com.ibm.jaggr.service.util.BundleVersionsHashBase.java Source code

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Here is the source code for com.ibm.jaggr.service.util.BundleVersionsHashBase.java

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/*
 * (C) Copyright 2012, IBM Corporation
 *
 * 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 com.ibm.jaggr.service.util;

import com.ibm.jaggr.core.NotFoundException;

import com.ibm.jaggr.service.IBundleResolver;

import org.apache.commons.codec.binary.Base64;
import org.osgi.framework.Bundle;

import java.security.MessageDigest;
import java.util.Arrays;
import java.util.Collections;
import java.util.Dictionary;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * Base class providing core (non-mozilla) functionality for generating a hash based on
 * the bundle header properties of a list of bundles.  This class is callable by
 * external packages (e.g. servlets) that wish to generate cache bust strings
 * in the same manner as the aggregator.
 */
public class BundleVersionsHashBase {
    private static final Logger log = Logger.getLogger(BundleVersionsHashBase.class.getName());

    private Bundle contributingBundle = null; // The contributing bundle
    private IBundleResolver bundleResolver; // The bundle resolver

    /**
     * Default constructor
     */
    public BundleVersionsHashBase() {
        bundleResolver = BundleResolverFactory.getResolver(null);
    }

    /**
     * @param contributingBundle
     */
    public BundleVersionsHashBase(Bundle contributingBundle) {
        setContributingBundle(contributingBundle);
    }

    /**
     * @return the contributing bundle
     */
    public Bundle getContributingBundle() {
        return contributingBundle;
    }

    /**
     * @param contributingBundle
     */
    public void setContributingBundle(Bundle contributingBundle) {
        this.contributingBundle = contributingBundle;
        bundleResolver = BundleResolverFactory.getResolver(contributingBundle);
    }

    /**
     * Returns the bundle headers for the specified bundle.
     *
     * @param bundleName
     *            the bundle name
     * @return the bundle headers for the bundle.
     * @throws NotFoundException if no matching bundle is found.
     */
    private Dictionary<?, ?> getBundleHeaders(String bundleName) throws NotFoundException {
        final String sourceMethod = "getBundleHeaders"; //$NON-NLS-1$
        boolean isTraceLogging = log.isLoggable(Level.FINER);
        if (isTraceLogging) {
            log.entering(BundleVersionsHashBase.class.getName(), sourceMethod, new Object[] { bundleName });
        }

        Bundle result = ".".equals(bundleName) ? contributingBundle : bundleResolver.getBundle(bundleName); //$NON-NLS-1$

        if (result == null) {
            throw new NotFoundException("Bundle " + bundleName + " not found."); //$NON-NLS-1$ //$NON-NLS-2$
        }
        if (isTraceLogging) {
            log.exiting(BundleVersionsHashBase.class.getName(), sourceMethod, result.getHeaders());
        }
        return result.getHeaders();
    }

    /**
     * Returns an MD5 hash of the concatenated bundle header values from each of the specified bundles.
     * If any of the specified bundles are not found, a {@link NotFoundException} is thrown.
     *
     * @param headerNames the bundle header values to include in the hash
     * @param bundleNames the bundle names to include in the hash
     *
     * @return the computed hash
     * @throws NotFoundException
     */
    public String generateHash(String[] headerNames, String[] bundleNames) throws NotFoundException {
        final String sourceMethod = "generateCacheBustHash"; //$NON-NLS-1$
        final boolean isTraceLogging = log.isLoggable(Level.FINER);
        if (isTraceLogging) {
            log.entering(BundleVersionsHashBase.class.getName(), sourceMethod);
        }

        // Sort the input lists so result is independent of the order the names are specified
        List<String> sortedHeaderNames = Arrays.asList(headerNames);
        List<String> sortedBundleNames = Arrays.asList(bundleNames);
        Collections.sort(sortedHeaderNames);
        Collections.sort(sortedBundleNames);

        StringBuffer sb = new StringBuffer();
        for (String bundleName : sortedBundleNames) {
            Dictionary<?, ?> bundleHeaders = getBundleHeaders(bundleName);
            for (String headerName : sortedHeaderNames) {
                Object value = bundleHeaders.get(headerName);
                if (isTraceLogging) {
                    log.finer("Bundle = " + bundleName + ", Header name = " + headerName + ", Header value = " //$NON-NLS-1$//$NON-NLS-2$//$NON-NLS-3$
                            + value);
                }
                sb.append(sb.length() == 0 ? "" : ",").append(value); //$NON-NLS-1$ //$NON-NLS-2$
            }
        }

        String result = null;
        if (sb.length() > 0) {
            MessageDigest md = null;
            try {
                md = MessageDigest.getInstance("MD5"); //$NON-NLS-1$
                result = Base64.encodeBase64URLSafeString(md.digest(sb.toString().getBytes("UTF-8"))); //$NON-NLS-1$
            } catch (Exception e) {
                if (log.isLoggable(Level.SEVERE)) {
                    log.log(Level.SEVERE, e.getMessage(), e);
                }
                throw new RuntimeException(e);
            }
        }
        if (isTraceLogging) {
            log.exiting(BundleVersionsHashBase.class.getName(), sourceMethod, result);
            ;
        }
        return result;
    }
}