How do I render a new .jsp file in the browser usi

My site goes to a login page that I want to redirect to another page when the user logs in. I have a "POST" method that sends the "username" and "password" to the server and the server checks if the username and password exist.

Here is my method

@POST
@Path("logIn")
public void signIn(@PathParam("profileName") String profileName, @PathParam("password") String password) {
    if (profileService.getProfile(profileName) != null && (profileService.getPassword(profileName)).equals(password)){
        //Render a new page ex "feed.jsp"
    }
    else {
          //send unsucessful message back to client?? 

}

The Client is able to POST the username and password properly and check if it exists... I just have no idea how to make it render (redirect to???) a new page

You could...

Redirect, (using Response.seeOther(URI), passing any needed values as query parameters. For example

@POST
@Path("logIn")
public Response login(@Context ServletContext context) {
    UriBuilder uriBuilder = UriBuilder.fromUri(URI.create(context.getContextPath()));
    uriBuilder.path(.. <path-to-your-jsp> ..);
    uriBuilder.queryParam("key1", "value1");
    uriBuilder.queryParam("key1", "value2");
    URI uri = uriBuilder.build();

    return Response.seeOther(uri).build();
}

Note: please see correction to this option in this answer. The above will not work.

Or you could..

Use Jersey's JSP MVC feature, and also clearly demonstrated here. For example

@POST
@Path("logIn")
public Viewable login() {
    Map<String, String> model = new HashMap<>();
    model.put("key1", "value1");
    model.put("key2", "value2");

    return new Viewable("/feed", model);
}

feed.jsp

<html>
    <body>
        <p>${it.key1}</p>
        <p>${it.key2}</p>
    </body>
</html>

Aside: Do you really want to pass the password in the URI path? hat's a huge security risk. Better actually pass it in the body of the request.

UPDATE

Now that I think about it, you should always redirect from the login POST, per the POST/REDIRECT/GET pattern. If you want to use the JSP MVC for the entire approach, you can have a controller returning a Viewable for the login page (on GET), and on success (POST), redirect to the feed controller, else redirect back the same login page (GET). There a are few different solutions.

For example

@Path("/login")
public class LoginController {

    @GET
    public Viewable loginPage() {
        ...
        return new Viewable("/login", model);  // to login.jsp
    }

    @POST
    public Response loginPost(Form form, @Context UriInfo uriInfo) {
        ...
        UriBuilder builder = uriInfo.getBaseUriBuilder();
        if (success) {
            builder.path("/feed");  // to FeedController GET
        } else {
            builder.path("/login"); // to LoginController GET
        }

        return Response.seeOther(builder.build()).build();
    }
}

@Path("/feed")
public class FeedController {

    @GET
    public Viewable getFeed() {
        ...
        return new Viewable("/feed", model);  // to feed.jsp
    }   
}