Category Archives: java

PowerDNS Makes Custom DNS Backends Easy

I ran into PowerDNS recently when I needed to find a DNS server that would allow me to produce custom responses to domain queries. I needed to have a request for a DNS entry return a different IP depending on some factors in a database and I needed that data to always be accurate (not cached locally). I found that PowerDNS allows for a lot of customization and I ended up using its piped backend for dynamic queries feature.

With this level of customization you can do things like write your own DNS black list, track who is making DNS requests, give out IP addresses based on a servers availability or use geographic information to return a different IP.

Continue reading

Spiffing up JFreeChart charts

I recently was given a copy of ChartFX for Java to evaluate as a charting solution for a Java project. After using it for a while it seemed nice despite having some odd ways of doing things that I think come from it originally being a C# and VB product. After playing with it for a while I decided to see if I could get JFreeChart charts to look the same way. As it turns out it wasn’t that hard.

Continue reading

Connection timeouts with the Apache commons TelnetClient

I recently used the Apache commons net package in a project to create a small telnet client that automated a login process. It is hard to find a lot of documentation on TelnetClient but there are some examples. For what I wanted to use the telnet client for I ran into a problem because I needed the connect call to time out. Try as I might I couldn’t get setDefaultTimeout to work as advertised.

Continue reading

Building firefox and mozilla tools on an AMD64

Sometimes I curse the day I decided to get a 64 bit box. Everything is fine until I want to build something by hand or upgrade something and then if it doesn’t just work it is like a maze of problems.

Recently I was trying to build firefox from source along with XULRunner so that I could try out JavaXPCOM. The first problem I ran into was a GCC 4 bug that breaks the build. Luckily someone out there had an easy fix for the problem (see GCC4.0 – relocation R_X86_64_PC32 against memcpy@@GLIBC_2.2.5 can not be used). After getting that problem fixed an a little fight with setting up XULRunner I got a very simple program working. That is when the 2nd problem showed up. When I tried to use some of the GUI functions I started getting core dumps from within GTK2. At that point I gave up and moved to my laptop. The same code worked right off using my laptop.

I should have instructions soon on how to embed gecko into a java app with JavaXPCOM. There isn’t much documentation or example code out there on making it work. As for the 64 bit box, I think I have had about as much of it as I can take. At least it can run in 32 bit mode when I decide to re-install.

[tags]xpcom, mozilla, xulrunner, amd64[/tags]

Thread pooling with Java concurrency utilities new (java 1.5) and old (util.concurrent)

Threading in java is fairly easy and now with java 1.5 some of the stuff that was harder has become even easier. A few years ago someone pointed me to a site that had some concurrency utils that where the precursor to what are now the concurrent utils in java 1.5. They are very close in functionality and if you can’t use java 1.5 the older version of the utils will work with older versions of java and give you a lot of the same functionality.

I’m going to give a quick thread pooling example using both the new and old concurrency utils. I picked the thread pooling out of both since that seems to be what I end up using the most out of all the new utilities. I may revisit this again at some point to go over the periodic executors or some of the other things I have used but just not as much.

Continue reading

JDBC + Batch updates + Non-Standard == Oracle

I recently ran into an issue where doing a large number of inserts and updates in an Oracle 8i database was taking forever. I was already using a prepared statement and commiting only after a certain number of rows. After some digging I found out that there is a special Oracle way of doing batch updates that made things a good bit faster. They do support the normal addBatch batch updates but it isn’t as fast as using their special way.

Continue reading