// Copyright 2007 The Apache Software Foundation
//
// 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.apache.tapestry;
import org.apache.tapestry.corelib.components.Select;
/**
* Used by {@link Select} (and similar components) to encode server side values into client-side
* strings, and back.
* <p>
* Most often a custom implementation is needed for entity type objects, where the
* {@link #toClient(Object)} method extracts a primary key, and the {@link #toValue(String)}
* re-acquires the corresponding entity object.
*
* @see SelectModel
*/
public interface ValueEncoder<V>
{
/**
* Converts a value into a client-side representation. The value should be parseable by
* {@link #toValue(String)}. In some cases, what is returned is an identifier used to locate
* the true object, rather than a string representation of the value itself.
*
* @param value
* to be encoded
* @return a string representation of the value, or the value's identity
*/
String toClient(V value);
/**
* Converts a client-side representation, provided by {@link #toClient(Object)}, back into a
* server-side value.
*
* @param clientValue
* string representation of the value's identity
* @return the corresponding entity, or null if not found
*/
V toValue(String clientValue);
}
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