hirondelle.web4j.model
Class MessageListImpl

Object
  hirondelle.web4j.model.MessageListImpl

All Implemented Interfaces:

MessageList

public class MessageListImpl
extends Object
implements MessageList

General implementation of MessageList.

Constructor Summary

MessageListImpl()
Create an empty MessageList.

MessageListImpl(String aMessage)
Create a MessageList having one simple AppResponseMessage.

MessageListImpl(String aMessage, Object... aParams)
Create a MessageList having one compound AppResponseMessage.

Method Summary

void	add(AppException ex) Add all AppResponseMessages attached to aAppEx to this list.
void	add(String aMessage) Add a simple AppResponseMessage to this list.
void	add(String aMessage, Object... aParams) Add a compound AppResponseMessage to this list.
boolean	getIsDisplayable() Return true only if messages exist and MessageList.getMessagesForSingleDisplay() has not yet been called.
List<AppResponseMessage>	getMessages() Return an unmodifiable List of AppResponseMessages.
List<AppResponseMessage>	getMessagesForSingleDisplay() Render the messages in a JSP.
boolean	isEmpty() Return true only if there are no messages in this list.
boolean	isNotEmpty() Return the negation of MessageList.isEmpty().
String	toString() Intended for debugging only.

Methods inherited from class Object

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

Constructor Detail

MessageListImpl

public MessageListImpl()

Create an empty MessageList.

MessageListImpl

public MessageListImpl(String aMessage)

Create a MessageList having one simple AppResponseMessage.

The argument satisfies the same conditions as AppResponseMessage.forSimple(java.lang.String).

MessageListImpl

public MessageListImpl(String aMessage,
                       Object... aParams)

Create a MessageList having one compound AppResponseMessage.

The arguments satisfy the same conditions as AppResponseMessage.forCompound(java.lang.String, java.lang.Object...).

Method Detail

add

public final void add(String aMessage)

Description copied from interface: MessageList

Add a simple AppResponseMessage to this list.

The argument satisfies the same conditions as AppResponseMessage.forSimple(java.lang.String).

Specified by:

add in interface MessageList

add

public final void add(String aMessage,
                      Object... aParams)

Description copied from interface: MessageList

Add a compound AppResponseMessage to this list.

The arguments satisfy the same conditions as AppResponseMessage.forCompound(java.lang.String, java.lang.Object...).

Specified by:

add in interface MessageList

add

public final void add(AppException ex)

Description copied from interface: MessageList

Add all AppResponseMessages attached to aAppEx to this list.

Specified by:

add in interface MessageList

getMessages

public final List<AppResponseMessage> getMessages()

Description copied from interface: MessageList

Return an unmodifiable List of AppResponseMessages.

JSPs must call MessageList.getMessagesForSingleDisplay() instead of this method.

Specified by:

getMessages in interface MessageList

isNotEmpty

public final boolean isNotEmpty()

Description copied from interface: MessageList

Return the negation of MessageList.isEmpty().

Specified by:

isNotEmpty in interface MessageList

isEmpty

public final boolean isEmpty()

Description copied from interface: MessageList

Return true only if there are no messages in this list.

Note that this method name conflicts with the empty keyword of JSTL. Thus, MessageList.isNotEmpty() is supplied as an alternative.

Specified by:

isEmpty in interface MessageList

getIsDisplayable

public final boolean getIsDisplayable()

Description copied from interface: MessageList

Return true only if messages exist and MessageList.getMessagesForSingleDisplay() has not yet been called.

Specified by:

getIsDisplayable in interface MessageList

getMessagesForSingleDisplay

public List<AppResponseMessage> getMessagesForSingleDisplay()

Description copied from interface: MessageList

Render the messages in a JSP.

JSPs must call this method when rendering messages.

This method solves the following problem. Some messages need to survive a redirect. This is implemented in WEB4J by placing the messages in session scope. However, the messages should be displayed to the user only once. So the problem arises of what to do with session-scope messages once they have been displayed.

Here, the technique used is to keep the object in session scope, but if the rendering task is performed a second time on the same messages (that is, if this method is called a second time on the same object), an empty List is returned, and no text will be rendered. This is an unusual policy for an object.

Specified by:

getMessagesForSingleDisplay in interface MessageList

Returns:

if this is the first time this method is called, return the same result as MessageList.getMessages() - otherwise, return an empty List.

toString

public String toString()

Intended for debugging only.

Overrides:

toString in class Object