Reading Servlet Response - Exercise

An Applet and Servlet that work together

Exercise scoring

Background/overview

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Instructions

1. First, copy Getter-skeleton.java to getter.java and add code to build the applet. Remember, it should:
   1. React to the button click: implement ActionListener, add yourself as a listener to the button, add code for actionPerformed()
   2. Get the text from the input field using input.getText()
   3. Build the URL for the GET request, including the parameter
   4. Send the GET to the servlet by opening the URL connection
   5. Build a BufferedReader from the connection and read the response
   6. Change the label using output.setText()
2. Compile your applet and fix any errors. Load it into a browser using the HTML provided and make sure you see the user interface you expect.
3. Next, write the servlet, naming it Greeter.java. It only needs a doGet() method, and it returns the same greeting we used in earlier versions of the servlet. If a name, such as Bill, is provided, it’s used in the greeting:

   Hello, Bill

   
   If the name is completely blank, the greeting is:
   

   Hello, whoever you are

   
   This servlet sends only the string – no HTML.
4. Compile your servlet.
5. Copy the applet’s class file; Getter.class; and the HTML, getter.html, to the directory where the Java Web Server expects to find Web pages. On my system, that’s C:\JWS\public_html.
6. Copy the servlet’s class file, Greeter.class, to the directory where the Java Web Server expects to find servlets. On my system, that’s C:\JWS\servlets.
7. Start the Java Web Server. Launch a browser, and enter this URL:

   http://localhost:8080/getter.html
   

8. Test your applet by entering a name in the input field and clicking Submit. Do you see the greeting you expect? Clear the name and click Submit again. Do you see the “Whoever you are” greeting?

Hints

1. Remember to add implements ActionListener to the line that defines your Getter applet class.
2. Remember to add a line at the end of init() that registers your applet as listening to the button:

   button.addActionListener(this);
   

3. Remember that the actionPerformed() method looks like this:

public void actionPerformed(ActionEvent event){
//deal with the event
}

1. Remember that the code in actionPerformed() to send the GET looks like this:

2. URL url = new URL(getCodeBase(),"/servlet/Greeter?name=" + name);
   URLConnection conn = url.openConnection();
   conn.setUseCaches(false);
   

   
   (You will need the name variable set before this point.)
   
3. To read the servlet response:

InputStream is = conn.getInputStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(is));String reply = reader.readLine();    is.close();