Package com.luciad.wms.server

Class TLcdWMSModelProvider

java.lang.Object
com.luciad.wms.server.ALcdMultiDimensionalModelProvider
com.luciad.wms.server.TLcdWMSModelProvider
All Implemented Interfaces:
ILcdOGCModelProvider, ILcdDisposable, ILcdModelProvider, AutoCloseable
public class TLcdWMSModelProvider extends ALcdMultiDimensionalModelProvider

Default model provider implementation that delegates to the given ILcdModelDecoderFactory. This implementation

  • supports multi-dimensions
  • adds a model cache

The getModelUpdateSequence method implementation is based on the use of System.currentTimeMillis(). When a model gets decoded, it is assigned an update sequence, based on the current time. When invalidate(String) or invalidateAll() is called, it will trigger the model to be re-decoded, and the model update sequence will be updated. When the model changes in-memory (detected using a model listener), the update sequence will be updated as well.

Since:
2017.0

  • Constructor Details

  • Method Details

    • getModel

      public ILcdModel getModel(String aSourceName, ALcdRequestContext aRequestContext) throws IOException
      Description copied from class: ALcdMultiDimensionalModelProvider
      Returns the ILcdModel corresponding to a source name.

      This method is used for all ALcdWMSLayer objects that don't have any dimensions defined.

      By default, an ILcdModelProvider implementation is used that maintains a cache for all decoded models. To prevent memory problems, it makes use of Soft reference objects, which are cleared at the discretion of the garbage collector in response to memory demand. Soft references are most often used to implement memory-sensitive caches.

      Specified by:
      getModel in interface ILcdModelProvider
      Specified by:
      getModel in interface ILcdOGCModelProvider
      Overrides:
      getModel in class ALcdMultiDimensionalModelProvider
      Parameters:
      aSourceName - the source name of the model.
      aRequestContext - the request context, which is an instance of type TLcdWMSRequestContext. This can be null if the method is called by a process which is not handling a request.
      Returns:
      the ILcdModel corresponding to a source name.
      Throws:
      IOException - if the model can not be returned (because decoding fails).

    • getModelUpdateSequence

      public String getModelUpdateSequence(String aSourceName, ALcdRequestContext aRequestContext) throws IOException
      Description copied from interface: ILcdModelProvider

      Returns the update sequence value associated with the mode identified by the given source name. The update sequence identifies the state of the model.

      The update sequence should comply with a number of conditions:

      • The sequence number should be different from all previous update sequences for this model (if the model has changed).
      • If the model is different, the sequence number should be different as well. Failing to do so will cause malfunctions in combination with caching.
      • If the model doesn't change, the sequence number should also remain the same. Failing to do so lowers the effect of caching, and will result in worse performance.
      • The sequence number should be unique across sessions. Failing to do so may cause malfunctions in combination with caching. An easy mistake to make would for example be to use a counter that is reset when the server is restarted.

      By default, this method always returns "0". This means that the default implementation assumes that models never change. If models change, this method should be implemented differently.

      One way to generate update sequences would be to use a (persistent) counter that gets incremented on every (file system) change. Another way would be to use System.currentTimeMillis() from a correct clock.

      This method must be used by model provider implementations that contain a model cache. The result of this method must be used to invalidate this cache if needed.

      Because of caching on the request/view level, it is possible that the getModel method is called infrequently. This method will need to be called at least once for each request though. This means that for performance reasons, this method needs to have a fast implementation, ideally avoiding any I/O.

      The ALcdWMSLayer class has an update sequence concept as well. See ALcdWMSLayer.getUpdateSequence() for more information.

      Parameters:
      aSourceName - the source name of the model.
      aRequestContext - the request context, which is an instance of type TLcdWMSRequestContext. This can be null if the method is called by a process which is not handling a request.
      Returns:
      the update sequence value associated with the mode identified by the given source name.
      Throws:
      IOException - if the update sequence can not be determined

    • invalidate

      public void invalidate(String aSourceName)
      Clears the model cache for the given source. Note that this will cause getModelUpdateSequence to return a different value for new calls for the given source name.
      Parameters:
      aSourceName - the source name.

    • invalidateAll

      public void invalidateAll()
      Clears the entire model cache. Note that this will cause getModelUpdateSequence to return a different value for new calls for all models.

    • dispose

      public void dispose()
      Description copied from interface: ILcdDisposable

      Disposes of this object and allows it to release any system resources that it is holding.

      The result of calling any other method (other than finalize) on this object subsequent to a call to this method is undefined.

      Specified by:
      dispose in interface ILcdDisposable
      Specified by:
      dispose in interface ILcdOGCModelProvider
      Overrides:
      dispose in class ALcdMultiDimensionalModelProvider