ch9.htm

JAVA Developing Professional JavaApplets

</TD></TR>
<TR VALIGN=TOP><TD WIDTH=151><CENTER>401</CENTER></TD><TD WIDTH=240>Unauthorized
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=151><CENTER>403</CENTER></TD><TD WIDTH=240>Forbidden
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=151><CENTER>404</CENTER></TD><TD WIDTH=240>Not Found
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=151><CENTER>500</CENTER></TD><TD WIDTH=240>Internal Server Error
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=151><CENTER>501</CENTER></TD><TD WIDTH=240>Not Implemented
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=151><CENTER>502</CENTER></TD><TD WIDTH=240>Bad Gateway
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=151><CENTER>503</CENTER></TD><TD WIDTH=240>Service Unavailable
</TD></TR>
</TABLE></CENTER>
<P>
<P>
Immediately after the response header, the requested file is sent.
When the file is completely transmitted, the socket connection
is closed. Each request-response pair consumes a new socket connection.
<P>
That's enough information to construct a basic Web server. Full
information on the HTTP protocol can be retrieved from <TT>HTTP://www.w3.org/</TT>.
<H3><A NAME="BasicWebServer">Basic Web Server</A></H3>
<P>
The basic Web server will follow the construction of the SimpleWebServer
from Listing 9.2. Many improvements will have to be made to method
and response handling. The simple server does not parse or store
the request header as it arrives. The new Web server will have
to parse and store the requests for later processing. To do this,
you need a class to contain an HTTP request.
<H4>HTTPrequest Class</H4>
<P>
Listing 9.5 shows the complete HTTPrequest class. The class must
contain all the information that could be conveyed in a request
header.
<HR>
<BLOCKQUOTE>
<B>Listing 9.5. The HTTPrequest class.<BR>
</B>
</BLOCKQUOTE>
<BLOCKQUOTE>
<TT>import java.io.*;<BR>
import java.util.*;<BR>
import java.net.*;<BR>
import NameValue;<BR>
<BR>
/**<BR>
 * This class maintains all the information from an HTTP request
<BR>
 */<BR>
public class HTTPrequest<BR>
{<BR>
&nbsp;&nbsp;&nbsp;&nbsp;public String version;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;public String method;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;public String file;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;public Socket clientSocket;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;public DataInputStream inbound;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;public NameValue headerpairs[];<BR>
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;/**<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * Create an instance of this class<BR>
&nbsp;&nbsp;&nbsp;&nbsp; */<BR>
&nbsp;&nbsp;&nbsp;&nbsp;public HTTPrequest()<BR>
&nbsp;&nbsp;&nbsp;&nbsp;{<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;version = null;
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;method = null;
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;file = null;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;clientSocket =
null;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;inbound = null;
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;headerpairs =
new NameValue[0];<BR>
&nbsp;&nbsp;&nbsp;&nbsp;}<BR>
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;/**<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * Add a name/value pair to the internal
array<BR>
&nbsp;&nbsp;&nbsp;&nbsp; */<BR>
&nbsp;&nbsp;&nbsp;&nbsp;public void addNameValue(String name,
String value)<BR>
&nbsp;&nbsp;&nbsp;&nbsp;{<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;try<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;NameValue
temp[] = new NameValue[ headerpairs.length + 1 ];<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;System.arraycopy(headerpairs,
0, temp, 0, headerpairs.length);<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;temp[
headerpairs.length ] = new NameValue(name, value);<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;headerpairs
= temp;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;catch (NullPointerException
npe)<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;System.out.println(&quot;NullPointerException
while adding name-value: &quot; + </TT><FONT FACE="ZapfDingbats">&Acirc;</FONT><TT>npe);
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<BR>
&nbsp;&nbsp;&nbsp;&nbsp;}<BR>
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;/**<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * Renders the contents of the class in
String format<BR>
&nbsp;&nbsp;&nbsp;&nbsp; */<BR>
&nbsp;&nbsp;&nbsp;&nbsp;public String toString()<BR>
&nbsp;&nbsp;&nbsp;&nbsp;{<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;String s = method
+ &quot; &quot; + file + &quot; &quot; + version + &quot;\n&quot;;
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;for (int x = 0;
x &lt; headerpairs.length; x++ )<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
s += headerpairs[x] + &quot;\n&quot;;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return s;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;}<BR>
}</TT>
</BLOCKQUOTE>
<HR>
<P>
The NameValue class simply stores two strings: name and value.
You can find the source code for it on the CD-ROM in NameValue.java.
When a new pair needs to be added, a new array is allocated. The
new array receives a copy of the old array as well as the new
member. The old array is then replaced with the newly created
entity.
<P>
Two data fields in the class are not directly part of an HTTP
request. The <TT>clientSocket</TT>
member allows response routines to get an output stream, and the
<TT>inbound</TT> member allows easy
closure after a request has been processed. The remaining members
are all part of an HTTP request. The method <TT>toString()</TT>
allows class objects to be printed using &quot;plus notation.&quot;
The following line will display the contents of a request by invoking
the <TT>toString()</TT> method:
<BLOCKQUOTE>
<TT>System.out.println(&quot;Request: &quot;
+ request);</TT>
</BLOCKQUOTE>
<P>
Now that the request container is finished, it's time to populate
it.
<H4>BasicWebServer Class</H4>
<P>
This is the main class for the server. It can be broken down into
request and response routines. Since this is a server, the request
routines will be activated first. After some validation, the response
routines will be called. Listing 9.6 provides the routines to
parse an HTTP request.
<HR>
<BLOCKQUOTE>
<B>Listing 9.6. HTTP request routines.<BR>
</B>
</BLOCKQUOTE>
<BLOCKQUOTE>
<TT>&nbsp;&nbsp;&nbsp;&nbsp;/**<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * Read an HTTP request into a continuous
String.<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * @param client a connected client stream
socket.<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * @return a populated HTTPrequest instance
<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * @exception ProtocolException If not
a valid HTTP header<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * @exception IOException<BR>
&nbsp;&nbsp;&nbsp;&nbsp; */<BR>
&nbsp;&nbsp;&nbsp;&nbsp;public HTTPrequest GetRequest(Socket client)
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;throws IOException,
ProtocolException<BR>
&nbsp;&nbsp;&nbsp;&nbsp;{<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;DataInputStream
inbound = null;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;HTTPrequest request
= null;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;try<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//
Acquire an input stream for the socket<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;inbound
= new DataInputStream(client.getInputStream());<BR>
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//
Read the header into a String<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;String
reqhdr = readHeader(inbound);<BR>
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//
Parse the string into an HTTPrequest instance<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;request
= ParseReqHdr(reqhdr);<BR>
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//
Add the client socket and inbound stream<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;request.clientSocket
= client;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;request.inbound
= inbound;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;catch (ProtocolException
pe)<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if
( inbound != null )<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;inbound.close();
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;throw
pe;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;catch (IOException
ioe)<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if
( inbound != null )<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;inbound.close();
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;throw
ioe;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return request;
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;}<BR>
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;/**<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * Assemble an HTTP request header String
<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * from the passed DataInputStream.<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * @param is the input stream to use<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * @return a continuous String representing
the header<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * @exception ProtocolException If a pre
HTTP/1.0 request<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * @exception IOException<BR>
&nbsp;&nbsp;&nbsp;&nbsp; */<BR>
&nbsp;&nbsp;&nbsp;&nbsp;private String readHeader(DataInputStream
is)<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;throws IOException,
ProtocolException<BR>
&nbsp;&nbsp;&nbsp;&nbsp;{<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;String command;
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;String line;<BR>
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;// Get the first
request line<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if ( (command
= is.readLine()) == null )<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;command
= &quot;&quot;;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;command += &quot;\n&quot;;
<BR>
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;// Check for HTTP/1.0
signature<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if (command.indexOf(&quot;HTTP/&quot;)
!= -1)<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//
Retrieve any additional lines<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;while
((line = is.readLine()) != null&nbsp;&nbsp;&amp;&amp;&nbsp;&nbsp;!line.equals(&quot;&quot;))
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;command
+= line + &quot;\n&quot;;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;else<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;throw
new ProtocolException(&quot;Pre HTTP/1.0 request&quot;);<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return command;
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;}<BR>
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;/**<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * Parsed the passed request String and
populate an HTTPrequest.<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * @param reqhdr the HTTP request as a
continous String<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * @return a populated HTTPrequest instance
<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * @exception ProtocolException If name,value
pairs have no ':'<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * @exception IOException<BR>
&nbsp;&nbsp;&nbsp;&nbsp; */<BR>
&nbsp;&nbsp;&nbsp;&nbsp;private HTTPrequest ParseReqHdr(String
reqhdr)<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;throws IOException,
ProtocolException<BR>
&nbsp;&nbsp;&nbsp;&nbsp;{<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nb