src/main/java/org/apache/sling/scripting/sightly/impl/engine/extension/ExtensionUtils.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 org.apache.sling.scripting.sightly.impl.engine.extension;

import java.util.LinkedHashMap;
import java.util.Map;

import org.apache.sling.api.SlingHttpServletRequest;
import org.apache.sling.scripting.sightly.SightlyException;
import org.apache.sling.scripting.sightly.extension.RuntimeExtension;

/**
 * Helper class for {@link RuntimeExtension} implementations.
 */
public class ExtensionUtils {

    /**
     * Helper method for checking if the number of arguments passed to a {@link RuntimeExtension} are equal to what the extension requires.
     *
     * @param extensionName the name of the extension
     * @param arguments     the arguments array
     * @param count         the expected number or arguments
     * @throws SightlyException if the number of supplied arguments differs from what's expected
     */
    public static void checkArgumentCount(String extensionName, Object[] arguments, int count) {
        if (arguments.length != count) {
            throw new SightlyException(String.format("Extension %s requires %d arguments", extensionName, count));
        }
    }

    /**
     * Helper method for setting specific attributes in a {@link SlingHttpServletRequest} scope
     *
     * @param request              the {@link SlingHttpServletRequest}
     * @param newRequestAttributes the {@link Map} of attributes to set
     * @return A {@link Map} of original attributes values for substituted keys
     */
    public static Map<String, Object> setRequestAttributes(SlingHttpServletRequest request, Map<String, Object> newRequestAttributes) {
        Map<String, Object> originalRequestAttributes = new LinkedHashMap<String, Object>();
        if (newRequestAttributes != null && request != null) {
            for (Map.Entry<String, Object> attr : newRequestAttributes.entrySet()) {
                String key = attr.getKey();
                Object value = attr.getValue();
                originalRequestAttributes.put(key, request.getAttribute(key));
                if (value == null) {
                    request.removeAttribute(key);
                } else {
                    request.setAttribute(key, value);
                }
            }
        }
        return originalRequestAttributes;
    }

}