ninja-core/src/main/java/ninja/template/TemplateEngineJsonP.java
public static boolean isThisASecureCallbackName(String callback) {
        return !Strings.isNullOrEmpty(callback)
                && !callback.contains("..") 
                && CALLBACK_SECURITY_VALIDATION_REGEXP.matcher(callback).matches();
    }
public static boolean isThisASecureCallbackName(String callback) {
        return !Strings.isNullOrEmpty(callback)
                && !callback.contains("..") 
                && CALLBACK_SECURITY_VALIDATION_REGEXP.matcher(callback).matches();
    }
Tests whether the given function name is a valid JSONP function
name/path.

@param callback Callback value to test.
@return Whether the given function name is a valid JSONP function
name/path.