This project is a proof of concept related to how you can integrate PF4J with Spring Framework.
- ExtensionsInjector allows PF4J's extensions to be exposed as Spring beans.
- SpringPlugin your plugin extends this class if your plugin contains Spring beans
- SpringExtensionFactory use this ExtensionFactory in your PluginManager if you have SpringPlugins
- SpringPluginManager a Spring aware PluginManager
In your pom.xml you must define the dependencies to PF4J-Spring artifact with:
<dependency>
<groupId>org.pf4j</groupId>
<artifactId>pf4j-spring</artifactId>
<version>${pf4j-spring.version}</version>
</dependency> where ${pf4j-spring.version} is the last pf4j-spring version.
You may want to check for the latest released version using Maven Search
Also you can use the latest SNAPSHOT via the Sonatype Maven Repository. For this, you must add above lines in your pom.xml:
<repositories>
<repository>
<id>sonatype-nexus-snapshots</id>
<url>https://oss.sonatype.org/content/repositories/snapshots</url>
<releases>
<enabled>false</enabled>
</releases>
<snapshots>
<enabled>true</enabled>
</snapshots>
</repository>
</repositories>Create the Spring configuration (declare some beans) using annotations with:
@Configuration
public class SpringConfiguration {
@Bean
public SpringPluginManager pluginManager() {
return new SpringPluginManager();
}
@Bean
@DependsOn("pluginManager")
public Greetings greetings() {
return new Greetings();
}
}SpringExtensionFactory creates a new extension instance every time a request is done.
If you want a singleton extension instance please use SingletonSpringExtensionFactory that always returns a specific instance. Optional you can specify the extension classes for which you want singletons.
Start your application (plain java code):
public class Boot {
public static void main(String[] args) {
// retrieves the Spring application context
ApplicationContext applicationContext = new AnnotationConfigApplicationContext(SpringConfiguration.class);
// retrieves automatically the extensions for the Greeting.class extension point
Greetings greetings = applicationContext.getBean(Greetings.class);
greetings.printGreetings();
// stop plugins
PluginManager pluginManager = applicationContext.getBean(PluginManager.class);
/*
// retrieves manually the extensions for the Greeting.class extension point
List<Greeting> greetings = pluginManager.getExtensions(Greeting.class);
System.out.println("greetings.size() = " + greetings.size());
*/
pluginManager.stopPlugins();
}
}Consume the PF4J extensions as Spring beans:
public class Greetings {
@Autowired
private List<Greeting> greetings;
public void printGreetings() {
System.out.println(String.format("Found %d extensions for extension point '%s'", greetings.size(), Greeting.class.getName()));
for (Greeting greeting : greetings) {
System.out.println(">>> " + greeting.getGreeting());
}
}
}The output is:
Found 2 extensions for extension point 'org.pf4j.demo.api.Greeting'
>>> Welcome
>>> Hello
Bellow I present you a more complex example where a plugin (see demo plugin2 - HelloPlugin) uses Spring Framework internally.
First, create an interface MessageProvider with an implementation class HelloMessageProvider
public interface MessageProvider {
String getMessage();
}
public class HelloMessageProvider implements MessageProvider {
@Override
public String getMessage() {
return "Hello";
}
}Declare the plugin's beans via Spring Configuration
@Configuration
public class SpringConfiguration {
@Bean
public MessageProvider messageProvider() {
return new HelloMessageProvider();
}
}Create my (Spring) plugin
public class HelloPlugin extends SpringPlugin {
public HelloPlugin(PluginWrapper wrapper) {
super(wrapper);
}
@Override
public void start() {
System.out.println("HelloPlugin.start()");
}
@Override
public void stop() {
System.out.println("HelloPlugin.stop()");
super.stop(); // to close applicationContext
}
@Override
protected ApplicationContext createApplicationContext() {
AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext();
applicationContext.setClassLoader(getWrapper().getPluginClassLoader());
applicationContext.register(SpringConfiguration.class);
applicationContext.refresh();
return applicationContext;
}
@Extension
public static class HelloGreeting implements Greeting {
@Autowired
private MessageProvider messageProvider;
@Override
public String getGreeting() {
// return "Hello";
// complicate a little bit the code
return messageProvider.getMessage();
}
}
}Ready, your extension is available in your application via PluginManager or Spring Autowire.
For more details please see the demo application.
ExtensionsInjector injects each PF4J's extension as a bean in Spring Framework. For example if you run the demo application you will see these lines in log:
2014-06-16 16:40:36,573 DEBUG org.pf4j.spring.ExtensionsInjector - Registering extensions of the plugin 'welcome-plugin' as beans
2014-06-16 16:40:36,586 DEBUG org.pf4j.spring.ExtensionsInjector - Register extension 'org.pf4j.demo.welcome.WelcomePlugin$WelcomeGreeting' as bean
2014-06-16 16:40:36,589 DEBUG org.pf4j.spring.ExtensionsInjector - Registering extensions of the plugin 'hello-plugin' as beans
2014-06-16 16:40:36,589 DEBUG org.pf4j.spring.ExtensionsInjector - Register extension 'org.pf4j.demo.hello.HelloPlugin$HelloGreeting' as bean
The bean name is the extension class name (for example 'org.pf4j.demo.welcome.WelcomePlugin$WelcomeGreeting').
For more information please see the demo sources.
I have a tiny demo application. The demo application is in demo package.
Run the pf4j-spring demo (Boot class contains the main method) from IDE (IntelliJ in my case) with these arguments as VM options:
-Dpf4j.mode=development
and working directory:
pf4j-spring/demo/app