com.lf.commons.web

Class AbstractService

java.lang.Object

javax.servlet.GenericServlet

javax.servlet.http.HttpServlet

com.lf.commons.web.AbstractService

All Implemented Interfaces:

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

public abstract class AbstractService
extends javax.servlet.http.HttpServlet

Abstract class for configurable web services based on HTTP GET and POST.

Requests can be received via HTTP GET by using parameters which are internally enbedded into a special XML request message based on 'parameter_message.dtd'. The HTTP POST method can also be used to receive more complex requests like XML or properties files. The implementing sub classes can be configured by setting the appropriate responders for the request messages. The responder classes normally produce some kind of output like XML files.

The constructor of each sub class should setup the dispatching rules with available responders. Incoming messages are then processed automatically by this servlet base class. Error output is standardized so the sub classes do not have to take care.

The only default responder currently is the ping responder, which receives XML payload based on 'ping_message.dtd' and returns it as it was received. This default message type can be used to check whether a certain service is online or not. Sub classes can add it easily by calling the addResponder() method. A global shared instance is provided by the WebSettings class.

Since:

1.6

Version:

$Revision: 1.12 $, $Date: 2012/12/28 11:44:24 $

Author:

Axel Schwolow

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected java.util.Hashtable<java.lang.String,AbstractMessage>	checkers Remembers the message instances doing the checking.
protected java.util.Hashtable<java.lang.String,AbstractResponder>	responders Remembers the responder instances registered with incoming message types.

Constructor Summary

Constructors

Constructor and Description
AbstractService() Constructor method for i18n purposes only.

Method Summary

Methods

Modifier and Type	Method and Description
void	addResponder(AbstractResponder responder) Registers a responder for the implemented web service.
void	doGet(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) Generates the response via HTTP GET.
void	doPost(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) Generates the response via HTTP POST.
protected void	finalize() Cares for proper cleanup when is not needed any longer (helps gc).
java.lang.String[]	getResponseTypes() Provides the list of generated outgoing message types.
void	removeResponder(AbstractResponder responder) Removes a responder instance.

Methods inherited from class javax.servlet.http.HttpServlet

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

Methods inherited from class javax.servlet.GenericServlet

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

Methods inherited from class java.lang.Object

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

Field Detail

responders

protected java.util.Hashtable<java.lang.String,AbstractResponder> responders

Remembers the responder instances registered with incoming message types.

checkers

protected java.util.Hashtable<java.lang.String,AbstractMessage> checkers

Remembers the message instances doing the checking.

Constructor Detail

AbstractService

public AbstractService()

Constructor method for i18n purposes only.

Can only be used if beans design time is set (e.g. by external tools like the I18NExtractor).

Since:

1.6

Method Detail

finalize

protected void finalize()
                 throws java.lang.Throwable

Cares for proper cleanup when is not needed any longer (helps gc).

Overrides:

finalize in class java.lang.Object

Throws:

java.lang.Throwable

Since:

1.5

addResponder

public void addResponder(AbstractResponder responder)

Registers a responder for the implemented web service.

Parameters:

responder - The instance generating for response

Throws:

java.lang.NullPointerException - If parameters are null

java.lang.IllegalArgumentException - If parameters are invalid

Since:

1.5

removeResponder

public void removeResponder(AbstractResponder responder)

Removes a responder instance.

Parameters:

responder - The responder to be deleted

Throws:

java.lang.NullPointerException - If parameters are null

java.lang.IllegalArgumentException - If parameters are invalid

Since:

1.5

getResponseTypes

public java.lang.String[] getResponseTypes()

Provides the list of generated outgoing message types.

Based on the installed message responders this method returns the list of message types to be expected by the callers. This list can be used for message auto-detection by clients using the underlying web service.

Returns:

Supported message class names in FQN

doGet

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

Generates the response via HTTP GET.

Normally this web service is called via HTTP GET. The optional parameters are embedded into an XML file based on 'parameter_message.dtd' and then processed as if the data was received via HTTP POST.

Overrides:

doGet in class javax.servlet.http.HttpServlet

Parameters:

request - HTTP request

response - HTTP response

Throws:

javax.servlet.ServletException - Error indication

java.io.IOException - Error indication

doPost

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

Generates the response via HTTP POST.

The payload must be a valid XML file based on the 'parameter_message.dtd'. Normally this web service is called via HTTP GET. The parameters like 'id' are then embedded into an XML file and processed as if the data was passed via HTTP POST.

Remember that the maximum length of incoming data is controlled by Tomcat. Normally, Tomcat accepts a maximum total of 2 megabytes of HTTP POST data.

IMPORTANT: If Tomcat calls doGet() is called instead of doPost() you have to include the trailing slash at the end of the URL. Tomcat does some buggy address mapping.

Found the solution here:

http://bytes.com/groups/java/17880-using-httpurlconnection-post-servlet-tomcat-5-results-get-not-post-server-side

Overrides:

doPost in class javax.servlet.http.HttpServlet

Parameters:

request - HTTP request

response - HTTP response

Throws:

javax.servlet.ServletException - Error indication

java.io.IOException - Error indication