Escaping string within a Java application that would be used for regex matching in Ruby

Question

I am trying to escape a string within my Java application that would be used for regex matching in a Ruby script

I tried to use Pattern.quote(s) in Java but it appears that only add a prefix of \\Q and a suffix of \\E .

For example, this is the string that I want to escaped from my Java application and would be used for my Ruby script.

export PATH=/usr/local/eclipse:${JAVA_HOME}/bin:${PATH}

I guess I can always use String.replace("/","\\\\/") , String.replace("$", "\\\\$") and etc but it would be nice if there's an easier way to do that.

Answer 1

Since Java doesn't have much knowledge of Ruby regexp's, I'd venture this would be much easier and convenient to do in Ruby.

string_from_java = 'export PATH=/usr/local/eclipse:${JAVA_HOME}/bin:${PATH}'
escaped_string = Regexp.escape(string_from_java)
pattern = /someprefix#{escaped_string}somesuffix/

Answer 2

Yeah, it's always bugged me that they chose that approach over backslash-escaping. Here's what I use:.

public static String quotemeta(String str)
{
  if (str == null)
  {
    throw new IllegalArgumentException("String cannot be null");
  }

  int len = str.length();
  if (len == 0)
  {
    return "";
  }

  StringBuffer sb = new StringBuffer(len * 2);
  for (int i = 0; i < len; i++)
  {
    char c = str.charAt(i);
    if ("\\[](){}.*+?$^|#/".indexOf(c) != -1)
    {
      sb.append("\\");
    }
    sb.append(c);
  }
  return sb.toString();
}

I'm reasonably certain this will produce Ruby-safe strings. I did have portability in mind when I wrote it. That's why it escapes all bracket characters (opening and closing) except angle brackets as well as the hash symbol ( # ) and the forward slash ( / ).