Our RPXResults servlet will do its thing silently, and then redirect back to the first page. We'll have to change the first page to be a servlet rather than a static HTML page, so that we can dynamically change it based on the user's logged in status.
Note that we could do the same thing with a static HTML page that included GWT components. We could in a GWT pane display the "Sign In" or "Sign Out" links, and use GWT calls to the server to see if the user is logged in or not. Eventually we'll get around to that sort of thing, but for now I'd like to keep it as simple as possible.
First step, change the main page of the site to be a servlet. Right click on war/WEB-INF/web.xml and choose Open With->Text Editor.
Enter the info for a new servlet (you remember how, right?) to be used as the main page. You don't need to have a servlet mapping for this servlet, but it might come in handy later to have it map to something like /front. Then copy the welcome-file-list section down to just before /web-app, and change the welcome file to be the name you gave to the servlet.
Now create the servlet (which you also remember, right?). Go ahead and put in the code to create the PrintWriter.
Let me describe the easy way (at least in the short term) to do this, which makes the code very ugly and the HTML almost impossible to maintain. Then we'll look at the hard way to do it, which makes the code nicer and the HTML easier to maintain.
The easy way is to output the HTML using our PrintWriter:
writer.println ("<html>");
writer.println ("<head>");
writer.println ("<meta http-equiv=\"content-type\" content=\"text/html; charset=UTF-8\">");
Etc, printing the entire HTML file using the PrintWriter. Notice the need to escape the double quotes inside the output using a backslash. This method is easy, because we don't have to work with anything but the servlet, but it makes it nearly impossible to easily change the HTML later.
The harder way (in the short run at least) is to use a templating engine. A templating engine is server side code that allows us to write the HTML in a file of its own, with a mini-programming language for making decisions. The servlet will execute that template file and provide any information it needs to make decisions. The result is the HTML that should be sent to the client.
There are lots of templating engines out there. I'm going to use FreeMarker, which integrates well with Java servlets and Eclipse.
So before we can use FreeMarker, we have to install it and the Eclipse plugin for it.
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