In every Java project where I need to do strong cryptography, I run into these dreaded unreadable stacktraces which send you into the woods. After a long search I usually discover that the Unlimited Strength Java Cryptography Extensions are not installed. To prevent frustration of users of your software, you can simply add a bit of informative logging to help him/her solve it when the solution is known.
Tag: Java
Solving the JAXB “unexpected element” problem
If you are using JAXB in a maven/java project to unmarshal an XML document and you get:
javax.xml.bind.UnmarshalException: unexpected element (uri:”urn:iso:std:somestuff:xsd:somestuff”, local:”Document”). Expected elements are (none)
Or if you are using JAXB to marshal an XML document and you get:
com.sun.istack.internal.SAXException2: unable to marshal type “generated.somestuff.Document” as an element because it is missing an @XmlRootElement annotation
You have probably fallen victim of the fact that JAXB does not do “Simple Binding” by default. If your project is a maven project and you generated classes based on an xsd file, this is how you fix it (without changing the xsd file):
Import/export an Oracle Schema using JDBC
When doing integration testing or fixing a bug in a piece of Java code that uses Oracle as a database, being able to do quick exports and imports of your schema can be a big help. Sometimes just calling Oracle’s imp/exp commandline tools from your code can be of help, but I was looking for something a bit more portable and less demanding on my local development machine. I found that Oracle’s datapump functionality can be called from stored procedures, which in turn can be called from a normal JDBC statement.
Open a port in OSX Mavericks’ Firewall
The new firewall in Mavericks is great. For the common user. For a developer, not so much. If you are a Java developer like me, and you just need to open one port (say, 8080) so that the web application you’re working on is accessable from another computer, you can’t. I disabled the Firewall altogether for a few days, but it didn’t feel right.
I googled around and to make a long story short, here’s how to open port 8080 on any interface to any application on your OSX Mavericks installation in 3 steps:
sudo vim /etc/pf.conf
Then add the following lines at the end of the file:
# Open port 8080 for TCP on all interfaces
pass in proto tcp from any to any port 8080
Test (and, according to the documentation, load) your edits with:
sudo pfctl -vnf /etc/pf.conf
Reboot.
(I have found at least 5 pieces of voodoo to make the Firewall restart and reload, but none of them seemed to work reliably, so pardon the reboot)
You can close it by commenting out the lines in pf.conf and reboot again. If anybody knows of an easier way to do this, preferably in one terminal command, and without rebooting, let me know.
Hope this helps.
Anonimatron: Quick Start
After reading my last blogpost on Anonimatron, you must have asked yourself “Great, but how do I actually use Anonimatron to de-personalize my database”? I tried my best to make basic Anonimatron configuration as self-explanatory as possible, just start it without any command line arguments and it will tell you.
Less adventurous or in a big hurry? This blogpost will show how simple it is to install and configure Anonimatron on an example MySQL database.
Anonimatron: Overview
In every software project, there comes a time where a bug pops up, nobody knows how to reproduce it, and somebody says “I know, let’s test this against a copy of the production database”. Even with the best intentions, once production data leaves the production machine with all its safeguards it becomes really hard to do access control on that data.
Most of the time, it’s not even needed to have that data. Developers just need a data set which resembles the production scenario close enough. Some brave souls have mixed succes with data generators, but those generators usually are tedious to maintain and die a slow death under the pressure of the daily grind.
In some ambitious projects automated integration testcases are built on top of the data which was inserted by the data generators. As the generators die, so die the tests. If you recognize this pattern, Anonimatron might be the answer for you.
Non-Java Binary Dependencies in Maven
Suppose you have a Java Server application, and some of the runtime binaries in that application are external to your application. Generated image files, compiled Silverlight components in your pages, or resource files which are managed by an external team.
Much like the jar files used by your application, these external binaries can be seen as dependencies, with versions. This blogpost assumes your project is built with Maven 2, because the real world isn’t always a greenfield project.
Because Maven is designed around jar file dependencies, and a lot of it’s internal decisions are based on file extensions, it looks like this problem can not be tackled with Maven. But there is a way to do this. It will decouple your sub-projects and make version and dependency management much better.
Why you should not use SOAP Headers
In the project I am working on right now we use apache XCF and Spring to provide a SOAP service to our customers. As part of the messages, there is a userid/password combo telling the application which user sent the request. I struggled with that today because I think that userid/password info should actually be in the SOAP Header, cleaning up my API, enable me to implement different authentication techniques in the future and generally be more “compliant” to the SOAP standard. Boy was I wrong.
Distributed jMeter through VPN and SSL
This week I created a jMeter test setup for distributed testing. I thought it would be straight forward but I ran into some interesting things you might want to know if you are considering distributed testing using jMeter.
In my case, I had to test an application which was inside our corporate network, while working from home through a VPN and a firewall. Normally that is no problem, but jMeter has this funny construction where the slave (jMeter server) wants to connect back to the master (jMeter gui). It took some fiddling with iptables, the jMeter configuration and ssh tunneling to get it to work. Here’s my setup:
Having fun at J-Fall 2011
This year’s Dutch Java Nerd event called J-Fall was held in Nijkerk, in a beautiful location called “Hart van Holland” . With plenty of sessions by speakers from all over the world it promised to be a great day for Java enthusiasts, at a great location for meeting friends and colleagues. I took a day off from work and it was well worth it.