java - quoting strings in Java

Question

Does anyone know of a library function to escape and surround a string value of an object with quotes unless it is null?

For example, the function should process:

• "hello" as "\"hello\""
• null as "null"
• Long.valueOf(2L) as "\"2\""
• "" as "\"\""
• "I\'m \"quoted\"" as "\"I\\\'m \\\"quoted\\\""

Clearly this is trivial to implement in Java, but I'm looking for a function in an existing library (e.g. JDK, Commons Lang, Spring ...) I'd be surprised if this hasn't been done before.

For reference, this is for converting objects to JavaScript strings.

Answer 1

Forget the Quoting, really. If you want to write Java to JS, use Jackson:

import java.util.Date;

import org.codehaus.jackson.map.ObjectMapper;

public class Teste {

    /**
     * @param args
     */
    public static void main(String[] args) throws Exception {
        printAsJs(null);
        printAsJs(5L);
        printAsJs("Hello!");
        printAsJs(new Date());
    }

    private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper();

    public static void printAsJs(Object o) throws Exception {
        System.out.println(OBJECT_MAPPER.writeValueAsString(o));
    }

}

If you need extra handlers to format as JS, extend ObjectMapper with your desired needs

Thank you come again

Answer 2

You can write your own using StringUtils.

import static org.apache.commongs.lang.StringUtils.*;
import org.apache.commons.lang.StringEscapeUtils.*;

public void quote(String x) {
  return escapeJavaScript(defaultString(x, "null").replaceFirst("^(.*)$", "\"$1\"")));
}

Answer 3

Your requirements are

• Surround output with quotes
• Escape quotes
• Handle null different (no surrounding quotes)

I don't know any library method fulfilling your requirements.

Anyway, it can be implemented with a one line method:

public static String quoteAndEscape(Object o) {
    return o == null ? "null" : "\"" + StringEscapeUtils.escapeJava(String.valueOf(o)) + "\"";
}