Volume: 6 Issue: 4
Enterprise Java
by Tony
Loton
Listing 1
public class LoginServlet extends HttpServlet
{
public void doGet(HttpServletRequest req
, HttpServletResponse res) throws IOException
{
// -- find out who the remote user is --
String user=req.getRemoteUser();
// -- get the current http session --
HttpSession session=req.getSession(true);
res.setContentType("text/html");
PrintWriter out =
res.getWriter();
if (user==null)
{
// -- authentication failed, show error --
}
else
{
// -- save user name for future servlets --
session.setAttribute("user", user);
// -- respond with HTML including --
// -- this link to an application --
out.println("<a href='AppPage'>Click here to run an
application.</a>");
}
}
}
Listing
2
public class AppServlet extends HttpServlet
{
public void doGet(HttpServletRequest req
, HttpServletResponse res) throws IOException
{
// -- get the current http session -
HttpSession session=req.getSession(true);
res.setContentType("text/html");
PrintWriter out = res.getWriter();
// -- get the current user --
String user=(String)
session.getAttribute("user");
if (user==null)
{
// -- not authenticated, show message --
}
else if (user.equals("bill"))
{
// -- we like this user, so run the app --
}
else
{
// -- authenticated, not allowed this app --
}
}
}
Listing 3
public void doGet(HttpServletRequest req
, HttpServletResponse res) throws IOException
{
// -- find out who the remote user is --
String user=req.getRemoteUser();
// -- get the current http session --
HttpSession session=req.getSession(true);
res.setContentType("text/html");
PrintWriter out = res.getWriter();
if (user==null)
{
// -- print the unauthorized message here --
}
else
{
// -- save the user name for future servlets --
session.setAttribute("user", user);
out.println("<html>");
out.println("<head><title>LoginServlet</title></head>");
out.println("<body>");
Vector options=new Vector();
try
{
// -- get DB connection from a datasource --
InitialContext ic = new InitialContext();
DataSource ds = (DataSource)
ic.lookup("java:comp/env/jdbc/LOTONtech");
Connection con =
ds.getConnection();
// -- select user's menu options --
Statement st=con.createStatement();
ResultSet results=st.executeQuery
("SELECT username, useroption
FROM useroptions WHERE username='"+user+"'");
while (results.next())
{
String useroption=results.getString(2);
options.addElement(useroption);
}
}
catch (Exception e)
{
out.println("ERROR: Connecting to database!");
}
//-- write the options out as html --
out.println("Welcome "+user+", choose an option:");
for (int opNum=0; opNum<options.size(); opNum++)
{
String thisOption=(String)
options.elementAt(opNum);
out.println("<a href='"+thisOption
+"' target='main'><font size=3><b>"
+thisOption+"</b></font></a>
");
}
out.println("</body>");
out.println("</html>");
}