Prentice Hall and Sun Microsystems. Personal use only; do not redistribute.

A.17 Using Applets As Servlet Front Ends

551

7. Put the data into the buffer. For form data, use 

print

. For 

high level serialized objects, use 

writeObject

.

String val1 = URLEncoder.encode(someVal1);

String val2 = URLEncoder.encode(someVal2);

String data = "param1=" + val1 +

"¶m2=" + val2; // Note '&'

out.print(data);

// Note print, not println

out.flush(); // Necessary since no println used

8. Set the 

Content Length

 header. This header is required for 

POST

 data, even though it is unused with 

GET

 requests.

connection.setRequestProperty

("Content Length", String.valueOf(byteStream.size()));

9. Set the 

Content Type

 header. Netscape uses 

multi 

part/form data

 by default, but regular form data requires a 

setting of 

application/x www form urlencoded

, which is 

the default with Internet Explorer. So, for portability you should 

set this value explicitly when sending regular form data. The 

value is irrelevant when you are sending serialized data.

connection.setRequestProperty

("Content Type", "application/x www form urlencoded");

10. Send the real data. 

byteStream.writeTo(connection.getOutputStream());

11. Open an input stream. You typically use a 

BufferedReader

for ASCII or binary data and an 

ObjectInputStream

 for serial 

ized Java objects.

BufferedReader in =

new BufferedReader(new InputStreamReader

(connection.getInputStream()));

12. Read the result. 

The specific details will depend on what type of data the server 

sends. Here is an example that does something with each line 

sent by the server:

String line;

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

doSomethingWith(line);

}

Bypassing the HTTP Server

Applets can talk directly to servers on their home host, using any of:

  Raw sockets

  Sockets with object streams

  JDBC

  RMI

  Other network protocols

Second edition of this book: www.coreservlets.com; Sequel: www.moreservlets.com.

Servlet and JSP training courses by book's author: courses.coreservlets.com.