FilePolicyLoader.java

/**
 * Copyright (c) Codice Foundation
 * <p>
 * This is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser
 * General Public License as published by the Free Software Foundation, either version 3 of the
 * License, or any later version.
 * <p>
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
 * even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details. A copy of the GNU Lesser General Public License
 * is distributed along with this program and can be found at
 * <http://www.gnu.org/licenses/lgpl.html>.
 */
package ddf.security.ws.policy.impl;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.apache.commons.io.IOUtils;
import org.osgi.framework.BundleContext;
import org.w3c.dom.Document;
import org.xml.sax.SAXException;

import ddf.security.ws.policy.PolicyLoader;

/**
 * Uses the filesystem to load a policy file.
 */
public class FilePolicyLoader implements PolicyLoader {

    private static volatile Document policyDoc;

    /**
     * Creates a new instance of the file policy loader.
     *
     * @param context        Used to obtain the file from the file system.
     * @param policyLocation Location of the file within the bundle classpath.
     * @throws IOException If an error occurs while trying to load the policy file.
     */
    public FilePolicyLoader(BundleContext context, String policyLocation) throws IOException {
        URL policyURL = context.getBundle()
                .getResource(policyLocation);
        FilePolicyLoader.policyDoc = loadFromFile(policyURL);
    }

    /**
     * Loads the policy and converts it into a Document.
     *
     * @param policyFileURL URL that is based in from the bundlecontext.
     * @return The policy in a Document format.
     * @throws IOException If an error occurs while trying to parse the file into a Document.
     */
    protected Document loadFromFile(URL policyFileURL) throws IOException {
        InputStream policyStream = null;
        Document doc = null;
        if (policyFileURL != null) {
            try {
                policyStream = policyFileURL.openStream();
                DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
                dbFactory.setNamespaceAware(true);
                try {
                    dbFactory.setFeature("http://apache.org/xml/features/nonvalidating/load-dtd-grammar", false);
                    dbFactory.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false);
                } catch (ParserConfigurationException e) {
                    throw new IOException(e);
                }
                DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
                doc = dBuilder.parse(policyStream);
            } catch (IOException e) {
                throw new IOException("Could not read policy file located at " + policyFileURL, e);
            } catch (ParserConfigurationException e) {
                throw new IOException("Could not read policy file located at " + policyFileURL, e);
            } catch (SAXException e) {
                throw new IOException("Could not read policy file located at " + policyFileURL, e);
            } finally {
                IOUtils.closeQuietly(policyStream);
            }
        }
        if (doc == null) {
            throw new IOException(
                    "Could not find policy file. No valid location given: " + policyFileURL);
        }
        return doc;
    }

    @Override
    public Document getPolicy() {
        return FilePolicyLoader.policyDoc;
    }

}