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HomeBackend DevelopmentPHP TutorialRegular expression verification IPV4 address function example analysis

本文实例讲述了正则表达式验证IPV4地址功能。分享给大家供大家参考,具体如下:

IPV4地址由4个组数字组成,每组数字之间以.分隔,每组数字的取值范围是0-255。

IPV4必须满足以下四条规则:

1、任何一个1位或2位数字,即0-99;
2、任何一个以1开头的3位数字,即100-199;
3、任何一个以2开头、第2位数字是0-4之间的3位数字,即200-249;
4、任何一个以25开头,第3位数字在0-5之间的3位数字,即250-255。

这样把规则全部罗列出来之后,构造一个正则表达式的思路就清晰了。

首先满足第一条规则的正则是:\d{1,2}
首先满足第二条规则的正则是:1\d{2}
首先满足第三条规则的正则是:2[0-4]\d
首先满足第四条规则的正则是:25[0-5]

把它们组合起来,就得到一个匹配0-255数字的正则表达式了:

(\d{1,2})|(1\d{2})|(2[0-4]\d)|( 25[0-5])

IPV4由四组这样的数字组成,中间由.隔开,或者说由三组数字和字符.和一组数字组成,所以匹配IPV4的正则表达式如下:

(((\d{1,2})|(1\d{2})|(2[0-4]\d)|(25[0-5]))\.){3}((\d{1,2})|(1\d{2})|(2[0-4]\d)|(25[0-5]))

Java测试代码如下:

public static void matchAndPrint(String regex, String sourceText){
  Pattern pattern = Pattern.compile(regex);
  Matcher matcher = pattern.matcher(sourceText);
  while(matcher.find()){
    System.out.println(matcher.group());
  }
}
public static void main(String[] args) {
  String regex = "^(((\\d{1,2})|(1\\d{2})|(2[0-4]\\d)|(25[0-5]))\\.){3}((\\d{1,2})|(1\\d{2})|(2[0-4]\\d)|(25[0-5]))$";
  matchAndPrint(regex, "23.135.2.255");
  matchAndPrint(regex, "255.255.0.256");
  matchAndPrint(regex, "0.0.0.0");
}

输出结果如下:

23.135.2.255
0.0.0.0

这个正则有一个缺陷,就是如果不使用边界匹配的话,像第二个测试IP 255.255.0.256也会被匹配到,匹配到的结果是255.255.0.25。可以添加限制条件,前后要么是边界,要么是非数字,并且使用前后查找(lookaround),前后查找将在后面介绍。即:

(?

String regex = "(?

这样即可解决这个问题。

希望本文所述对大家正则表达式学习有所帮助。

更多正则表达式验证IPV4地址功能实例分析相关文章请关注PHP中文网!

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