Package org.apache.commons.configuration2.builder

Class ReloadingFileBasedConfigurationBuilder<T extends FileBasedConfiguration>

java.lang.Object
org.apache.commons.configuration2.builder.BasicConfigurationBuilder<T>
org.apache.commons.configuration2.builder.FileBasedConfigurationBuilder<T>
org.apache.commons.configuration2.builder.ReloadingFileBasedConfigurationBuilder<T>
Type Parameters:
T - the concrete type of Configuration objects created by this builder
All Implemented Interfaces:
ConfigurationBuilder<T>, EventSource, ReloadingControllerSupport
public class ReloadingFileBasedConfigurationBuilder<T extends FileBasedConfiguration> extends FileBasedConfigurationBuilder<T> implements ReloadingControllerSupport

A specialized ConfigurationBuilder implementation which can handle configurations read from a FileHandler and supports reloading.

This builder class exposes a ReloadingController object controlling reload operations on the file-based configuration produced as result object. For the FileHandler defining the location of the configuration a configurable ReloadingDetector is created and associated with the controller. So changes on the source file can be detected. When ever such a change occurs, the result object of this builder is reset. This means that the next time getConfiguration() is called a new Configuration object is created which is loaded from the modified file.

Client code interested in notifications can register a listener at this builder to receive reset events. When such an event is received the new result object can be requested. This way client applications can be sure to work with an up-to-date configuration. It is also possible to register a listener directly at the ReloadingController.

This builder does not actively trigger the ReloadingController to perform a reload check. This has to be done by an external component, e.g. a timer.

Since:
2.0

  • Field Details

    • DEFAULT_DETECTOR_FACTORY

      private static final ReloadingDetectorFactory DEFAULT_DETECTOR_FACTORY
      The default factory for creating reloading detector objects.

    • reloadingController

      private final ReloadingController reloadingController
      The reloading controller associated with this object.

    • resultReloadingDetector

      private volatile ReloadingDetector resultReloadingDetector
      The reloading detector which does the actual reload check for the current result object. A new instance is created whenever a new result object (and thus a new current file handler) becomes available. The field must be volatile because it is accessed by the reloading controller probably from within another thread.

  • Constructor Details

    • ReloadingFileBasedConfigurationBuilder

      public ReloadingFileBasedConfigurationBuilder(Class<? extends T> resCls)
      Creates a new instance of ReloadingFileBasedConfigurationBuilder which produces result objects of the specified class.
      Parameters:
      resCls - the result class (must not be null
      Throws:
      IllegalArgumentException - if the result class is null

    • ReloadingFileBasedConfigurationBuilder

      public ReloadingFileBasedConfigurationBuilder(Class<? extends T> resCls, Map<String,Object> params)
      Creates a new instance of ReloadingFileBasedConfigurationBuilder which produces result objects of the specified class and sets initialization parameters.
      Parameters:
      resCls - the result class (must not be null
      params - a map with initialization parameters
      Throws:
      IllegalArgumentException - if the result class is null

    • ReloadingFileBasedConfigurationBuilder

      public ReloadingFileBasedConfigurationBuilder(Class<? extends T> resCls, Map<String,Object> params, boolean allowFailOnInit)
      Creates a new instance of ReloadingFileBasedConfigurationBuilder which produces result objects of the specified class and sets initialization parameters and the allowFailOnInit flag.
      Parameters:
      resCls - the result class (must not be null
      params - a map with initialization parameters
      allowFailOnInit - the allowFailOnInit flag
      Throws:
      IllegalArgumentException - if the result class is null

  • Method Details

    • fetchDetectorFactory

      private static ReloadingDetectorFactory fetchDetectorFactory(FileBasedBuilderParametersImpl params)
      Returns a ReloadingDetectorFactory either from the passed in parameters or a default factory.
      Parameters:
      params - the current parameters object
      Returns:
      the ReloadingDetectorFactory to be used

    • configure

      public ReloadingFileBasedConfigurationBuilder<T> configure(BuilderParameters... params)
      Appends the content of the specified BuilderParameters objects to the current initialization parameters. Calling this method multiple times will create a union of the parameters provided. This method is overridden here to change the result type. This method is overridden here to change the result type.
      Overrides:
      configure in class FileBasedConfigurationBuilder<T extends FileBasedConfiguration>
      Parameters:
      params - an arbitrary number of objects with builder parameters
      Returns:
      a reference to this builder for method chaining

    • createReloadingController

      private ReloadingController createReloadingController()
      Creates the ReloadingController associated with this object. The controller is assigned a specialized reloading detector which delegates to the detector for the current result object. ( FileHandlerReloadingDetector does not support changing the file handler, and ReloadingController does not support changing the reloading detector; therefore, this level of indirection is needed to change the monitored file dynamically.)
      Returns:
      the new ReloadingController

    • createReloadingDetector

      protected ReloadingDetector createReloadingDetector(FileHandler handler, FileBasedBuilderParametersImpl fbparams) throws ConfigurationException
      Creates a ReloadingDetector which monitors the passed in FileHandler. This method is called each time a new result object is created with the current FileHandler. This implementation checks whether a ReloadingDetectorFactory is specified in the current parameters. If this is the case, it is invoked. Otherwise, a default factory is used to create a FileHandlerReloadingDetector object. Note: This method is called from a synchronized block.
      Parameters:
      handler - the current FileHandler
      fbparams - the object with parameters related to file-based builders
      Returns:
      a ReloadingDetector for this FileHandler
      Throws:
      ConfigurationException - if an error occurs

    • createReloadingDetectorForController

      private ReloadingDetector createReloadingDetectorForController()
      Creates a ReloadingDetector wrapper to be passed to the associated ReloadingController. This detector wrapper simply delegates to the current ReloadingDetector if it is available.
      Returns:
      the wrapper ReloadingDetector

    • getReloadingController

      public ReloadingController getReloadingController()
      Gets the ReloadingController associated with this builder. This controller is directly created. However, it becomes active (i.e. associated with a meaningful reloading detector) not before a result object was created.
      Specified by:
      getReloadingController in interface ReloadingControllerSupport
      Returns:
      the ReloadingController

    • initFileHandler

      protected void initFileHandler(FileHandler handler) throws ConfigurationException
      Initializes the new current FileHandler. When a new result object is created, a new FileHandler is created, too, and associated with the result object. This new handler is passed to this method. If a location is defined, the result object is loaded from this location. Note: This method is called from a synchronized block. This implementation also takes care that a new ReloadingDetector for the new current FileHandler is created. Also, the reloading controller's reloading state has to be reset; after the creation of a new result object changes in the underlying configuration source have to be monitored again.
      Overrides:
      initFileHandler in class FileBasedConfigurationBuilder<T extends FileBasedConfiguration>
      Parameters:
      handler - the new current FileHandler
      Throws:
      ConfigurationException - if an error occurs