01: /*
02: * Copyright 2004-2007 the original author or authors.
03: *
04: * Licensed under the Apache License, Version 2.0 (the "License");
05: * you may not use this file except in compliance with the License.
06: * You may obtain a copy of the License at
07: *
08: * http://www.apache.org/licenses/LICENSE-2.0
09: *
10: * Unless required by applicable law or agreed to in writing, software
11: * distributed under the License is distributed on an "AS IS" BASIS,
12: * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13: * See the License for the specific language governing permissions and
14: * limitations under the License.
15: */
16: package org.springframework.webflow.engine;
17:
18: import org.springframework.webflow.execution.RequestContext;
19: import org.springframework.webflow.execution.ViewSelection;
20:
21: /**
22: * Factory that produces a new, configured {@link ViewSelection} object on each
23: * invocation, taking into account the information in the provided flow
24: * execution request context.
25: * <p>
26: * Note: this class is a runtime factory. Instances are used at flow execution
27: * time by objects like the {@link ViewState} to produce new
28: * {@link ViewSelection view selections}.
29: * <p>
30: * This class allows for easy insertion of dynamic view selection logic, for
31: * instance, letting you determine the view to render or the available model
32: * data for rendering based on contextual information.
33: *
34: * @see org.springframework.webflow.execution.ViewSelection
35: * @see org.springframework.webflow.engine.ViewState
36: * @see org.springframework.webflow.engine.EndState
37: *
38: * @author Keith Donald
39: * @author Erwin Vervaet
40: */
41: public interface ViewSelector {
42:
43: /**
44: * Will the primary selection returned by 'makeEntrySelection' for the given
45: * request context be renderable in this request?
46: * <p>
47: * "Renderable" view selections typically can have 'render-actions' execute
48: * before they are created. An example would be an ApplicationView that
49: * forwards to a view template like a JSP. "Non-renderable" view selections
50: * are things like a flow execution redirect--no render actually occurs, but
51: * only a redirect--rendering happens on the new redirect request.
52: * @param context the current request context of the executing flow
53: * @return true if yes, false otherwise
54: */
55: public boolean isEntrySelectionRenderable(RequestContext context);
56:
57: /**
58: * Make a new "entry" view selection for the given request context. Called
59: * when a view-state, end-state, or other interactive state type is entered.
60: * @param context the current request context of the executing flow
61: * @return the entry view selection
62: */
63: public ViewSelection makeEntrySelection(RequestContext context);
64:
65: /**
66: * Reconstitute a renderable view selection for the given request context to
67: * support a ViewState 'refresh' operation.
68: * @param context the current request context of the executing flow
69: * @return the view selection
70: */
71: public ViewSelection makeRefreshSelection(RequestContext context);
72:
73: }
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