core/src/main/java/com/opensymphony/xwork2/conversion/NullHandler.java

/*
 * 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.
 */
package com.opensymphony.xwork2.conversion;

import java.util.Map;

/**
 * <p>
 * Interface for handling null results from Chains.
 * Object has the opportunity to substitute an object for the
 * null and continue.
 * </p>
 *
 * @author Luke Blanshard (blanshlu@netscape.net)
 * @author Drew Davidson (drew@ognl.org)
 */
public interface NullHandler
{
    /**
     *  Method called on target returned null.
     *  @param context context
     *  @param target target object
     *  @param methodName method name
     *  @param args arguments
     *
     *  @return object
     */
    Object nullMethodResult(Map<String, Object> context, Object target, String methodName, Object[] args);
    
    /**
     *   Property in target evaluated to null.  Property can be a constant
     *   String property name or a DynamicSubscript.
     *
     *  @param context context
     *  @param target target object
     *  @param property property
     *
     *  @return object
     */
    Object nullPropertyValue(Map<String, Object> context, Object target, Object property);
}