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Java, XML and XStream

January 22, 2010 / Ant posted in Java, Technobable, xml / 9 Comments

What’s an object/xml serializaing/deserializaing library?

If you’ve never worked with an object/xml serializer and are considering writing your own from scratch, you may want to consider using a library like XStream. XStream is very good at moving java into xml and back. It allows a high level of control over how the xml can be organized and structured and even allows the user to create their own converters for even more flexibility.

But still, why use something like this when you can be perfectly happy writing your own data conversion scheme? The problem really boils down to…

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Using Jboss Datasource files, JBoss 5.1

January 20, 2010 / Ant posted in Java, Jboss / No Comments

If you’re using jboss and you’re storing database connection info in a properties file, you might be doing something wrong. Specifically, you’re probably not using the data source files jboss ships with to configure all that plumbing.

What’s a Datasource file?

Simply put, its a file that contains all the connection properties an application needs in order to connect to a database in xml format. Here’s an example:

<datasources>
	<local-tx-datasource>
        <jndi-name>DefaultDS</jndi-name>
        <connection-url>jdbc:postgres://dbUrl:5432/schema</connection-url>
        <driver-class>org.postgresql.Driver</driver-class>
	    <user-name>username</user-name>
	    <password>password</password>
		<metadata>
			<type-mapping>PostgreSQL</type-mapping>
		</metadata>
	</local-tx-datasource>
</datasources>

So, the “jndi-name” node gives this datasource configuration the jndi name it will be bound to…

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Ejb3 Basics: Bean Managed Transactions

January 14, 2010 / Ant posted in Java, Jboss / 4 Comments

I’m Lazy, why would I want to do my own transaction management?

While its true that the ejb3 container is usually pretty smart about persisting and handling transactions, its also not as smart as a real human being and probably isn’t able to handle complex database transactions and rollbacks. This is where bean managed transactions come in. By handling your own transactions you can avoid some major pitfalls.

The first problem with Container Managed Transactions (CMT) is there’s a time limit imposed by the container (although it’s a configurable timeout). If you are performing a lengthy task and are…

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Using Jboss System Properties

January 11, 2010 / Ant posted in Java, Jboss / 12 Comments

So if I have a jboss application set up on different environments, is there an easy way for me to load environment specific properties on a per instance basis?

Yes there is, read on.

So normally, in most applications you might end up with some property values you’ll want to override based on the environment. For example, login credentials to some third party service, environment specific file locations, environment specific jnp servers, or properties that flag the application’s mode as test or production environments.

It’s generally a good idea for an application to have properties bundled within the deployable artifact…

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Set up postgres

January 2, 2010 / Ant posted in Fedora, sql / No Comments

Most linux oses come with postgres and mysql out of the box. If yours doesn’t or you want to run a newer version than the the one your os comes with you should be able to install it using the yum installer. Fedora 11 comes with a visual installer you can use to pick and choose what rpms you want running on your machine. Once you have postgres installed on your box you’ll want to initialize some dbs stuff: