Class FileHandlerReloadingDetector
- All Implemented Interfaces:
ReloadingDetector
- Direct Known Subclasses:
VFSFileHandlerReloadingDetector
A specialized implementation of ReloadingDetector which monitors a file specified by a FileHandler.
An instance of this class is passed a FileHandler at construction time. Each time the
isReloadingRequired() method is called, it checks whether the FileHandler points to a valid location.
If this is the case, the file's last modification time is obtained and compared with the last stored time. If it has
changed, a reload operation should be performed.
Because file I/O may be expensive it is possible to configure a refresh delay as a time in milliseconds. This is the
minimum interval between two checks. If the isReloadingRequired() method is called in shorter intervals, it
does not perform a check, but directly returns false.
To initialize an instance either isReloadingRequired() or reloadingPerformed() can be called. The
first call of isReloadingRequired does not perform a check, but obtains the initial modification date of the
monitored file. reloadingPerformed() always obtains the file's modification date and stores it internally.
- Since:
- 2.0
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Constructor Summary
ConstructorsConstructorDescriptionCreates a new instance ofFileHandlerReloadingDetectorwith an uninitializedFileHandlerobject.FileHandlerReloadingDetector(FileHandler handler) Creates a new instance ofFileHandlerReloadingDetectorand initializes it with theFileHandlerto monitor and a default refresh delay.FileHandlerReloadingDetector(FileHandler handler, long refreshDelayMillis) Creates a new instance ofFileHandlerReloadingDetectorand initializes it with theFileHandlerto monitor and the refresh delay. -
Method Summary
Modifier and TypeMethodDescriptionprotected FilegetFile()Gets theFileobject which is monitored by this object.Gets theFileHandlerassociated with this object.protected longGets the date of the last modification of the monitored file.longGets the refresh delay.booleanChecks whether all criteria for a reload operation are fulfilled.voidrefresh()Tells this implementation that the internally stored state should be refreshed.voidNotifies this object that a reload operation has been performed.protected voidupdateLastModified(long timeMillis) Updates the last modification date of the monitored file.
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Constructor Details
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FileHandlerReloadingDetector
public FileHandlerReloadingDetector()Creates a new instance ofFileHandlerReloadingDetectorwith an uninitializedFileHandlerobject. The file to be monitored has to be set later by manipulating the handler object returned bygetFileHandler(). -
FileHandlerReloadingDetector
Creates a new instance ofFileHandlerReloadingDetectorand initializes it with theFileHandlerto monitor and a default refresh delay.- Parameters:
handler- theFileHandlerassociated with this detector (can be null)
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FileHandlerReloadingDetector
Creates a new instance ofFileHandlerReloadingDetectorand initializes it with theFileHandlerto monitor and the refresh delay. The handler is directly used, no copy is created. So it is possible to change the location monitored by manipulating theFileHandlerobject.- Parameters:
handler- theFileHandlerassociated with this detector (can be null)refreshDelayMillis- the refresh delay; a value of 0 means that a check is performed in all cases
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Method Details
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getFile
Gets theFileobject which is monitored by this object. This method is called every time the file's last modification time is needed. If it returns null, no check is performed. This base implementation obtains theFilefrom the associatedFileHandler. It can also deal with URLs to jar files.- Returns:
- the
Fileto be monitored (can be null)
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getFileHandler
Gets theFileHandlerassociated with this object. The underlying handler is directly returned, so changing its location also changes the file monitored by this detector.- Returns:
- the associated
FileHandler
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getLastModificationDate
Gets the date of the last modification of the monitored file. A return value of 0 indicates, that the monitored file does not exist.- Returns:
- the last modification date in milliseconds.
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getRefreshDelay
Gets the refresh delay. This is a time in milliseconds. TheisReloadingRequired()method first checks whether the time since the previous check is more than this value in the past. Otherwise, no check is performed. This is a means to limit file I/O caused by this class.- Returns:
- the refresh delay used by this object
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isReloadingRequired
Checks whether all criteria for a reload operation are fulfilled. This method is called by external components to find out when reloading should take place. This implementation checks whether the associatedFileHandlerpoints to a valid file and whether the last modification time of this time has changed since the last check. The refresh delay is taken into account, too; a check is only performed if at least this time has passed since the last check.- Specified by:
isReloadingRequiredin interfaceReloadingDetector- Returns:
- true if a reload operation should be performed, false otherwise
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refresh
Tells this implementation that the internally stored state should be refreshed. This method is intended to be called after the creation of an instance. -
reloadingPerformed
Notifies this object that a reload operation has been performed. This method is called afterreloadingRequired()has returned true. It can be used to reset internal state in order to detect the next reload operation. This implementation updates the internally stored last modification date with the current modification date of the monitored file. So the next change is detected when this file is changed again.- Specified by:
reloadingPerformedin interfaceReloadingDetector
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updateLastModified
Updates the last modification date of the monitored file. The need for a reload is detected only if the file's modification date is different from this value.- Parameters:
timeMillis- the new last modification date
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