Package org.apache.commons.configuration2.io

Class FileLocatorUtils

java.lang.Object
org.apache.commons.configuration2.io.FileLocatorUtils
public final class FileLocatorUtils extends Object

A utility class providing helper methods related to locating files.

The methods of this class are used behind the scenes when retrieving configuration files based on different criteria, e.g. URLs, files, or more complex search strategies. They also implement functionality required by the default FileSystem implementations. Most methods are intended to be used internally only by other classes in the io package.

Since:
2.0

  • Field Details

    • DEFAULT_FILE_SYSTEM

      public static final FileSystem DEFAULT_FILE_SYSTEM
      Constant for the default FileSystem. This file system is used by operations of this class if no specific file system is provided. An instance of DefaultFileSystem is used.

    • DEFAULT_LOCATION_STRATEGY

      public static final FileLocationStrategy DEFAULT_LOCATION_STRATEGY
      Constant for the default FileLocationStrategy. This strategy is used by the locate() method if the passed in FileLocator does not define its own location strategy. The default location strategy is roughly equivalent to the search algorithm used in version 1.x of Commons Configuration (there it was hard-coded though). It behaves in the following way when passed a FileLocator:
      • If the FileLocator has a defined URL, this URL is used as the file's URL (without any further checks).
      • Otherwise, base path and file name stored in the FileLocator are passed to the current FileSystem's locateFromURL() method. If this results in a URL, it is returned.
      • Otherwise, if the locator's file name is an absolute path to an existing file, the URL of this file is returned.
      • Otherwise, the concatenation of base path and file name is constructed. If this path points to an existing file, its URL is returned.
      • Otherwise, a sub directory of the current user's home directory as defined by the base path is searched for the referenced file. If the file can be found there, its URL is returned.
      • Otherwise, the base path is ignored, and the file name is searched in the current user's home directory. If the file can be found there, its URL is returned.
      • Otherwise, a resource with the name of the locator's file name is searched in the classpath. If it can be found, its URL is returned.
      • Otherwise, the strategy gives up and returns null indicating that the file cannot be resolved.

  • Method Details

    • fileFromURL

      public static File fileFromURL(URL url)
      Tries to convert the specified URL to a file object. If this fails, null is returned.
      Parameters:
      url - the URL
      Returns:
      the resulting file object

    • fileLocator

      public static FileLocator.FileLocatorBuilder fileLocator()
      Returns an uninitialized FileLocatorBuilder which can be used for the creation of a FileLocator object. This method provides a convenient way to create file locators using a fluent API as in the following example: 
       FileLocator locator = FileLocatorUtils.fileLocator().basePath(myBasePath).fileName("test.xml").create();
      Returns:
      a builder object for defining a FileLocator

    • fileLocator

      public static FileLocator.FileLocatorBuilder fileLocator(FileLocator src)
      Returns a FileLocatorBuilder which is already initialized with the properties of the passed in FileLocator. This builder can be used to create a FileLocator object which shares properties of the original locator (e.g. the FileSystem or the encoding), but points to a different file. An example use case is as follows: 
       FileLocator loc1 = ...
 FileLocator loc2 = FileLocatorUtils.fileLocator(loc1)
     .setFileName("anotherTest.xml")
     .create();
      Parameters:
      src - the source FileLocator (may be null)
      Returns:
      an initialized builder object for defining a FileLocator

    • fromMap

      public static FileLocator fromMap(Map<String,?> map)
      Creates a new FileLocator object with the properties defined in the given map. The map must be conform to the structure generated by the put(FileLocator, Map) method; unexpected data can cause ClassCastException exceptions. The map can be null, then an uninitialized FileLocator is returned.
      Parameters:
      map - the map
      Returns:
      the new FileLocator
      Throws:
      ClassCastException - if the map contains invalid data

    • fullyInitializedLocator

      public static FileLocator fullyInitializedLocator(FileLocator locator)
      Returns a FileLocator object based on the passed in one whose location is fully defined. This method ensures that all components of the FileLocator pointing to the file are set in a consistent way. In detail it behaves as follows:
      • If the FileLocator has already all components set which define the file, it is returned unchanged. Note: It is not checked whether all components are really consistent!
      • locate(FileLocator) is called to determine a unique URL pointing to the referenced file. If this is successful, a new FileLocator is created as a copy of the passed in one, but with all components pointing to the file derived from this URL.
      • Otherwise, result is null.
      Parameters:
      locator - the FileLocator to be completed
      Returns:
      a FileLocator with a fully initialized location if possible or null

    • isFullyInitialized

      public static boolean isFullyInitialized(FileLocator locator)
      Returns a flag whether all components of the given FileLocator describing the referenced file are defined. In order to reference a file, it is not necessary that all components are filled in (for instance, the URL alone is sufficient). For some use cases however, it might be of interest to have different methods for accessing the referenced file. Also, depending on the filled out properties, there is a subtle difference how the file is accessed: If only the file name is set (and optionally the base path), each time the file is accessed a locate() operation has to be performed to uniquely identify the file. If however the URL is determined once based on the other components and stored in a fully defined FileLocator, it can be used directly to identify the file. If the passed in FileLocator is null, result is false.
      Parameters:
      locator - the FileLocator to be checked (may be null)
      Returns:
      a flag whether all components describing the referenced file are initialized

    • isLocationDefined

      public static boolean isLocationDefined(FileLocator locator)
      Checks whether the specified FileLocator contains enough information to locate a file. This is the case if a file name or a URL is defined. If the passed in FileLocator is null, result is false.
      Parameters:
      locator - the FileLocator to check
      Returns:
      a flag whether a file location is defined by this FileLocator

    • locate

      public static URL locate(FileLocator locator)
      Locates the provided FileLocator, returning a URL for accessing the referenced file. This method uses a FileLocationStrategy to locate the file the passed in FileLocator points to. If the FileLocator contains itself a FileLocationStrategy, it is used. Otherwise, the default FileLocationStrategy is applied. The strategy is passed the locator and a FileSystem. The resulting URL is returned. If the FileLocator is null, result is null.
      Parameters:
      locator - the FileLocator to be resolved
      Returns:
      the URL pointing to the referenced file or null if the FileLocator could not be resolved
      See Also:

    • locateOrThrow

      public static URL locateOrThrow(FileLocator locator) throws ConfigurationException
      Tries to locate the file referenced by the passed in FileLocator. If this fails, an exception is thrown. This method works like locate(FileLocator); however, in case of a failed location attempt an exception is thrown.
      Parameters:
      locator - the FileLocator to be resolved
      Returns:
      the URL pointing to the referenced file
      Throws:
      ConfigurationException - if the file cannot be resolved

    • put

      public static void put(FileLocator locator, Map<String,Object> map)
      Stores the specified FileLocator in the given map. With the fromMap(Map) method a new FileLocator with the same properties as the original one can be created.
      Parameters:
      locator - the FileLocator to be stored
      map - the map in which to store the FileLocator (must not be null)
      Throws:
      IllegalArgumentException - if the map is null