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本来mysql数据库有类似ip2long的函数，但它返回的是无符号整形值，而数据库以前的字段设计为有符号的，这样当ip 以 128以上开头的ip都不能正常保存，特写了如下方法：
/**
* 包名：com.lvye.test
* 文件：Ip2Number.java
* 作者：towenc@gmail.com
* 时间：2009下午01:29:49
*
* Current revision $Revision:Revision$
* Latest change by $Author:Author$
* $Log:$
*/

package com.lvye.test;

import java.net.InetAddress;
import java.net.UnknownHostException;

/**
* @author wenc
*
*/
public class Ip2Number {

/**
* @param ip
* @return 有符号的整形数；当ip>128.0.0.0时为负数；
* @throws UnknownHostException
* @author wenc
*/
public static int ip2Int(String ip) throws UnknownHostException {
InetAddress address = InetAddress.getByName(ip);// 在给定主机名的情况下确定主机的 IP 址。
byte[] bytes = address.getAddress();// 返回此 InetAddress 对象的原始 IP 地址
int a, b, c, d;
a = byte2int(bytes[0]);
b = byte2int(bytes[1]);
c = byte2int(bytes[2]);
d = byte2int(bytes[3]);
int result = (a << 24) | (b << 16) | (c << 8) | d; return result; }
public static int byte2int(byte b) {
int l = b & 0x07f;
if (b < 0) { l |= 0x80; } return l; }
/**
* @param ip
* @return IP转化为长整形数值
* @throws UnknownHostException
* @author wenc
*/
public static long ip2long(String ip) throws UnknownHostException {
int ipNum = ip2Int(ip);
return int2long(ipNum);
}

public static long int2long(int i) {
long l = i & 0x7fffffffL;
if (i < 0) { l |= 0x080000000L; } return l; }
/**
* @param ip
* @return 长整形数值转化为ip地址
* @author wenc
*/
public static String long2ip(long ip) {
int[] b = new int[4];
b[0] = (int) ((ip >> 24) & 0xff);
b[1] = (int) ((ip >> 16) & 0xff);
b[2] = (int) ((ip >> 8) & 0xff);
b[3] = (int) (ip & 0xff);
String x;
Integer p;
p = new Integer(0);
x = p.toString(b[0]) + “.” + p.toString(b[1]) + “.” + p.toString(b[2])
+ “.” + p.toString(b[3]);

return x;

}

// 测试函数
public static void main(String[] args) throws Exception {
Integer ip = ip2Int(“192.168.0.250”);

System.out.println(ip);
System.out.println(ip2long(“192.168.0.250”));
System.out.println(long2ip(ip));

}
}