Package ch.cern.dirq

Class QueueNull

  • All Implemented Interfaces:
    Queue, java.lang.Iterable<java.lang.String>
    public class QueueNull
extends java.lang.Object
implements Queue
    QueueNull - object oriented interface to a null directory based queue.
    The goal of this module is to offer a null queue system using the same API as the other directory queue implementations. The queue will behave like a black hole: added data will disappear immediately so the queue will therefore always appear empty.
    This can be used for testing purposes or to discard data like one would do on Unix by redirecting output to /dev/null.
    Please refer to Queue for general information about directory queues.
    All the methods that add data will return an invalid element name.
    All the methods that work on elements will throw an UnsupportedOperationException exception.

    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description
      private static class  QueueNull.QueueNullIterator
      Iterator for the null directory queue (private).

    • Constructor Summary

      Constructors 
      Constructor Description
      QueueNull()
      Constructor for the null directory queue.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      java.lang.String add​(byte[] data)
      Add byte array data to the queue.
      java.lang.String add​(java.lang.String data)
      Add String data to the queue.
      java.lang.String addPath​(java.lang.String path)
      Add the given file (identified by its path) to the queue and return the corresponding element name, the file must be on the same filesystem and will be moved to the queue.
      int count()
      Return the number of elements in the queue.
      java.lang.String get​(java.lang.String name)
      Get the given locked element as String data.
      byte[] getAsByteArray​(java.lang.String name)
      Get the given locked element as byte array data.
      java.lang.String getId()
      Return a unique identifier for the queue.
      java.lang.String getPath​(java.lang.String path)
      Get the path of the given locked element.
      java.lang.String getQueuePath()
      Return the path of the queue.
      java.util.Iterator<java.lang.String> iterator()
      Iterator for the null directory queue.
      boolean lock​(java.lang.String name)
      Lock an element in permissive mode.
      boolean lock​(java.lang.String name, boolean permissive)
      Lock an element.
      void purge()
      Purge the queue by removing unused intermediate directories, removing too old temporary elements and unlocking too old locked elements (aka staled locks); note: this can take a long time on queues with many elements.
      void purge​(int maxLock)
      Purge the queue by removing unused intermediate directories, removing too old temporary elements and unlocking too old locked elements (aka staled locks); note: this can take a long time on queues with many elements.
      void purge​(int maxLock, int maxTemp)
      Purge the queue by removing unused intermediate directories, removing too old temporary elements and unlocking too old locked elements (aka staled locks); note: this can take a long time on queues with many elements.
      void remove​(java.lang.String name)
      Remove a locked element from the queue.
      boolean unlock​(java.lang.String name)
      Unlock an element in non-permissive mode.
      boolean unlock​(java.lang.String name, boolean permissive)
      Unlock an element.

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

      • Methods inherited from interface java.lang.Iterable

        forEach, spliterator

    • Constructor Detail

      • QueueNull

        public QueueNull()
        Constructor for the null directory queue.

    • Method Detail

      • getQueuePath

        public java.lang.String getQueuePath()
        Description copied from interface: Queue
        Return the path of the queue.
        Specified by:
        getQueuePath in interface Queue
        Returns:
        queue path

      • getId

        public java.lang.String getId()
        Description copied from interface: Queue
        Return a unique identifier for the queue.
        Specified by:
        getId in interface Queue
        Returns:
        unique queue identifier

      • add

        public java.lang.String add​(java.lang.String data)
        Description copied from interface: Queue
        Add String data to the queue.
        Specified by:
        add in interface Queue
        Parameters:
        data - data to be added
        Returns:
        element name (as directory_name/file_name)

      • add

        public java.lang.String add​(byte[] data)
        Description copied from interface: Queue
        Add byte array data to the queue.
        Specified by:
        add in interface Queue
        Parameters:
        data - data to be added
        Returns:
        element name (as directory_name/file_name)

      • addPath

        public java.lang.String addPath​(java.lang.String path)
                         throws java.io.IOException
        Description copied from interface: Queue
        Add the given file (identified by its path) to the queue and return the corresponding element name, the file must be on the same filesystem and will be moved to the queue.
        Specified by:
        addPath in interface Queue
        Parameters:
        path - path of the file to be added
        Returns:
        element name (as directory_name/file_name)
        Throws:
        java.io.IOException - if any file operation fails

      • get

        public java.lang.String get​(java.lang.String name)
        Description copied from interface: Queue
        Get the given locked element as String data.
        Specified by:
        get in interface Queue
        Parameters:
        name - name of the element to be retrieved
        Returns:
        data associated with the given element

      • getAsByteArray

        public byte[] getAsByteArray​(java.lang.String name)
        Description copied from interface: Queue
        Get the given locked element as byte array data.
        Specified by:
        getAsByteArray in interface Queue
        Parameters:
        name - name of the element to be retrieved
        Returns:
        data associated with the given element

      • getPath

        public java.lang.String getPath​(java.lang.String path)
        Description copied from interface: Queue
        Get the path of the given locked element.
        This pathFile can be read but not removed, you must use the remove() method for this purpose.
        Specified by:
        getPath in interface Queue
        Parameters:
        path - name of the element
        Returns:
        path of the element

      • lock

        public boolean lock​(java.lang.String name)
        Description copied from interface: Queue
        Lock an element in permissive mode.
        Specified by:
        lock in interface Queue
        Parameters:
        name - name of the element to be locked
        Returns:
        true on success, false if the element could not be locked

      • lock

        public boolean lock​(java.lang.String name,
                    boolean permissive)
        Description copied from interface: Queue
        Lock an element.
        Specified by:
        lock in interface Queue
        Parameters:
        name - name of the element to be locked
        permissive - work in permissive mode
        Returns:
        true on success, false if the element could not be locked

      • unlock

        public boolean unlock​(java.lang.String name)
        Description copied from interface: Queue
        Unlock an element in non-permissive mode.
        Specified by:
        unlock in interface Queue
        Parameters:
        name - name of the element to be unlocked
        Returns:
        true on success, false if the element could not be unlocked

      • unlock

        public boolean unlock​(java.lang.String name,
                      boolean permissive)
        Description copied from interface: Queue
        Unlock an element.
        Specified by:
        unlock in interface Queue
        Parameters:
        name - name of the element to be unlocked
        permissive - work in permissive mode
        Returns:
        true on success, false if the element could not be unlocked

      • remove

        public void remove​(java.lang.String name)
        Description copied from interface: Queue
        Remove a locked element from the queue.
        Specified by:
        remove in interface Queue
        Parameters:
        name - name of the element to be removed

      • count

        public int count()
        Description copied from interface: Queue
        Return the number of elements in the queue.
        Locked elements are counted but temporary elements are not.
        Specified by:
        count in interface Queue
        Returns:
        number of elements in the queue

      • purge

        public void purge()
        Description copied from interface: Queue
        Purge the queue by removing unused intermediate directories, removing too old temporary elements and unlocking too old locked elements (aka staled locks); note: this can take a long time on queues with many elements.
        It uses default value for maxTemp and maxLock
        Specified by:
        purge in interface Queue

      • purge

        public void purge​(int maxLock)
        Description copied from interface: Queue
        Purge the queue by removing unused intermediate directories, removing too old temporary elements and unlocking too old locked elements (aka staled locks); note: this can take a long time on queues with many elements.
        Specified by:
        purge in interface Queue
        Parameters:
        maxLock - maximum time for a locked element (in seconds); if set to 0, locked elements will not be unlocked; if set to null, the object's default value will be used

      • purge

        public void purge​(int maxLock,
                  int maxTemp)
        Description copied from interface: Queue
        Purge the queue by removing unused intermediate directories, removing too old temporary elements and unlocking too old locked elements (aka staled locks); note: this can take a long time on queues with many elements.
        Specified by:
        purge in interface Queue
        Parameters:
        maxLock - maximum time for a locked element (in seconds); if set to 0, locked elements will not be unlocked; if set to null, the object's default value will be used
        maxTemp - maximum time for a temporary element (in seconds); if set to 0, temporary elements will not be removed if set to null, the object's default value will be used

      • iterator

        public java.util.Iterator<java.lang.String> iterator()
        Iterator for the null directory queue.
        Specified by:
        iterator in interface java.lang.Iterable<java.lang.String>