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/*
* Copyright 2004-2008 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.webflow.execution;
import java.io.IOException;
import java.io.Serializable;
import org.springframework.webflow.engine.ViewState;
/**
* Allows a client to participate in flow execution. Encapsulates behavior to send the client an appropriate response
* and handle the resulting event once the client responds.
*
* @author Keith Donald
* @author Jeremy Grelle
* @see ViewFactory
*/
public interface View {
/**
* Well-known attribute name for storing a render fragments value.
*/
String RENDER_FRAGMENTS_ATTRIBUTE = "flowRenderFragments";
/**
* Well-known attribute name for storing the results of processing a user event
*/
String USER_EVENT_STATE_ATTRIBUTE = "viewUserEventState";
/**
* Render this view's content.
* @throws IOException if an IO Exception occured rendering the view
*/
void render() throws IOException;
/**
* True if there is a user event queued this view should process.
* @return true if a user event is queued, false if not
*/
boolean userEventQueued();
/**
* Process the queued user event. Should only be called when {@link #userEventQueued()} returns true. After calling
* this method, a flow event may be raised that should be handled in the Web Flow system.
* @see #hasFlowEvent()
*/
void processUserEvent();
/**
* True if a call to {@link #processUserEvent()} raised a flow event the current state should handle. Call
* {@link #getFlowEvent()} to access the Event.
* @return true if yes, false otherwise
*/
boolean hasFlowEvent();
/**
* Get the flow event the current state should handle. Returns an Event object when {@link #hasFlowEvent()} returns
* true. Returns null otherwise.
* @return the event, or null if there is no event for the flow system to handle
*/
Event getFlowEvent();
/**
* A memento holding the results of processing a user event. Used to allow transient view state such as binding and
* validation errors to survive a flow execution redirect.
* @return the serializable user event state object, or null if no event state needs managing
* @see #processUserEvent()
*/
Serializable getUserEventState();
/**
* Saves any state associated with this view out to view scope. Called when exiting a {@link ViewState} to allow for
* any changes applied after postback processing to be captured and reflected when going back. Can be a no-op for
* views that store no view state.
*/
void saveState();
}