qtiscoringengine.CustomOperatorRegistry.java Source code

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Here is the source code for qtiscoringengine.CustomOperatorRegistry.java

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/*******************************************************************************
 * Educational Online Test Delivery System Copyright (c) 2014 American
 * Institutes for Research
 * 
 * Distributed under the AIR Open Source License, Version 1.0 See accompanying
 * file AIR-License-1_0.txt or at http://www.smarterapp.org/documents/
 * American_Institutes_for_Research_Open_Source_Software_License.pdf
 ******************************************************************************/
package qtiscoringengine;

import java.util.List;
import java.util.ArrayList;

import org.jdom2.Attribute;
import org.jdom2.Element;

public class CustomOperatorRegistry {
    private static final Object _lock = new Object();
    private static CustomOperatorRegistry _instance = null;
    private final List<ICustomOperatorFactory> _registeredFactories = new ArrayList<ICustomOperatorFactory>();

    public static CustomOperatorRegistry getInstance() {
        if (_instance != null)
            return _instance;
        synchronized (_lock) {
            if (_instance != null)
                return _instance;
            _instance = new CustomOperatorRegistry();
            return _instance;
        }
    }

    private CustomOperatorRegistry() {
    }

    public void addOperatorFactory(ICustomOperatorFactory factory) {
        _registeredFactories.add(factory);
    }

    public Expression createExpression(Element customOperatorNode) {
        for (ICustomOperatorFactory factory : _registeredFactories) {
            if (factory.supportsOperator(customOperatorNode)) {
                return factory.createExpression(customOperatorNode);
            }
        }

        return null;
    }

    private static String getOperatorType(Element customOperatorNode) {
        for (Attribute attribute : customOperatorNode.getAttributes()) {
            if ("CLASS".equalsIgnoreCase(attribute.getName())) {
                return attribute.getValue();
            }
        }
        return "";
    }
}