Package org.apache.tapestry5.commons

## Interface Resource

- All Known Implementing Classes:
    `AbstractResource`, `ClasspathResource`, `ClientLocalizationMessageResource`, `ContextResource`, `MessageCatalogResource`, `UrlResource`, `VirtualResource`

      public interface Resource

  Represents a resource on the server that may be used for server side processing, or may be exposed to the client side. Generally, this represents an abstraction on top of files on the class path and files stored in the web application context. Resources are often used as map keys; they should be immutable and should implement hashCode() and equals().

- - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `boolean` | `exists()` | Returns true if the resource exists; if a stream to the content of the file may be opened.
    `Resource` | `forFile​(String relativePath)` | Returns a Resource based on a relative path, relative to the folder containing the resource.
    `Resource` | `forLocale​(Locale locale)` | Returns a localized version of the resource.
    `String` | `getFile()` | Returns the file portion of the Resource path, everything that follows the final forward slash.
    `String` | `getFolder()` | Returns the portion of the path up to the last forward slash; this is the directory or folder portion of the Resource.
    `String` | `getPath()` | Return the path (the combination of folder and file).
    `boolean` | `isVirtual()` | Returns true if the resource is virtual, meaning this is no underlying file.
    `InputStream` | `openStream()` | Opens a stream to the content of the resource, or returns null if the resource does not exist.
    `URL` | `toURL()` | Returns the URL for the resource, or null if it does not exist.
    `Resource` | `withExtension​(String extension)` | Returns a new Resource with the extension changed (or, if the resource does not have an extension, the extension is added).

- - ### Method Detail

    - #### exists

          boolean exists()

      Returns true if the resource exists; if a stream to the content of the file may be opened. A resource exists if `toURL()` returns a non-null value. Starting in release 5.3.4, the result of this is cached. Starting in 5.4, some "virtual resources", may return true even though `toURL()` returns null.
      Returns:
        true if the resource exists, false if it does not

    - #### isVirtual

          boolean isVirtual()

      Returns true if the resource is virtual, meaning this is no underlying file. Many operations are unsupported on virtual resources, including `toURL()`, `forLocale(java.util.Locale)`, `withExtension(String)`, `getFile()`, `getFolder()`, `getPath()`}; these operations will throw an `UnsupportedOperationException`.
      Since:
        5.4

    - #### openStream

          InputStream openStream()
                          throws IOException

      Opens a stream to the content of the resource, or returns null if the resource does not exist. The native input stream supplied by the resource is wrapped in a `BufferedInputStream`.
      Returns:
        an open, buffered stream to the content, if available
      Throws:
        `IOException`

    - #### toURL

          URL toURL()

      Returns the URL for the resource, or null if it does not exist. This value is lazily computed; starting in 5.3.4, subclasses may cache the result. Starting in 5.4, some "virtual resources" may return null.

    - #### forLocale

          Resource forLocale​(Locale locale)

      Returns a localized version of the resource. May return null if no such resource exists. Starting in release 5.3.4, the result of this method is cached internally.

    - #### forFile

          Resource forFile​(String relativePath)

      Returns a Resource based on a relative path, relative to the folder containing the resource. Understands the "." (current folder) and ".." (parent folder) conventions, and treats multiple sequential slashes as a single slash. Virtual resources (resources fabricated at runtime) return themselves.

    - #### withExtension

          Resource withExtension​(String extension)

      Returns a new Resource with the extension changed (or, if the resource does not have an extension, the extension is added). The new Resource may not exist (that is, `toURL()` may return null.
      Parameters:
        `extension` - to apply to the resource, such as "html" or "properties"
      Returns:
        the new resource

    - #### getFolder

          String getFolder()

      Returns the portion of the path up to the last forward slash; this is the directory or folder portion of the Resource.

    - #### getFile

          String getFile()

      Returns the file portion of the Resource path, everything that follows the final forward slash. Starting in 5.4, certain kinds of "virtual resources" may return null here.

    - #### getPath

          String getPath()

      Return the path (the combination of folder and file). Starting in 5.4, certain "virtual resources", may return an arbitrary value here.