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440

Chapter 17 Using Applets As Servlet Front Ends

2. Create a 

URLConnection

  object. The 

openConnection

method of 

URL

 returns a 

URLConnection

 object. This object 

will be used to obtain streams with which to communicate. 

URLConnection connection = dataURL.openConnection();

3. Instruct the browser not to cache the URL data. The first 

thing you do with the 

URLConnection

 object is to specify that 

the browser not cache it. This guarantees that you get a fresh 

result each time. 

connection.setUseCaches(false); 

4. Set any desired HTTP headers. If you want to set HTTP 

request headers (see Chapter 4), you can use 

setRequest 

Property

 to do so. 

connection.setRequestProperty("header", "value");

5. Create an input stream. There are a variety of appropriate 

streams, but a common one is 

BufferedReader

. It is at the 

point where you create the input stream that the connection to 

the Web server is actually established behind the scenes.

BufferedReader in =

new BufferedReader(new InputStreamReader(

connection.getInputStream()));

6. Read each line of the document. The HTTP specification 

stipulates that the server closes the connection when it is done. 

When the connection is closed, 

readLine

 returns 

null

. So, 

simply read until you get 

null

.

String line;

while ((line = in.readLine()) != null) {

doSomethingWith(line);

}

7. Close the input stream.

in.close();

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