public class DynamicConfigHandler extends java.lang.Object implements Handler
DynamicConfigHandler
allows the user to change the
configuration of the server and its handlers on the fly. This handler
can therefore be used to swap in and out functionality, for example,
by dynamically adding a new AuthHandler
to add a new
form of authentication to a running server.
This handler uses a special set of URLs to allow a new set of configuration properties to be uploaded. The new configuration replaces the old configuration.
The name of another Handler
is supplied when this
DynamicConfigHandler
is initialized. This Handler
is the helper or sub-handler for the DynamicConfigHandler
.
When the DynamicConfigHandler
receives a regular HTTP
request (that matches the URL prefix described below), it redirects
that request to the respond
method of the sub-handler.
The uploaded configuration properties are kept in a separate properties
object from the server's properties. The server's properties
are in fact not accessible from the sub-handler; the sub-handler can
only access and/or change the properties owned by the
DynamicConfigHandler
.
This handler uses the following configuration properties:
DynamicConfigHandler
will use to process requests. When
new properties are uploaded, the sub-handler will be replaced with
whatever is specified in the newly uploaded handler
property.
DynamicConfigHandler
and is not changed when
new properties are uploaded. The default is "/".
DynamicConfigHandler
and is not
changed when new properties are uploaded. The default
is "/config/".
Properties may be uploaded by sending them as "name=value" pairs in the body of a POST or in the "?" query parameters. The URL for uploading properties is "config/set".
The current set of properties may be retrieved from this handler by sending the URL "config/get"
handler=sunlabs.brazil.server.ChainHandler port=8081 log=5 handlers=dyn cgi dyn.class=sunlabs.brazil.server.DynamicConfigHandler dyn.prefix=/sparky/ dyn.config=/config-sparky/ dyn.handler=chain chain.class=sunlabs.brazil.server.ChainHandler chain.handlers=foo baz garply foo.class=sunlabs.brazil.handler.HomeDirHandler foo.home=/home/users/ baz.class=sunlabs.brazil.handler.FileHandler garply.class=sunlabs.brazil.handler.NotFoundHandler garply.root="/errors/" garply.fileName="nofile.html" cgi.class = sunlabs.brazil.handler.CgiHandler . . .These parameters set up a normal
Server
on port 8081,
running a ChainHandler
which dispatches to a
DynamicConfigHandler
and a CgiHandler
.
The DynamicConfigHandler
will listen for HTTP requests
beginning with "/sparky/" and dispatch to its dynamically generated
list of handlers, and listen for requests beginning with "/config-sparky/"
to dynamically change that set of handlers.
To give this DynamicConfigHandler
something to do, an initial
set of handlers is provided with the same prefix ("dyn") as the
DynamicConfigHandler
itself. The prefix is stripped off
those properties and the revised set of properties is passed to the
DynamicConfigHandler
to initialize its dynamically
configurable world.
Constructor and Description |
---|
DynamicConfigHandler() |
Modifier and Type | Method and Description |
---|---|
boolean |
init(Server server,
java.lang.String prefix)
Initializes this
DynamicConfigHandler by loading the
initial handler. |
boolean |
respond(Request request)
Responds to an HTTP request by examining the "Host:" request header
and dispatching to the main handler of the server that handles
that virtual host.
|
public boolean init(Server server, java.lang.String prefix)
DynamicConfigHandler
by loading the
initial handler. An initial handler does not need to be defined,
however, since the handler configuration can be downloaded later.init
in interface Handler
server
- The HTTP server that created this handler.prefix
- A prefix to prepend to all of the keys that this
handler uses to extract configuration information.false
if the initial handler was specified but
could not be initialized, true
otherwise.public boolean respond(Request request) throws java.io.IOException
init
from the list of virtual hosts, this method returns without
handling the request.respond
in interface Handler
request
- The HTTP request to be forwarded to one of the sub-servers.true
if the sub-server handled the message,
false
if it did not. false
is
also returned if the "Host:" was unspecified or unknown.java.io.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.