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Dynamic URL routes with java EE

I'm super new to java web application development. Working on basic Todos app. So far app is working fine. I wish to add dynamic url routes like updateTodos, deleteTodos to existing path.
Expected behavior as shown below
/todos
*render todos list*
/todos/update
*render updateTodos.jsp*
/todos/delete
*render deleteTodos.jsp*
Below is my code
#WebServlet(urlPatterns = "/todos")
public class UserTodos extends HttpServlet {
private TodoService todoService = new TodoService();
#Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException {
if(request.isRequestedSessionIdValid()){
request.setAttribute("userName", request.getParameter("userName"));
request.setAttribute("allTodos", todoService.retrieveTodos());
request.getRequestDispatcher("WEB-INF/views/todos.jsp").forward(request, response);
}else{
response.sendRedirect("/login");
}
}
}
My understanding is so far that the annotation #WebServlet triggers the class file based on route defined. Can I achieve the above with a single class file?
Something like being done in JS web-framework Express-JS
If I sum-up my whole query is - Is it possible to multiple doGet and doPost methods in a single class file which will be executed based on user's URL accessed?
Update
I was able to achieve this, not sure whether this is correct implementation or not :/

How to handle a POST request with a Servlet API

I am trying to make an API with Jetty Server, and I have this simple GET request:
#GET
public String helloWorld(){
return "Hello world";
}
In order to make a POST request, I assume that one must save the input to the Jetty server. I have tried to research for quite a while, but found nothing.
I imagine something like this:
#POST
public void Save(String stringToSave) {
// Save to DB?
}

You could likely google this but let me give you a quick overview. A Servlet is a chunk of code that is normally run during an HTTP action - GET, POST, etc. It is the original technology of the JavaEE world, having been released in the late 1990's.
A simple Java servlet, using modern annotations, would look something like:
#WebServlet(name = "SampleServlet", urlPatterns = "/sampleServlet")
public class SampleServlet extends HttpServlet {
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// called when an HTTP POST is sent
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// called when an HTTP GET is sent
}
}
The important parts to note are that the class extends HttpServlet and that you have to write code to pull data out of the request and push it into the response. This isn't bad to do but it does have to be done.
JAX-RS is a newer standard, aimed simplifying the creation of REST services. It too is a chunk of code that runs during an HTTP interaction.
A simple example of this would be:
#Path("/sampleService")
public class SampleService{
#Consumes({MediaType.APPLICATION_JSON, MediaType.APPLICATION_XML})
#Produces({MediaType.APPLICATION_JSON, MediaType.APPLICATION_XML})
#POST
#Path("/v1/hello")
public Response sayHello( SomeObject someobject ) {
The code here is both simpler and a bit more complex. The use of annotations helps determine the path that the service exists on a URL (in this case /sampleService/v1/hello), the HTTP method, and the Content-Type for both the request and response. Additionally, if the SomeObject object is defined correctly, the JAX-RS framework will automatically deserialize the incoming JSON or XML payload into an object for you.
The Response object contains the HTTP response code (perhaps a teapot) and a response body. In this example, the body will be automatically serialized back to the requestor in a way that matches the Accept header of the HTTP request (i.e., JSON for an application/json Accept header and XML for application/xml).
Note that while not directly related the JAX-RS framework takes advantage of the Servlet framework. Indeed in JAX-RS you can access the HttpServletRequest and HttpServletResponse object in your methods.
Which way is "better"? In general I would recommend using JAX-RS where possible as it is the newer standard and is a bit easier to implement. However, if you do any work in the JavaEE world you're very likely to run into Servlet code so it's important to understand it too.
Note that both Servlets and JAX-RS require an application server of some sort. Jetty is one of those. Another very common one is Tomcat. The application server sets up the environment for your code and listens for incoming HTTP messages. When it gets one it looks to see if it knows how to handle the URL and routes to the appropriate place. In the servlet world the server routes solely on the URL. In the JAX-RS world the server routes on the URL and, if specified by the #Consumes annotation, the HTTP Content-Type header too.
There is much more but let's start there and see if it answers what you're after.

Adding cookie to all responses in Jersey / JAX-RS (Scala)

Thought this would be a common use case but I'm coming up short. Also, I'm using Scala but a Java answer would be fine, too.
In Jersey I'd like to set a simple cookie on all responses coming out of my app.
A quick google shows that I can set cookies on a single response by performing the following:
return Response.ok(new Viewable("/index", model))
.cookie(new NewCookie("name", "Hello, world!"))
.build();
That's great if I just want to set a cookie on a per-response basis, but I want it on every response. This seems like a job for middleware. The Jersey Docs recommend this for setting up middleware:
class MyResponseMiddleware ContainerResponseFilter {
override def filter(req: ContainerRequestContext, res: ContainerResponseContext) = {
// do stuff here
}
}
The problem is there's no way to set a cookie on the ContainerResponseContext as .getCookies returns a read-only map, unlike .getHeaders() which is mutable.
I also tried to create a cookie by setting the headers:
containerResponseContext.getHeaders().add(HttpHeaders.SET_COOKIE, new NewCookie(...)) but this did not make it to the browser.
It seems like if I could get a reference to ServletResponse or HttpServletResponse this would be simple but that doesn't appear to be possible in Jersey's middleware (filters).
This seems like a pretty straightforward use-case so I feel like I'm missing something obvious.

You can simply Inject HttpServletResponse into the filter.
Use #Context annotation as follows.
#Provider
public class ResponseHTTPStatusFilter implements ContainerResponseFilter{
#Context HttpServletResponse resp;
#Override
public void filter(ContainerRequestContext requestContext, ContainerResponseContext responseContext) throws IOException {
resp.addCookie(cookie);
}
}

Configure Response object for Rest Services inside a Jersey-Grizzly server, in OSGi container (CORS error prevention with Jersey 1x)

The last couple of days, I have been struggling with an issue. I've created a rest service hosted by a Grizzly server inside an OSGi container. Everything is working perfectly at this point.
Now, I want to add a header in every response.Not so complex or illogical right? Yet, I can't find a way to do it.
I have tried to:
1) Get the response object inside the rest functions as this question suggests (pretty textbook when you are not under OSGi).
2) Add a handler using the code above (in this case the service method is never called)
server.getServerConfiguration().addHttpHandler(
new HttpHandler() {
#Override
public void service(Request arg0, Response arg1)
throws Exception {
arg1.setHeader("Access-Control-Allow-Origin", "*");
}
});
I am using jersey-server/client/core 1.18.1 and grizzly2-server 1.18.1, hence i prefer a solution that can be applied in this version, but I am willing to update jar versions if it cannot be done in 1.18.x.

You could give a try to Jersey filters.
In a nutshell, you should create class implementing ContainerResponseFilter:
public class MyFilter implements ContainerResponseFilter {
#Override
public void filter(
ContainerRequest request,
ContainerResponse response
) throws IOException {
request.getHttpHeaders().add(<header name>, <header value>);
}
}
Then, you should register this filter in your Jersey server configuration.
Please, note, that this filter would be invoked on every response. To bind it only to specific resources, you could use annotation-binding, that is described here.
All other information you could find here.

Jersey Async ContainerRequestFilter

I have a Jersey REST API and am using a ContainerRequestFilter to handle authorization. I'm also using #ManagedAsync on all endpoints so that my API can serve thousands of concurrent requests.
My authorization filter hits a remote service, but when the filter is run, Jersey hasn't yet added the current thread to it's internal ExecutorService, so I'm completely losing the async benefits.
Can I tell Jersey that I want this ContainerRequestFilter to be asynchronous?
#Priority(Priorities.AUTHORIZATION)
public class AuthorizationFilter implements ContainerRequestFilter
{
#Inject
private AuthorizationService authSvc;
#Override
public void filter(ContainerRequestContext requestContext) throws IOException
{
String authToken = requestContext.getHeaderString(HttpHeaders.AUTHORIZATION);
// HITS A REMOTE SERVER
AuthorizationResponse authResponse = authSvc.authorize(authToken);
if (!authResponse.isAuthorized())
{
requestContext.abortWith(Response.status(Response.Status.UNAUTHORIZED)
.entity("unauthorized!")
.build());
}
}
}
And here's an example resource:
#Path("/stuff")
#Produces(MediaType.APPLICATION_JSON)
public class StuffResource
{
#GET
#Path("/{id}")
#ManagedAsync
public void getById(#PathParam("id") long id, #Suspended final AsyncResponse ar)
{
Stuff s;
// HIT THE DATABASE FOR STUFF
ar.resume(s);
}
}
UPDATE Just heard back from the Jersey guys, and this is not possible as of 2.7. Only the resource method itself is invoked asynchronously, not filters. Any suggestions for proceeding still welcome.

This is not built in to Jersey as of 2.7.
#ManagedAsync is useless if you have any filters or interceptors that do any serious work (like hit a remote authorization service). They may add the ability to run filters asynchronously in the future, but for now you're on your own.
UPDATE - there are other ways...
After a long and perilous journey, I have found a very hacky solution that I'm using in the short term. Here is a rundown of what I tried and why it failed/worked.
Guice AOP - failed
I use Guice for DI (getting Guice injection to work with Jersey is a feat in itself!), so I figured I could use Guice AOP to get around the issue. Though Guice injection works, it is impossible to get Guice to create resource classes with Jersey 2, so Guice AOP cannot work with resource class methods. If you are trying desperately to get Guice to create resource classes with Jersey 2, don't waste your time because it will not work. This is a well-known problem.
HK2 AOP - RECOMMENDED SOLUTION
HK2 just recently released an AOP feature, see this question for details on how to get it working.
Monitoring - also worked
This is not for the faint of heart, and it is completely discouraged in the Jersey docs. You can register and ApplicationEventListener and override onRequest to return a RequestEventListener that listens for RESOURCE_METHOD_START and calls an authentication/authorization service. This event is triggered from the #ManagedAsync thread, which is the whole goal here. One caveat, the abortWith method is a no-op, so this won't work quite like a normal ContainerRequestFilter. Instead, you can throw an exception if auth fails instead, and register an ExceptionMapper to handle your exception. If someone is bold enough to give this a try, let me know and I'll post code.

I am not sure if this is what you were looking for but, have you looked into Spring's OncePerRequestFilter? I am currently using it for my authorization layer where each request goes through some filter that extends this OncePerRequestFilter depending on how my filters are mapped to the URLs. Here's a quick overview of how I am using it:
Authentication/Authorization of a resource in Dropwizard
I am not very clear on the async dispatch parts of these filters but I hope this link atleast sheds some light to what you are trying to achieve!

We use Spring security for authentication/authorization. I worked around the problem using a sub-resource locator with empty path as shown below:
#Path("/customers")
public class CustomerResource {
#Inject
private CustomerService customerService;
#Path("")
public CustomerSubResource delegate() {
final Authentication auth = SecurityContextHolder.getContext().getAuthentication();
return new CustomerSubResource(auth);
}
public class CustomerSubResource {
private final Authentication auth;
public CustomerSubResource(final Authentication auth) {
this.auth = auth;
}
#POST
#Path("")
#Produces(MediaType.APPLICATION_JSON)
#Consumes(MediaType.APPLICATION_JSON)
#ManagedAsync
public void createCustomer(final Customer customer, #Suspended final AsyncResponse response) {
// Stash the Spring security context into the Jersey-managed thread
SecurityContextHolder.getContext().setAuthentication(this.auth);
// Invoke service method requiring pre-authorization
final Customer newCustomer = customerService.createCustomer(customer);
// Resume the response
response.resume(newCustomer);
}
}
}