Note : Spigot has been renamed to DataValve.

(Edit : I renamed this post so it doesn’t seem like Spigot is just for Seam, Spigot can be used with different frameworks or without any at all. However, I wrote this post since Spigot is so familiar to the Seam EntityQuery that it should be easy for Seam users to get the idea)

Seam developers should become familiar with Spigot concepts fairly quickly since they are very similar to those found in the Seam EntityQuery which was one of the main inspirations for the framework. If you imagine taking the entity query class and splitting it in two, one part to keep hold of state and the other to actually fetch the data. The stateful part is the Paginator that keeps track of what the current ordering of the data is, what is the current page and how big the pages are. The stateless part takes the Ejbql and the pagination information and returns a subset of the data. Now imaging that the data provider has the JPA pieces taken out and replaced with an abstract fetchResults method. This method is implemented in subclasses for specific data providers for text files, sql queries, jpa queries, native jpa queries, xml files, comma delimited or just an in memory dataset.
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Note : Spigot has been renamed to DataValve and is hosted over on FlutterCode.com.

It’s been a while since I’ve posted anything new as I’ve been busy with a new Open Source software project called Spigot. It’s a java library that sits between your application code and your data sources (Hibernate, JPA, JDBC or any arbitrary source of data) and helps with things like pagination and sorting using a common interface so you can switch out data providers and use alternatives.

For query language data providers, Spigot also facilitates excluding restrictions from WHERE clauses when parameters are resolved to null. Parameters are handled using parameter resolvers so there is more than one way to parameterize the query including EL expressions, reflection or a value map on the data provider.

Spigot also provides a few other add-ins like converting any dataset into an in-memory dataset that can itself be paginated and sorted and shared across an application (such as commonly used data in a web application). The IndexedDataProviderCache can give you random access into a dataset with caching and look ahead loading. This lets you hook a dataset with thousands of rows up to a Swing JTable with an instant response and a very small memory footprint since it doesn’t need to load all the objects at once as the provider will load the records as needed and cache the results. This is demonstrated in the Swing Demo in the download. There are also demos for Wicket and CDI with JSF.

You can ready about why I created Spigot in the documentation

Spigot is currently hosted on Project Kenai, where you can download the release, view documentation online or read about 10 ways Spigot helps developers.

Using composition over inheritance is a common design pattern that is often discussed in terms of designing business logic components. However, composition can solve a number of problems in domain object modeling that are created by relying on inheritance to share interface or functionality. Composition is used to delegate implementation in logical units by enlisting the help of a reference to an object that implements the required functionality instead of inheriting from it. This reference can be changed to different implementations depending on the needs at the time making for a more flexible design. This same design can be used in domain modeling to overcome some of the problems caused by inheritance. The typical flawed example of using inheritance in object modeling is the Person class which is often subclassed into Employee, User , Customer and Vendor classes.
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Dan Allen posted that the latest CR version of Weld is available. This should contain a number of bug fixes from the initial release of Weld, including the two problems I had with the request scope being available in EJB timeouts and problems with the ability to proxy stateless beans. This last bug was for me rather crucial since there was no easy way to implement DAO (just data management) type components with transactional annotations that could be injected into business logic beans. Without that, you end up having to write your own transaction handling code.

Also in the comments of the announcement, Max Anderson notes that the nightly builds of JBoss Tools 3.1 now supports CDI auto completion and JSF 2.0. I had a very quick look at it yesterday and it looks promising. I also tried it out with the latest JBoss 6 snapshot and am very pleased to say that the redeployment times on JBoss 6 are much faster and more in line with the performance on Glassfish which is something I have raved about.

I’ll be looking at it some more and probably write up a couple of tutorial posts.

Last time we looked more in depth at CDI and how we can define beans and inject them into other beans. This time we are going to look at how we can use events to decouple the handling of actions in the system.
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I had a bit of epiphany on the subject of nested conversations the other day when I was thinking about them and thought I’d share. I think nested conversations have been a little misunderstood with people unsure of how to use them, myself included, but I think I have found the best way to think of them.
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In part 1, we looked at creating a JEE 6 application with Netbeans using JSF and CDI running on Glassfish. Now we’ll take a closer look at using CDI for managing dependencies in a Java EE 6 environment.
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With Weld 1.0, the reference implementation of JSR 299 – Java Contexts and Dependency Injection now released, attention at JBoss has no doubt turned to Seam 3 which is going to be built on top of Weld. Red Hat and JBoss are committed to returning innovations back the JCP as is the case with Seam which not only resulted in JSR 299, but has also influenced a number of other JSRs especially JSF 2. With JSR 299 standardizing the Seam ’style’ of development it also brings about a some fundamental game changes for Seam 3 (hence the title) as much of the strength of Seam becomes part of the JEE standards.
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Seam conversations have certain rules that you need to be aware of when using them. This article came about because for the last couple of years, the same questions have been asked on the Seam forums regarding conversations. It is also a couple of issues that cropped up while I was working on the Seam vs. Spring Web Flow articles. Some of the problems are uncannily similar with similar solutions, so parts of this series may be of interest to non-Seam users. Additionally, it seems like a lot of this stuff will also apply to the conversational pieces of JSR 299 – Contexts and Dependency Injection which will be a part of JEE 6.
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I’ve spent some time in the last couple of weeks playing around with Glassfish, Netbeans 6.8 Beta (and milestone 2 before it) and JSF 2.0, and I have to say that this is turning out to be a really good set of development libraries and tools.
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