Adding a new Servlet/API to SUSI Server for Skill Wiki

Susi skill wiki is an editor to write and edit skill easily. It follows an API-centric approach where the Susi server acts as API server and a web front-end  act as the client for the API and provides the user interface. A skill is a set of intents. One text file represents one skill, it may contain several intents which all belong together.

The schema for storing a skill is as following:

Using this, one can access any skill based on four tuples parameters model, group, language, skill.  To achieve this on server side let’s create an API endpoint to list all skills based on given model, groups and languages. To check the source for this endpoint clone the susi_server repository from here.

git clone https://github.com/fossasia/susi_server.git

Have a look at documentation for more information about Susi Server.

The Servlet java file is placed in susi_server/ai/susi/server/api/cms/ListSkillService. To implement the endpoint we will use the HttpServlet class which provides methods, such as doGet and doPost, for handling HTTP-specific services.

In Susi Server an abstract class AbstractAPIHandler extending HttpServelets and implementing API handler interface is provided.  Next we will inherit our ListSkillService class from AbstractAPIHandler and implement APIhandler interface.

To implement our servlet we will be overriding 4 methods namely

  • Minimal Base User role 

public BaseUserRole getMinimalBaseUserRole() {
return BaseUserRole.ANONYMOUS;
}

This method tells the minimum Userrole required to access this servlet it can also be ADMIN, USER. In our case it is Anonymous. A User need not to log in to access this endpoint.

  • Default Permissions  

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

This method returns the default permission attached with base user role, our servlets has nothing to do with it, therefore we can simply return null for this case.

  • The API Path 

public String getAPIPath() {
return "/cms/getSkillList.json";
}

This methods sets the API endpoint path, it gets appended to base path which is 127.0.0.1:4000/cms/getSkillList.json for the local host and http://api.susi.ai/cms/getSkillList.json for the server.

  • The ServiceImpl method 

public ServiceResponse serviceImpl(Query call, HttpServletResponse response, Authorization rights, final JsonObjectWithDefault permissions) {

        String model_name = call.get("model", "general");
        File model = new File(DAO.model_watch_dir, model_name);
        String group_name = call.get("group", "knowledge");
        File group = new File(model, group_name);
        String language_name = call.get("language", "en");
        File language = new File(group, language_name);

        ArrayList fileList = new ArrayList();
        fileList =  listFilesForFolder(language, fileList);
        JSONArray jsArray = new JSONArray(fileList);

        JSONObject json = new JSONObject(true)
                .put("model", model_name)
                .put("group", group_name)
                .put("language", language_name)
                .put("skills", jsArray);
        return new ServiceResponse(json);

    }

    ArrayList listFilesForFolder(final File folder,  ArrayList fileList) {

        File[] filesInFolder = folder.listFiles();
        if (filesInFolder != null) {
            for (final File fileEntry : filesInFolder) {
                if (!fileEntry.isDirectory()) {
                    fileList.add(fileEntry.getName()+"");
                }
            }
        }
        return  fileList;
    }

To access any skill we need parameters model, group, language. We get this through call.get method where first parameter is the key for which we want to get the value and second parameter is the default value. Based on received model, group and language browse files in that folder and put them in Json array to return the Service Json response.
That’s all you have successfully implemented the API endpoint to list all the skills in given model group and language. Move on and test it.

And see the resultsTo access any skill we need  parameters model, group, language. We get this through call.get method where first parameter is the key for which we want to get the value and second parameter is the default value. Based on received model, group and language browse files in that folder and put them in Json array to return the Service Json response.

 You have  successfully implemented the API endpoint to list all the skills in given model group and language. Move on and test it.

It’s easy isn’t it you have learnt how to add an endpoint in the server, it’s time to go ahead and create more endpoints to enhance Susi Server, take a look and contribute to Susi Server.