core/src/main/java/flex/messaging/config/XPathServerConfigurationParser.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 flex.messaging.config;

import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;

/**
 * Uses Sun's JDK 1.5 XPath implementation on a DOM
 * representation of a messaging configuration file.
 * <p>
 * Note: Since reference ids are used between elements, certain
 * sections of the document need to be parsed first.
 * </p>
 */
public class XPathServerConfigurationParser extends ServerConfigurationParser {
    private XPath xpath;

    protected void initializeExpressionQuery() {
        this.xpath = XPathFactory.newInstance().newXPath();
    }

    protected Node selectSingleNode(Node source, String expression) {
        try {
            return (Node) xpath.evaluate
                    (expression, source, XPathConstants.NODE);
        } catch (XPathExpressionException expressionException) {
            throw wrapException(expressionException);
        }
    }

    protected NodeList selectNodeList(Node source, String expression) {
        try {
            return (NodeList) xpath.evaluate
                    (expression, source, XPathConstants.NODESET);
        } catch (XPathExpressionException expressionException) {
            throw wrapException(expressionException);
        }
    }

    protected Object evaluateExpression(Node source, String expression) {
        try {
            return xpath.evaluate(expression, source, XPathConstants.STRING);
        } catch (XPathExpressionException expressionException) {
            throw wrapException(expressionException);
        }
    }

    private ConfigurationException wrapException
            (XPathExpressionException exception) {
        ConfigurationException result = new ConfigurationException();
        result.setDetails(PARSER_INTERNAL_ERROR);
        result.setRootCause(exception);
        return result;
    }

}