API filters

In this blog post, we will learn how to add filters to the API responsible for fetching the list of skills i.e. the endpoint - https://api.susi.ai/cms/getSkillList.json. The purpose of adding filters is to return a list of skills based on some parameters associated with the skill, that would be required to allow the user to get the desired response that s/he may be using to display it on the UI. Overview of the API API to fetch the list of skills - URL -  https://api.susi.ai/cms/getSkillList.json It takes 5 optional parameters - model - It is the name of the model that user is requesting group - It is the name of the group that user is requesting language - It is the name of the language that user is requesting skill - It is the name of the skill that user is requesting applyFilter - It has true/false values, depending whether filtering is required If the request URL contains the parameter applyFilter as true, in that case the other 2 compulsory parameters are - filter_name - ascending/descending, depending upon the type of sorting the user wants filter_type - lexicographical, rating, etc based on what basis the filtering is going to happen So, we will now look into adding a new filter_type to the API. Detailed explanation of the implementation We can add filters based on the key values of the Metadata object of individual skills. The Metadata object for each skill is similar to the following object - { "model": "general", "group": "Knowledge", "language": "en", "developer_privacy_policy": null, "descriptions": "A skill that returns the anagrams for a word", "image": "images/anagrams.jpg", "author": "vivek iyer", "author_url": "https://github.com/Remorax", "author_email": null, "skill_name": "Anagrams", "protected": false, "terms_of_use": null, "dynamic_content": true, "examples": ["Anagram for best"], "skill_rating": { "negative": "0", "positive": "0", "stars": { "one_star": 0, "four_star": 0, "five_star": 0, "total_star": 0, "three_star": 0, "avg_star": 0, "two_star": 0 }, "feedback_count": 0 }, "creationTime": "2017-12-17T14:32:15Z", "lastAccessTime": "2018-06-19T17:50:01Z", "lastModifiedTime": "2017-12-17T14:32:15Z" }   We will now add provision for URL parameter, filter_type=feedback in the API, which will filter the results based on the feedback_count key, which tells the number of feedback/comments a skill has received. In the serviceImpl method of the ListSkillService class, we can see a code snippet that handles the filtering part, It checks the filter_type parameter received in the URL on if-else block. The code snippet looks like this - if (filter_type.equals("date")) { . . } else if (filter_type.equals("lexicographical")) { . . } else if (filter_type.equals("rating")) { . . }   Similarly, we will need to add an else if condition with feedback_type=feedback and write the code block inside it. Here is the code for it, which is explained in detail. . . else if (filter_type.equals("feedback")) { if (filter_name.equals("ascending")) { Collections.sort(jsonValues, new Comparator<JSONObject>() { @Override public int compare(JSONObject a, JSONObject b) { Integer valA; Integer valB; int result=0; try { valA = a.getJSONObject("skill_rating").getInt("feedback_count"); valB = b.getJSONObject("skill_rating").getInt("feedback_count"); result = Integer.compare(valA, valB); } catch (JSONException e) { e.printStackTrace(); } return result; } }); } else { Collections.sort(jsonValues, new Comparator<JSONObject>() {…