on THRIFT-5333:
---------------------------------------------

You right, [~ctubbsii] my code was indeed tweaked.

However, I did it because the code suggested by [~fishywang] does not solve the original
problem - it hides all IDL-based exceptions under an umbrella of TException, effectively erasing
their signature. The second suggestion pushes class checks to runtime, which is no better.

It is not possible to have something like this:
{code:java}
try {
  api.myCall(xyz);
} catch (TApplicationException | TTransportException | TProtocolException e) {
  // handling thrift exception
} catch (MyException e) {
  // handling call-specific, IDL-defined exception
}{code}
and so one cannot have safe code, statically checked by compiler.

 

> Exceptions defined in IDL to extend Exception rather than TException
> --------------------------------------------------------------------
>
>                 Key: THRIFT-5333
>                 URL: https://issues.apache.org/jira/browse/THRIFT-5333
>             Project: Thrift
>          Issue Type: Improvement
>          Components: Java - Compiler
>    Affects Versions: 0.13.0
>            Reporter: Denys Rtveliashvili
>            Priority: Major
>
> At the moment, if an exception is defined in IDL and Java code is generated for it, the
exception would be defined as extending TException like this:
> {code:java}
> public class MyException extends org.apache.thrift.TException implements ...
> {code}
> At the same time, definition of methods looks like this:
> {code:java}
> public int myMethod(int argument) throws MyException, org.apache.thrift.TException {
> ...
> }{code}
> Here, TException has to be included as that is the only way to signal that RPC call has
failed for whatever reason.
> Now the problem with this is that if one calls a method like that, it is obvious that
TException covers all those exceptions defined in IDL and so there is no way to clearly see
which exceptions are result of internal workings of Thrift and which ones correspond to situations
described in IDL:
> {code:java}
> try {
>   myMethod(123);
> } catch (TException e) {
>   log.error("Problem spotted", e);
> }{code}
>  
> Why not make extensions extend java.lang.Exception instead?
> {code:java}
> public class MyException extends java.lang.Exception implements ...{code}
> This would have made it clear which exceptions are throwable by the call as "catch (TException
e)" would not catch them and explicit catching would be in order:
> {code:java}
> try {
>  myMethod(123);
> } catch (MyException e) {
>  log.error("MyException has been thrown");
> } catch (TException e) {
>  log.error("Problem spotted", e);
> }
> {code}



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