src/main/java/org/apache/sling/commons/osgi/bundleversion/BundleVersionInfo.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.commons.osgi.bundleversion;

import org.osgi.framework.Version;

/** Provides bundle version information, which can be
 *  extracted from bundle files or Bundle objects.
 */
public abstract class BundleVersionInfo<T> implements Comparable<BundleVersionInfo<?>> {
    
    private static final int A_GREATER = 1; 
    private static final int B_GREATER = -1;
    private static final int EQUAL = 0;
    
    /** Marker used by Maven to identify snapshots */
    public static final String SNAPSHOT_MARKER = "SNAPSHOT";
    
    /** Name of the BND attribute that provides the bundle's last modified timestamp */
    public static final String BND_LAST_MODIFIED = "Bnd-LastModified";
    
    /** Value for {@link #getBundleLastModified} if corresponding header
     *  is not present
     */
    public static final long BND_LAST_MODIFIED_MISSING = -1L;
    
    /** @return Return the source of information: underlying File or Bundle */
    public abstract T getSource();
    
    /** @return True if the provided data is a valid bundle */
    public abstract boolean isBundle();
    
    /** @return Return the bundle symbolic name, null if not available */
    public abstract String getBundleSymbolicName();
    
    /** @return Return the bundle version, null if not available */
    public abstract Version getVersion();
    
    /** @return True if the bundle version indicates a snapshot */
    public abstract boolean isSnapshot();
    
    /** Return the bundle last modification time, based on the BND_LAST_MODIFIED 
     *  manifest header, if available. This is *not* the Bundle.getLastModified()
     *  value, which refers to actions in the OSGi framework.
     *  @return BND_LAST_MODIFIED_MISSING if header not supplied */
    public abstract long getBundleLastModified();
    
    
    /** Compare based on bundle version info, and for snapshots
     *  based on {@link #getBundleLastModified}
     */
    public int compareTo(BundleVersionInfo<?> other) {
        // Handle null values
        if(other == null) {
            throw new IllegalArgumentException("b is null, cannot compare");
        }
        
        // Handle non-bundles: we don't want them!
        if(!isBundle()) {
            throw new IllegalArgumentException("Not a bundle, cannot compare: " + this);
        }
        if(!other.isBundle()) {
            throw new IllegalArgumentException("Not a bundle, cannot compare:" + other);
        }
        
        // First compare symbolic names
        int result = getBundleSymbolicName().compareTo(other.getBundleSymbolicName());
        
        // Then compare versions
        if(result == EQUAL) {
            final Version va = getVersion();
            final Version vb = other.getVersion();
            if(va == null && vb == null) {
                // result = EQUAL
            } else if(vb == null) {
                result = A_GREATER;
            } else if(va == null) {
                result = B_GREATER;
            } else {
                result = va.compareTo(vb);
            }
        }
        
        // Then, if snapshots, compare modification times, more recent comes first
        if(result == EQUAL && isSnapshot()) {
            final long ma = getBundleLastModified();
            final long mb = other.getBundleLastModified();
            if(ma > mb) {
                result = A_GREATER;
            } else if(mb > ma) {
                result = B_GREATER;
            }
        }
        
        return result;
    }

}