1 // Copyright 2008 The Apache Software Foundation
2 //
3 // Licensed under the Apache License, Version 2.0 (the "License");
4 // you may not use this file except in compliance with the License.
5 // You may obtain a copy of the License at
6 //
7 // http://www.apache.org/licenses/LICENSE-2.0
8 //
9 // Unless required by applicable law or agreed to in writing, software
10 // distributed under the License is distributed on an "AS IS" BASIS,
11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 // See the License for the specific language governing permissions and
13 // limitations under the License.
14
15 package org.apache.tapestry5;
16
17 /**
18 * Defines a strategy, used by {@link Field} components such as {@link org.apache.tapestry5.corelib.components.TextField},
19 * to handle the case where either the server-side value to be sent (as a string) to the client, or the client-side
20 * string passed back up to the server, is null or blank.
21 *
22 * @see org.apache.tapestry5.services.NullFieldStrategySource
23 */
24 public interface NullFieldStrategy
25 {
26 /**
27 * Provides a replacement value for null, when converting the server-side object to a client-side string. The
28 * replacement value, if non-null, will be passed to {@link org.apache.tapestry5.Translator#toClient(Object)}.
29 */
30 Object replaceToClient();
31
32 /**
33 * Provides a replacement value for a null or blank string passed from the client to the server as part of a form
34 * submission. This replacement value will be passed to {@link Translator#parseClient(Field, String, String)} as if
35 * it were the value supplied by the user.
36 *
37 * @return replacement value (this must not be null)
38 */
39 String replaceFromClient();
40 }
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