Class DynamicConfigHandler
- All Implemented Interfaces:
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:
- handler
- The name of the initial sub-handler that this
DynamicConfigHandler
will use to process requests. When new properties are uploaded, the sub-handler will be replaced with whatever is specified in the newly uploadedhandler
property. - prefix
- Only URLs beginning with this string will be redirected to the
sub-handler. This property belongs to the
DynamicConfigHandler
and is not changed when new properties are uploaded. The default is "/". - config
- URLs beginning with this prefix can be used to upload or download
new configuration properties to this handler, which will also
dynamically change which sub-handler is installed. This property
belongs to the
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.
- Version:
- 2.1, 02/10/01
- Author:
- Colin Stevens (colin.stevens@sun.com)
-
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionboolean
Initializes thisDynamicConfigHandler
by loading the initial handler.boolean
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.
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Constructor Details
-
DynamicConfigHandler
public DynamicConfigHandler()
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-
Method Details
-
init
Initializes thisDynamicConfigHandler
by loading the initial handler. An initial handler does not need to be defined, however, since the handler configuration can be downloaded later.- Specified by:
init
in interfaceHandler
- Parameters:
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.- Returns:
false
if the initial handler was specified but could not be initialized,true
otherwise.
-
respond
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. If the "Host:" request header was not specified, or named a virtual host that was not initialized ininit
from the list of virtual hosts, this method returns without handling the request.- Specified by:
respond
in interfaceHandler
- Parameters:
request
- The HTTP request to be forwarded to one of the sub-servers.- Returns:
true
if the sub-server handled the message,false
if it did not.false
is also returned if the "Host:" was unspecified or unknown.- Throws:
IOException
- if there was an I/O error while sending the response to the client. Typically, in that case, theServer
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 aFileNotFoundException
due to not being able to open a file). In that case, theHandler
's duty is to turn thatIOException
into a HTTP response indicating, in this case, that a file could not be found.
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