application.preview.DocumentWatcher Maven / Gradle / Ivy
package application.preview;
import java.io.File;
import java.util.logging.Logger;
/**
* Provides a runnable that performs an action whenever
* the specified file's modified date is updated to a later
* date.
* @author Joel Håkansson
*
*/
abstract class DocumentWatcher implements Runnable {
private static final Logger logger = Logger.getLogger(DocumentWatcher.class.getCanonicalName());
protected final File file;
private final long pollTime;
private long modified;
/**
* Creates a new document watcher for the specified file.
* @param input the file to watch
*/
DocumentWatcher(File input) {
this(input, 1000);
}
/**
* Creates a new document watcher for the specified file and
* poll time.
* @param input the file to watch
* @param pollTime the time to sleep between polling, in milliseconds
*/
DocumentWatcher(File input, long pollTime) {
this.file = input;
this.pollTime = pollTime;
this.modified = input.lastModified();
}
/**
* Returns true if the watcher should stay alive. Unless overridden,
* the file should be monitored as long as it exists.
* @return true if the watcher should stay alive, false otherwise
*/
boolean shouldMonitor() {
return true;
}
/**
* Returns true if the watcher should perform its action at this time.
* Unless overridden, the action should be performed if the file's modified
* date is more recent than what it was last time the action was performed.
* @return true if the watcher should perform its action, false otherwise
*/
boolean shouldPerformAction() {
return file.exists() && modified