radioAe6rt

Creating signed tags in git

radioae6rt — Thu, 29 Sep 2011 23:51:10 +0000

http://www.evernote.com/shard/s57/sh/b82cdb18-d501-422b-aaa7-d6f331ab930e/de9a93a005f62aa9ad2a9c8c6aabd675

Tomcat7 port of distributed session manager

radioae6rt — Sat, 20 Aug 2011 18:41:42 +0000

Jon Brisbin wrote a super-clean Tomcat6 distributed session manager based on RabbitMQ. If you want to read clean code, read that stuff. It’s beautiful.

https://github.com/jbrisbin/vcloud

I ported the session manager to Tomcat7, here:

https://github.com/ae6rt/vcloud/tree/Tomcat7

Caching Struts Tiles

radioae6rt — Sat, 30 Jul 2011 20:43:13 +0000

This is not an easy nut to crack, but if you want to cache Struts Tiles, you can clone the Tiles JSP InsertTag to suit the need. Around where doInclude(page) appears, render the referenced JSP page using an HTTPResponseWrapper, and ehcache the result before writing it to the tag pageContext writer. You might also consider augmenting the tile controller with a getCacheKey() method that returns a rich cache key in the form of a java.lang.Object with judiciously implemented overrides of equals() and hashcode(). Then, in the tag code, you can get a reference to the controller and therefore to getCacheKey() and cache the rendered-in-place content.

Java TimeUUID vs UUID.randomUUID()

radioae6rt — Thu, 30 Jun 2011 01:24:51 +0000

This is a great video of SriSatish Ambati discussing a number of useful Java garbage collection and concurrency issues

Among the many things I learned: at 38:00, use TimeUUID instead of UUID.randomUUID(). The latter is affected by SHA overhead and filesystem calls to /dev/urandom, while the former is not.

Here’s a reference to where you can find an implementation for TimeUUID:

http://wiki.apache.org/cassandra/FAQ#working_with_timeuuid_in_java

Nice.

EL vs. JSTL in JSP pages

radioae6rt — Wed, 29 Jun 2011 14:04:23 +0000

I recently had a chance to examine the difference between using JSTL tags and Expression Language (EL) in outputting content in JSPs.

For these two lines of JSP code that output the same content:

   // JSTL

and

${header["host"]}   // EL

the following diff obtains in the generated JSP Java source code:

bmac:jstlvsel> diff --suppress-common-lines -y jstl_jsp.java el_jsp.java
  private org.apache.jasper.runtime.TagHandlerPool _005fjspx_ <
							      <
    _005fjspx_005ftagPool_005fc_005fout_0026_005fvalue_005fno <
    _005fjspx_005ftagPool_005fc_005fout_0026_005fvalue_005fno <
      if (_jspx_meth_c_005fout_005f0(_jspx_page_context))     |	      out.write((java.lang.String) org.apache.jasper.runtime.
        return;						      <
							      <
  private boolean _jspx_meth_c_005fout_005f0(javax.servlet.js <
          throws java.lang.Throwable {			      <
    javax.servlet.jsp.PageContext pageContext = _jspx_page_co <
    javax.servlet.jsp.JspWriter out = _jspx_page_context.getO <
    //  c:out						      <
    org.apache.taglibs.standard.tag.rt.core.OutTag _jspx_th_c <
    _jspx_th_c_005fout_005f0.setPageContext(_jspx_page_contex <
    _jspx_th_c_005fout_005f0.setParent(null);		      <
    // /out.jsp(4,6) name = value type = null reqTime = true  <
    _jspx_th_c_005fout_005f0.setValue((java.lang.Object) org. <
    int _jspx_eval_c_005fout_005f0 = _jspx_th_c_005fout_005f0 <
    if (_jspx_th_c_005fout_005f0.doEndTag() == javax.servlet. <
      _005fjspx_005ftagPool_005fc_005fout_0026_005fvalue_005f <
      return true;					      <
    }							      <
    _005fjspx_005ftagPool_005fc_005fout_0026_005fvalue_005fno <
    return false;					      <
  }

where the first file is the JSTL version and the second file the EL version.

As one can see, the JSTL version traverses the JSTL tag handling layer before output, while EL goes straight to output. It’s no secret that EL is more efficient for simple output tasks, but it’s always good to see why.

JSTL 1.2 that GlassFish v2 uses

radioae6rt — Fri, 24 Jun 2011 01:01:19 +0000

I believe this is the JSTL 1.2 implementation that GlassFish v2 uses:

https://svn.java.net/svn/jstl~svn/tags/jstl-1.2

Preparing Tomcat instances with Groovy

radioae6rt — Thu, 23 Jun 2011 14:08:02 +0000

Zemian Deng has a nice set of Groovy scripts for dealing with Java webapps. He also has a good boilerplate script for preparing Tomcat server.xml config:

http://docs.codehaus.org/download/attachments/16580630/NewTomcatInstance.groovy

The four ways to deploy a webapp under Tomcat

radioae6rt — Thu, 23 Jun 2011 02:50:37 +0000

There are four different ways one can deploy a webapp to Tomcat. If TCHOME is the Tomcat top-level directory:

Copy the war file foo.war or exploded war directory to TCHOME/webapps
Create a context file context.xml in the webapp’s META-INF/ directory that contains a fragment that describes the webapp deployment
Add a element to the element in Tomcat’s server.xml that describes the webapp deployment, including docBase. docBase is a attribute that locates the war file or exploded war directory in the filesystem.
Create a context file foo.xml in TCHOME/conf/Catalina/localhost/foo.xml that contains a fragment that describes the webapp deployment, including docBase.

The first two methods do not provide the freedom to name the servlet context independent of file system names for the war file or exploded war directory, whereas the last two do. Of the two methods that provide control over context naming, the most appealing is the use of a context file foo.xml placed in TCHOME/conf/Catalina/localhost/foo.xml, as it avoids modifying the stock server.xml file for pure context deployment purposes. For the root context “/”, the context file name is ROOT.xml.

Petition to bring Iris Dement to the Mystic in Petaluma

radioae6rt — Sat, 05 Feb 2011 18:35:33 +0000

If you want Iris Dement to return to the Mystic Theatre in Petaluma in 2011, please leave a comment to the same effect.

Where the hams are

radioae6rt — Wed, 29 Sep 2010 15:11:53 +0000

Plotting the license address of amateur radio operators in Petaluma, CA as a vehicle for learning a bit of Google Maps API and jQuery:

http://www.petrovic.org/content/petaham.html

Source code for porting the result to your town is here.