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package org.apache.velocity.app.event;
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.
*/
import org.apache.velocity.context.Context;
import org.apache.velocity.util.introspection.Info;
/**
* Event handler called when an invalid reference is encountered. Allows
* the application to report errors or substitute return values. May be chained
* in sequence; the behavior will differ per method.
*
* <p>This feature should be regarded as experimental.
*
* @author <a href="mailto:wglass@forio.com">Will Glass-Husain</a>
* @version $Id$
* @since 1.5
*/
public interface InvalidReferenceEventHandler extends EventHandler
{
/**
* Called when object is null or there is no getter for the given
* property. Also called for invalid references without properties.
* invalidGetMethod() will be called in sequence for
* each link in the chain until the first non-null value is
* returned.
*
* @param context the context when the reference was found invalid
* @param reference string with complete invalid reference
* @param object the object referred to, or null if not found
* @param property the property name from the reference
* @param info contains template, line, column details
* @return substitute return value for missing reference, or null if no substitute
*/
Object invalidGetMethod(Context context, String reference,
Object object, String property, Info info);
/**
* Called when object is null or there is no setter for the given
* property. invalidSetMethod() will be called in sequence for
* each link in the chain until a true value is returned. It's
* recommended that false be returned as a default to allow
* for easy chaining.
*
* @param context the context when the reference was found invalid
* @param leftreference left reference being assigned to
* @param rightreference invalid reference on the right
* @param info contains info on template, line, col
*
* @return if true then stop calling invalidSetMethod along the
* chain.
*/
boolean invalidSetMethod(Context context, String leftreference,
String rightreference, Info info);
/**
* Called when object is null or the given method does not exist.
* invalidMethod() will be called in sequence for each link in
* the chain until the first non-null value is returned.
*
* @param context the context when the reference was found invalid
* @param reference string with complete invalid reference
* @param object the object referred to, or null if not found
* @param method the name of the (non-existent) method
* @param info contains template, line, column details
* @return substitute return value for missing reference, or null if no substitute
*/
Object invalidMethod(Context context, String reference,
Object object, String method, Info info);
}
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