Password Recovery Link Generation in SUSI with JSON

In this blog, I will discuss how the SUSI server processes requests using JSON when a request for password recovery is made.. The blog post will also cover some parts of the client side implementation as well for better insight.
All the clients function in the same way. When you click on forget password button, client asks you that whether you want to recover password for your own custom server or the standard one. This choice of user defines the base URL where to make the forget password request. If you select custom server radio button, then you will be asked to enter the URL to your server, Otherwise standard base URL will be used. The API endpoint used will be


The client will make a POST request with “forgotemail” parameter containing the email id of the user making the request. Following the email id provided, server generates a client identity if and only if the email id is registered. If email id is not found in the database, server throws an exception with error code 422.

String usermail = call.get("forgotemail", null);
ClientCredential credential = new ClientCredential(ClientCredential.Type.passwd_login, usermail);
ClientIdentity identity = new ClientIdentity(, credential.getName());
if (!DAO.hasAuthentication(credential)) {
	throw new APIException(422, "email does not exist");

If the email id is found to be registered against a valid user in the database, call to a method is made which returns a random string of length passed in as a parameter. This returned random string acts as a token.
Below is the implementation of the createRandomString(int length) method.

public static String createRandomString(Integer length){
    	char[] chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789".toCharArray();
    	StringBuilder sb = new StringBuilder();
    	Random random = new Random();
    	for (int i = 0; i < length; i++) {
    	    char c = chars[random.nextInt(chars.length)];
    	return sb.toString();

This method is defined in AbsractAPIHandler class. The function createRandomString(int length) initialises an array with alphabet (both upper and lower cases) and integers 1 to 10. An object of StringBuilder is declared and initialised in the fol loop.
Next, the token generated is hashed against the user’s email id. Since we have used a token of length 30, there will be 30! (30 factorial) combinations and hence chances of two tokens to be same is ver very low (approximately Zero). Validity for token is set for 7 days (i.e. one week). After that the token will expire and to reset the password a new token will be needed.

String token = createRandomString(30);
		ClientCredential tokenkey = new ClientCredential(ClientCredential.Type.resetpass_token, token);
		Authentication resetauth = new Authentication(tokenkey, DAO.passwordreset);
		resetauth.setExpireTime(7 * 24 * 60 * 60);
		resetauth.put("one_time", true);

Everything is set by now. Only thing left is send a mail to the user. For that we call a method sendEmail() of EmailHandler class. This requires 3 parameters. User email id, subject for the email, and the body of the email. The body contains a verification link. To get this verification link, getVerificationMailContent(String token) is called and token generated in the previous step is sent to it as a parameter.

String verificationLink = DAO.getConfig("host.url", "") + "/apps/resetpass/index.html?token=" + token;

The above command gets the base URL for the server and appends the link to reset password app along with the token it received in the method call. Rest of the body is saved as a template in /conf//templates/reset-mail.txt file. Finally, if no exception was catched during the process, the message “Recovery email sent to your email ID. Please check” and accepted = true is encoded into JSON data and sent to the client. If some exceptions was encountered, The exception message and accepted = false is sent to client.
Now the client processes the JSON object and notifies the user appropriately.

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