package org.frameworkset.schedule;
import java.util.concurrent.Future;
import org.apache.log4j.Logger;
import org.frameworkset.util.ReflectionUtils;
public abstract class TaskUtils {
/**
* An ErrorHandler strategy that will log the Exception but perform
* no further handling. This will suppress the error so that
* subsequent executions of the task will not be prevented.
*/
public static final ErrorHandler LOG_AND_SUPPRESS_ERROR_HANDLER = new LoggingErrorHandler();
/**
* An ErrorHandler strategy that will log at error level and then
* re-throw the Exception. Note: this will typically prevent subsequent
* execution of a scheduled task.
*/
public static final ErrorHandler LOG_AND_PROPAGATE_ERROR_HANDLER = new PropagatingErrorHandler();
/**
* Decorate the task for error handling. If the provided {@link ErrorHandler}
* is not {@code null}, it will be used. Otherwise, repeating tasks will have
* errors suppressed by default whereas one-shot tasks will have errors
* propagated by default since those errors may be expected through the
* returned {@link Future}. In both cases, the errors will be logged.
*/
public static DelegatingErrorHandlingRunnable decorateTaskWithErrorHandler(
Runnable task, ErrorHandler errorHandler, boolean isRepeatingTask) {
if (task instanceof DelegatingErrorHandlingRunnable) {
return (DelegatingErrorHandlingRunnable) task;
}
ErrorHandler eh = (errorHandler != null ? errorHandler : getDefaultErrorHandler(isRepeatingTask));
return new DelegatingErrorHandlingRunnable(task, eh);
}
/**
* Return the default {@link ErrorHandler} implementation based on the boolean
* value indicating whether the task will be repeating or not. For repeating tasks
* it will suppress errors, but for one-time tasks it will propagate. In both
* cases, the error will be logged.
*/
public static ErrorHandler getDefaultErrorHandler(boolean isRepeatingTask) {
return (isRepeatingTask ? LOG_AND_SUPPRESS_ERROR_HANDLER : LOG_AND_PROPAGATE_ERROR_HANDLER);
}
/**
* An {@link ErrorHandler} implementation that logs the Throwable at error
* level. It does not perform any additional error handling. This can be
* useful when suppression of errors is the intended behavior.
*/
private static class LoggingErrorHandler implements ErrorHandler {
private final Logger logger = Logger.getLogger(LoggingErrorHandler.class);
@Override
public void handleError(Throwable t) {
logger.error("Unexpected error occurred in scheduled task.", t);
}
}
/**
* An {@link ErrorHandler} implementation that logs the Throwable at error
* level and then propagates it.
*/
private static class PropagatingErrorHandler extends LoggingErrorHandler {
@Override
public void handleError(Throwable t) {
super.handleError(t);
ReflectionUtils.rethrowRuntimeException(t);
}
}
}