Rory Winston

Category: Coding

Topics related to software development

Coding

Process Ids and Log4J Appenders

Post author By Rory Winston
Post date September 24, 2007

If you ever need to create log files that are automatically prefixed by the process id of the native OS-level JVM process (or any other unique identifier for the VM process), it can be difficult, due to the lack of a straightforward mechanism in Java for obtaining the process handle or id. However, you can work around the limitation like this (JDK 1.5+ only):






    

import org.apache.log4j.FileAppender;



public class PidPrefixFileAppender extends FileAppender {

  

  @Override

  public void setFile(String file) {

    RuntimeMXBean rt = ManagementFactory.getRuntimeMXBean();

    super.setFile(rt.getName() + "-" + file);

  }



}

This will automatically prefix any log files created via this appender, for example:
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">

<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">

  <appender name="ConsoleAppender" class="org.apache.log4j.ConsoleAppender">
    <layout class="org.apache.log4j.PatternLayout">
      <param name="ConversionPattern" value="%d{DATE} %-5p %-15c (%F:%M:%L) – %m%n"/>
    </layout>
  </appender>

        <appender name="CacheLoadCsvAppender" class="co.uk.researchkitchen.PidPrefixFileAppender">
                <param name="File" value="cacheload.log"/>
                <layout class="org.apache.log4j.PatternLayout">
                     <param name="ConversionPattern" value="%m%n"/>
                </layout>
        </appender>

        <category name="cacheLoadLogger" additivity="false">
                <priority value="info"/>
                <appender-ref ref="CacheLoadCsvAppender"/>
        </category>


  <root>
    <priority value="info" />
  </root>

</log4j:configuration>

Will produce log files in the format processid@machine_id-cacheload.log.

Coding

Financial Engineering Cheat Sheet

Post author By Rory Winston
Post date July 1, 2007

Here is a small cheat sheet that I wrote up a week or so ago to aid in one of my exams…if you’re into this kind of stuff, then you might find it useful. I’ll just upload the PDF for now, but if you want the TeX source then let me know.

Click here :cheatsheet.pdf

Coding

Maxima, a GPL Computer Algebra System

Post author By Rory Winston
Post date February 28, 2007

The most powerful computer algebra systems available are normally commercial programs (i.e. Matlab, Mathematica or Maple). However, there is an old (and very powerful) GPL computer algebra system called Maxima, which I recently discovered. The newer versions come bundled with a WXWindows GUI called WxMaxima, which makes Maxima a friendlier environment. Maxima is capable of many of the standard numerical procedures, such as differentiation, integration, solving systems of linear equations, and matrix algrebra, and even has inline plot integration with Gnuplot and equation rendering with LateX! I would recommend giving Maxima a try.