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Caching is the most important performance optimization technique. There are many things that can be cached in persistence, objects, data, database connections, database statements, query results, meta-data, relationships, to name a few. Caching in object persistence normally refers to the caching of objects or their data. Caching also influences object identity, that is that if you read an object, then read the same object again you should get the identical object back (same reference). JPA 1.0 does not define a shared object cache, JPA providers can support a shared object cache or not, however most do. Caching in JPA is required with-in a transaction or within an extended persistence context to preserve object identity, but JPA does not require that caching be supported across transactions or persistence contexts. JPA 2.0 defines the concept of a shared cache. The @Cacheable annotation or cacheable XML attribute can be used to enable or disable caching on a class.

"EMF URI handler implementation that can persist EMF object instances to MongoDB. "

The CDO (Connected Data Objects) Model Repository is a distributed shared model framework for EMF models and meta models. CDO is also a model runtime environment with a focus on orthogonal aspects like model scalability, transactionality, persistence, distribution, queries and more. CDO has a 3-tier architecture supporting EMF-based client applications, featuring a central model repository server and leveraging different types of pluggable data storage back-ends like relational databases, object databases and file systems. The default client/server communication protocol is implemented with the Net4j Signalling Platform.

"Neo4j is a graph database. It is an embedded, disk-based, fully transactional Java persistence engine that stores data structured in graphs rather than in tables. A graph (mathematical lingo for a network) is a flexible data structure that allows a more agile and rapid style of development."

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).

"Let's imagine we want to create an application for orders. People can sign in to the system, place orders for various items, check out and have them sent to their address. Very simple, but we can show a lot of things here. As we expect to be writing more than one application of this type and as we also would like to be able to express the structure of the application on a business level (one of the major drivers for DSLs and MDSD for that matter), we come up with the idea of using a DSL to describe what the application does. Defining the DSL is what we did last week. This week, we need to map the concepts of the DSL to some code and some APIs we're going to program against. So, we're going to create a set of code templates for a code generator that can then read our DSL models and create persistence code for us."

"Clojure is a dynamic programming language that targets the Java Virtual Machine (and the CLR ). It is designed to be a general-purpose language, combining the approachability and interactive development of a scripting language with an efficient and robust infrastructure for multithreaded programming. Clojure is a compiled language - it compiles directly to JVM bytecode, yet remains completely dynamic. Every feature supported by Clojure is supported at runtime. Clojure provides easy access to the Java frameworks, with optional type hints and type inference, to ensure that calls to Java can avoid reflection. Clojure is a dialect of Lisp, and shares with Lisp the code-as-data philosophy and a powerful macro system. Clojure is predominantly a functional programming language, and features a rich set of immutable, persistent data structures. When mutable state is needed, Clojure offers a software transactional memory system and reactive Agent system that ensure clean, correct, multithreaded designs. I hope you find Clojure's combination of facilities elegant, powerful, practical and fun to use."

Sample of using Hibernate Annotations by reducing XML configuration files thus making it simpler to define required metadata directly into our Java code. When using annotations, we no longer need the additional mapping file (*.hbm.xml). The metadata for the ORM is specified in the individual classes.