In debugging my Velocity web-app I've been frustrated in that there
seemed to be no way to get velocity to log the stack trace when
an error happens. Setting of VelocityEngine.RUNTIME_LOG_ERROR_STACKTRACE
or even VelocityEngine.RUNTIME_LOG_WARN_STACKTRACE seemed
to not do anything. After a few hours of poking around, I discovered
that in fact the code was not there to log stack traces.
There were two problems:
1) RuntimeInstance.showStackTrace() first checks
configuration.isInitialized(), which
always seems to return false. :(
2) Parse.render did not pass the exception to the logging system, it just
constructed a message with catch(Exception e) { log("...message.."
+e.getMessage());}
I propose the following fixes :
1) In RuntimeInstance.showStackTrace() do not check
configuration.isInitialized().
2) To RuntimeLogger interface add a error(String message, Throwable t)
method.
I have implemented the above, please consider the attached patches, I think
they will
greatly help anyone debugging their Velocity applications.
Also note that as far as I can tell the
VelocityEngine.RUNTIME_LOG_ERROR_STACKTRACE
setting is not referenced anywhere. I would suggest replacing
RUNTIME_LOG_ERROR_STACKTRACE
and RUNTIME_LOG_WARN_STACKTRACE, with RUNTIME_LOG_STACKTRACE, since that
seems to be the actual behaviour. I have not implemented this.
Regards,
Victor Wiewiorowski
ValueCommerce Co., Ltd.Index: java/org/apache/velocity/runtime/RuntimeInstance.java
===================================================================
RCS file:
/home/cvspublic/jakarta-velocity/src/java/org/apache/velocity/runtime/RuntimeInstance.java,v
retrieving revision 1.17
diff -u -r1.17 RuntimeInstance.java
--- java/org/apache/velocity/runtime/RuntimeInstance.java 9 Aug 2002 00:54:53
-0000 1.17
+++ java/org/apache/velocity/runtime/RuntimeInstance.java 3 Apr 2003 01:46:00
-0000
@@ -1011,7 +1011,24 @@
{
log(LogSystem.ERROR_ID, message);
}
-
+
+ /**
+ * Log an error message.
+ *
+ * @param Object message to log
+ */
+ public void error(String message, Throwable t)
+ {
+ String msg = message;
+ if(showStackTrace()) {
+ msg += "Exception : ";
+ msg += t.getMessage();
+ msg += "\n";
+ msg += StringUtils.stackTrace(t);
+ }
+ log(LogSystem.ERROR_ID, msg);
+ }
+
/**
* Log a debug message.
*
Index: java/org/apache/velocity/runtime/RuntimeLogger.java
===================================================================
RCS file:
/home/cvspublic/jakarta-velocity/src/java/org/apache/velocity/runtime/RuntimeLogger.java,v
retrieving revision 1.1
diff -u -r1.1 RuntimeLogger.java
--- java/org/apache/velocity/runtime/RuntimeLogger.java 21 Apr 2002 18:35:18 -0000
1.1
+++ java/org/apache/velocity/runtime/RuntimeLogger.java 3 Apr 2003 01:46:00 -0000
@@ -84,6 +84,14 @@
public void error(Object message);
/**
+ * Log an error caused by an exception.
+ *
+ * @param Object message to log
+ * @param Throweable t the exception that caused this error
+ */
+ public void error(String message, Throwable t);
+
+ /**
* Log a debug message.
*
* @param Object message to log
Index: java/org/apache/velocity/runtime/directive/Parse.java
===================================================================
RCS file:
/home/cvspublic/jakarta-velocity/src/java/org/apache/velocity/runtime/directive/Parse.java,v
retrieving revision 1.26
diff -u -r1.26 Parse.java
--- java/org/apache/velocity/runtime/directive/Parse.java 10 Oct 2002 17:10:30
-0000 1.26
+++ java/org/apache/velocity/runtime/directive/Parse.java 3 Apr 2003 01:46:00
-0000
@@ -209,7 +209,7 @@
}
catch ( Exception e)
{
- rsvc.error("#parse() : arg = " + arg + ". Exception : " + e);
+ rsvc.error("#parse() : arg = " + arg + ".", e);
return false;
}
@@ -232,7 +232,7 @@
throw (MethodInvocationException) e;
}
- rsvc.error( "Exception rendering #parse( " + arg + " ) : " + e );
+ rsvc.error( "Exception rendering #parse( " + arg + " ) : ", e );
return false;
}
finally
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