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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 March 02, 2011 11:39:18    Last update: March 09, 2011 12:19:30
Some peculiarities about Java PrintWriter: PrintWriter never throws any exceptions. From JavaDoc : Methods in this class never throw I/O exceptions, although some of its constructors may. The client may inquire as to whether any errors have occurred by invoking checkError(). When error occurs, you'll never know anything more than that it occured, because checkError returns boolean. When a character is out of the range of the character encoding of the PrintWriter, it prints a question mark (?). But this is not an error. Test code: import java.io.*; public class TestPrintWri... Latin1 test result: java TestPrintWriter iso-8859-1 | od -bc 000000... UTF-8 test result: java TestPrintWriter utf-8 | od -bc 0000000 141... Also, the constructor throws a FileNotFoundException when you try to write to a...
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 nogeek on February 08, 2011 13:46:18    Last update: February 08, 2011 13:46:18
Simple Java code that does XSLT on an XML file. The transform results go to STDOUT. import java.io.*; import javax.xml.parsers....
Created by Dr. Xi on February 01, 2011 14:38:55    Last update: February 01, 2011 14:40:59
Create the stuff you want to manufacture with the factory: package tc.demo; public class Junk { ... Create the factory: package tc.demo; import java.util.Enumerati... Tell Tomcat to use your factory. Create file context.xml and put it under the directory META-INF of your web application: <Context> <Resource name="/find/junk/here" ... Note that beside name , type and factory , you can put any arbitrary attribute in the Resource element. Access the thing with JNDI: <%@page language="java" import="javax.naming.*,tc.... The server side log looked like this: INFO: jndiName: here INFO: name: scope, value: ... Also note that, in contrast to Tomcat documentation , resource-ref is not needed in web.xml .
Created by voodoo on November 24, 2010 23:43:29    Last update: November 24, 2010 23:43:29
Two of the three PreparedStatement.setBinaryStream methods are not implemented as of version 9.0-801 of the PostgreSQL JDBC driver. Test program: import java.io.*; import java.sql.*; pub... Also note that setBinaryStream only works on a bytea column.
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.
Created by Dr. Xi on October 26, 2010 16:07:40    Last update: October 26, 2010 16:07:40
This is a more generic version, which can be expanded to accommodate additional file signatures. import java.io.*; import java.util.*; pu...
Created by Dr. Xi on August 03, 2010 16:23:55    Last update: October 22, 2010 15:35:20
According to Java documentation: The Java compiler and other Java tools can only process files which contain Latin-1 and/or Unicode-encoded (\udddd notation) characters. This utility converts a utf-8 encoded file to ascii with unicode escape strings for non-ascii characters. import java.io.*; /** * Reads file in U... It is equivalent to: native2ascii -encoding utf-8 using the standard Java native2ascii utility.
Created by nogeek on September 29, 2010 19:22:15    Last update: September 29, 2010 19:22:15
Assuming you are using the default server. Edit the file server/default/conf/login-config.xml Copy & paste the section: <application-policy name="web-console"> ... Change the copy to: <application-policy name="myapp"> <auth... Create users properties file Copy server/default/conf/props/jmx-console-users.properties to server/default/conf/props/myapp-users.properties . Change contents to: # users.properties file for use with the Users... Create roles properties file Copy server/default/conf/props/jmx-console-roles.properties to server/default/conf/props/myapp-roles.properties . Change contents to: # roles.properties file for use with the Users... Edit web.xml in the application myapp . Add security constraints: <security-constraint> <web-resource-col... Add file WEB-INF/jboss-web.xml with the following contents: <?xml version='1.0' encoding='UTF-8' ?> ... where myapp corresponds to the name attribute for application-policy in step 1.
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