SUSI Server uses DAO in which accounting object is stored as JSONTray. SUSI clients are using this accounting object for user settings data. In this blogpost we will focus on how to use accounting JSONTray to write the user settings, so that a client can use such endpoint to store the user related settings in Susi server. The Susi server provides the required API endpoints to its web and mobile clients. Before starting with the implementation of servlet let’s take a look at Accounting.java file, to check how Susi server stores the accounting data.

public class Accounting {

        private JsonTray parent;
        private JSONObject json;
        private UserRequests requests;
        private ClientIdentity identity;
    ...
}

The JsonTray is class to hold the volume as <String,JsonObject> pairs as a Json file. The UserRequests  class holds all the user activities. The ClientIdentity class extend the base class Client and provides an Identification String for authentication of users. Now that we have understood about accounting in SUSI server let’s proceed for making an API endpoint to Store Webclient User settings. To make an endpoint we will use the HttpServlet class which provides methods, such as doGet and doPost, for handling HTTP-specific services. We will inherit our ChangeUserSettings class from AbstractAPIHandler yand implement APIhandler interface. In Susi Server the AbsrtactAPI handler extends a HTTPServlet which implements doGet and doPost ,all servlet in SUSI Server extends this class to increase code reusability.  

Since a User has to store its setting, set the minimum base role to access this endpoint to User. Apart from ‘User’ there are Admin and Anonymous roles too.

   @Override
    public BaseUserRole getMinimalBaseUserRole() {
        return BaseUserRole.USER;
    }

Next set the path for using this endpoint, by overriding getAPIPath method().

 @Override
    public String getAPIPath() {
        return "/aaa/changeUserSettings.json";
    }

We won’t be dealing with getdefault permissions so null can be return.

  @Override
    public JSONObject getDefaultPermissions(BaseUserRole baseUserRole) {
        return null;
    }

Next we implement serviceImpl method which takes four parameters the query, response, authorization and default permissions.

@Override
    public ServiceResponse serviceImpl(Query query, HttpServletResponse response, Authorization authorization, JsonObjectWithDefault permissions) throws APIException {
       String key = query.get("key", null);
       String value =query.get("value", null);
       if (key == null || value == null ) {
           throw new APIException(400, "Bad Service call, key or value parameters not provided");
       } else {
           if (authorization.getIdentity() == null) {
               throw new APIException(400, "Specified User Setting not found, ensure you are logged in");
           } else {
               Accounting accounting = DAO.getAccounting(authorization.getIdentity());
               JSONObject jsonObject = new JSONObject();
               jsonObject.put(key, value);
               if (accounting.getJSON().has("settings")) {
                   accounting.getJSON().getJSONObject("settings").put(key, value);
               } else {
                   accounting.getJSON().put("settings", jsonObject);
               }
               JSONObject result = new JSONObject();
               result.put("message", "You successfully changed settings to your account!");
               return new ServiceResponse(result);
           }
       }

    }

We will be storing the setting in Json object using key, value pairs. Take the values from user using query.get(“param”,”default value”) and set the default value to null. So that in case the parameters are not present the servlet can return “Bad service call”. To get the accounting object user identity string given by authorization.getIdentity() method is used. Now check if the same user settings is already present, if yes, overwrite it and if not append a new Json object with received key and value. And return the success message through ServiceResponse method.

Proceed to test the working of endpoint at http://127.0.0.1:4000/aaa/changeUserSettings.json?key=theme&value=dark and see if it’s stored using   http://127.0.0.1:4000/aaa/listUserSettings.json.

You have successfully created an endpoint to store user settings and  enhanced Susi Server, take a look and contribute to Susi Server.

Resources

• Read more about Servlets – https://www.tutorialspoint.com/servlets/
• The source code – ListUserSettings.java , ChangeUserSettings.java
• DAO- https://en.wikipedia.org/wiki/Data_access_object