Communication between 2 servlets

Question

Hi,
I’ve a problem. Not sure if it’s a simple one.
I have a web app with servlets (say Servlet1, Servlet2, etc.) in it. I use a SQL query in Servlet1 and fetch an employee’s information (say empinfo) from the database. This is a string value. Now, I need to pass this “empinfo” to Servlet2.
I might sound dumb till here but please continue till the end to know what I still have to say…
1.     I tried using getters and setters. Servlet2 has the “empinfo” value I need. This is the first time Servlet2 is accessed.
2.     But, think that Servlet1 is transferring the control to an html page. And, this html page submits its parameters (say manager) to Servlet2. And, when this html passes its control to Servlet2, the “empinfo” value I need is gone because I used “empinfo” as a class member/global.
3.     So, when the control enters the Servlet2 the second time everything is lost and this is when I need the “empinfo” value.
4.     I cannot make the “empinfo” value in Servlet2 “static” because it keeps changing.
Note: I tried with all these: httpsession, reflection, etc. but nothing seems to fulfill my task.
If I could find a way to cache the Servlet1 object to use it in Servlet2 then I think my job is half done because even if I let Servlet2 keep a reference of the Servlet1, the html page is ruining the desired result.
Hope I’m clear and it is understandable.
Any help is appreciated.
Thanks in advance.

Answer 1

Depending on your need you could use one of these:
a) use ServletContext to store the emp data, so that all other webapp elements (servlets, jsp) could access thit information:
String empInfo = ...//get it from the db
ServletContext sc = getServletContext();
sc.setAttribute("com.myapp.empInfo", empInfo);
// you can either forward / include servlet2 here, or simply let the user click a link or sth, the value will still be accessible until some other web component removes it, or you shutdown the serverb) if the flow of control in your app is that servlet1 takes the info from the db, and then the user goes to servlet2, you could store the emp info in the request as an attribute, and use a RequestDispatcher:
String empInfo = ...//get it from the db
request.setAttribute("com.myapp.empInfo", empInfo);
RequestDispatcher rd = request.getRequestDispatcher("servlet2"); // maybe this could be a JSP if it is used to present the result to the user?
if (rd != null) {
    rd.forward(request, response);
} else {
/// probably should not happen, but do take care of this
}This would require you to prevent the user form being allowed to go to servlet2 directly, not through servlet1
c) httpsession should work fine, unless you have cookies disabled, and you don't use URL rewriting, but you gave us to little information to know what is wrong
Hope I could help a little, I'm still lerning this stuff myself.