Java Servlet - @WebServlet Examples

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

@WebServlet(name = "searchController", urlPatterns = {"/search/*"})
public class SearchController extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req,
                         HttpServletResponse resp) throws ServletException, IOException {
        try {
            //we are going to pause for a while
            // to simulate the expensive search process
            Thread.sleep(100);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        PrintWriter writer = resp.getWriter();
        writer.println("Test Search Result");
    }
}

import com.google.common.cache.LoadingCache;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.concurrent.ExecutionException;

@WebServlet(name = "appController", urlPatterns = {"/*"},
        loadOnStartup = 1)
public class AppController extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req,
                         HttpServletResponse resp) throws ServletException, IOException {
        Object cache = req.getServletContext().getAttribute("GLOBAL_CACHE");
        if (cache instanceof LoadingCache) {
            try {
                resp.getWriter().println((((LoadingCache) cache).get("key")));
            } catch (ExecutionException e) {
                e.printStackTrace();
            }
        }
    }

    @Override
    public void init() throws ServletException {
        super.init();
        System.out.println("servlet loaded " + this);
    }
}

import javax.servlet.ServletException;
import javax.servlet.annotation.WebInitParam;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

@WebServlet(name = "viewController", urlPatterns = {"/view/*"},
        initParams = @WebInitParam(name = "renderer-class-name"
                , value = "com.logicbig.HtmlRenderer"),
        loadOnStartup = 1)
public class ViewController extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req,
                         HttpServletResponse resp) throws ServletException, IOException {

        String renderer = getServletConfig().getInitParameter("renderer-class-name");
        PrintWriter writer = resp.getWriter();
        writer.println("renderer: " + renderer);

        String servletName = getServletConfig().getServletName();
        writer.println("servlet name " + servletName);
    }
}

import javax.servlet.AsyncContext;
import javax.servlet.AsyncEvent;
import javax.servlet.AsyncListener;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebInitParam;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.concurrent.ThreadLocalRandom;

@WebServlet(name = "myServlet", urlPatterns = {"/async-test"},
                    asyncSupported = true)
public class MyServlet extends HttpServlet {
    @Override
    protected void doGet (HttpServletRequest req,
                          HttpServletResponse resp) throws ServletException, IOException {

        PrintWriter writer = resp.getWriter();
        AsyncContext asyncContext = req.startAsync();
        asyncContext.addListener(new MyAsyncListener());

        AsyncContext finalAsyncContext = asyncContext;
        asyncContext.start(new Runnable() {
            @Override
            public void run () {
                String msg = task();
                writer.println(msg);
                finalAsyncContext.complete();
            }
        });
    }

    private String task () {
        long start = System.currentTimeMillis();
        try {
            int i = ThreadLocalRandom.current()
                                     .nextInt(1, 5);
            Thread.sleep(i * 1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return "time to complete long task " + (System.currentTimeMillis() - start);
    }
}

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.io.PrintWriter;

@WebServlet(name = "appController", urlPatterns = {"/*"},
                    loadOnStartup = 1)
public class AppController extends HttpServlet {
    @Override
    protected void doGet (HttpServletRequest req,
                          HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("Request: " + req.getRequestURL());

        resp.setContentType("text/html");
        PrintWriter writer = resp.getWriter();

        if (req.getRequestURL()
               .toString()
               .contains("secondPage")) {
            writer.write("You are on the second page<br/>");
            writer.write("myAttribute = " + req.getSession(false)
                                               .getAttribute("myAttribute"));

        } else {
            HttpSession session = req.getSession(true);
            System.out.println("session id : " + session.getId());
            session.setAttribute("myAttribute", "attrVal");
            writer.write("<a href='" + req.getContextPath() + "/secondPage;jsessionid=" + session.getId() + "'>Visit the Second page</a>");
        }

        writer.close();

    }
}