Class AbstractImageSessionContext

java.lang.Object
org.apache.xmlgraphics.image.loader.impl.AbstractImageSessionContext
All Implemented Interfaces:
ImageSessionContext
Direct Known Subclasses:
DefaultImageSessionContext

public abstract class AbstractImageSessionContext extends Object implements ImageSessionContext
Abstract base class for classes implementing ImageSessionContext. This class provides all the special treatment for Source creation, i.e. it provides optimized Source objects where possible.
  • Constructor Details

    • AbstractImageSessionContext

      public AbstractImageSessionContext()
    • AbstractImageSessionContext

      public AbstractImageSessionContext(AbstractImageSessionContext.FallbackResolver fallbackResolver)
      Parameters:
      fallbackResolver - the fallback resolution mechanism to be used when simply getting an InputStream that backs a Source isn't possible.
  • Method Details

    • resolveURI

      protected abstract Source resolveURI(String uri)
      Attempts to resolve the given URI.
      Parameters:
      uri - URI to access
      Returns:
      A Source object, or null if the URI cannot be resolved.
    • newSource

      public Source newSource(String uri)
      Attempts to create a Source object from the given URI. If possible this method returns an ImageSource instance which provides the best possible method to access the image.
      Specified by:
      newSource in interface ImageSessionContext
      Parameters:
      uri - URI to access
      Returns:
      A Source object, or null if the URI cannot be resolved.
    • createImageInputStream

      protected static ImageInputStream createImageInputStream(InputStream in) throws IOException
      Throws:
      IOException
    • toFile

      public static File toFile(URL url)
      Convert from a URL to a File.

      This method will decode the URL. Syntax such as file:///my%20docs/file.txt will be correctly decoded to /my docs/file.txt.

      Note: this method has been copied over from Apache Commons IO and enhanced to support UNC paths.

      Parameters:
      url - the file URL to convert, null returns null
      Returns:
      the equivalent File object, or null if the URL's protocol is not file
      Throws:
      IllegalArgumentException - if the file is incorrectly encoded
    • getSource

      public Source getSource(String uri)
      Returns a Source object for a URI. This method is not guaranteed to return an instance. Implementations normally return already created Sources from a pool (normally populated through the ImageSessionContext.returnSource(String, Source) method).
      Specified by:
      getSource in interface ImageSessionContext
      Parameters:
      uri - the URI of the image
      Returns:
      the Source object to load the image from, or null
    • needSource

      public Source needSource(String uri) throws FileNotFoundException
      Returns a Source object for a URI. This method is guaranteed to return a Source object. If the image cannot be found, a FileNotFoundException is thrown.
      Specified by:
      needSource in interface ImageSessionContext
      Parameters:
      uri - the URI of the image
      Returns:
      the Source object to load the image from
      Throws:
      FileNotFoundException - if the image cannot be found
    • returnSource

      public void returnSource(String uri, Source src)
      Returns a Source object to a pool. This is provided in order to reuse a Source object between the preloading and the final loading of an image. Note that not all Source objects can be reused! Non-reusable Sources are discarded.
      Specified by:
      returnSource in interface ImageSessionContext
      Parameters:
      uri - the URI of the image
      src - the Source object belonging to the URI
    • isReusable

      protected boolean isReusable(Source src)
      Indicates whether a Source is reusable. A Source object is reusable if it's an ImageSource (containing an ImageInputStream) or a DOMSource.
      Parameters:
      src - the Source object
      Returns:
      true if the Source is reusable