There’s still a lot of confusion over the difference types of managed beans provided in Java EE 6 with EJBs, CDI beans and JSF managed beans all being available. This article aims to clear up some of the differences between the them and define when to use them. Read More »
In this second article on implementing Spring MVC in Java EE 6 we’ll take the metadata we extracted in part one and use it to invoke request mapped controller methods in response to web requests and then direct the user to a web page based on the result of the method. Read More »
One of the opinions I’ve had over the last couple of years is that Spring makes things look really easy, and CDI is a great dependency injection framework. Throw in this article suggesting you can build your own Java EE 7 and it sounds like a challenge, so for fun, I thought I might have a go at implementing a subset of Spring MVC on top of CDI with Java EE 6. Read More »
In the last few weeks I have been rather busy working on a new project with Rick Hightower, who is fairly well known for his training and writings on Spring and JSF, and Rob WIlliams who is a blogger known as much for meddling in new technologies (and getting mad at them) as he is for intertwining various historical and literary references in his posts. The result of this is the CDISource project which aims to advocate and facilitate the use of the JSR 299 – Java Contexts and Dependency Injection framework across the Java landscape.
If you’ve seen my posts or my site before, you’ll no doubt be aware that I have written at great length about Java EE 6, JSF, CDI , EJB and so on. What I haven’t written about is the many frustrations I’ve come up against in dealing with these frameworks on their own and especially when combined, or how their usefulness is often constrained to the application server container.
Java EE in some ways is an archipelago of frameworks that lacks the cohesiveness and all in one wide screen vision that software developers need. Java EE is about the enterprise, in reality its about the web, or even more specifically about Java EE containers. There’s a whole slew of uses for a good type safe and flexible dependency injection and AOP framework and such as CDI outside of Java EE containers but there is very little information and code to make it actually work.
Our goal is to make CDI useful and usable on its own without Java EE 6, and to give developers the tools and information to do so. To let them write vendor neutral and portable code, and apply agile and best practices. Developers know how to write good software and don’t want to sacrifice that for the sake of using a framework to make things easier. To that end we aim to provide code and information that will help facilitate those practices.
There will be some learning for ourselves along the way and we will have to change some of our previously held concepts. I know over the last few weeks having been getting CDI working and useful outside of the web container it has really altered my perspective on how I think about the dependencies and structure in CDI applications. My perspective has changed even more than when I wrote A Little Less Conversation.
As much as I hate to say it, we did come up with a mission statement, although we found it fairly easy and enjoyable to clearly defined the goals and attitudes of the project.
Our mission is to :
- Promote and facilitate the use of the Java Context and Dependency Injection (CDI) framework in relation to as many aspects of application development as possible.
- Enable developers to take advantage of CDI independently of Java EE.
- Provide lightweight, lean and agile access to the underlying CDI container as a core principle in our efforts.
- Make testing easy without requiring a complex set of tools or complex deployment scenarios.
- Enhance both Java EE development as well as the use of CDI in non Java EE application where possible.
- Promote and enable the use of CDI in a vendor neutral environment and maximize the portability of application code across CDI implementations.
- Not reject the ideas of Java EE but expand the usability of CDI outside the borders of Java EE application servers with frameworks that are not a part of the specification.
- Not reject other CDI efforts but to provide another venue to promote those efforts. This is an addition. This is another voice in support of CDI.
We are pretty excited that so far we have been able to live up to the intent of our mission statement with everything we’ve done so far. Over the next few days and weeks you will see articles and tutorials come out of Rick, Rob and I as we write about the CDISource project and we start to showcase some of the code we have written and start giving you an idea of where we are heading.
Right now we have vendor neutral support for starting up CDI outside of the web container and also for testing CDI beans with minimal configuration and intrusion on your test cases. We also have a few other pieces that are nearly ready, as well as dozens of ideas to get started on.
You can start by looking at Ricks brand new introduction of CDI over on JavaLobby.
In part 2 of this article, we are going to create a data driven web service that will return JSON and XML to the client, and then use jQuery to add a new item to the database and display it in our page.
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Adam Bien wrote about the Troubled with the crippled Java EE 6 APIs in Maven and a solution for them. Another solution has presented itself now that JBoss has finalized the Java EE 6 spec pom and added it to their public repositories as of early January 2011.
You can include the spec in your own project by adding the following to your
<dependency> <groupId>org.jboss.spec</groupId> <artifactId>jboss-javaee-6.0</artifactId> <version>1.0.0.Final</version> <type>pom</type> </dependency>
You may also need to add the JBoss repository to your
pom.xml which is defined as :
<repositories> <repository> <id>repository.jboss.org</id> <name>JBoss Repository</name> <url>http://repository.jboss.org/nexus/content/groups/public-jboss/</url> </repository> </repositories>
I’ll be adding this pom to the Knappsack archetypes to resolve some of the issues people have been facing with the broken spec dependency.
One thing that I wrote that I haven’t really gotten around to examining and verifying in closer detail and validating my position on is the production of the conversational entity manager in the Knappsack archetypes. This article looks at this and re-evaluates my thinking on the use of conversational contexts in CDI.
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In part 1, we created a simple application that made use of string resource bundles in JSF and in part 2 we extended it by using CDI to inject the resource provider into beans so we can re-use our code for accessing locale specific string based resources.
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In this post we looked at adding String resource bundles to our JSF applications to move our string constants into external resources that we can define for different locales. Now I want to extend that example to show how you can expand on that by using injection to access those resources.
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The @Alternative CDI annotation allows you to have multiple matching dependencies for a given injection point. This means you can define beans that provide implementations for the same interface without worrying about ambigious dependency errors. When you mark a class with the @Alternative annotation, it is effectively disabled and cannot be considered for injection. The only exception is for the class that is defined in the
beans.xml configuration file.
<alternatives> <class>org.company.project.bean.SomeBean</class> </alternatives>
Once this bean is identified, it is then used in any injection point that matches for this bean. No other beans for similar injection points can be declared as the ‘active’ alternative.
Alternative is really an odd name for it, but all it does is disable the bean while adding it to the
beans.xml file enables it and makes it available to CDI.