/*
* Copyright 2002-2011 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.scheduling.support;
import java.util.concurrent.Future;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.util.ErrorHandler;
import org.springframework.util.ReflectionUtils;
/**
* Utility methods for decorating tasks with error handling.
*
* <p><b>NOTE:</b> This class is intended for internal use by Spring's scheduler
* implementations. It is only public so that it may be accessed from
* implementations within other packages. It is <i>not</i> intended for general
* use and may change in the future.
*
* @author Mark Fisher
* @since 3.0
*/
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();
/**
* Decorates the task for error handling. If the provided
* {@link ErrorHandler} is not 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.
*/
static class LoggingErrorHandler implements ErrorHandler {
private final Log logger = LogFactory.getLog(LoggingErrorHandler.class);
public void handleError(Throwable t) {
if (logger.isErrorEnabled()) {
logger.error("Unexpected error occurred in scheduled task.", t);
}
}
}
/**
* An {@link ErrorHandler} implementation that logs the Throwable at error
* level and then propagates it.
*/
static class PropagatingErrorHandler extends LoggingErrorHandler {
public void handleError(Throwable t) {
super.handleError(t);
ReflectionUtils.rethrowRuntimeException(t);
}
}
}