Error occurred during initialization of VM

Good post on resolving the error:

Error occurred during initialization of VM Unable to load dependent libraries: Can't find dependent libraries

The culprit is too many java.exe's and the wrong one being put to use.

http://geekycoder.wordpress.com/2009/07/08/java-tips-adventure-in-resolving-the-java-error-error-occurred-during-initialization-of-vm/

What I am curious about is how did the java.exe get in the Windows directory that caused this error? Not going further with this (I'm busy) but the things I did recently include upgrading to the latest version of Java which I did twice due to putting it in a directory I didn't want it in the first time around, install some software from Fluke Networks, and go to a bunch of Java programming pages on the net. While looking at one of them an error was thrown. Not sure that was related to the web site or just a coincidence.

Oh well, renamed all the java.exe's except the one I wanted so they wouldn't get run and put the path to the one I intended to use on my system path so all good it seems.

Using JavasScript and Ant

If you hate the fact that you are doing programming like tasks with XML in Ant, consider using JavaScript if you don't want to write new custom Java classes to use as targets. I would probably opt for new targets but some people seem to prefer scripting languages so here you go:

JavaScript and Ant

In general I try to keep the configuration in the XML file separate from the executable code, which is why I would opt for custom Java class targets configured by XML, rather than try to incorporate executable code into an XML file. That's just me.

I also read you can integrate Groovy with Ant.

Conditionally Call and Ant Target

If you want to set a target to only run if you set a particular value, easy. Just use the if attribute as follows:

<target name="whatever" if="my.value">
  <echo message="target executed"/>
</target>

If you want the above target to run - set my.value to something in your property file before that target and it will run.

<property name="my.value" value="yada"/>

If you leave the property out of your file altogether the target won't run.

You can also have other tasks set values and use those values to determine if targets should run or not based on whether a file was available, etc. Details about conditional values can be found in the Ant FAQ:

Conditionally Execute Ant Target

Ant - Copy Files That Have Changed

If you want to copy files that have changed from one directory to another use a file set with the "modified" option like this:

 <copy todir="${dir.copy.to}">
  <fileset dir="${dir.copy.from}">
         <modified/>
        </fileset>
        
 </copy>

Ant will set up a cache.properties file which tracks file information so it knows the state of files after each build. Then when it runs a task it can refer to the cache file to determine which files have changed since the last successful build and need to be included in the fileset.

If you want the build to include a file that is getting excluded by the cache file just delete that file from the cache.properties file and it will be included in the file set the next time the ant build is run.

Get Ant to Call a Java Class

To get Ant to call you own Java class to do some processing you can write your own custom Ant task. Here's the info on how to do that:

http://ant.apache.org/manual/develop.html

Running Ant from within a Java Class

Here's a good article on running Ant within another Java program.

http://www.ibm.com/developerworks/websphere/library/techarticles/0502_gawor/0502_gawor.html

You might want to do this if wrapping your ant build in a process that needs additional auditing and security, or to create a friendly user interface for running builds, for example.

Ant, Gradle, Maven, Build Software and Processes

Still pondering all my options for a build solution for a particular project but these are my thoughts going into further testing and proof of concept for a new build and deploy solution.

What build solution you choose really depends on the requirements of your particular project, security concerns and the staff you have available to support the solution.

I find Ant simple to use and manage. I like the control of what is getting into my code when and how. Because I put it there.

For all these dependency management issues addressed by Maven and some other build solutions: I think it is not difficult for experienced programmers to find and download a jar file or source code, though I think some companies and organizations providing software libraries and open source software could make this more straight forward and manage their repository of code and libraries better.

Tangent: And when getting source from the Internet not require SVN to download source (dislike). Make it easy for me to download a zip. It's a lot faster and I want a stable version that's not going to change the next time I download it. I also don't want those .svn files in my source if I don't want the software changing on me or to upload changes to your repo.

That being said large companies managing what software their developers include in production software have other concerns. These companies should have a process for requesting and downloading new libraries off the Internet to a central repository so they know what is being deployed to production systems, regardless of what build software they are using. This process should include making sure the code is from a trusted source, checking downloads with provided security keys and possibly even compiling open source libraries to make sure no rogue code has slipped in, and/or (crazy thought I know) removing questionable code in these libraries which is not needed and may introduce security problems (but let your dev's know so they don't try to use features that are not available).

You may not have these next problems with Maven, if working on a project that is small and does not have a lot of dependencies or using an internal repo at your company where Maven is not allowed to access the Internet (but you might in any case). My experience with Maven on complex projects has in general, been a lot of overhead managing things even though Maven is supposed to make things simpler. Maven's plus is that it handles dependency management by going out and grabbing all the libraries you need off the Internet or internal repo for you. Yes I know it does other stuff too. In my case, it seemed like I ended up with a bunch of compile errors to fix every time I turned on my computer. On a recent project, Maven kept updating things when it seemed like dependencies should be stable because I wasn't changing versions. This bothered me. As did having to re-fix my code every time I turned on my computer for no apparent reason. I think when you know what you're doing with the dependencies, Maven can actually make things more complicated, time consuming, and less secure. I stopped using Maven for that project and have been much more productive ever since.

Also with Maven, there are security concerns with pulling random code from the Internet (unless your company has a well managed internal repository which is well managed and secured). If you don't believe that last point, please don't work on any type of financial application or anything that stores personal private data or store anything important on the machine you dev with or let it on a network where valuable data is stored. Thanks.

I know a lot of system administrators use various scripting languages to manage various things and may not prefer an XML configuration file for managing builds. However when it comes to a build system I would prefer separation of execution from configuration. Like MVC separates the model from the view, the steps to run and files to move are in XML while the programmatic execution is in Java. Personal preference, but separation of duties can make things cleaner, easier to manage, less error prone, and more secure as we have learned from MVC.

I'd also rather work with languages I and a lot of other dev's know: Java and XML, vs. learning another new scripting language specific to a particular build software solution. That makes it hard to find employees to support that system, and less people in the organization knowing it who can help fix problems. I also don't want to have to extend (rewrite) the build system to support Java when other solutions alrady exist that meets my needs.

PS as you can see from my resume I have learned a lot of new languages besides Java over the years. This is why consideration for when a new language is really needed and the pros and cons of each is important to me: WebDatabaseProgrammer.com

As for the need to customize, if you're looking for something Ant can't do, I don't think it's that difficult for an experienced Java programmer to figure out how to add new classes that can perform tasks under the Ant framework, or customize Ant itself. I have customized open source code that didn't do exactly what I wanted. It's not that tough. Download the source, grab the dependencies and edit the Java as needed. Just like any other project. If you intend to get updates however, keep your custom code separate from the open source library you downloaded, using and appropriate design pattern.

It seems to me that using a universal language that many developers know should cover whatever the build system needs to do. Java + XML can do pretty much anything you can imagine. I think rare would be the project where Java couldn't get the job done well enough. Of course adding new Java tasks requires compiling code but it also adds some control to what your build system is allowed to do and universal logging can ensure you can audit what your build system is doing, regardless of who edits the XML file. You can add a layer of security also based on who can edit the Java classes and who can edit the XML.

I actually like that variables are immutable once the Ant build process starts. This ensures your variables aren't changing mid stream and avoids tricky errors related to variables changing in random places during the build. XSL transformation works the same way and it took a bit of getting used to, but now I like it because once you get to the point of transforming, or building, certain things should be set.

In general, your build system is probably one of the most important places you don't want to take security risks. That's where you can audit everything and make sure nothing unintended gets into your production software. Whatever build solution you choose, I recommend making sure your processes for updating your builds are secure and audited, including database updates, compilation, and deploying all types of files. It doesn't matter how much development and testing you do on the source code if someone can alter it when it gets deployed and after everyone's done scrutinizing it. Make sure this process is secure.

Eclipse: Selection Does Not Contain A Main Type

If you are having a problem launching your project as a Java Application in Eclipse due to the error: "Selection does not contain a main type" a simple work around is to simply create a new Java project and copy your class files into the source folder of the new project.

You can also create a new Java project in Eclipse and change the build path to point to your existing source folders. Right click on the project and select "Java Build Path". Click on the "Source" tab. Remove any folders you don't want and point to your existing source folders.

Then your Eclipse Java project configuration should be accurate (without having to figure out the problem with it - which is the other option) and you should be able to right click on a class file with a main method and run it.

Related posts:

http://dev.eclipse.org/newslists/news.eclipse.newcomer/msg04471.html

http://stackoverflow.com/questions/4252472/java-launch-error-selection-does-not-contain-a-main-type

SSL Certificates for Java Web Servers

Digicert makes it pretty simple to get SSL certificates for Java web servers. I like.

They have a tool to generate the command line code you need to enter to generate your certificate request here:

https://www.digicert.com/easy-csr/keytool.htm

Just enter the appropriate information. Open a command prompt window on the server on which you intend to install the certificate. Navigate to the folder where you want to store the certificate files. Copy and paste the command into the command prompt window.

A file will be created for the keystore, and for the CSR (certificate request). Copy and paste the certificate request (in the .csr file that gets created) into the box on the order form where it asks for that information.

Once your certificate is approved, download and copy it to the folder you created above. Run the command on this page but replace the domain name with the domain name for which you ordered the certificate:

http://www.digicert.com/ssl-certificate-installation-java.htm

Syntax and Result Differences - Sybase and SQL Server

SQL Server is based off Sybase. They both use Transact SQL. However I've found some differences in behavior (at least in the version of Sybase and driver I'm using).

You cannot do a count in a select in sybase without a group by and get accurate results.

COUNT without GROUP BY:

Select count(some_field) from whatever_table will return every row in the table. That select statement works in SQL Server without the group by. In Sybase you'll need to add group by like this:

select count(some_field) from whatever_table group by (some_field)

COLUMNS and GROUP BY:

If you don't have all the columns you are selecting in the group by you may get incorrect results but no error. In SQL this will give you an error like this:

Column 'some_field' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.

In Sybase something like this will just give you inaccurate results:

select some_field, other_field
from whatever_table
group by other_field

EMPTY STRING, LTRIM, LEN

- insert

If you try to insert an empty string using an insert statement with Sybase it inserts a 1 character space instead of an empty string. Length will equal 1.

insert into some_table (id, some_field) values(23, '')
select len(some_field) from some_table where id = 23 (this will give you length of 1)

In SQL Server the above statements would 1.) insert a true empty string and 2.) return a length of 0.

- ltrim and length

In Sybase ltrim(some_field) above would give you a null and len(ltrim(some_field)) will give you null - no matter how many spaces you have in some_field.

In SQL Server the same scenario would give you an empty string after trim and 0 for the length.