sunlabs.brazil.handler
Class MultiHostHandler

java.lang.Object
  sunlabs.brazil.handler.MultiHostHandler (view source)

All Implemented Interfaces:

Handler

Direct Known Subclasses:

RestartingMultiHostHandler

public class MultiHostHandler
extends Object
implements Handler

The MultiHostHandler allows the user to handle a set of host names that are all running on the same IP address. This handler looks at the http "Host" header and redispatches the request to the appropriate sub-server.

Only the main server is actually listening to the port on the specified IP address. The sub-servers are not running in separate threads. Indeed, they are not "running" at all. They exist merely as a convenient bag to hold each of the server-specific configuration parameters.

The respond method of the main handler for the appropriate sub-server is called directly from the respond method of this handler.

This handler uses the following configuration parameters:

servers

The list of prefixes for the other servers. Each server will be initialized from the main server.props with the specified prefix. In this way, the configuration parameters for all the sub-servers can be stored in the same Properties object.

prefix.host

Each server is started with a given prefix. The property prefix.host specifies a Glob pattern for a virtual hostname the server will be expected to handle. If this property is not specified, the server's virtual hostname will just be prefix. If multiple host patterns could match a given "Host" header, the first match in the "servers" list matches first.

prefix.handler

The main handler for the server with the given prefix. If this property is not specified, it defaults to the FileHandler.

prefix.config

Read in the file specified by "config" to initialize this sub-server's server properties. The file is expected to be in java properties format. If not specified, this sub-server shares a copy of the main server's properties, otherwise, the main server's properties are used as the "default". If this property is specified and no config file is found, then the sub-server isn't started.

The property "root", if included in the "config" file, is treated specially: If it does not represent an absolute path, then it is resolved relative to the main server's root.

prefix.log

The log level for the server with the given prefix. If this property is not specified, it defaults to the log level of the parent server. A sample set of configuration parameters illustrating how to use this handler follows:

 handler=host
 port=8081
 log=5
 
 host.class=sunlabs.brazil.server.MultiHostHandler
 host.servers=mars jupiter saturn
 
 mars.host=www.mars.com
 mars.log=2
 mars.handler=mars.file
 mars.file.class=sunlabs.brazil.server.FileHandler
 mars.file.root=public_html/mars
 
 jupiter.host=jupiter.planet.org
 jupiter.handler=sunlabs.brazil.server.FileHandler
 jupiter.root=public_html/jupiter
 
 saturn.host=*.saturn.planet.org
 saturn.handler=sunlabs.brazil.server.FileHandler
 saturn.root=public_html/saturn
 

These parameters set up a normal Server on port 8081, running a MultiHostHandler. The MultiHostHandler will create three additional servers that respond to the virtual hosts "www.mars.com", "jupiter.planet.org", and ".saturn.planet.org". The "mars" server will have a Server.prefix of "mars", so that all other configuration parameters that the "mars" server examines can begin with "mars" and be kept distinct from the "jupiter" and "saturn" parameters.

The main server and the three sub-servers will all share the same properties object, but can use their own individual prefixes to keep their data separate (because "inherit" is not set).

Constructor Summary

MultiHostHandler()

Method Summary

boolean	init(Server server, String prefix) Initializes the servers for the virtual hosts.
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.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

MultiHostHandler

public MultiHostHandler()

Method Detail

init

public boolean init(Server server,
                    String prefix)

Initializes the servers for the virtual hosts. After creating and initializing each sub-server, the init method of the main handler for each sub-server is called.

Specified by:

init in interface Handler

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:

true if at least one sub-server was found and could be initialized, false otherwise. Diagnostic messages are logged for each sub-server started.

respond

public boolean respond(Request request)
                throws IOException

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 in init from the list of virtual hosts, this method returns without handling the request. Port numbers are not used for host matching.

Specified by:

respond in interface Handler

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, 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.