[转]仿照hibernate 生成无重复主键

Published by admin on 01月 15, 2008

用过hibernate的人一定都知道uuid.hex主键生成方式，非常爽。

由于其生成的ID的特殊方式，很受大家喜爱。

我把hibernate这段代码搬了出来。整理了一下。方便大家用在其它地方,如附件名生成等。

代码如下：

/*
* Last Modify: 2005年1月13日 1:57:4
*/
package com.schoolwx.core.id;

import java.net.InetAddress;
import java.util.Properties;

/**
* Filename: UUIDHex.java <br>
* Ttitle: HEX类型主键生成器生成类 <br>
* Description: <br>
* Copyright:    Copyright (c) 2001-2004 schoolwxr,Inc.All Rights Reserved. <br>
* Company:     bluestar <br>
* Author:      <a href=”mailto:webmaster@schoolwx.com”>dkmilk</a> <br>
* Telephone:   86-28-85239210 <br>
* Date: 2004-9-14 <br>
* Time: 12:50:43 <br>
* Version: 2.0.0 <br>
*/
public class UUIDHex {

    private static final int IP;

    private String sep = “”;

    static {
        int ipadd;
        try {
            ipadd = toInt(InetAddress.getLocalHost().getAddress());
        } catch (Exception e) {
            ipadd = 0;
        }
        IP = ipadd;
    }

    private static short counter = (short) 0;
    private static final int JVM = (int) (System.currentTimeMillis() >>> 8);
    /**
     * Unique across JVMs on this machine (unless they load this class
     * in the same quater second - very unlikely)
     */
    private int getJVM() {
        return JVM;
    }

    /**
     * Unique in a millisecond for this JVM instance (unless there
     * are > Short.MAX_VALUE instances created in a millisecond)
     */
    private short getCount() {
        synchronized (UUIDHex.class) {
            if (counter < 0) counter = 0;
            return counter++;
        }
    }

    /**
     * Unique in a local network
     */
    private int getIP() {
        return IP;
    }

    /**
     * Unique down to millisecond
     */
    private short getHiTime() {
        return (short) (System.currentTimeMillis() >>> 32);
    }

    private int getLoTime() {
        return (int) System.currentTimeMillis();
    }

    private static int toInt(byte[] bytes) {
        int result = 0;
        for (int i = 0; i < 4; i++) {
            result = (result << - Byte.MIN_VALUE + (int) bytes[i];
        }
        return result;
    }

    public void configure(Properties params) {
        sep = params.getProperty(”seperator”);
    }
    protected String format(int intval) {
        String formatted = Integer.toHexString(intval);
        StringBuffer buf = new StringBuffer(”00000000″);
        buf.replace(8 - formatted.length(), 8, formatted);
        return buf.toString();
    }

    protected String format(short shortval) {
        String formatted = Integer.toHexString(shortval);
        StringBuffer buf = new StringBuffer(”0000″);
        buf.replace(4 - formatted.length(), 4, formatted);
        return buf.toString();
    }

    public String generate() {
        return new StringBuffer(36)
                .append(format(getIP())).append(sep)
                .append(format(getJVM())).append(sep)
                .append(format(getHiTime())).append(sep)
                .append(format(getLoTime())).append(sep)
                .append(format(getCount()))
                .toString();
    }

    public static String getUUIDHex() {
        Properties props = new Properties();
        props.setProperty(”seperator”, “”);
        UUIDHex uh = new UUIDHex();
        uh.configure(props);
        return uh.generate();
    }

    /**
     * 实例
     *
     * @param arg
     */
    public static void main(String[] arg) {
        System.out.println(UUIDHex.getUUIDHex());
    }

}