hirondelle.web4j.action
Class ActionTemplateListAndEdit

Object
  hirondelle.web4j.action.ActionImpl
      hirondelle.web4j.action.ActionTemplateListAndEdit

All Implemented Interfaces:

Action

public abstract class ActionTemplateListAndEdit
extends ActionImpl

Template for "all-in-one" Actions, which perform common operations on a Model Object.

Typically a single JSP is used, for displaying both a listing of Model Objects, and an accompanying form for editing these Model Objects one at a time. This style is practical when :

• the number of items in the listing is not excessively large.
• the Model Objects can be rendered reasonably well in a "one-per-line" style. (If the Model Object itself has a large number of items, it may be difficult to render them well in such a listing.)

The SupportedOperations for this template are a subset of the members of the Operation enumeration. If other operations are desired, then this template class cannot be used.

This class interacts a bit with its JSP - the form changes from "Add" mode to "Change" mode according to the value of the Operation.

If an operation is not appropriate in a given case, then simply provide an empty implementation of its corresponding abstract method (or an implementation that throws an UnsupportedOperationException).

To communicate messages to the end user, the implementation must use the various addMessage and addError methods.

Field Summary

static RequestParameter

SupportedOperation The operations supported by this template.

Fields inherited from class hirondelle.web4j.action.ActionImpl

DATA, ERRORS, ITEM_FOR_EDIT, ITEMS_FOR_LISTING, MESSAGES, USER_ID

Constructor Summary

protected

ActionTemplateListAndEdit(ResponsePage aForward, ResponsePage aRedirect, RequestParser aRequestParser) Constructor.

Method Summary

protected void	addDynamicParameterToRedirectPage(String aParamName, String aParamValue) Add a dynamic query parameter to the redirect ResponsePage.
protected abstract void	attemptAdd() Attempt an INSERT operation on the database.
protected abstract void	attemptChange() Attempt an UPDATE operation on the database.
protected abstract void	attemptDelete() Attempt a DELETE operation on the database.
protected abstract void	attemptFetchForChange() Attempt to fetch a single Model Object from the database, in preparation for editing it (SELECT operation).
protected abstract void	doList() Retrieve a listing of Model Objects from the database (SELECT operation).
ResponsePage	execute() Template method.
protected abstract void	validateUserInput() Validate items input by the user into a form.

Methods inherited from class hirondelle.web4j.action.ActionImpl

addError, addError, addError, addMessage, addMessage, addToRequest, addToSession, copyFromSessionToRequest, createSessionAndCsrfToken, endSession, getErrors, getExistingSession, getFromSession, getIdParam, getIdParams, getLocale, getLoggedInUserName, getMessages, getOperation, getOrderBy, getParam, getParamUnsafe, getRequestParser, getResponsePage, getTimeZone, getUserId, hasErrors, removeFromSession, setResponsePage

Methods inherited from class Object

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

Field Detail

SupportedOperation

public static final RequestParameter SupportedOperation

The operations supported by this template.

This action supports :

• Operation.List
• Operation.Add
• Operation.FetchForChange
• Operation.Change
• Operation.Delete

The source of the Operation is described by ActionImpl.getOperation().

Constructor Detail

ActionTemplateListAndEdit

protected ActionTemplateListAndEdit(ResponsePage aForward,
                                    ResponsePage aRedirect,
                                    RequestParser aRequestParser)

Constructor.

Parameters:

aForward - used for Operation.List and Operation.FetchForChange operations, and also for failed Operation.Add, Operation.Change, and Operation.Delete operations. This is the default response.

aRedirect - used for successful Operation.Add, Operation.Change, and Operation.Delete operations.

aRequestParser - passed to the superclass constructor.

Method Detail

execute

public final ResponsePage execute()
                           throws AppException

Template method.

In order to clearly understand the operation of this method, here is the core of its implementation, with all abstract methods in italics :

    if (Operation.List == getOperation() ){
      doList();
    }
    else if (Operation.FetchForChange == getOperation()){
      attemptFetchForChange();
    }
    else if (Operation.Add == getOperation()) {
      validateUserInput();
      if ( ! hasErrors() ){
        attemptAdd();
        ifNoErrorsRedirectToListing();
      }
    }
    else if (Operation.Change == getOperation()) {
      validateUserInput();
      if ( ! hasErrors() ){
        attemptChange();
        ifNoErrorsRedirectToListing();
      }
    }
    else if(Operation.Delete == getOperation()) {
      attemptDelete();
      ifNoErrorsRedirectToListing();
    }
    //Fresh listing WITHOUT a redirect is required if there is an error, 
    //and for successful FetchForChange operations.
    if( hasErrors() || Operation.FetchForChange == getOperation() ){
      doList();
    }
   

Specified by:

execute in interface Action

Specified by:

execute in class ActionImpl

Throws:

AppException

validateUserInput

protected abstract void validateUserInput()

Validate items input by the user into a form.

Applied to Operation.Add and Operation.Change. If an error occurs, then addError must be called.

Example of a typical implementation :

  protected void validateUserInput() {
    try {
      ModelFromRequest builder = new ModelFromRequest(getRequestParser());
      fResto = builder.build(Resto.class, RESTO_ID, NAME, LOCATION, PRICE, COMMENT);
    }
    catch (ModelCtorException ex){
      addError(ex);
    }    
  }
   

Note that the Model Object constructed in this example (fResto) is retained as a field, for later use when applying an edit to the database. This is the recommended style.

doList

protected abstract void doList()
                        throws DAOException

Retrieve a listing of Model Objects from the database (SELECT operation).

Throws:

DAOException

attemptAdd

protected abstract void attemptAdd()
                            throws DAOException

Attempt an INSERT operation on the database. The data will first be validated using validateUserInput().

Throws:

DAOException

attemptFetchForChange

protected abstract void attemptFetchForChange()
                                       throws DAOException

Attempt to fetch a single Model Object from the database, in preparation for editing it (SELECT operation).

Throws:

DAOException

attemptChange

protected abstract void attemptChange()
                               throws DAOException

Attempt an UPDATE operation on the database. The data will first be validated using validateUserInput().

Throws:

DAOException

attemptDelete

protected abstract void attemptDelete()
                               throws DAOException

Attempt a DELETE operation on the database.

Throws:

DAOException

addDynamicParameterToRedirectPage

protected void addDynamicParameterToRedirectPage(String aParamName,
                                                 String aParamValue)

Add a dynamic query parameter to the redirect ResponsePage.

This method will URL-encode the name and value.