Eclipse and Web Application

I originally wrote this post at the end of 2010, so now it is slightly outdated, when I ported the Beer Selector Web Application, originally written on NetBeans, to Eclipse. But the changes relevant here are minimal, so this post could still be useful for some readers.

I had Java 6 and Tomcat 7 already installed on my (Windows 7) machine, what I missed was just the IDE itself.

Installing Eclipse

I went to the Eclipse Web Tools Platform downloads page and I got a recent build (your choice, be daring or more conservative as you like). I downloaded the zipped file, put it somewhere on my machine, unzip it, and specify in the eclipse.ini file how to reach the java virtual machine, specifying the -vm option:

-vm
C:\Program Files (x86)\Java\jdk1.6.0_20\bin\javaw.exe

Then I started Eclipse, and I went on for creating a new project. The shortcut to do that is Ctrl-N. What I wanted to create was a "Dynamic Web Project", you'll find it in the Web folder.

I gave a fancy name to the project, specified the target runtime accordingly to my container (Apache Tomcat 7) and clicked the Finish button. After that I saw in the project explorer a folder for my new web app.

Model

The beer selection is done by a POJO so I created a Java class in the project Java Resources folder:

package ch03;

public class BeerExpert {
    public String getBrand(String color, String body) {
        StringBuilder brand = new StringBuilder("Our");

        if(body.equals("light"))
            brand.append(" Wishwash ");
        else if(body.equals("medium"))
            brand.append(" GoodOl' ");
        else
            brand.append(" McCoy ");

        brand.append(color);
        return brand.toString();
    }
}

Control

Time to create the servlet BeerSelector. You can do that in a number of way, for instance you can right click on the Deployment Descriptor (DD), then in the "New..." menu item you'll find a "Servlet" item to click and start the wizard process to generate a servlet.

I specified the Java package (ch03) and the class name (BeerSelector), then clicked on next, to use a URL mapping, "/BeerSelector.do", different from the default one. I confirmed, and let the wizard doing its job.

The doGet() asks the BeerExpert for a beer name and then forward to a JSP page for displaying the result. The doPost() simply calls doGet():

protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
    String color = request.getParameter("color");
    String body = request.getParameter("body");
    String beer = new BeerExpert().getBrand(color, body);
    request.setAttribute("beer", beer);

    RequestDispatcher view = request.getRequestDispatcher("beerSelection.jsp");
    view.forward(request, response);
}

protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
    this.doGet(request, response);
}

View

I created a couple of pages in the current WebContent folder.

The user access to the Beer Selector via an HTML page that sports a form like this:

<h1 align="center">Beer Selection Page</h1>
<form method="POST" action="./BeerSelector.do">
    <p>Select beer characteristics ...</p>
    <p>Color:
    <select name="color">
        <option value="light">light</option>
        <option value="amber">amber</option>
        <option value="brown">brown</option>
        <option value="dark">dark</option>
    </select></p>

    <p>Body:
    <select name="body">
        <option value="light">light</option>
        <option value="medium">medium</option>
        <option value="heavy">heavy</option>
    </select></p>

    <p><input type="SUBMIT"></p>
</form>

And the feedback is shown in beerSelection.jsp, where the main point in it, is represented by this line:

Our beer recommendation: <%= request.getAttribute("beer") %>