Java by API/javax.servlet/ServletRequest

ServletRequest: getRemoteHost()

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 ExportRestriction extends HttpServlet {
  public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException,
      IOException {
    res.setContentType("text/html");
    PrintWriter out = res.getWriter();
    // Get the client"s hostname
    String remoteHost = req.getRemoteHost();
    // See if the client is allowed
    if (!isHostAllowed(remoteHost)) {
      out.println("Access <BLINK>denied</BLINK>");
    } else {
      out.println("Access granted");
      // Display download links, etc...
    }
  }
  // Disallow hosts ending with .ru
  private boolean isHostAllowed(String host) {
    return (!host.endsWith(".ru"));
  }
}

ServletRequest: getScheme()

import java.io.IOException;
import java.io.PrintWriter;
import java.security.cert.X509Certificate;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class X509Snoop extends HttpServlet {
  public void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException,
      IOException {
    res.setContentType("text/plain");
    PrintWriter out = res.getWriter();
    X509Certificate[] certs = (X509Certificate[]) req
        .getAttribute("javax.servlet.request.X509Certificate");
    if (certs != null) {
      for (int i = 0; i < certs.length; i++) {
        out.println("Client Certificate [" + i + "] = " + certs[i].toString());
      }
    } else {
      if ("https".equals(req.getScheme())) {
        out.println("This was an HTTPS request, " + "but no client certificate is available");
      } else {
        out.println("This was not an HTTPS request, " + "so no client certificate is available");
      }
    }
  }
}

ServletRequest: getServerName()

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;
  }
}

ServletRequest.getServerPort()

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;
  }
}