org.infohazard.maverick
Class Dispatcher

java.lang.Object
  |
  +--javax.servlet.GenericServlet
        |
        +--javax.servlet.http.HttpServlet
              |
              +--org.infohazard.maverick.Dispatcher

All Implemented Interfaces:

java.io.Serializable, javax.servlet.Servlet, javax.servlet.ServletConfig

public class Dispatcher

extends javax.servlet.http.HttpServlet

Dispatcher is the central command processor of the Maverick framework. All commands are routed to this servlet by way of extension mapping (say, *.m). From here requests are routed through the "workflow" tree of Command, View, and Pipeline objects built from the maverick config file.

Commands can be gracefully chained together; if a view references another Maverick command, the same MaverickContext object is used.

The Dispatcher object is made available to Controllers (or anyone else as an object in the application-scope aka ServletContext attribute collection. The attribute key is the value of the MAVERICK_APPLICATION_KEY constant.

Note that there is are two special pseudocommands defined by this servlet: "*" and "reload".

"reload" triggers a reload of the maverick config file. This can safely be done on running system; all commands currently being processed will complete using the old data. New command requests will use the new data as soon as it is finished loading. Note that the actual command name used for "reload" is determined by an init param.

"*" is a special command which can be defined in the config file. If a command request cannot be mapped to a command (because the requested command was not defined), the "*" command will be used instead. If there is no "*" command defined in the config file, bad requests return 404.

See Also:

Serialized Form

Field Summary

protected java.util.Map	commands Maps command name -> Command objects.
protected org.jdom.Document	configDocument The current configuration document.
protected static java.lang.String	DEFAULT_CONFIG_FILE Default location of the xml configuration file.
protected java.lang.String	defaultRequestCharset If set, this string is set as the character encoding for http requests.
protected static java.lang.String	INITPARAM_CONFIG_FILE Name of the servlet init parameter which defines the path to the Maverick configuration file.
protected static java.lang.String	INITPARAM_CONFIG_TRANSFORM Name of the servlet init parameter which defines the path to a transform which will be applied to the config XML before loading.
protected static java.lang.String	INITPARAM_CURRENT_CONFIG_COMMAND Name of the servlet init parameter which defines the name of the command which displays the current configuration.
protected static java.lang.String	INITPARAM_DEFAULT_REQUEST_CHARSET Name of the servlet init parameter which defines the charset to use by default for request parameter decoding.
protected static java.lang.String	INITPARAM_LIMIT_TRANSFORMS_PARAM The name of an http request parameter which, if specified, causes transformation to be halted after the specified number of transforms.
protected static java.lang.String	INITPARAM_RELOAD_COMMAND Name of the servlet init parameter which defines the name of the reload command.
protected java.lang.String	limitTransformsParam If set, the name of a http request parameter which determines the number of transforms to run before halting.
static java.lang.String	MAVERICK_APPLICATION_KEY The key in the Application (ServletContext) attribute collection under which the Dispatcher will be made available.
protected static java.lang.String	SAVED_MAVCTX_KEY The MaverickContext object is stored in the request attributes with this key so that it can be recovered for recursive maverick execution.

Constructor Summary

Dispatcher()

Method Summary

protected java.lang.String	extractCommandName(javax.servlet.http.HttpServletRequest request) Extracts the command name from the request.
protected Command	getCommand(java.lang.String name) Returns the command object associated with the specified name.
org.jdom.Document	getConfigDocument()
java.lang.String	getLimitTransformsParam() The name of the parameter to use to limit transformation, or null if this should be disabled.
void	init() Initializes the Dispatcher by loading the config file.
protected org.jdom.Document	loadConfigDocument()
protected void	reloadConfig() Reloads the xml configuration data.
protected void	service(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) The main entry point of the servlet; this processes an HTTP request.

Methods inherited from class javax.servlet.http.HttpServlet

doDelete, doGet, doHead, doOptions, doPost, doPut, doTrace, getLastModified, service

Methods inherited from class javax.servlet.GenericServlet

destroy, getInitParameter, getInitParameterNames, getServletConfig, getServletContext, getServletInfo, getServletName, init, log, log

Methods inherited from class java.lang.Object

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

Field Detail

MAVERICK_APPLICATION_KEY

public static final java.lang.String MAVERICK_APPLICATION_KEY

The key in the Application (ServletContext) attribute collection under which the Dispatcher will be made available.

See Also:

Constant Field Values

INITPARAM_CONFIG_FILE

protected static final java.lang.String INITPARAM_CONFIG_FILE

Name of the servlet init parameter which defines the path to the Maverick configuration file. Defaults to DEFAULT_CONFIG_FILE.

See Also:

Constant Field Values

INITPARAM_CONFIG_TRANSFORM

protected static final java.lang.String INITPARAM_CONFIG_TRANSFORM

Name of the servlet init parameter which defines the path to a transform which will be applied to the config XML before loading. Defaults to null, which means perform no transformation.

See Also:

Constant Field Values

INITPARAM_RELOAD_COMMAND

protected static final java.lang.String INITPARAM_RELOAD_COMMAND

Name of the servlet init parameter which defines the name of the reload command. The value will typically be something like "reload".

See Also:

Constant Field Values

INITPARAM_CURRENT_CONFIG_COMMAND

protected static final java.lang.String INITPARAM_CURRENT_CONFIG_COMMAND

Name of the servlet init parameter which defines the name of the command which displays the current configuration. The value will typically be something like "currentConfig".

See Also:

Constant Field Values

INITPARAM_DEFAULT_REQUEST_CHARSET

protected static final java.lang.String INITPARAM_DEFAULT_REQUEST_CHARSET

Name of the servlet init parameter which defines the charset to use by default for request parameter decoding. If not present, the default charset will be whatever the container chooses (probably ISO-8859-1 aka Latin-1).

See Also:

Constant Field Values

INITPARAM_LIMIT_TRANSFORMS_PARAM

protected static final java.lang.String INITPARAM_LIMIT_TRANSFORMS_PARAM

The name of an http request parameter which, if specified, causes transformation to be halted after the specified number of transforms. If this initparam is not specified, this feature is disabled and all transforms will run to completion.

See Also:

Constant Field Values

DEFAULT_CONFIG_FILE

protected static final java.lang.String DEFAULT_CONFIG_FILE

Default location of the xml configuration file.

See Also:

Constant Field Values

SAVED_MAVCTX_KEY

protected static final java.lang.String SAVED_MAVCTX_KEY

The MaverickContext object is stored in the request attributes with this key so that it can be recovered for recursive maverick execution.

See Also:

Constant Field Values

commands

protected java.util.Map commands

Maps command name -> Command objects.

configDocument

protected org.jdom.Document configDocument

The current configuration document.

defaultRequestCharset

protected java.lang.String defaultRequestCharset

If set, this string is set as the character encoding for http requests. This affects the input form parameters. It is set from a servlet init parameter. Null means do nothing special.

limitTransformsParam

protected java.lang.String limitTransformsParam

If set, the name of a http request parameter which determines the number of transforms to run before halting.

Constructor Detail

Dispatcher

public Dispatcher()

Method Detail

init

public void init()
          throws javax.servlet.ServletException

Initializes the Dispatcher by loading the config file.

Overrides:

init in class javax.servlet.GenericServlet

javax.servlet.ServletException

service

protected void service(javax.servlet.http.HttpServletRequest request,
                       javax.servlet.http.HttpServletResponse response)
                throws java.io.IOException,
                       javax.servlet.ServletException

The main entry point of the servlet; this processes an HTTP request.

Overrides:

service in class javax.servlet.http.HttpServlet

java.io.IOException

javax.servlet.ServletException

extractCommandName

protected java.lang.String extractCommandName(javax.servlet.http.HttpServletRequest request)

Extracts the command name from the request. Extension and leading / will be removed.

reloadConfig

protected void reloadConfig()
                     throws ConfigException

Reloads the xml configuration data. Can be done on-the-fly. Any requests being serviced are allowed to complete with the old data.

ConfigException

getCommand

protected Command getCommand(java.lang.String name)

Returns the command object associated with the specified name. If the command is not found, a command with name "*" is returned. If there is no command with id "*", null is returned.

loadConfigDocument

protected org.jdom.Document loadConfigDocument()
                                        throws ConfigException

Returns:

a loaded JDOM document containing the configuration information.

ConfigException

getConfigDocument

public org.jdom.Document getConfigDocument()

Returns:

the current configuration as a JDOM Document.

getLimitTransformsParam

public java.lang.String getLimitTransformsParam()

The name of the parameter to use to limit transformation, or null if this should be disabled.