« Archives in January, 2010

Ejb3 basics: Entities

January 29, 2010 / posted in Java / No Comments

Entity Beans? Better than 2.1, I promise.

Ejb3 Entity beans are a type of enterprise java bean construct used to model data used by the ejb framework. The basic idea is to manipulate simple java objects, which represent in concrete terms your database data, and then have the framework handle as much of the plumbing as possible when you persist the data. Persisting means to store for later use in some data repository – usually some kind of database. By persisting these entities within the ejb framework we are able to abstract out tasks like updating a table and its…

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XML, Xalan, Endorsed dirs and &..

January 28, 2010 / posted in Jboss, Technobable / 3 Comments

So recently, we’ve been working on a project that makes use of OpenSAML. As it turns out OpenSAML required newer Xalan libraries (2.7.1 to be precise), the kind that don’t ship with the older incarnation of jboss we are using for the project – version 4.02. Some of you might be more familiar with the jboss system properties and will know there’s a property jboss used specifically to override the standard xml libraries that ship with the jdk/jre (entry in the console output bolded and marked with a *). Jboss will allow you to pass in…

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War deployment file structure

January 25, 2010 / posted in Java, Jboss / 1 Comment

What’s a war deployment, do I need my own army?

When it comes to deploying an web based application we have a few options on the table. Well only one really if you stick to J2EE standards, not counting Ear deployments which also deploy web apps via wars. Outside the world of J2EE though, it becomes a crap shoot based on the web framework you’re using. So what’s a war look like?

webapp.war
	|-- images/
	|   `-- banner.jpg
	|-- index.html
	|-- jsps/
	|   |-- public/
	|   |   `-- login.jsp
	|   `-- private/
	|       |-- application.jsp
	|

…

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Java, XML and XStream

January 22, 2010 / 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 / 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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5 ways to make XML more XPath friendly

January 19, 2010 / posted in Technobable, xml / No Comments

As java developers we should always do what we can to optimize outbound xml from our side of the fence. I mean, its our job to build and design awesome, elegant and efficient software whenever possible right? We have our data and we want to serialize it into xml, how can we make our xml as efficient and xpath friendly as possible?

1) Keep the structure simple

Consolidate data nodes whenever possible before marshaling your object into xml. You really don’t want to have to resort to using xpath for any unnecessary lookups across nodes. Keep those lookups confined to…

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Virtual hosting with Jboss 5.1

January 17, 2010 / posted in Jboss / 10 Comments

How do I map a web application to a url in jboss?

If you have multiple web apps deployed in a single jboss instance, you’ll probably want to figure out an effective way to tell them apart when you try to access them from a browser. On startup jboss can be configured to bind to a single url which will act as the default host for all the deployed applications. You can then set up a separate context for each web app you are running. If they’re totally separate applications though, it might not make sense to use a single…

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Install Fedora

January 14, 2010 / posted in Fedora / No Comments

Fedora?

“Fedora is a Linux-based operating system that showcases the latest in free and open source software. Fedora is always free for anyone to use, modify, and distribute. It is built by people across the globe who work together as a community: the Fedora Project. The Fedora Project is open and anyone is welcome to join.” – from the Fedora homepage

I’m using this to run jboss 5.1, postgres, mysql and all my other goodies. Why Fedora? No real reason in particular, other than I wanted to have experience working with more than one flavor of linux, since I use…

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Ejb3 Basics: Bean Managed Transactions

January 14, 2010 / 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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Basic Ant scripts

January 13, 2010 / posted in Technobable, xml / No Comments

What’s an Ant script? Do I need bug spray?

Ant is a scripting tool commonly used to build, compile and deploy projects. This is in no way an all encompassing inventory of what Ant can do. It is extensible and its instructions are expressed in an xml format whose nodes comprise a framework of abilities designed to make menial tasks automated.

From a developer’s perspective, the most basic Ant tasks are the compile, package and copy tasks. All java projects must do these three things many, many, many times during a development cycle. Its very boring and tedious if you…

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