src/main/java/org/jmxtrans/agent/util/json/Json.java
public static org.jmxtrans.agent.util.json.JsonValue value(String string) {
    return string == null ? NULL : new JsonString(string);
  }
public static org.jmxtrans.agent.util.json.JsonValue value(String string) {
    return string == null ? NULL : new JsonString(string);
  }
Returns a JsonValue instance that represents the given string.

@param string
the string to get a JSON representation for
@return a JSON value that represents the given string