/*
* Copyright 2002-2009 the original author or authors.
*
* 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 net.sf.json.util;
import net.sf.json.JSONArray;
import net.sf.json.JSONException;
import net.sf.json.JSONObject;
/**
* Base class for cycle detection in a hierarchy.<br>
* The JSON spec forbides cycles in a hierarchy and most parsers will raise and
* error when a cycle is detected. This class defines a contract for handling
* those cycles and two base implementations:
* <ul>
* <li>STRICT - will throw a JSONException if a cycle is found.</li>
* <li>LENIENT - will return an empty array or null object if a cycle is found.</li>
* </ul>
*
* @author Andres Almiray <[email protected]>
*/
public abstract class CycleDetectionStrategy {
public static final JSONArray IGNORE_PROPERTY_ARR = new JSONArray();
public static final JSONObject IGNORE_PROPERTY_OBJ = new JSONObject();
/** Returns empty array and null object */
public static final CycleDetectionStrategy LENIENT = new LenientCycleDetectionStrategy();
/**
* Returns a special object (IGNORE_PROPERTY_OBJ) that indicates the entire
* property should be ignored
*/
public static final CycleDetectionStrategy NOPROP = new LenientNoRefCycleDetectionStrategy();
/** Throws a JSONException */
public static final CycleDetectionStrategy STRICT = new StrictCycleDetectionStrategy();
/**
* Handle a repeated reference<br>
* Must return a valid JSONArray or null.
*
* @param reference the repeated reference.
*/
public abstract JSONArray handleRepeatedReferenceAsArray( Object reference );
/**
* Handle a repeated reference<br>
* Must return a valid JSONObject or null.
*
* @param reference the repeated reference.
*/
public abstract JSONObject handleRepeatedReferenceAsObject( Object reference );
private static final class LenientCycleDetectionStrategy extends CycleDetectionStrategy {
public JSONArray handleRepeatedReferenceAsArray( Object reference ) {
return new JSONArray();
}
public JSONObject handleRepeatedReferenceAsObject( Object reference ) {
return new JSONObject( true );
}
}
/**
* A cycle detection strategy that prevents any mention of the possible
* conflict from appearing.
*
* @author small
*/
private static final class LenientNoRefCycleDetectionStrategy extends CycleDetectionStrategy {
public JSONArray handleRepeatedReferenceAsArray( Object reference ) {
return IGNORE_PROPERTY_ARR;
}
public JSONObject handleRepeatedReferenceAsObject( Object reference ) {
return IGNORE_PROPERTY_OBJ;
}
}
private static final class StrictCycleDetectionStrategy extends CycleDetectionStrategy {
public JSONArray handleRepeatedReferenceAsArray( Object reference ) {
throw new JSONException( "There is a cycle in the hierarchy!" );
}
public JSONObject handleRepeatedReferenceAsObject( Object reference ) {
throw new JSONException( "There is a cycle in the hierarchy!" );
}
}
}
|