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Appendix A

Servlet and JSP Quick Reference

2. Create an ObjectOutputStream. 

ObjectOutputStream out = 

new ObjectOutputStream(response.getOutputStream());

3. Write the data structure by using 

writeObject

. Most 

built in data structures can be sent this way. Classes you write, 

however, must implement the 

Serializable

 interface. 

SomeClass value = new SomeClass(...);

out.writeObject(value);

4. Flush the stream to be sure all content has been sent to 

the client. 

out.flush();

Sending Data by POST and Processing the 

Results Directly (HTTP Tunneling)

1. Create a 

URL

 object referring to the applet's home host. It is 

best to specify a URL suffix and construct the rest of the URL 

automatically.

URL currentPage = getCodeBase();

String protocol = currentPage.getProtocol();

String host = currentPage.getHost();

int port = currentPage.getPort();

String urlSuffix = "/servlet/SomeServlet";

URL dataURL = 

new URL(protocol, host, port, urlSuffix);

2. Create a 

URLConnection

 object. 

URLConnection connection = dataURL.openConnection();

3. Instruct the browser not to cache the results. 

connection.setUseCaches(false); 

4. Tell the system to permit you to send data, not just read 

it. 

connection.setDoOutput(true);

5. Create a 

ByteArrayOutputStream

 to buffer the data that 

will be sent to the server. The purpose of the 

ByteArray 

OutputStream

 here is the same as it is with the persistent 

(keep alive) HTTP connections shown in Section 7.4   to 

determine the size of the output so that the 

Content Length

header can be set.

ByteArrayOutputStream byteStream =

new ByteArrayOutputStream(512);

6. Attach an output stream to the 

ByteArrayOutputStream

. 

Use a 

PrintWriter

 to send normal form data. To send serial 

ized data structures, use an 

ObjectOutputStream

 instead.

PrintWriter out = new PrintWriter(byteStream, true);

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