Java by API/javax.servlet/GenericServlet

extends GenericServlet

import java.io.IOException;
import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.UnknownHostException;
import javax.servlet.GenericServlet;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
public class GetKey extends GenericServlet {
  public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {
    res.setContentType("text/plain");
    PrintWriter out = res.getWriter();
    String key = getInitParameter("key");
    String host = req.getServerName();
    int port = req.getServerPort();
    if (!keyFitsServer(key, host, port)) {
      out.println("Pirated!");
    } else {
      out.println("Valid");
    }
  }
  private boolean keyFitsServer(String key, String host, int port) {
    return true;
  }
}

GenericServlet: getInitParameterNames()

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;
import javax.servlet.GenericServlet;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
public class GetInitParams extends GenericServlet {
  public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {
    res.setContentType("text/plain");
    PrintWriter out = res.getWriter();
    out.println("Init Parameters:");
    Enumeration e = getInitParameterNames();
    while (e.hasMoreElements()) {
      String name = (String) e.nextElement();
      out.println(name + ": " + getInitParameter(name));
    }
  }
}

GenericServlet: getInitParameter(String arg0)

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class MainServlets extends HttpServlet {
  int count;
  public void init() throws ServletException {
    String initial = getInitParameter("initial");
    try {
      count = Integer.parseInt(initial);
    } catch (NumberFormatException e) {
      count = 0;
    }
  }
  public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException,
      IOException {
    res.setContentType("text/plain");
    PrintWriter out = res.getWriter();
    count++;
    out.println("Since loading (and with a possible initialization");
    out.println("parameter figured in), this servlet has been accessed");
    out.println(count + " times.");
  }
}

GenericServlet: getServletContext()

import java.io.IOException;
import java.io.PrintWriter;
import java.util.Enumeration;
import javax.servlet.GenericServlet;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
public class ServerSnoop extends GenericServlet {
  public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {
    res.setContentType("text/plain");
    PrintWriter out = res.getWriter();
    ServletContext context = getServletContext();
    out.println("req.getServerName(): " + req.getServerName());
    out.println("req.getServerPort(): " + req.getServerPort());
    out.println("context.getServerInfo(): " + context.getServerInfo());
    out.println("getServerInfo() name: " + getServerInfoName(context.getServerInfo()));
    out.println("getServerInfo() version: " + getServerInfoVersion(context.getServerInfo()));
    out.println("context.getAttributeNames():");
    Enumeration e = context.getAttributeNames();
    while (e.hasMoreElements()) {
      String name = (String) e.nextElement();
      out.println("  context.getAttribute(\"" + name + "\"): " + context.getAttribute(name));
    }
  }
  private String getServerInfoName(String serverInfo) {
    int slash = serverInfo.indexOf("/");
    if (slash == -1)
      return serverInfo;
    else
      return serverInfo.substring(0, slash);
  }
  private String getServerInfoVersion(String serverInfo) {
    // Version info is everything between the slash and the space
    int slash = serverInfo.indexOf("/");
    if (slash == -1)
      return null;
    int space = serverInfo.indexOf(" ", slash);
    if (space == -1)
      space = serverInfo.length();
    return serverInfo.substring(slash + 1, space);
  }
}

GenericServlet: init()

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class MainServlets extends HttpServlet {
  int count;
  public void init() throws ServletException {
    String initial = getInitParameter("initial");
    try {
      count = Integer.parseInt(initial);
    } catch (NumberFormatException e) {
      count = 0;
    }
  }
  public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException,
      IOException {
    res.setContentType("text/plain");
    PrintWriter out = res.getWriter();
    count++;
    out.println("Since loading (and with a possible initialization");
    out.println("parameter figured in), this servlet has been accessed");
    out.println(count + " times.");
  }
}