java - 编写正则表达式模式以便于理解/维护？

Question

正则表达式模式如下:

".*/.*/.*/.*/.*/.*/(.*)-\d{2}\.\d{2}\.\d{2}.\d{4}.*"

确实很难维护。

我想知道，有没有这样的东西:

".*<userName>/.*<envName>/.*<serviceName>/.*<dataType>/.*<date>/.*<host>/(.*)-\d{2}\.\d{2}\.\d{2}.\d{4}.*<fileName>"

帮助更轻松地阅读/理解正则表达式？

更新于 2018-12-07

感谢@Liinux的帮助，它叫free-spacing一个简单的 Java 演示是:

public static void main(String[] args) {
    String re = "(?x)"
            + "# (?x) is the free-spacing flag\n"
            + "#anything here between the first and last will be ignored\n"
            + "#in free-spacing mode, whitespace between regular expression tokens is ignored\n"
            + "(19|20\\d\\d)       # year (group 1)\n"
            + "[-/\\.]             # separator\n"
            + "(\\d{2})            # month (group 2)\n"
            + "[-/\\.]             # separator\n"
            + "(\\d{2})            # day (group 3)";
    Pattern pattern = Pattern.compile(re);
    Stream.of("2018-12-07", "2018.12.07", "2018/12/07").forEach(aTest -> {
        System.out.println("**************** Testing: " + aTest);
        final Matcher matcher = pattern.matcher(aTest);
        if (matcher.find()) {
            for (int i = 1; i <= matcher.groupCount(); i++) {
                System.out.println("Group - " + i + ": " + matcher.group(i));
            }
        }
    });
}

Answer 1

如果您使用 Perl，则只需启用 /x 标志并在正则表达式中添加空格和注释即可:

qr{
    .*  # userName
    /
    .*  # envName
    /
    .*  # serviceName
    /
    .*  # dataType
    /
    .*  # date
    /
    .*  # host
    /
    (.*)-\d{2}\.\d{2}\.\d{2}.\d{4}.*  # fileName
}x

也就是说，所有这些 .* 可能应该是 [^/]* 如果这就是您的意思(一系列非斜杠字符)。

您还可以从具有合理名称的变量构建模式:

my $userName =
my $envName =
my $serviceName =
my $dataType =
my $date =
my $host = qr{[^/]*};

my $fileName = qr{(.*)-\d{2}\.\d{2}\.\d{2}.\d{4}.*};

...
qr{$userName/$envName/$serviceName/$dataType/$date/$host/$fileName}