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Created by Dr. Xi on March 28, 2011 20:51:30    Last update: March 28, 2011 20:53:46
HTTP basic authentication is just Base64 encoded user name and password passed in as the Authorization header. So the following code works: // encode user name and password String credent... However, since JDK 1.2, there's a more Java friendly way: Authenticator.setDefault(new Authenticator() { ... Test code: import java.net.*; import java.io.*; pub...
Created by Dr. Xi on October 16, 2008 20:45:40    Last update: March 28, 2011 20:23:22
Java's built-in classes are way too complex/flexible for a simple protocol like HTTP. This is a wrapper to simplify HTTP GET and POST. import java.io.*; import java.net.*; imp... A simple test: import java.io.*; import java.util.*; ...
Created by Dr. Xi on March 24, 2011 12:11:14    Last update: March 24, 2011 12:22:03
This is the task: your client wants to know how the web application is used. That is pretty easy. A plethora of commercial tools or any of the free log analysis tools such as analog and AWStats would fit the bill. But here's the catch: they want to know not only what pages are visited by how many people and when, but also who logged in and did what. Your application is using form based authentication and therefore, everyone is anonymous in the web access log. What to do? This is a servlet filter that generates a web access log with authenticated user info that can be fed to log analysis tools such as analog and AWStats . Filter code (the output format is Apache...
Created by Dr. Xi on November 23, 2010 20:20:01    Last update: March 01, 2011 13:38:51
I tried to find a GZIP compression servlet filter to compress a large log file that we send down to the browser. Most of the implementations I found were overly complicated and many buggy. This is a simple implementation that worked for me. The filter: package filter.demo; import java.io.*; i... Config web.xml : <filter> <filter-name>gzipFilter</filte... The ugly anonymous inner class could have been avoided if the servlet API did not insist on ServletResponse.getOutputStream returning the bogus ServletOutputStream class (instead of the plain OutputStream ). Additional Note: In an earlier version of this filter, the gzip headers were added in doFilter , like this: // This is NOT good! if (supportsGzip) { ... It turned out that the ServletResponse methods sendError bypasses the gzip...
Created by James on February 14, 2011 12:10:19    Last update: February 14, 2011 20:22:05
I have long noticed that IE8 displays a "broken page" icon while showing my web pages, but didn't pay much attention. Since the world in general considers IE to be broken, it's not so unlogical for IE to see much of the world as broken. Until one day I noticed that the Google home page was not "broken". Then I thought may be I should fix my pages also. So I moused over the "broken page" icon, and this is what I saw: Compatibility View: websites designed for older browsers will often look better, and problems such as out-of-place menus, images, or text will be corrected. Very descriptive indeed! Older browsers? Such as Firefox 1.5? When it comes to MS products, I often had better...
Created by James on March 29, 2010 03:11:38    Last update: January 11, 2011 20:19:39
This is an age old problem. Since it comes up time and time again, I'm writing this down for future reference. Let's start with a two-column layout generated by the 2 Column Layout Generator : <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Trans... It renders like this: The left column is shorter than the right column. How to make the left and right column the same height? Adding height: 100% to the style sheet of the left column doesn't cut it. There are several hacks, none of them are straightforward: In search of the One True Layout Faux Columns Creating Liquid Layouts with Negative Margins In short, there's no instruction in CSS that tells a DIV that its height should be 100% of that of the...
Created by James on July 19, 2009 20:51:23    Last update: January 11, 2011 20:14:18
If CSS3 border-image is properly supported, making a rounded corner box is very easy. You just need a round corner image like this: The following markup: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" ... would render like this (try it in Firefox 3.5 and Google Chrome): However, IE as of version 8.0 does not support border-image . So until border-image is reliably supported in all major browsers, we still have to rely on tried and true tricks to make it work. In general, I found three general categories of tricks to make rounded corners: Good old tables. This trick creates a table of 9 cells and uses the 8 cells on the perimeter to render the borders and rounded corners. The central cell is used for...
Created by Dr. Xi on November 23, 2010 22:11:54    Last update: November 23, 2010 22:12:49
JavaDoc says that you can call getOutputStream or getWriter on ServletResponse , but you cannot call both. The second call will get IllegalStateException . So this works: import java.io.*; import javax.servlet.*; im... So does this: import java.io.*; import javax.servlet.*; im... But not this: import java.io.*; import javax.servlet.*; im... You can make the last servlet work if you insert a filter like this: import java.io.*; import javax.servlet.*; im... But depending on the underlying implementation, the order of the output strings may be undetermined.
Created by nogeek on November 11, 2010 00:26:08    Last update: November 11, 2010 00:29:43
This one is even more weird: it worked on Windows but failed on Linux, using default tools JDK1.6.0_20 on both. The exception thrown was: java.lang.RuntimeException: Invalid conversion fro... And the stack trace: java.lang.RuntimeException: Invalid conversion fro... This was the XSL used: <?xml version="1.0" encoding="ISO-8859-1"?> <xs... The problem was , DateUtil.java had two getDate methods, one taking long parameter, the other taking a String parameter. And Java's XSLT get confused about which one to use: import java.util.Date; import java.text.SimpleD...
Created by nogeek on November 04, 2010 20:00:15    Last update: November 05, 2010 14:38:43
Following are some bugs in the Xalan jar shipped with JBoss 5.1.0 GA and JBoss 6.0. The Xalan jar file is located in jboss-5.1.0.GA/lib/endorsed ( %JBOSS_HOME%/common/lib for JBoss 6.0). Test xml: <?xml version="1.0" encoding="ISO-8859-1"?> ... Test xsl: <?xml version="1.0" encoding="ISO-8859-1"?> <xs... XSLT Java code: import org.w3c.dom.*; import javax.xml.parsers.... DateUtil.java import java.util.Date; public class DateUti... XSLT output: Transformer Factory class: class org.apache.xalan.... Apparently, the output is wrong. The string "A test event" should not have been displayed.
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