Problems with Extension and Scopes

[hnrkdmsk]

Hey,
I want to extend an class that needs a other scope then the singleton. How can I specify the bean scope for the @Extension annotated class?

I want to use your library with Spring and Vaadin 8. All works fine! But now I want to test to get SpringView annotated classes loaded out of the plugin. And there I have problems with the scopes of the bean that will be created by your library. The SpringView cannot be a singleton.

Is there any option to set the singleton explicitly?

Greetings!

[decebals]

I don't use Spring in my projects so I don't use this PF4J's extension (pf4j-spring).
This project is very tiny and easy to hack. All the business is available in two classes: SpringExtensionFactory and ExtensionsInjector.
My idea is to add a new annotation (for example @SpringScope) on class annotated with @extension. In this mode if you have the class (name) of extension you can read the value from @SpringScope.
All you need to do is to modify SpringExtensionFactory or ExtensionsInjector and to use the scope value when register the extension as Spring's bean.

Make sense for you?

[hnrkdmsk]

You mean something like this?

protected void registerExtension(Object extension, BeanDefinitionRegistry beanDefinitionRegistry) {
        BeanDefinitionBuilder definitionBuilder = BeanDefinitionBuilder.rootBeanDefinition(extension.getClass())
            .setScope(extension.getClass().getAnnotation(SomeSpringScopeAnnotation.class).value()) // here make use of the new added annotation e.g. @springscope
            .addPropertyReference("propertyName", extension.getClass().getName())
            .addPropertyValue("propertyValue", extension);
        beanDefinitionRegistry.registerBeanDefinition(extension.getClass().getName(), definitionBuilder.getBeanDefinition());
}

There I have edit the ExtensionsInjector. I don't tested it yet and don't know if this work, but it can be an idea for it. The biggest change would be the switch from the SingleBeanRegistry to BeanDefinitionRegistry.

@PostConstruct
public void injectExtensions(BeanDefinitionRegistry beanDefinitionRegistry) {
...
}

[decebals]

Yes. Something like this.

[decebals]

What it's not clear for me is the comment from 1139d13#comments that says that

PostConstruct cannot work with parameters of the method

Can you validate this affirmation. Did you able to run the demo without problem?

The modification with ExtensionsInjector.injectExtensions(SingletonBeanRegistry beanRegistry) is an attempt to solve #3.

Thanks!

[decebals]

I see that exists org.springframework.context.annotation.Scope. It's an idea to use this annotation.

[hnrkdmsk]

org.springframework.context.annotation.Scope would be great for this!

I can get it running, but not fully. The application context of the plugin is not resolved anymore. But with my fix, the scope will be set right.

protected void registerExtension(Object extension, BeanDefinitionRegistry beanDefinitionRegistry) {
        BeanDefinitionBuilder definitionBuilder = BeanDefinitionBuilder.rootBeanDefinition(extension.getClass())
            .addPropertyReference("propertyName", extension.getClass().getName())
            .addPropertyValue("propertyValue", extension);

        if (extension.getClass().isAnnotationPresent(ExtensionSpringScope.class)) {
            String scope = extension.getClass().getAnnotation(ExtensionSpringScope.class).value();
            log.info("Registering {} with scope: {}", extension.getClass().getName(), scope);
            definitionBuilder.setScope(scope);
        }

        beanDefinitionRegistry.registerBeanDefinition(extension.getClass().getName(), definitionBuilder.getBeanDefinition());
    }

What I had to change was the @PostConstruct method.

@Autowired
    private ApplicationContext applicationContext;

    public ExtensionsInjector(PluginManager pluginManager) {
        this.pluginManager = pluginManager;
    }

    @PostConstruct
    public void injectExtensions() {
      BeanDefinitionRegistry beanDefinitionRegistry = (BeanDefinitionRegistry) applicationContext.getAutowireCapableBeanFactory();
...}

The post construct method don't allow parameters anymore. I don't checked if this has a relation to my changes. But now I don't get my beans from the plugin loaded... Can you check it?

[decebals]

Can you fork the project (via GitHub), add your modifications to pippo-spring and give me the link?

[hnrkdmsk]

Yes, I can! Here: https://github.com/loefflefarn/pf4j-spring/tree/pippo-spring

[decebals]

@loefflefarn
I made some modifications on master to organize better the code and to prepare things for Scope implementation.
I created a new branch "scope" that contains all modifications. I added scope "prototype" on one of extension from demo and it works. I will create a PR to have the possibility to review the code and add comments.

[hnrkdmsk]

Nice, okay. I will check it tomorow in my application and will give you feedback! Thanks a lot for you help.

[hnrkdmsk]

The scopes are now setted right but they cannot resolve there beans from the plugin. You can test it, if you set the scope to prototype in the demo application-plugin2.

[decebals]

@loefflefarn
I explained yesterday in some comments of PR #6 why this problem appear.

[hnrkdmsk]

Ah, yes. Okay, I will look around for a possible solution to help you with it. I've tested around with this, but nothing has work fine.