Logo Questions Linux Laravel Mysql Ubuntu Git Menu
 

How should I escape strings in JSON?

People also ask

How do you escape space in JSON?

You can use \u0020 to escape the ' ' character in JSON.

Can JSON have escape characters?

If the source data contains special characters, the FOR JSON clause escapes them in the JSON output with \ , as shown in the following table. This escaping occurs both in the names of properties and in their values.

How do you escape a JSON string in Java?

You can escape String in Java by putting a backslash in double quotes e.g. " can be escaped as \" if it occurs inside String itself. This is ok for a small JSON String but manually replacing each double quote with an escape character for even a medium-size JSON is time taking, boring, and error-prone.

How do you escape a string?

In the platform, the backslash character ( \ ) is used to escape values within strings. The character following the escaping character is treated as a string literal.


Ideally, find a JSON library in your language that you can feed some appropriate data structure to, and let it worry about how to escape things. It'll keep you much saner. If for whatever reason you don't have a library in your language, you don't want to use one (I wouldn't suggest this¹), or you're writing a JSON library, read on.

Escape it according to the RFC. JSON is pretty liberal: The only characters you must escape are \, ", and control codes (anything less than U+0020).

This structure of escaping is specific to JSON. You'll need a JSON specific function. All of the escapes can be written as \uXXXX where XXXX is the UTF-16 code unit¹ for that character. There are a few shortcuts, such as \\, which work as well. (And they result in a smaller and clearer output.)

For full details, see the RFC.

¹JSON's escaping is built on JS, so it uses \uXXXX, where XXXX is a UTF-16 code unit. For code points outside the BMP, this means encoding surrogate pairs, which can get a bit hairy. (Or, you can just output the character directly, since JSON's encoded for is Unicode text, and allows these particular characters.)


Extract From Jettison:

 public static String quote(String string) {
         if (string == null || string.length() == 0) {
             return "\"\"";
         }

         char         c = 0;
         int          i;
         int          len = string.length();
         StringBuilder sb = new StringBuilder(len + 4);
         String       t;

         sb.append('"');
         for (i = 0; i < len; i += 1) {
             c = string.charAt(i);
             switch (c) {
             case '\\':
             case '"':
                 sb.append('\\');
                 sb.append(c);
                 break;
             case '/':
 //                if (b == '<') {
                     sb.append('\\');
 //                }
                 sb.append(c);
                 break;
             case '\b':
                 sb.append("\\b");
                 break;
             case '\t':
                 sb.append("\\t");
                 break;
             case '\n':
                 sb.append("\\n");
                 break;
             case '\f':
                 sb.append("\\f");
                 break;
             case '\r':
                sb.append("\\r");
                break;
             default:
                 if (c < ' ') {
                     t = "000" + Integer.toHexString(c);
                     sb.append("\\u" + t.substring(t.length() - 4));
                 } else {
                     sb.append(c);
                 }
             }
         }
         sb.append('"');
         return sb.toString();
     }

Try this org.codehaus.jettison.json.JSONObject.quote("your string").

Download it here: http://mvnrepository.com/artifact/org.codehaus.jettison/jettison


org.json.simple.JSONObject.escape() escapes quotes,\, /, \r, \n, \b, \f, \t and other control characters. It can be used to escape JavaScript codes.

import org.json.simple.JSONObject;
String test =  JSONObject.escape("your string");

There is now a StringEscapeUtils#escapeJson(String) method in the Apache Commons Text library.

The methods of interest are as follows:

  • StringEscapeUtils#escapeJson(String)
  • StringEscapeUtils#unescapeJson(String)

This functionality was initially released as part of Apache Commons Lang version 3.2 but has since been deprecated and moved to Apache Commons Text. So if the method is marked as deprecated in your IDE, you're importing the implementation from the wrong library (both libraries use the same class name: StringEscapeUtils).

The implementation isn't pure Json. As per the Javadoc:

Escapes the characters in a String using Json String rules.

Escapes any values it finds into their Json String form. Deals correctly with quotes and control-chars (tab, backslash, cr, ff, etc.)

So a tab becomes the characters '\' and 't'.

The only difference between Java strings and Json strings is that in Json, forward-slash (/) is escaped.

See http://www.ietf.org/rfc/rfc4627.txt for further details.


org.json.JSONObject quote(String data) method does the job

import org.json.JSONObject;
String jsonEncodedString = JSONObject.quote(data);

Extract from the documentation:

Encodes data as a JSON string. This applies quotes and any necessary character escaping. [...] Null will be interpreted as an empty string