/* ====================================================================
* Limited Evaluation License:
*
* This software is open source, but licensed. The license with this package
* is an evaluation license, which may not be used for productive systems. If
* you want a full license, please contact us.
*
* The exclusive owner of this work is the OpenRate project.
* This work, including all associated documents and components
* is Copyright of the OpenRate project 2006-2015.
*
* The following restrictions apply unless they are expressly relaxed in a
* contractual agreement between the license holder or one of its officially
* assigned agents and you or your organisation:
*
* 1) This work may not be disclosed, either in full or in part, in any form
* electronic or physical, to any third party. This includes both in the
* form of source code and compiled modules.
* 2) This work contains trade secrets in the form of architecture, algorithms
* methods and technologies. These trade secrets may not be disclosed to
* third parties in any form, either directly or in summary or paraphrased
* form, nor may these trade secrets be used to construct products of a
* similar or competing nature either by you or third parties.
* 3) This work may not be included in full or in part in any application.
* 4) You may not remove or alter any proprietary legends or notices contained
* in or on this work.
* 5) This software may not be reverse-engineered or otherwise decompiled, if
* you received this work in a compiled form.
* 6) This work is licensed, not sold. Possession of this software does not
* imply or grant any right to you.
* 7) You agree to disclose any changes to this work to the copyright holder
* and that the copyright holder may include any such changes at its own
* discretion into the work
* 8) You agree not to derive other works from the trade secrets in this work,
* and that any such derivation may make you liable to pay damages to the
* copyright holder
* 9) You agree to use this software exclusively for evaluation purposes, and
* that you shall not use this software to derive commercial profit or
* support your business or personal activities.
*
* This software is provided "as is" and any expressed or impled warranties,
* including, but not limited to, the impled warranties of merchantability
* and fitness for a particular purpose are disclaimed. In no event shall
* The OpenRate Project or its officially assigned agents be liable to any
* direct, indirect, incidental, special, exemplary, or consequential damages
* (including but not limited to, procurement of substitute goods or services;
* Loss of use, data, or profits; or any business interruption) however caused
* and on theory of liability, whether in contract, strict liability, or tort
* (including negligence or otherwise) arising in any way out of the use of
* this software, even if advised of the possibility of such damage.
* This software contains portions by The Apache Software Foundation, Robert
* Half International.
* ====================================================================
*/
package OpenRate.exception;
import java.util.ArrayList;
/**
* The handler class is designed for dealing with failures during plug in
* processing. Since plug ins are executed within one or more threads, they
* cannot propagate errors up the call stack to the main thread. To remedy
* this problem, the ExceptionHandler is made available to all processing
* elements as a way to report critical processing errors. It is shared by all
* the threads (including the main thread running the pipeline) and is checked
* at the end of each cycle so that application shutdown can happen cleanly as
* soon as possible. This is a common pattern for error reporting in a multi-
* threaded environment.
*
* The exception handling strategy in OpenRate is ("*" means that this element
* has an exception handler and deals with exceptions from all lower levels):
*
* Framework(*)
* |
* +---Resources
* |
* +---Pipe(*)
* |
* +---Input Adapter
* |
* +---processing Modules
* |
* +---Output Adapter(s)
*
* - This then means that exceptions that are caused as processing or
* initialisation in a pipeline are normally reported to the exception handler
* for the pipeline. These are then reported in the Error log and/or the
* pipeline log.
*
* - Exceptions that happen in Caches or other resources normally are reported
* to the exception handler for the framework. These are reported to the Error
* log and/or the Framework log.
*
* Normal run time log messages (for exceptions that are "expected" or
* functional application level error messages are not to be reported via
* exception, but by writing to the log directly.
*
* In order to keep the pipeline and framework logs clean, we report the
* exception text to the log, and the stack trace to the Error log. In a well
* running system, the Error log should remain empty.
*
* Any exceptions thrown in modules that are not directly part of the above
* structure (e.g. Utilities or records) are not to report to the exception
* handler directly, but instead propagate the exception back up to the
* relevant pipeline or framework level for reporting there.
*
* NOTE: This does not mean that you can't report exceptions in a record. It
* means only that the reporting to an exception handler must be managed at
* pipe or framework level. There is therefore no need to have access to an
* exception handler at record or Utility level!
*/
public class ExceptionHandler
{
/**
* list of reported exceptions. Normally the pipeline will
* shutdown as soon as a fatal error occurs, but the timing
* may allow for multiple exceptions to be reported before
* the pipeline is notified and/or can react. Therefore a list
* is maintained to store any subsequent errors reporting
* during the interim.
*/
private ArrayList<Exception> exceptionQueue = new ArrayList<>();
// lock for thread safety.
private final Object lock = new Object();
private boolean hasError = false;
/**
* Default constructor
*/
public ExceptionHandler()
{
super();
}
/**
* Clear down reported exceptions
*/
public void clearExceptions()
{
synchronized (lock)
{
exceptionQueue.clear();
hasError = false;
}
}
/**
* Method used by modules to report a fatal error.
*
* @param exception The processing exception to report
*/
public void reportException(ProcessingException exception)
{
synchronized (lock)
{
exceptionQueue.add(exception);
hasError = true;
}
}
/**
* Method used by modules to report a fatal error.
*
* @param exception The processing exception to report
*/
public void reportException(InitializationException exception)
{
synchronized (lock)
{
exceptionQueue.add(exception);
hasError = true;
}
}
/**
* Re-throw the first reported exception.
*
* @throws ProcessingException
*/
public void rethrowException() throws ProcessingException
{
synchronized (lock)
{
// locks are re-entrant, it's ok that hasError is
// synchronized on 'lock' also.
if (hasError())
{
// get first exception
throw (ProcessingException) exceptionQueue.get(0);
}
}
}
/**
* Get a list of all the exceptions. We get a copy rather than the list
* itself so that we do not get concurrent access problems.
*
* @return The exception list
*/
public ArrayList<Exception> getExceptionList()
{
synchronized (lock)
{
// locks are re-entrant, it's ok that hasError is
// synchronized on 'lock' also.
// We make a copy to avoid concurrent modification exception
ArrayList<Exception> queueCopy = new ArrayList<>();
queueCopy.addAll(exceptionQueue);
return queueCopy;
}
}
/**
* True/False flag allowing the pipeline components to recognize
* when a fatal error has been reported.
*
* @return true if a fatal error has been reported
*/
public boolean hasError()
{
synchronized (lock)
{
return this.hasError;
}
}
}