[FIXED] servlet route with GET, POST, PUT and DELETE

Issue

I'm new to Java server-side programming, my question is basically to get to a starting point using Servlets (low level without using spring mvc etc.) and then build my way up from there, coming from node.js background where a route definition would start with a function (app.get(request, response) {}, app.post(request, response) {} etc.), and the function would receive request and response in parameters for one of http methods (GET, POST, PUT, DELETE).

If someone can please help on the starting point of how do I define methods against a route (let's say /users) inside a servlet class that'd map to http methods while providing request and response in it's parameters.

My attempt

public class FirstServlet extends HttpServlet {

  public void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException , IOException {

}

Solution

I believe what you want are Servlet mappings. You can also find a bit more info here

But basically this is the way you tell the webserver (e.g. Tomcat) what servlet to use to answer requests sent to a given url pattern. Thus you map the pattern with the servlet you want to use to serve it.

You can also find more info on the inner workings here.

Edit: If you want to handle all verbs you can use a service. From the first link:

You may have seen other servlet examples implement the doPost() and/or doGet() methods. These methods reply only to POST or GET requests; if you want to handle all request types from a single method, your servlet can simply implement the service() method. (However, if you choose to implement the service() method, you cannot implement the doPost() or doGet() methods, unless you call super.service() at the beginning of the service() method.) The HTTP servlet specification describes other methods used to handle other request types, but all of these methods are collectively referred to as service methods.

All the service methods take the same parameter arguments. An HttpServletRequest provides information about the request, and your servlet uses an HttpServletResponse to reply to the HTTP client. The service method looks like the following:

public void service(HttpServletRequest req, HttpServletResponse res) throws IOException { ... }

Answered By - Acapulco
Answer Checked By - Marilyn (JavaFixing Volunteer)