Class DeferredHandler

java.lang.Object
sunlabs.brazil.handler.DeferredHandler
All Implemented Interfaces:
Handler
public class DeferredHandler extends Object implements Handler
Wrap another handler, deferring its initialization until request time. This allows handlers to be configured, but not initialized until a first use is attempted.

Normally, when a handler's class is first resolved, if any of the dependent classes are not available, an error will occur, terminating the server. Using this handler, other handlers can be conditionally configured based on the availability of other specified classes at run time.

NOTE: This functionallity should be integrated into the ChainHandler, eliminating the need for this one.

Request Properties

handler
The token representing the handler to conditionally configure. This is used as the handler's prefix
requires
The names of classes required to be resolvable before configuring the handler
[handler].prefix
Used to trigger the configuration
[handler].class
The name of the handler class.

  • Constructor Details

    • DeferredHandler

      public DeferredHandler()

  • Method Details

    • init

      public boolean init(Server server, String prefix)
      Remember the server for deferred initialization.
      Specified by:
      init in interface Handler
      Parameters:
      server - The HTTP server that created this Handler. Typical Handlers will use Server.props to obtain run-time configuration information.
      prefix - The handlers name. The string this Handler may prepend to all of the keys that it uses to extract configuration information from Server.props. This is set (by the Server and ChainHandler) to help avoid configuration parameter namespace collisions.
      Returns:
      true if this Handler initialized successfully, false otherwise. If false is returned, this Handler should not be used.

    • respond

      public boolean respond(Request request) throws IOException
      Dispatch to the handler, installing it if needed
      Specified by:
      respond in interface Handler
      Parameters:
      request - The Request object that represents the HTTP request.
      Returns:
      true if the request was handled. A request was handled if a response was supplied to the client, typically by calling Request.sendResponse() or Request.sendError.
      Throws:
      IOException - if there was an I/O error while sending the response to the client. Typically, in that case, the Server will (try to) send an error message to the client and then close the client's connection.

      The IOException should not be used to silently ignore problems such as being unable to access some server-side resource (for example getting a FileNotFoundException due to not being able to open a file). In that case, the Handler's duty is to turn that IOException into a HTTP response indicating, in this case, that a file could not be found.