jaseninetaddressresolver.java

来自「spam source codejasen-0.9jASEN - java An」· Java 代码 · 共 165 行

/*
 * @(#)JasenInetAddressResolver.java	4/11/2004
 *
 * Copyright (c) 2004, 2005  jASEN.org
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistributions of source code must retain the above copyright notice,
 *      this list of conditions and the following disclaimer.
 *
 *   2. Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in
 *      the documentation and/or other materials provided with the distribution.
 *
 *   3. The names of the authors may not be used to endorse or promote products
 *      derived from this software without specific prior written permission.
 *
 *   4. Any modification or additions to the software must be contributed back
 *      to the project.
 *
 *   5. Any investigation or reverse engineering of source code or binary to
 *      enable emails to bypass the filters, and hence inflict spam and or viruses
 *      onto users who use or do not use jASEN could subject the perpetrator to
 *      criminal and or civil liability.
 *
 * THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESSED OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL JASEN.ORG,
 * OR ANY CONTRIBUTORS TO THIS SOFTWARE BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
 * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */
package org.jasen.net;

import java.net.InetAddress;
import java.net.UnknownHostException;
import java.security.Security;
import java.util.HashMap;

import org.jasen.error.ErrorHandlerBroker;
import org.jasen.interfaces.InetAddressResolver;

/**
 * <P>
 * 	Simple implementation of an InetAddress resolver.  This class uses a VERY rudamentary caching system
 * </P>
 * <p>
 * 	This is the default InetAddress resolver, however if full caching etc is required, it is recommended that
 *  an alternate resolver be used
 * </p>
 * @author Jason Polites
 */
public class JasenInetAddressResolver implements InetAddressResolver
{
    private HashMap inetAddressCache;
    private long ttl = 86400; // 1 day
    private int maxCache = 10000;

    /**
     *
     */
    public JasenInetAddressResolver() {
        super ();

        // attempt to cache inetaddresses for 24 hours...
        try
        {
            // TODO This doesn't seem to make any difference
            // I think we need to add an additional security policy file
            // maybe find a better way?
            Security.setProperty("networkaddress.cache.ttl", "86400");
            Security.setProperty("networkaddress.cache.negative.ttl", "86400");
        }
        catch (SecurityException e)
        {
            // Just leave the caching as it is...
            ErrorHandlerBroker.getInstance().getErrorHandler().handleException(e);
        }

    }

    /* (non-Javadoc)
     * @see org.jasen.interfaces.InetAddressResolver#getByName(java.lang.String)
     */
    public InetAddress getByName(String host) throws UnknownHostException {

        CachedInetAddress cached = null;
        InetAddress addr = null;

        if(inetAddressCache == null) {
            inetAddressCache = new HashMap();
        }

        // Try the cache first...
        cached = (CachedInetAddress)inetAddressCache.get(host);

        long time = System.currentTimeMillis() / 60L;

        if(cached != null) {
            // Have we expired?
            if(time - cached.getCachedAt() > cached.getTtl() && cached.getTtl() > 0) {
                inetAddressCache.remove(host);

                // recurse
                return getByName(host);
            }
            else
            {
                return cached.getInetAddress();
            }
        }
        else
        {
            // Perform the lookup
            if(inetAddressCache.size() <= maxCache) {
                cached = new CachedInetAddress();
                cached.setCachedAt(time);
                cached.setTtl(ttl);
                cached.setHostname(host);
            }

            try
            {
                addr = InetAddress.getByName(host);

                // Cache the hostnames
                addr.getHostName();
                addr.getAddress();
                addr.getHostAddress();

                if(cached != null) {
                    cached.setInetAddress(addr);
                }
            }
            catch (UnknownHostException e) {
                if(cached != null) {
                    cached.unknown = true;
                }

                throw e;
            }
            finally {
                inetAddressCache.put(host, cached);
            }

            return addr;
        }
    }

    /* (non-Javadoc)
     * @see org.jasen.interfaces.InetAddressResolver#getAllByName(java.lang.String)
     */
    public InetAddress[] getAllByName(String host) throws UnknownHostException {
        return InetAddress.getAllByName(host);
    }

}