Writing activator - 3.2

Owned by Maciej Majchrzak
Last updated: Oct 10, 2013
2 min read

In order Slice to work, you have to write and set up activator of your application. The activator will be responsible for creating and storing injector of your application.

Example activator

Below code presents how an activator of your application should look like:

package com.cognifide.app.core;

import java.util.ArrayList;
import java.util.List;

import org.osgi.framework.BundleActivator;
import org.osgi.framework.BundleContext;

import com.cognifide.slice.api.context.ContextScope;
import com.cognifide.slice.api.injector.InjectorRunner;
import com.cognifide.slice.commons.SliceModulesFactory;
import com.cognifide.slice.core.internal.context.SliceContextScope;
import com.cognifide.slice.cq.module.CQModulesFactory;
import com.cognifide.slice.validation.ValidationModulesFactory;
import com.google.inject.Module;

public class Activator implements BundleActivator {

    private static final String BUNDLE_NAME_FILTER = "com\\.cognifide\\.app\\..*";

    private static final String BASE_PACKAGE = "com.cognifide.app";

    private static final String INJECTOR_NAME = "myapp";

    @Override
    public void start(BundleContext bundleContext) throws Exception {
        final ContextScope scope = new SliceContextScope();
        final InjectorRunner injectorRunner = new InjectorRunner(bundleContext, INJECTOR_NAME, scope);

        List<Module> sliceModules = SliceModulesFactory.createModules(bundleContext, INJECTOR_NAME,
                BUNDLE_NAME_FILTER, BASE_PACKAGE);
        List<Module> cqModules = CQModulesFactory.createModules();
        List<Module> validationModules = ValidationModulesFactory.createModules();
        List<Module> customModules = createCustomModules();

        injectorRunner.installModules(sliceModules);
        injectorRunner.installModules(cqModules);
        injectorRunner.installModules(validationModules);
        injectorRunner.installModules(customModules);

        injectorRunner.start();
    }

    private List<Module> createCustomModules() {
        List<Module> applicationModules = new ArrayList<Module>();
        //populate the list with your modules
        return applicationModules;
    }
}

You have to change the following things to adjust to your application:

  • BUNDLE_NAME_FILTER value
  • BASE_PACKAGE value
  • INJECTOR_NAME value
  • populate a list of your application modules

What's going on here?

Here's what's happening in start method:

  1. Slice context is created.
  2. InjectorRunner is created. It's a helper which allows you to add modules, creates injector and register it in injector repository. It needs INJECTOR_NAME to register injector under this String. Please read more about injectors repository to get to know how does it work and what name to choose.
  3. List of Slice modules is created. The meaning of constants is as follows:
    • INJECTOR_NAME - name of the injector under which is registered
    • BUNDLE_NAME_FILTER - the pattern that defines which bundles to scan in order to find classes annotated by @SliceResource annotation. Only bundles which symbolic names matche the pattern are scanned.
    • BASE_PACKAGE - the base package that defines which packages inside bundles specified above to scan in order to find classes annotated by @SliceResource annotation.
  4. CQ modules are created
  5. Validation modules are created
  6. List of your modules is created. You should instantiate all the custom modules of your application in the createCustomModules method.
  7. All the modules are installed
  8. InjectorRunner is started which means that it creates the Guice injector, install all the provided modules and registered the injector in the injector repository under the specified name.

Register your activator

Don't forget about registering your activator by putting it in the maven-bundle-plugin configuration:

<plugin>
	<groupId>org.apache.felix</groupId>
	<artifactId>maven-bundle-plugin</artifactId>
	<extensions>true</extensions>
	<configuration>
		<instructions>
			<Export-Package>com.cognifide.app.core*;version="${project.version}"</Export-Package>
			<Bundle-Activator>com.cognifide.app.core.Activator</Bundle-Activator>
			<Bundle-SymbolicName>com.cognifide.app.core</Bundle-SymbolicName>
		</instructions>
	</configuration>
</plugin>