ch12.htm

JAVA Developing Professional JavaApplets

<P>
There are many third-party tools available to analyze server log
files, provided they are in a &quot;common log format&quot;:
<BLOCKQUOTE>
<TT>hostname identd authuser [date] &quot;request&quot;
status length</TT>
</BLOCKQUOTE>
<P>
The first entry, <TT>hostname</TT>,
is the name of the host this connection was received from. If
the name cannot be established, this field will display the numeric
IP address of the caller. The next two fields contain information
for &quot;login&quot; and authorized user names. The HTTP server
does not support remote identification dialogs, so these fields
will appear as a single dash (<TT>-</TT>).
The date field has this format:
<BLOCKQUOTE>
<TT>DD/MMM/YYY:HH:MM:SS GGGG</TT>
</BLOCKQUOTE>
<P>
All these fields are evident except GGGG, which represents the
number of time zones away from GMT.
<P>
The request field is the first line from the request header. <TT>status</TT>
is the HTTP response code that was sent, typically 200, and <TT>length</TT>
is the total number of file bytes sent in the response. Here is
a sample log entry:
<BLOCKQUOTE>
<TT>some.name.com - - [25/Mar/1996:08:48:23
-0400] &quot;GET / HTTP/1.0&quot; 200 342</TT>
</BLOCKQUOTE>
<P>
The 200 indicates that a response containing 342 bytes was sent.
<H3><A NAME="BuildingLogInformation">Building Log Information</A>
</H3>
<P>
HTTP requests are already stored in the HTTPrequest class, so
it's reasonable to also store the log information in this class.
If the server is ever made to work concurrently, the log information
will have to travel with each request, so just add it there now:
<BLOCKQUOTE>
<TT>/**<BR>
 * This class maintains all of the information from a HTTP request
<BR>
 */<BR>
public class HTTPrequest<BR>
{<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;...<BR>
&nbsp;&nbsp;&nbsp;&nbsp;public StringBuffer log;<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;...<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;log = null;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;}<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;...<BR>
}</TT>
</BLOCKQUOTE>
<P>
A StringBuffer is used because the string will grow and be altered.
Java String objects are immutable-they can never be altered after
they are created. If you use the plus operator to grow a String,
you are actually creating a new String:
<BLOCKQUOTE>
<TT>String first = new String(&quot;This
is the first string.&quot;);<BR>
first += &quot;  This is the second string&quot;;</TT>
</BLOCKQUOTE>
<P>
The <TT>first</TT> variable now contains
a completely different string, constructed from the first string
and the addition of the second string. The original contents of
the variable are lost.
<P>
The log string will need some tweaking to bring it in line with
the common log format. That is why a StringBuffer class is used.
<P>
After a request is parsed, a new routine is added to HTTPrequest
to format the initial portions of the log entry:
<BLOCKQUOTE>
<TT>/**<BR>
 * Log a complete request.<BR>
 */<BR>
public void logRequest()<BR>
{<BR>
&nbsp;&nbsp;&nbsp;&nbsp;Date current = new Date();<BR>
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;log = new StringBuffer(&quot;&quot;);
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;if ( clientSocket == null )<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;log.append(&quot;-&quot;);
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;else<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;log.append(clientSocket.getInetAddress().getHostName());
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;log.append(&quot; - - &quot;);<BR>
&nbsp;&nbsp;&nbsp;&nbsp;log.append(formatDate(current));<BR>
&nbsp;&nbsp;&nbsp;&nbsp;log.append(&quot; \&quot;&quot; + firstLine
+ &quot;\&quot; &quot;);<BR>
}</TT>
</BLOCKQUOTE>
<H4>The Date Class</H4>
<P>
The Date class is part of the java.util package. It provides full
support for both date and time. Six different constructors for
the class, shown in the following list, offer a great deal of
flexibility in how a date is specified.<BR>
<P><CENTER><TABLE BORDERCOLOR=#000000 BORDER=1 WIDTH=80%>
<TR VALIGN=TOP><TD WIDTH=505><I>Date Class Constructors</I></TD></TR>
<TR VALIGN=TOP><TD WIDTH=505>
<BLOCKQUOTE>
<TT>Date()<BR>
Date(long totalSecs)<BR>
Date(int yr, int mth, int day)<BR>
Date(int yr, int mth, int day, int hrs, int min)<BR>
Date(int yr, int mth, int day, int hrs, int min, int sec)<BR>
Date(String s)</TT>
</BLOCKQUOTE>

</TD></TR>
</TABLE></CENTER>
<P>
<P>
The first constructor, the most commonly used, constructs a Date
class reflecting the current date and time. The other constructors
are used mainly to construct Date objects that are either forward
or backward in time. This could be done for comparison purposes:
<BLOCKQUOTE>
<TT>Date c = new Date();<BR>
Date p = new Date( c.getYear() - 1, c.getMonth(), c.getDate()
);<BR>
Date n = new Date( c.getYear() + 1, c.getMonth(), c.getDate()
);<BR>
if ( p.before( c ) )<BR>
&nbsp;&nbsp;&nbsp;&nbsp;System.out.println(&quot;Date &quot; +
p + &quot; is before Date &quot; + c);<BR>
if ( n.after( c ) )<BR>
&nbsp;&nbsp;&nbsp;&nbsp;System.out.println(&quot;Date &quot; +
n + &quot; is after Date &quot; + c);</TT>
</BLOCKQUOTE>
<P>
The Date class provides three useful comparison functions:
<UL>
<LI><TT>boolean before(Date d)</TT>
<LI><TT>boolean after(Date d)</TT>
<LI><TT>boolean equals(Date d)</TT>
</UL>
<P>
Several public methods get and manipulate Date class variables.
Table 12.2 lists the remaining public methods of the Date class.
<BR>
<P>
<CENTER><B>Table 12.2. Public methods of the Date class.</B></CENTER>
<P><CENTER><TABLE BORDERCOLOR=#000000 BORDER=1 WIDTH=80%>
<TR VALIGN=TOP><TD WIDTH=291><I>Method</I></TD><TD WIDTH=227><I>Synopsis</I>
</TD></TR>
<TR VALIGN=TOP><TD WIDTH=291><TT>int getYear()</TT>
</TD><TD WIDTH=227>Year since 1900</TD></TR>
<TR VALIGN=TOP><TD WIDTH=291><TT>void setYear(int y)</TT>
</TD><TD WIDTH=227>Year since 1900</TD></TR>
<TR VALIGN=TOP><TD WIDTH=291><TT>int getMonth()</TT>
</TD><TD WIDTH=227>Month (0-11)</TD></TR>
<TR VALIGN=TOP><TD WIDTH=291><TT>void setMonth(int m)</TT>
</TD><TD WIDTH=227>Month (0-11)</TD></TR>
<TR VALIGN=TOP><TD WIDTH=291><TT>int getDate()</TT>
</TD><TD WIDTH=227>Day of month (1-31)</TD></TR>
<TR VALIGN=TOP><TD WIDTH=291><TT>void setDate(int d)</TT>
</TD><TD WIDTH=227>Day of month (1-31)</TD></TR>
<TR VALIGN=TOP><TD WIDTH=291><TT>int getDay()</TT>
</TD><TD WIDTH=227>Day of week (0-6)[0=Sunday]</TD></TR>
<TR VALIGN=TOP><TD WIDTH=291><TT>int getHours()</TT>
</TD><TD WIDTH=227>(0-23)</TD></TR>
<TR VALIGN=TOP><TD WIDTH=291><TT>void setHours(int h)</TT>
</TD><TD WIDTH=227>(0-23)</TD></TR>
<TR VALIGN=TOP><TD WIDTH=291><TT>int getMinutes()</TT>
</TD><TD WIDTH=227>(0-59)</TD></TR>
<TR VALIGN=TOP><TD WIDTH=291><TT>void setMinutes(int m)</TT>
</TD><TD WIDTH=227>(0-59)</TD></TR>
<TR VALIGN=TOP><TD WIDTH=291><TT>int getSeconds()</TT>
</TD><TD WIDTH=227>(0-59)</TD></TR>
<TR VALIGN=TOP><TD WIDTH=291><TT>void setSeconds(int s)</TT>
</TD><TD WIDTH=227>(0-59)</TD></TR>
<TR VALIGN=TOP><TD WIDTH=291><TT>long getTime()</TT>
</TD><TD WIDTH=227>Milliseconds since 1970</TD></TR>
<TR VALIGN=TOP><TD WIDTH=291><TT>void setTime(long totalSecs)</TT>
</TD><TD WIDTH=227>Milliseconds since 1970</TD></TR>
<TR VALIGN=TOP><TD WIDTH=291><TT>int hashCode()</TT>
</TD><TD WIDTH=227>Return the object's hash code</TD></TR>
<TR VALIGN=TOP><TD WIDTH=291><TT>String toString()</TT>
</TD><TD WIDTH=227>Uses UNIX ctime conventions</TD></TR>
<TR VALIGN=TOP><TD WIDTH=291><TT>String toLocaleString()</TT>
</TD><TD WIDTH=227>Uses locale conventions</TD></TR>
<TR VALIGN=TOP><TD WIDTH=291><TT>String toGMTString()</TT>
</TD><TD WIDTH=227>Uses Internet GMT conventions</TD></TR>
<TR VALIGN=TOP><TD WIDTH=291><TT>int getTimezoneOffset()</TT>
</TD><TD WIDTH=227>Minutes from GMT</TD></TR>
</TABLE></CENTER>
<P>
<H4>Creating Common Log Date Format</H4>
<P>
None of the <TT>toString()</TT> variants
in the Date class match common log format. The following routines
use a Date class to create the correct common log date format:
<BLOCKQUOTE>
<TT>&nbsp;&nbsp;&nbsp;&nbsp;/**<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * Return the passed date as a common
log format String.<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * @param d contains the date to convert
<BR>
&nbsp;&nbsp;&nbsp;&nbsp; */<BR>
&nbsp;&nbsp;&nbsp;&nbsp;public String formatDate(Date d)<BR>
&nbsp;&nbsp;&nbsp;&nbsp;{<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return &quot;[&quot;
+ formatFor2(d.getDate()) + &quot;/&quot; + getMonthName(d) +
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&quot;/&quot;
+ (d.getYear() + 1900) +<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&quot;:&quot;
+ formatFor2(d.getHours()) +<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&quot;:&quot;
+ formatFor2(d.getMinutes()) +<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&quot;:&quot;
+ formatFor2(d.getSeconds()) +<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&quot;
&quot; + getTimezone(d) + &quot;]&quot;;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;}<BR>
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;/**<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * return a String of the passed int.&nbsp;&nbsp;The
String will<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * be formatted to take up at least two
places.<BR>
&nbsp;&nbsp;&nbsp;&nbsp; */<BR>
&nbsp;&nbsp;&nbsp;&nbsp;public String formatFor2(int n)<BR>
&nbsp;&nbsp;&nbsp;&nbsp;{<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;String ret;<BR>
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if ( n &lt; 10
)<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;ret
= new String(&quot;0&quot; + n);<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;else<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;ret
= new String(&quot;&quot; + n);<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return ret;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;}<BR>
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;/**<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * Return the timezone formatted for common
log format.<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * @param d contains the date to convert
<BR>
&nbsp;&nbsp;&nbsp;&nbsp; */<BR>
&nbsp;&nbsp;&nbsp;&nbsp;public String getTimezone(Date d)<BR>
&nbsp;&nbsp;&nbsp;&nbsp;{<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;String ret;<BR>
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;int tz = d.getTimezoneOffset();
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;int lf = tz %
60;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//
check for remainders<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tz /= 60;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;//
change to hours<BR>
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;// The polarity
of getTimezoneOffset is backwards.<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;// Positive values
mean you are behind GMT.<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;// Negative values
mean GMT is behind you.<BR>
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if ( tz &gt; 0
)<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;ret
= &quot;-&quot;;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;else if ( tz &lt;
0 )<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;ret
= &quot;+&quot;;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;else<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;ret
= &quot;&quot;;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;ret += formatFor2(tz)
+ formatFor2(lf);<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;return ret;<BR>
&nbsp;&nbsp;&nbsp;&nbsp;}<BR>
<BR>
&nbsp;&nbsp;&nbsp;&nbsp;/**<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * Return a String representing the month
name in<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * common log format.<BR>
&nbsp;&nbsp;&nbsp;&nbsp; * @param d contains the date to convert
<BR>
&nbsp;&nbsp;&nbsp;&nbsp; */<BR>
&nbsp;&nbsp;&nbsp;&nbsp;public String getMonthName(Date d)<BR>
&nbsp;&nbsp;&nbsp;&nbsp;{<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;switch ( d.getMonth()
)<BR>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{<BR>