[转]仿照hibernate 生成无重复主键

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

* Ttitle: HEX类型主键生成器生成类

* Description:

* Copyright: Copyright (c) 2001-2004 schoolwxr,Inc.All Rights Reserved.

* Company: bluestar

* Author: dkmilk

* Telephone: 86-28-85239210

* Date: 2004-9-14

* Time: 12:50:43

* Version: 2.0.0

*/
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());
}

}