SessionIdKit.java

/**
 * Copyright (c) 2011-2013, James Zhan 詹波 (jfinal@126.com).
 *
 * 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 net.tooan.ynpay.third.jfinal.ext.kit;

import javax.servlet.http.HttpServletRequest;
import java.security.SecureRandom;
import java.util.Random;

/**
 * SessionIdKit.
 */
public class SessionIdKit {

    protected static Random random;
    private static boolean weakRandom;
    private static volatile Object lock = new Object();

    private static final SessionIdKit me = new SessionIdKit();

    private SessionIdKit() {
        try {
            // This operation may block on some systems with low entropy. See
            // this page
            // for workaround suggestions:
            // http://docs.codehaus.org/display/JETTY/Connectors+slow+to+startup
            System.out.println("Init SecureRandom.");
            random = new SecureRandom();
            weakRandom = false;
        } catch (Exception e) {
            System.err.println("Could not generate SecureRandom for session-id randomness");
            random = new Random();
            weakRandom = true;
        }
    }

    public static final SessionIdKit me() {
        return me;
    }

    public String generate(HttpServletRequest request) {
        synchronized (lock) {
            String id = null;
            while (id == null || id.length() == 0) {    //)||idInUse(id))
                long r0 = weakRandom ? (hashCode() ^ Runtime.getRuntime().freeMemory() ^ random.nextInt() ^ (((long) request.hashCode()) << 32)) : random.nextLong();
                long r1 = random.nextLong();
                if (r0 < 0) r0 = -r0;
                if (r1 < 0) r1 = -r1;
                id = Long.toString(r0, 36) + Long.toString(r1, 36);
            }
            return id;
        }
    }
}