How should I escape strings in JSON?

Question

When creating JSON data manually, how should I escape string fields? Should I use something like Apache Commons Lang's StringEscapeUtilities.escapeHtml, StringEscapeUtilities.escapeXml, or should I use java.net.URLEncoder?

The problem is that when I use SEU.escapeHtml, it doesn't escape quotes and when I wrap the whole string in a pair of 's, a malformed JSON will be generated.

Answer 1

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");

Answer 2

If you are using fastexml jackson, you can use the following: com.fasterxml.jackson.core.io.JsonStringEncoder.getInstance().quoteAsString(input)

If you are using codehaus jackson, you can use the following: org.codehaus.jackson.io.JsonStringEncoder.getInstance().quoteAsString(input)

Answer 3

Apache commons lang now supports this. Just make sure you have a recent enough version of Apache commons lang on your classpath. You'll need version 3.2+

Release Notes for version 3.2

LANG-797: Added escape/unescapeJson to StringEscapeUtils.

Answer 4

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

Answer 5

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

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

Answer 6

Consider Moshi's JsonWriter class. It has a wonderful API and it reduces copying to a minimum, everything can be nicely streamed to a filed, OutputStream, etc.

OutputStream os = ...;
JsonWriter json = new JsonWriter(Okio.buffer(Okio.sink(os)));
json.beginObject();
json.name("id").value(getId());
json.name("scores");
json.beginArray();
for (Double score : getScores()) {
  json.value(score);
}
json.endArray();
json.endObject();

If you want the string in hand:

Buffer b = new Buffer(); // okio.Buffer
JsonWriter writer = new JsonWriter(b);
//...
String jsonString = b.readUtf8();