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Last weekend while pondering the question "Is Scala ready for the enterprise?" I decided to write a simple Java EE 6 app entirely in Scala, without using any Java. I had three main reasons for doing this: one was just to see how easy/difficult it would be to write everything in Scala (it was easy).  Another was to document the process for others journeying down the same road (the entire project is on github).  Finally, I wanted to identify advantages of using Scala instead of Java that are specific to Java EE apps (I found several). Background The specific app I created was an adaptation of the Books example from Chapter 10 of Beginning Java™ EE 6 Platform with GlassFish™ 3. It's a simple web app that displays a list of books in a database and lets you add new books. Although it's a pretty trivial app, it does touch on several important Java EE 6 technologies: JPA 2.0, EJB 3.1 and JSF 2.0.

There is no migration system in vanilla grails (although possibly in Grails 2.0 …. ?) but there do exist several plugins that provide  some migration functionality. As of this post I am aware of three: dbMigrate, Liquibase, and Autobase. Of these, I prefer Liquibase and cannot recommend it enough. While it uses XML to describe its changesets it is a mature open-source Java project that works flawlessly (and has some excellent documentation). I did not have much luck using DbMigrate and Autobase when including in an existing project… which is a shame as Autobase (which is built on Liquibase) uses a nice DSL syntax to build the migrations.

"The goal of JavaMelody is to monitor Java or Java EE applications servers in QA and production environments. It is not a tool to simulate requests from users, it is a tool to measure and calculate statistics on real operation of an application depending on the usage of the application by users. JavaMelody is opensource (LGPL) and production ready: in production in an application of 25 person years. JavaMelody is easy to integrate in most applications and is lightweight (no profiling and no database). JavaMelody is mainly based on statistics of requests and on evolution charts. "

"OpenI is an open source Business Intelligence application for on-demand or SaaS deployments. Based on J2EE, OpenI is an out-of-box solution to easily visualize data from OLAP and relational databases, where users intuitively build and publish interactive reports, analyses, and dashboards."

Eclipse Rich Client Platform has come a looong way since it was first introduced (and used in Eclipse IDE). The new Eclipse RAP (Rich Application Platform) is also becoming more and more attractive for deploying existing or new Eclipse RCP applications to the web. One of my the projects I'm working on is developed on top of Eclipse RCP. It uses additional plugins such as EMF (Eclipse Modeling Framework) including EMF Editor UI, Teneo (EMF Persistence for Relational Databases), and Hibernate. After some work, I managed to run the whole application on both Eclipse RCP (desktop) and Eclipse RAP (web-based). See the screenshots for proof. Thanks to the recently released EMF Support for RAP I don't have to let go any of the nice EMF generated editor UIs for the web-based RAP version. What's amazing is how little the work I have to do to port the RCP app to RAP. The changes I needed to do is not changing code, but juggling dependencies to plugins and/or packages. Also creating a few platform-specific plugins (different based on whether I deploy on RCP or RAP).

"OpenXava is a tool for Rapid Java Web Development, well-suited for business and database oriented applications. Write simple domain classes with Java or Groovy, and get an AJAX application ready for production. Since v4.2 OpenXava also produces iPad Web applications that behaves and looks like iPad native applications."

Besides being able to query and manipulate the underlying data management system with Blueprints, a GraphML reader and writer package is provided with Blueprints for streaming XML graph representations into and out of the underlying graph framework. The GraphML package uses StAX to process a GraphML graph. This section discusses the use of the GraphML library for reading and writing XML-encoded graphs.

Remus Information Management. It is a free OpenSource client application for the management of information with a connection to multitude of data repositories and a desktop-integration for an optimal usage for the offline management, visualization and easy accessibility of information to the user. The biggest efforts are the linking of information throughout different repositories, the offline storage, the clean representation and the fast search through the information.

COPE, a tool based on EMF that eases the migration of models in response to an evolving metamodel. COPE explicitly records the history of the metamodel as a sequence of changes and allows to attach information of how to migrate models (which is referred to as coupled evolution). The attached information can be used to automatically migrate models to the new version of the metamodel. COPE even goes one step further and allows to reuse combinations of metamodel adaptation and model migration steps across metamodels.

Teiid is a data virtualization system that allows applications to use data from multiple, heterogenous data stores. Teiid is comprised of tools, components and services for creating and executing bi-directional data services.  Through abstraction and federation, data is accessed and integrated in real-time across distributed data sources without copying or otherwise moving data from its system of record. 

"JCR v2.0 Specification (HTML version) Content Repository for Java Technology API Specification (JSR-283) "

" Apache SlingTM is an innovative web framework that is intended to bring back the fun to web development. Discussions about Sling happen on our mailing lists, see the Project Information page for more info. Apache Sling in five bullets points REST based web framework Content-driven, using a JCR content repository Powered by OSGi Scripting inside, multiple languages (JSP, server-side javascript, Scala, etc.) Apache Open Source project"

Each node in a Jackrabbit workspace tree has a node type that defines the child nodes and properties it may (or must) have. Developers can use node types to define a custom content model for their application domain and have Jackrabbit enforce the constraints of that model at the repository level.

The Java Content Repository (JCR) standard, which is based on the Java Specification Requests JSR170 (version 1.0) and JSR 283 (version 2.0), provides a Java-centric object-oriented storage API specifically targeted at content management scenarios. The JCR is not a content management system or a full-fledged content management system API, but rather a content repository API. A content repository provides a common API for all content-driven applications and CMS components, which require access to the content. It provides methods to read, write, and query content. The primary motivation of the JCR standard is to provide a standard and vendor-neutral programmatic interface for content repositories, allowing applications of multiple vendors to interact efficiently.

The previous sections have extensively used the CND notation to illustrate the examples. Now that the most important concepts have been demonstrated, this section will give an in-depth overview of the CND. JSR 283 further defines an XML-based format for defining node type definitions, however, it has not been finalized yet at the time of writing. A CND file contains a series of namespace declarations, node type definitions, as well as comments which are denoted with a double slash (//).

The Compact Namespace and Node Type Definition (CND) notation provides a compact standardized syntax for defining node types and making namespace declarations. The notation is intended both for documentation and for programmatically registering node types (if you are unfamiliar with JCR node types, you may want to read the general Node Types section first).