Interface Location


  • public interface Location
    A Location represents a URL which may have a default value, may be read only, may or may not have a current value and may be cascaded on to a parent location.

    This interface is not intended to be implemented by clients.

    Since:
    3.0
    Restriction:
    This interface is not intended to be implemented by clients.
    • Field Summary

      Fields 
      Modifier and Type Field Description
      static String CONFIGURATION_FILTER
      Constant which defines the filter string for acquiring the service which specifies the configuration location.
      static String ECLIPSE_HOME_FILTER
      Constant which defines the filter string for acquiring the service which specifies the eclipse home location.
      static String INSTALL_FILTER
      Constant which defines the filter string for acquiring the service which specifies the install location.
      static String INSTANCE_FILTER
      Constant which defines the filter string for acquiring the service which specifies the instance location.
      static String USER_FILTER
      Constant which defines the filter string for acquiring the service which specifies the user location.
    • Method Summary

      All Methods Instance Methods Abstract Methods Deprecated Methods 
      Modifier and Type Method Description
      boolean allowsDefault()
      Returns true if this location allows a default value to be assigned and false otherwise.
      Location createLocation​(Location parent, URL defaultValue, boolean readonly)
      Constructs a new location.
      URL getDataArea​(String path)
      Returns a URL to the specified path within this location.
      URL getDefault()
      Returns the default value of this location if any.
      Location getParentLocation()
      Returns the parent of this location or null if none is available.
      URL getURL()
      Returns the actual URL of this location.
      boolean isLocked()
      Returns true if this location is locked and false otherwise.
      boolean isReadOnly()
      Returns true if this location represents a read only location and false otherwise.
      boolean isSet()
      Returns true if this location has a value and false otherwise.
      boolean lock()
      Attempts to lock this location with a canonical locking mechanism and return true if the lock could be acquired.
      void release()
      Releases the lock on this location.
      boolean set​(URL value, boolean lock)
      Sets and optionally locks the location's value to the given URL.
      boolean set​(URL value, boolean lock, String lockFilePath)
      Sets and optionally locks the location's value to the given URL using the given lock file.
      boolean setURL​(URL value, boolean lock)
      Deprecated.
      use set(URL, boolean) instead.
    • Field Detail

      • INSTANCE_FILTER

        static final String INSTANCE_FILTER
        Constant which defines the filter string for acquiring the service which specifies the instance location.
        Since:
        3.2
      • INSTALL_FILTER

        static final String INSTALL_FILTER
        Constant which defines the filter string for acquiring the service which specifies the install location.
        Since:
        3.2
      • CONFIGURATION_FILTER

        static final String CONFIGURATION_FILTER
        Constant which defines the filter string for acquiring the service which specifies the configuration location.
        Since:
        3.2
      • USER_FILTER

        static final String USER_FILTER
        Constant which defines the filter string for acquiring the service which specifies the user location.
        Since:
        3.2
      • ECLIPSE_HOME_FILTER

        static final String ECLIPSE_HOME_FILTER
        Constant which defines the filter string for acquiring the service which specifies the eclipse home location.
        Since:
        3.4
    • Method Detail

      • allowsDefault

        boolean allowsDefault()
        Returns true if this location allows a default value to be assigned and false otherwise.
        Returns:
        whether or not this location can have a default value assigned
      • getDefault

        URL getDefault()
        Returns the default value of this location if any. If no default is available then null is returned. Note that even locations which allow defaults may still return null.
        Returns:
        the default value for this location or null
      • getParentLocation

        Location getParentLocation()
        Returns the parent of this location or null if none is available.
        Returns:
        the parent of this location or null
      • getURL

        URL getURL()
        Returns the actual URL of this location. If the location's value has been set, that value is returned. If the value is not set and the location allows defaults, the value is set to the default and returned. In all other cases null is returned.
        Returns:
        the URL for this location or null if none
      • isSet

        boolean isSet()
        Returns true if this location has a value and false otherwise.
        Returns:
        boolean value indicating whether or not the value is set
      • isReadOnly

        boolean isReadOnly()
        Returns true if this location represents a read only location and false otherwise. The read only character of a location is not in enforced in any way but rather expresses the intention of the location's creator.
        Returns:
        boolean value indicating whether the location is read only
      • setURL

        boolean setURL​(URL value,
                       boolean lock)
                throws IllegalStateException
        Deprecated.
        use set(URL, boolean) instead.
        Sets and optionally locks the location's value to the given URL. If the location already has a value an exception is thrown. If locking is requested and fails, false is returned and the URL of this location is not set.
        Parameters:
        value - the value of this location
        lock - whether or not to lock this location
        Returns:
        whether or not the location was successfully set and, if requested, locked.
        Throws:
        IllegalStateException - if the location's value is already set
      • set

        boolean set​(URL value,
                    boolean lock)
             throws IllegalStateException,
                    IOException
        Sets and optionally locks the location's value to the given URL. If the location already has a value an exception is thrown. If locking is requested and fails, false is returned and the URL of this location is not set.
        Parameters:
        value - the value of this location
        lock - whether or not to lock this location
        Returns:
        whether or not the location was successfully set and, if requested, locked.
        Throws:
        IllegalStateException - if the location's value is already set
        IOException - if there was an unexpected problem while acquiring the lock
        Since:
        3.4
      • set

        boolean set​(URL value,
                    boolean lock,
                    String lockFilePath)
             throws IllegalStateException,
                    IOException
        Sets and optionally locks the location's value to the given URL using the given lock file. If the location already has a value an exception is thrown. If locking is requested and fails, false is returned and the URL of this location is not set.
        Parameters:
        value - the value of this location
        lock - whether or not to lock this location
        lockFilePath - the path to the lock file. This path will be used to establish locks on this location. The path may be an absolute path or it may be relative to the given URL. If a null value is used then a default lock path will be used for this location.
        Returns:
        whether or not the location was successfully set and, if requested, locked.
        Throws:
        IllegalStateException - if the location's value is already set
        IOException - if there was an unexpected problem while acquiring the lock
        Since:
        3.5
      • lock

        boolean lock()
              throws IOException
        Attempts to lock this location with a canonical locking mechanism and return true if the lock could be acquired. Not all locations can be locked.

        Locking a location is advisory only. That is, it does not prevent other applications from modifying the same location

        Returns:
        true if the lock could be acquired; otherwise false is returned
        Throws:
        IOException - if there was an unexpected problem while acquiring the lock
      • release

        void release()
        Releases the lock on this location. If the location is not already locked, no action is taken.
      • isLocked

        boolean isLocked()
                  throws IOException
        Returns true if this location is locked and false otherwise.
        Returns:
        boolean value indicating whether or not this location is locked
        Throws:
        IOException - if there was an unexpected problem reading the lock
        Since:
        3.4
      • createLocation

        Location createLocation​(Location parent,
                                URL defaultValue,
                                boolean readonly)
        Constructs a new location.
        Parameters:
        parent - the parent location. A null value is allowed.
        defaultValue - the default value of the location. A null value is allowed.
        readonly - true if the location is read-only.
        Returns:
        a new location.
        Since:
        3.4
      • getDataArea

        URL getDataArea​(String path)
                 throws IOException
        Returns a URL to the specified path within this location. The path of the returned URL may not exist yet. It is the responsibility of the client to create the content of the data area returned if it does not exist.

        This method can be used to obtain a private area within the given location. For example use the symbolic name of a bundle to obtain a data area specific to that bundle.

        Clients should check if the location is read only before writing anything to the returned data area. An IOException will be thrown if this method is called and the location URL has not been set and there is no default value for this location.

        Parameters:
        path - the name of the path to get from this location
        Returns:
        the URL to the data area with the specified path.
        Throws:
        IOException - if the location URL is not already set
        Since:
        3.6