Open Source

Open Source is a generic term that usually refers to software that doesn't require you to pay a license fee to use and that comes with full source code. Because the cost of entry is low (zero), most Open Source projects have many users. Some users are playing with the software to get ideas for their own development. Some of them want to see the source to discover the secrets behind some functionality they like. The most interesting users, at least from the perspective of the project community, are the ones who use the software, fix some bugs or add some new features, and contribute their work back to the project. In this fashion, the overall quality and value of the Open Source project continues to grow indefinitely.

The Apache Software Foundation hosts many Open Source projects in quite a few categories, including Java and XML:

• Android: is a software platform and operating system for mobile devices, based on the Linux kernel, developed by Google and later the Open Handset Alliance. It allows developers to write managed code in the Java language, controlling the device via Google-developed Java libraries. The unveiling of the Android platform in 2007 was announced with the founding of the Open Handset Alliance, a consortium of 48 hardware, software, and telecom companies devoted to advancing open standards for mobile devices. Google has made most of the Android platform available under the Apache free-software and open source license.
• Ant: Is an amazingly useful tool for building, testing, deploying, and managing Java-based projects. It replaces make as the tool of choice for building projects, as well as providing an excellent cross-platform utility for basic programming-task-related scripting. We have used it on dozens of projects and can't live without it. If you use no other open source tools, use Ant.
• Axis: Is the third generation of the Java-based Apache SOAP (Simple Object Access Protocol) toolkit which began at IBM as "SOAP4J". It with no doubt is the most successfull open source Java Web services framework. Axis plugs into servlet engines such as Tomcat, offers "drop-in" SOAP services (Java source files that match a special naming scheme are recognized, and the Web service made immediately available) as well as extensive support for the Web Service Description Language (WSDL) and for SOAP Attachments. It also includes emitter tooling that generates Java classes from WSDL, and a tool for monitoring TCP/IP packets.
• Log4j: A logging framework that was being used heavily long before the JDK 1.4 logging implementation came into existence. It is more configurable, and arguably, more powerful than the standard, which is one reason why it remains the logging mechanism of choice for many Open Source projects. Another key reason for its continued popularity is that it works with JDK 1.1 and later JDK's and is therefore available to "legacy" Java applications.
• Commons: The Commons project is a good place to look for code if you don't want to reinvent the wheel. It contains collection classes, a logging package that can delegate to Log4J, JDK 1.4 logging, and more, web utilities, XPath helpers, data validators, testing tools, XML mappers, a command-line parser, and more.
• Xerces: One of most well-known XML parsers for two reasons: it was one of the first and it's included in other Open Source and commercial application servers and other products. Although the competition is stiff, Xerces continues to evolve and grow by adding XML Schema support, complying to the JAXP (Java API for XML Parsing) standard.
• Xalan: The most common XSLT processing engine and, in fact, is now included as part of JDK 1.4.
• Tomcat: Tomcat was chosen to be the Sun JSP/servlet container Reference Implementation. For this reason, using Tomcat as your development environment is a good choice for those desiring web application portability. Tomcat generally supports the latest servlet and JSP specifications, which makes it a wonderful place to try out new features that will eventually be implemented by all the major container vendors. JBoss works well with Tomcat to provide a unified J2EE container.
• JSTL: Much like Tomcat, the Java Server Pages Standard Tag Library (JSTL) is a Jakarta project that serves as one of the Sun standard Reference Implementations. This tag library is essentially a subset of all the existing tag libraries chosen to become a standard for implementation by all the JSP/servlet container vendors. Using this tag library is a smart choice for developers who want to make sure their code is portable across Tomcat, WebLogic, WebSphere, etc. with minimal work.
• Struts: Is a good framework for web site development. It has become more and more popular over the last year or so and is now entering the corporate mainstream. If you need to process a lot of forms in your JSP/servlet development projects, take a look at what Struts can do for you. Tiles is an included add-on to Struts that provides simple templating behavior for web pages. If you need to implement a full-blown portal, diving into Jetspeed or Liferay may be worth your time.
• Velocity: A template engine that competes with JSP as a method for Java developers to render web sites.
• Jetspeed: Is a Java- and XML-based portal server that supports JSP, Velocity, content aggregation and syndication, WAP browsers, user-driven view customization and internationalization, caching, and much more. It is very similar to powerful commercial portal servers such as Epicentric (now part of Vignette) that give each individual user control over what he sees and how it's presented. The Jetspeed administrator can easily obtain news and other content from external sources and distribute original content to others.
• JMeter : A load testing and performance analysis tool mainly for web applications. It supports multi-threaded load simulation, pluggable samplers and timers, and off-line visualization tools for data analysis.

SourceForge.net is the largest repository of Open Source code and applications available on the Internet. It hosts thousands of projects in every conceivable category of software development, including a multitude of Java and XML efforts:

• JBoss: A very popular J2EE container that hosts Enterprise JavaBeans (EJB), supports the Container Managed Persistence (CMP) 2.0 specification, provides a Java Message Service (JMS) implementation, dynamically deploys and redeploys components, exposes its management API's through Java Management Extensions (JMX) API's, and more. For-pay documentation is available and it has strong community support. It can come bundled with Tomcat which makes it a natural for web applications. We believe JBoss is the best choice among the Open Source J2EE containers.
• HSQLDB: Is a continuation of the closed Hypersonic SQL project. It is a 100% Java, embeddable relational database with transactional support, relational integrity, subqueries, views, stored procedures, security, and much more. HSQLDB is the default database embedded in JBoss.
• Hibernate: An excellent Java framework that provides nearly transparent persistence for Java classes. It supports association, inheritance, polymorphism, composition, and the standard Java collection classes. Instead of invasive inheritance, manual interface implementation, code generation, or post-processing, Hibernate uses run-time reflection at system initialization to generate SQL and proxy implementations. The API and query language let you feel like you're working with an object-oriented database, yet it supports blazing fast access to MySQL, PostgreSQL, Oracle, and many other relational databases. Though Hibernate works well both inside and outside of application servers, many programmers are beginning to consider Hibernate as a preferred alternative to CMP in J2EE environments. We believe Hibernate will begin to dominate the Open Source object/relational mapping tool market in the near future.
• Liferay: Liferay Enterprise Portal is a fully J2EE compatible portal system that provides personalization, web email, document library, message boards, shopping (e-commerce), Wiki and many other web tools all available in one place. Liferay has built its its portlet container and portlets around Session EJBs with the use of Hibernate, Struts and Tiles.
• Java Service Wrapper: A tool that allows Java applications to be installed and controlled like a native NT/Unix service. It can also automatically restart crashed or frozen virtual machines.
• XDoclet: XDoclet lets you do interesting things with special source code comments. XDoclet is an extensible system that generates documentation, source code, metadata, or anything else you might want using templates and Ant tasks. It comes with templates and examples of how to get your source code comments to create EJB artifacts, such as component and home interfaces, value objects, and deployment descriptors. There are templates and examples of creating web application artifacts, such as JSP tag library and servlet deployment descriptors and Struts configuration files. There is also an XDoclet template used to create Hibernate mapping files.
• JUnit: Is the unit testing backbone of any good Java-based development project. It's a simple, easy to use, and incredibly powerful tool used to demonstrate that Java code does what it is supposed to do. JUnitReport (an Ant task) turns the test results into a very attractive and fantastically useful HTML report for easy bug fixing. This is one utility that should be in every Java programmer's toolchest.
• HttpUnit: An extension of JUnit, HttpUnit is used to perform blackbox testing on web sites. Simply put, HttpUnit allows a developer to hit a web site and examine the results using a powerful yet straightforward API. As an example of a test, a developer can write code that states if the contents of a particular row in a certain table is not an expected value, the test case fails. It supports following links, form submission, Javascript, and more.

Outside of Apache and SourceForge, there are an enormous number of Open Source projects hosted by both well-known and lesser known Open Source groups, corporations, and individuals:

• Castor: Castor is a Java framework that provides data binding services for XML and SQL, and supports a JDO interface. Castor is especially suited to loading, modifying, and saving XML documents based on XML Schema Definitions. Given a sample XML document, it can also generate an XML Schema Definition and Java source able to read and write any XML document based on the schema.
• JDOM and dom4j: Similar to Xerces, JDOM (JSR-102) and dom4j are both XML manipulation technologies for Java. They both have the goal of making XML parsing, printing, and transformation fast and easy. Only time will tell if one will gain momentum and replace the others as a tool of choice.
• NetBeans: NetBeans is a robust Java IDE, including a visual GUI builder, written in Java. It has dozens of available plug-ins, including those for J2EE development, XML editing, database browsing, Ant integration, profiling, testing, debugging, web service generation, and more. It also has lots of community support and a full-featured prototypical application ready for copying.

J2EE

Java 2 Enterprise Edition. Sun's very successful expansion of Java into the business and Internet domain. The primary focus of the Java 2 Platform, Enterprise Edition is a set of component technologies (Enterprise JavaBeans, JavaServer Pages, and Servlets) that simplify the process of developing enterprise applications. Mostly J2EE is not software,but rather a Java interface definitions ("APIs") that have been agreed upon and adhered to by a collection of different companies and organizations called the Java Community Process. Areas of expertise include:

• Server Technologies: Servlets, JavaServer Pages (JSP), Enterprise JavaBeans (EJB), Java Naming and Directory Interface (JNDI), Java Database Connectivity (JDBC), and Java Message Service (JMS).
• Security: Web Application security, Java Authentication and Authorization Service (JAAS), Java Secure Socket Extension (JSSE) as well as commercially available SSL tool kits such as SSLava.
• J2EE Compliant Commercial Software: WebLogic from BEA, iPlanet from Sun-Netscape alliance, Oracle App Server from Oracle, and JBoss, an Open Source implementation, all adhere and play to the J2EE standard, and for the most part are interchangeable with competitor's products. JRun from Macromedia, Tomcat and JServe from Apache Jakarta project, ServletExec from New Atlanta Communications, GNU JSP from GNU are the ones implementing J2EE component containers for Servlets and JSPs.

XML

Extensible Markup Language. Also known as the ASCII language of the Internet. It is not a programming language like Java, C++, or VB, rather is simply a means of structuring information that is not only humanly readable, but high computer consumable. Areas of expertise include:

• DTD and XMLSchema: Methods of qualifying and validating a given XML document type.
• DOM and SAX: DOM (Document Object Model) is a universal API to a static "in-memory" XML document. SAX ("Simple API for XML" but "Sequential Access XML" would be better) is an API for handling XML documents as a sequence of events and thus the entire document need not completely reside in memory and also processing can be performed in a streaming manner.
• JAXB: Rather than parse XML with the Java API for XML Processing (JAXP) and convert it to Java objects by hand, you can define a generalized mapping between XML elements and Java objects with JAXB (Java Architecture for XML Binding).
• XSL and XSLT: Language and tools of document translation and transformation.
• XPath: A sub-query or navigation language that can express sub-trees of an XML document.
• XQuery: An emerging successor to XPath with broader functionality.
• SOAP: Stands for "Simple Object Access Protocol", a standard by which XML documents (or "messages") are moved across the Internet most commonly over HTTP.

Reusable Components

During the years of experience in developing software solutions using a variety of platforms and tools, we have accumulated a solid framework of reusable components. These have become central to our delivery model, and have allowed us to deliver time and cost advantages to our clients:

XML Web services, JAX-RPC Web services, Web security, JSP Tag Libraries, Session and Entity enterprise beans, Relational to XML-structured data transformation, Persistent storage management,

SQL and legacy data system connectivity, HTTP file transfer, E-mail utilities, Performance and load testing tools, Event logging, J2EE application packaging and deployment, J2EE server/application management,

and much, much more...