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org.scopemvc.controller.servlet
Class ScopeServlet  

java.lang.Object
  javax.servlet.GenericServlet
      javax.servlet.http.HttpServlet
          org.scopemvc.controller.servlet.ScopeServlet

All Implemented Interfaces:

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

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public abstract class ScopeServlet

extends javax.servlet.http.HttpServlet

Base class for a web app's servlet dispatcher: subclass this to implement application startup and initialisation (use a static initializer). This class accepts incoming requests, collects the parameters into a mutable HashMap, parses them to create a Control and to find a ViewID to identify the View the user interacted with. The request parameters are then passed to the View to populate its Model, before the View issues the Control for the owning Controller to handle.

A configurable number of Application Controllers (and sub-Controllers and their Views and Models) are created on the first request. These are put into a pool to be shared between all future requests. For this reason, Controllers that are shared must be aware of the possible need to reset their model's state before handling a Control.

A form request is handled as follows:

Most steps in this sequence are implemented by Template Methods that can be overridden to change the default behaviour.

The issue of session state management and model scope is not resolved here.

See the various XML/XSLT and JSP servlet samples for examples of use.

Version:

$Revision: 1.12 $ $Date: 2002/01/26 09:46:21 $

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Nested Class Summary
protected  class	ScopeServlet.SharedControllerFactory

 

Field Summary
static java.lang.String	CONTROL_PARAM           The key used to identify the Control ID in the request parameters for this implementation.
private static org.apache.commons.logging.Log	LOG
protected  org.scopemvc.util.ObjectPool	sharedControllerPool           Pool of shared application Controllers for this servlet instance.
static java.lang.String	VALIDATION_FAILURES           The default validation error handler in handleValidationFailures(org.scopemvc.view.servlet.Page, java.util.List) 55 puts the list of ValidationFailures in the properties of the org.scopemvc.controller.basic.ViewContext under this key for later retrieval by a Controller.
static java.lang.String	VIEW_ID_PARAM           The request's key that identifies the View ID used to find the active View that a Control was sent from.

 

Fields inherited from class javax.servlet.http.HttpServlet

 

Fields inherited from class javax.servlet.GenericServlet

 

Constructor Summary

ScopeServlet()

 

Method Summary
protected abstract  org.scopemvc.core.Controller	createApplicationController()            Override this to create the root application Controller.
protected  org.scopemvc.core.Control	createControl(java.util.HashMap ioFormParameters)            Return a Control instance from request form parameters getting the Control ID from the CONTROL_PARAM form value, and setting the formParameters HashMap as the Control's parameter.
protected abstract  ServletContext	createServletContext(javax.servlet.http.HttpServletRequest req, javax.servlet.http.HttpServletResponse resp, java.util.HashMap inFormParameters)           Create a ViewContext that will be used for a request: default impl here returns a new ServletContext.
protected  void	doGet(javax.servlet.http.HttpServletRequest req, javax.servlet.http.HttpServletResponse resp)           This implementation maps GET requests onto POST requests.
protected  void	doPost(javax.servlet.http.HttpServletRequest req, javax.servlet.http.HttpServletResponse resp)           Default implementation uses shared application instances.
protected  org.scopemvc.view.servlet.Page	findDefaultPage(org.scopemvc.core.Controller inRootController)           If the request ViewID doesn't match any Page then this provides a default Page: could be the start page of the application that the user gets to by invoking the servlet with no parameters.
protected  org.scopemvc.view.servlet.Page	findPageByID(org.scopemvc.core.Controller inRootController, java.lang.String inViewID)           Search through application's Controller hierarchy to find a Page matching the ViewID.
protected  java.lang.String	findViewID(java.util.HashMap inParameters)           Could be overidden to provide a default ViewID if none in the parameters, but also see getFormParameters(javax.servlet.http.HttpServletRequest) 55 .
protected  java.util.HashMap	getFormParameters(javax.servlet.http.HttpServletRequest inRequest)           Copy references to all form parameters into a mutable Map.
protected  void	handleRequest(java.util.HashMap formParameters)
protected  boolean	handleValidationFailures(org.scopemvc.view.servlet.Page inPage, java.util.List inFailures)            Called if an exception is thrown by Page.populateModel 55 .
protected  void	initSharedControllerPool()
static void	redirect(java.util.HashMap inFormParameters)           Call from a Controller instead of showing a View to force an internal redirect.

 

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

 

Field Detail

LOG

private static final org.apache.commons.logging.Log LOG

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sharedControllerPool

protected org.scopemvc.util.ObjectPool sharedControllerPool

Pool of shared application Controllers for this servlet instance.

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CONTROL_PARAM

public static java.lang.String CONTROL_PARAM

The key used to identify the Control ID in the request parameters for this implementation. Initialised from the "org.scopemvc.controller.servlet.ScopeServlet.ControlParam" value from ScopeConfig.

See Also:

createControl(java.util.HashMap) 55

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VIEW_ID_PARAM

public static java.lang.String VIEW_ID_PARAM

The request's key that identifies the View ID used to find the active View that a Control was sent from. Initialised from the "org.scopemvc.controller.servlet.ScopeServlet.ViewIDParam" value of ScopeConfig.

See Also:

findPageByID(org.scopemvc.core.Controller, java.lang.String) 55

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VALIDATION_FAILURES

public static final java.lang.String VALIDATION_FAILURES

The default validation error handler in handleValidationFailures(org.scopemvc.view.servlet.Page, java.util.List) 55 puts the list of ValidationFailures in the properties of the org.scopemvc.controller.basic.ViewContext under this key for later retrieval by a Controller.

See Also:

Constant Field Values

Constructor Detail

ScopeServlet

public ScopeServlet()

Method Detail

doGet

protected void doGet(javax.servlet.http.HttpServletRequest req,
                     javax.servlet.http.HttpServletResponse resp)
              throws javax.servlet.ServletException,
                     java.io.IOException

This implementation maps GET requests onto POST requests.

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doPost

protected void doPost(javax.servlet.http.HttpServletRequest req,
                      javax.servlet.http.HttpServletResponse resp)
               throws javax.servlet.ServletException,
                      java.io.IOException

Default implementation uses shared application instances.

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handleRequest

protected void handleRequest(java.util.HashMap formParameters)

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createServletContext

protected abstract ServletContext createServletContext(javax.servlet.http.HttpServletRequest req,
                                                       javax.servlet.http.HttpServletResponse resp,
                                                       java.util.HashMap inFormParameters)

Create a ViewContext that will be used for a request: default impl here returns a new ServletContext. For example to implement your own error handling, extend the default ServletContext to override showError, and then override this method in your servlet subclass to create an instance of your own ServletContext.

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getFormParameters

protected java.util.HashMap getFormParameters(javax.servlet.http.HttpServletRequest inRequest)

Copy references to all form parameters into a mutable Map. If a parameter has multiple values then the parameter value will be a String[] else a String.

This is a useful place to insert default values for missing parameters, for example to map .../servlet/MyServlet onto some default "action" and "view" by inserting those default parameters into the returned HashMap if missing in incoming request.

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createControl

protected org.scopemvc.core.Control createControl(java.util.HashMap ioFormParameters)

Return a Control instance from request form parameters getting the Control ID from the CONTROL_PARAM form value, and setting the formParameters HashMap as the Control's parameter. Also handles imagemap requests of the form imagename.x=ControlId.

Override this for an application to create a default Control when none is supplied in the request, eg for a simple home request:

http://localhost:8080/myapp/MyServlet

with no parameters to display the application's home page. But also see getFormParameters(javax.servlet.http.HttpServletRequest) 55 .

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findViewID

protected java.lang.String findViewID(java.util.HashMap inParameters)

Could be overidden to provide a default ViewID if none in the parameters, but also see getFormParameters(javax.servlet.http.HttpServletRequest) 55 .

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findPageByID

protected org.scopemvc.view.servlet.Page findPageByID(org.scopemvc.core.Controller inRootController,
                                                      java.lang.String inViewID)

Search through application's Controller hierarchy to find a Page matching the ViewID. Return null if not found.

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findDefaultPage

protected org.scopemvc.view.servlet.Page findDefaultPage(org.scopemvc.core.Controller inRootController)

If the request ViewID doesn't match any Page then this provides a default Page: could be the start page of the application that the user gets to by invoking the servlet with no parameters. Here returns the first Page found by a depth-first traversal of the application hierarchy.

If you manage the getFormParameters(javax.servlet.http.HttpServletRequest) 55 method to validate form parameters then this method might never be used. But if there's a single page that you want to use when an invalid ViewID is passed (eg an error page) then this is the place to do it.

Don't like this. Should be allowed to redirect to an error handler on invalid ViewID? *****

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handleValidationFailures

protected boolean handleValidationFailures(org.scopemvc.view.servlet.Page inPage,
                                           java.util.List inFailures)

Called if an exception is thrown by Page.populateModel 55 .

Default implementation here puts the List of ValidationFailures into the ViewContext under the VALIDATION_FAILURES 55 key for retrieval (org.scopemvc.controller.basic.ViewContext#getProperty() and handling by Controllers, ie:

 protected void doSomeHandler() throws ControlException {
 	List validationFailures = (List)ViewContext.getViewContext().getProperty(ScopeServlet.VALIDATION_FAILURES);
 	if (validationFailures != null) {
 		// TODO: Handle the validation failures
 	} else {
 		// TODO: No validation failures so handle the control
 	}
 }
 

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redirect

public static void redirect(java.util.HashMap inFormParameters)

Call from a Controller instead of showing a View to force an internal redirect. Pass a HashMap of form parameters for the new request.

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createApplicationController

protected abstract org.scopemvc.core.Controller createApplicationController()
                                                                     throws java.lang.Exception

Override this to create the root application Controller. The application Controller should setup any child Controllers that it needs to handle parts of the application for it.

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initSharedControllerPool

protected void initSharedControllerPool()
                                 throws java.lang.Exception

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Overview  Package   Class  Use  Deprecated  Index
Home >> All >> org >> scopemvc >> controller >> [ servlet overview ]	PREV CLASS  NEXT CLASS
SUMMARY:  JAVADOC |  SOURCE |  DOWNLOAD | NESTED | FIELD | CONSTR | METHOD	DETAIL: FIELD | CONSTR | METHOD

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