The first part of this article reviewed some relevant open-source Web applications in both the PHP and Java worlds. The conclusion was that there are massively popular PHP projects and somewhat popular if not obscure Java counterparts. I'm a Java fan and it pains me to discover this reality. The user comments also underlined this feeling.
Is it the technical merits of PHP?
In my experience, the technical merits of PHP are below those of Java as a language and as a runtime environment (standard API, virtual machine).
Compared to Java, the code quality of PHP projects has a faster decreasing rate as the codebase size grows. The root cause is that PHP was created to solve small size problems and this makes it difficult to manage larger projects.
PHP 3 and 4 had basic object-oriented features, while PHP 5 improved them considerably, both at the language and the runtime level. There are several PHP MVC frameworks to ease the structuring of larger projects, but these are most effective when running on PHP 5. Most popular open-source PHP projects still run on PHP 4 and tend not to use MVC frameworks at all.
Looking at the staggering number of plugins available for the popular PHP open-source projects, one could conclude that their code is easily understandable and that PHP has well-rounded application extension mechanisms. Well, not exactly true.
The typical PHP extension mechanism is procedural and works like this:
- list the subdirectories of the extensions directory,
- analyze the predefined directory structure for each extension,
- execute some predefined PHP files that should auto-register their resources and actions.
The greatest concern – no protection of the core code. All the important internal structures of the PHP runtime are map-like data structures to which the PHP code has full access: the global variables map, the functions map, the classes map etc.
As a long-time Java developer, I see these as drawbacks. But they don't seem to reflect as such on these popular projects with very large user and developer communities. But if it's not the language, what is it?
The execution models
Compared to Java, developing and hosting PHP projects is dead-simple because of the execution model.
In a typical setup, each request to a PHP application is handled by a separate Apache process that uses its own instance of the PHP interpreter. After handling the request, the process is killed with no garbage left behind. This sounds inefficient for high-concurrency usage, but works great in a shared hosting environment. If a hosted application has no active requests, it doesn't use memory at all. Development-wise, each PHP script is written like every script instance (process) is the only one running.
The Java Web application model uses servlets and multiple threads to handle requests. It scales upwards very well, hence its success in the enterprise space. Problems arise if you want to host many smaller and less frequently used applications inside the same Web container, precisely because of the threads. Developers have to be careful about concurrency issues.
The process control mechanisms available at the OS level are vastly superior than those available for Java threads. The result is that a hosting provider has strict control over the resources used by each PHP request. On the other hand, a Java thread backing a request is an object that you cannot control once started: it stops when it wants to, it uses as much system resources as it pleases. The Web containers only have mechanisms for controlling the pool of threads.
The end result is that there are technical limitations in setting up a competitively priced reliable Java hosting solution. This brings us to two fundamental questions: do we need successful open-source Java Web projects suitable for non-enterprise use? Can Java survive without such projects?
Java can probably survive, but survival and flourishing are two different things. If the average present-day college student or hobbyist finds pleasure in using and extending open-source PHP (and generally non-Java) Web applications, I believe that it is only a matter of time until the effects are felt in the enterprise space: less enthusiastic Java specialists, less innovation, decreasing quality of products and so on. Some say that the effects are already present – what do you think?
Instead, wouldn't you like to run your blog on a Java-based highly extensible engine? Wouldn't you like to build complex sites using a Java-based CMS with many high quality, readily available, easy to develop modules? Something that can be as small or as large as you want. I would.
Building successful open-source Java Web applications – your input is needed
In my opinion, there are three important premises for an open-source Web project to succeed:
- the intrinsic value of the project,
- the enthusiasm of its community (both developers and users),
- easy hosting.
If Java presence is to increase in the area of open-source Web applications, all three are needed. The first two items are crucial because valuable projects and enthusiastic communities can even help improve the existing entry-level hosting options.
The fastest way to obtain Java projects with the same functionality as PHP ones is by automated software translation. The company I co-founded has developed technology that allows translating PHP applications to Java. I have already talked about this while presenting the nBB2 project, the Java equivalent of phpBB 2. The migration algorithms can be customized to produce various output flavors, ranging from plain servlets and JSP pages to Web frameworks like Struts or Spring MVC.
We would like to translate more open-source PHP projects to Java, but this would be just a first step. The Java community would then have to step in by using and extending them.
The projects I see as the most useful are from two categories: a CMS (like Joomla or Drupal) and a blog engine (probably WordPress). We have opened a forum topic with a poll, as a discussion starting point: http://www.numiton.com/vote. Before we start such an undertaking, we want to make sure it makes sense. What do you think?
In the comments following the first part of this article it has been suggested that Sun act and sponsor key open-source Java Web projects. I my opinion, Sun already provides the Java platform and an open-source stack to support such endeavors. It is up to the Java community to make proper use of the technologies at hand. I look forward to hearing your thoughts on this topic, both online and in person. Next week I'll be at JavaOne, so if you are around feel free to pass by the Numiton booth 1224-8 in the startup row.