[jboss-dev-forums] [Design the new POJO MicroContainer] - Annotations scanning part 2

[alesj]

I'm slowly adding more and more tests to this (resolved) issue:
 - http://www.jboss.com/index.html?module=bb&op=viewtopic&t=134098

I've added a deployer that knows how to scan newly added @Bean and @BeanFactory annotations - corresponding to MC beans and beanfactories.

The code that does this is pretty simple:

  |    public void deploy(DeploymentUnit unit, AnnotationEnvironment env) throws DeploymentException
  |    {
  |       Set<Class<?>> beans = env.classIsAnnotatedWith(Bean.class);
  | 
then you can do what ever you like with that information. ;-)
This is what I do in my case (create new BeanMetaData if it doesn't exist yet):

  |          for (Class<?> beanClass : beans)
  |          {
  |             Bean bean = beanClass.getAnnotation(Bean.class);
  |             String name = bean.name();
  |             if (name == null)
  |                throw new IllegalArgumentException("Null bean name: " + beanClass);
  | 
  |             DeploymentUnit component = components.get(name);
  |             BeanMetaData bmd = null;
  |             if (component != null)
  |                bmd = component.getAttachment(BeanMetaData.class);
  | 
  |             if (bmd == null)
  |             {
  |                BeanMetaDataBuilder builder = BeanMetaDataBuilder.createBuilder(name, beanClass.getName());
  |                String[] aliases = bean.aliases();
  |                if (aliases != null && aliases.length > 0)
  |                   builder.setAliases(new HashSet<Object>(Arrays.asList(aliases)));
  |                builder.setMode(bean.mode())
  |                       .setAccessMode(bean.accessMode())
  |                       .setAutowireType(bean.autowireType())
  |                       .setErrorHandlingMode(bean.errorHandlingMode())
  |                       .setAutowireCandidate(bean.autowireCandidate());
  | 
  |                addBeanComponent(unit, builder.getBeanMetaData());
  |             }
  | 

For all those who missed recent annotations scanning work, this is the class that should be of interest - AnnotationEnvironment - simply pull it out from the right DeploymentUnit as attachment:

  | /**
  |  * Information holder about annotation processing.
  |  *
  |  * @author <a href="mailto:ales.justin at jboss.com">Ales Justin</a>
  |  */
  | public interface AnnotationEnvironment
  | {
  |    /**
  |     * Get all classes annotated with annotation param.
  |     *
  |     * @param annotation the annotation we're querying for
  |     * @return set of matching classes
  |     */
  |    Set<Class<?>> classIsAnnotatedWith(Class<? extends Annotation> annotation);
  | 
  |    /**
  |     * Get all classes who have some constructor annotated with annotation param.
  |     *
  |     * @param annotation the annotation we're querying for
  |     * @return set of matching classes
  |     */
  |    <A extends Annotation> Set<Element<A, Constructor>> classHasConstructorAnnotatedWith(Class<A> annotation);
  | 
  |    /**
  |     * Get all classes who have some field annotated with annotation param.
  |     *
  |     * @param annotation the annotation we're querying for
  |     * @return set of matching classes
  |     */
  |    <A extends Annotation> Set<Element<A, Field>> classHasFieldAnnotatedWith(Class<A> annotation);
  | 
  |    /**
  |     * Get all classes who have some method annotated with annotation param.
  |     *
  |     * @param annotation the annotation we're querying for
  |     * @return set of matching classes
  |     */
  |    <A extends Annotation> Set<Element<A, Method>> classHasMethodAnnotatedWith(Class<A> annotation);
  | 
  |    /**
  |     * Get all classes who have some method's/constructor's parameter annotated with annotation param.
  |     *
  |     * @param annotation the annotation we're querying for
  |     * @return set of matching classes
  |     */
  |    <A extends Annotation> Set<Element<A, AccessibleObject>> classHasParameterAnnotatedWith(Class<A> annotation);
  | }
  | 

The code handles class loading lazily (Javassist + keeping weak ref to classloader from unit), meaning class won't get loaded until you actually need the information, e.g. AOP could modify it before.

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