What it does

The Java Simple Plugin Framework was built to reduce development time while increasing code maintainability of small to medium sized projects.

• Completely hides implementation details of components. Only use their interfaces.
• Components may be loaded with only two(!) lines of code
• Heavily annotation based: @PluginImplementation, @InjectPlugin, @PluginLoaded, @Timer and @Thread, ...
• Through usage of generics it is usually type safe.
• Additional plugins to export other plugins by JavaScript, JSON, LipeRMI, XMLRPC, XMLRPC Delight or ERMI. Plugins may be discovered on the local net using ZeroConf. Initial support for RDF.
• Only 120k core size.

(See the Usage Guide, FAQ or Introduction-Video for more information).

What is new in this version (0.7.0, August 2009)

• Removed requiredPlugins() inside @PluginImplementation, these are automatically inferred by looking at the @InjectPlugin options.
• Removed TrueZip. We now handle JARs on our own. This results in
• A greatly reduced core size, now only 120k
• Revised caching. Plugins should load faster now.
• Introduced weak hashing. Should improve startup even more ("cache.mode"="weak" must be enabled)
• Improved startup speed of discovery plugin.

A short example

The following lines demonstrate how easy it is to load existing plugins. All .JAR files inside the given directory will be examined for contained plugins which will be loaded afterwards and are automatically started. No configuration files are required, nothing else has to be done.

PluginManager pm = PluginManagerFactory.createPluginManager();

// and then one or more of these ...

pm.addPluginsFrom(new File("myPluginDir/").toURI());
pm.addPluginsFrom(new File("myPluginDir/myPlugin.jar").toURI());
pm.addPluginsFrom(new URI("classpath://*"));
pm.addPluginsFrom(new URI("http://server.com/plugin.jar"));

Creating a new plugin is equally straightforward. After an interface has been designed the rest can be done by a simple annotation. The next example shows a plugin implementation that could be loaded by JSPF, and also here: no XML- or whatsoever-files have to be created to make this work.

/**
 * CoolPlugin may be an (almost) arbitrary interface, in only has to extend Plugin.
 */
@PluginImplementation
public class CoolPluginImpl implements CoolPlugin {

    public String provideData() {
        return "Hello World";
    }

}

Our last two snippes indicates how plugins can be obtained from outside, and the inside of plugins. Notice the type-safety:

CoolPlugin cool = pm.getPlugin(CoolPlugin.class);

Or, from inside of plugins:

@InjectPlugin
public CoolPlugin cool;

When to use it

If you

• are, for example, a researcher and want to develop a prototype quickly
• intend to change implementations frequently but want to keep your code clean
• are coding some software where you expect plugins to be loaded using some kind of easy IoC
• think about reusing components in other prototypes

then you might want to give it a try.

Functionality Checklist

(aka the unbiased JSPF-is-great feature matrix)

Below you find a brief overview of the most important features JSPF has to offer. This list is not complete, and the framework offers various other goodies here and there, like flexible options, easy configuration support and some more.

Feature	JSPF
Can load ... plugins from JAR files	Yes
... multiple plugins from path	Yes
... automatically all plugins in classpath	Yes
... plugins over HTTP	Yes (1)
Threadsafe	Yes
Typesafe	Yes
Dependency Injection	Yes
XML free	Yes
Heavily annotation based	Yes
Supports caching	Yes
Plugins can be isolated using a separate ClassLoader	Yes (2)
Official support to export plugins over ... ERMI	Yes
... LipeRMI	Yes (3)
... JSON (easily export Plugins to web pages!)	Yes
... XMLRPC	Yes
Transparent and easy network callbacks	Yes (w. LipeRMI)
Remote plugins may be discovered automatically	Yes
Requires Java version	>5.0
Supported Platforms	Windows, Mac, Linux
Works in applets	Yes (4)
Core size	120k (5)
Time to get started	5 minutes (6)
License	Free (beer and speech)
Proper end user documentation	:-(

(1) Works, but unsafe and not recommended.

(2) Only if the plugins are packed into a self contained JAR.

(3) We even use a greatly enhanced version of LipeRMI with fewer bugs and more featues.

(4) Applets have to be signed, does not work with classpath autodetection

(5) Likely to increase with every new version, remote plugins add extra size

(6) If you watch the introduction video and have profound Java experience.

Known Users

• German Research Center for Artificial Intelligence (various projects)

Help & Feedback

We know the documentation is in a bad shape. However, in case you have any questions, comments or requests, don't hesitate to visit my web page and drop me a mail. I will add the items to the wiki afterwards.

History

This project was created by Ralf Biedert. Nicolas Delsaux started the hosting on code.google.com and added some features. Thomas Lottermann contributed to various plugins.