An application is often comprised of a number of modules. For example, a Java EE deployment may contain a number of EJB modules (containing business logic) and war modules (containing the user interface). A container may enforce certain accessibility rules which limit the visibility of classes between modules. CDI allows these same rules to apply to bean and observer method resolution. As the accessibility rules vary between containers, Weld requires the container to describe the deployment structure, via the Deployment SPI.

The CDI specification discusses Bean Archives (BAs)—archives which are marked as containing beans which should be deployed to the CDI container, and made available for injection and resolution. Weld reuses this description and uses Bean Deployment Archives (BDA) in its deployment structure SPI.

Each deployment exposes the containing BDAs that form a graph. A node in the graph represents a BDA. Directed edges between nodes designate visibility. Visibility is not transitive (i.e. a bean from BDA A can only see beans in BDAs with which A is directly connected by a properly oriented edge).

To describe the deployment structure to Weld, the container should provide an implementation of Deployment. Deployment.getBeanDeploymentArchives() allows Weld to discover the modules which make up the application. The CDI specification also allows beans to be specified programmatically as part of the bean deployment. These beans may, or may not, be in an existing BDA. For this reason, Weld will call Deployment.loadBeanDeploymentArchive(Class clazz) for each programmatically described bean.

As programmatically described beans may result in additional BDAs being added to the graph, Weld will discover the BDA structure every time an unknown BDA is returned by Deployment.loadBeanDeploymentArchive.

BeanDeploymentArchive provides three methods which allow it’s contents to be discovered by Weld—BeanDeploymentArchive.getBeanClasses() must return all the classes in the BDA, BeanDeploymentArchive.getBeansXml() must return a data structure representing the beans.xml deployment descriptor for the archive, and BeanDeploymentArchive.getEjbs() must provide an EJB descriptor for every EJB in the BDA, or an empty list if it is not an EJB archive.

To aid container integrator, Weld provides a built-in beans.xml parser. To parse a beans.xml into the data-structure required by BeanDeploymentArchive, the container should call Bootstrap.parse(URL). Weld can also parse multiple beans.xml files, merging them to become a single data-structure. This can be achieved by calling Bootstrap.parse(Iterable<URL>).

When multiple beans.xml files are merged, Weld keeps duplicate enabled entries (interceptors, decorators or alternatives). This may cause validation problems when multiple physical archives which define an overlapping enabled entries are merged. A version of the Bootstrap.parse() method that provides control over whether duplicate enabled entries are remove or not is provided: Bootstrap.parse(Iterable<URL> urls, boolean removeDuplicates).

BDA X may also reference another BDA Y whose beans can be resolved by, and injected into, any bean in BDA X. These are the accessible BDAs, and every BDA that is directly accessible by BDA X should be returned. A BDA will also have BDAs which are accessible transitively, and the transitive closure of the sub-graph of BDA X describes all the beans resolvable by BDA X.

To specify the directly accessible BDAs, the container should provide an implementation of BeanDeploymentArchive.getBeanDeploymentArchives().

Certain services are provided for the whole deployment, whilst some are provided per-BDA. BDA services are provided using BeanDeploymentArchive.getServices() and only apply to the BDA on which they are provided.

The contract for Deployment requires the container to specify the portable extensions (see chapter 12 of the CDI specification) which should be loaded by the application. To aid the container integrator, Weld provides the method Bootstrap.loadExtensions(ClassLoader) which will load the extensions for the specified classloader.

Weld delegates EJB 3 bean discovery to the container so that it doesn’t duplicate the work done by the EJB container, and respects any vendor-extensions to the EJB definition.

The EjbDescriptor should return the relevant metadata as defined in the EJB specification. Each business interface of a session bean should be described using a BusinessInterfaceDescriptor.

By default, Weld uses the EJB component class when creating new EJB instances. This may not always be desired especially if the EJB container uses subclassing internally. In such scenario, the EJB container requires that the subclass it generated is used for creating instances instead of the component class. An integrator can communicate such layout to Weld by additionally implementing the optional SubclassedComponentDescriptor interface in the EjbDescriptor implementation. The return value of the SubclassedComponentDescriptor.getComponentSubclass() method determines which class will be used by Weld when creating new EJB instances.

All the EE resource services are per-BDA services, and may be provided using one of two methods. Which method to use is at the discretion of the integrator.

The integrator may choose to provide all EE resource injection services themselves, using another library or framework. In this case the integrator should use the EE environment, and implement the Section A.1.9, “Injection Services” SPI.

Alternatively, the integrator may choose to use CDI to provide EE resource injection. In this case, the EE_INJECT environment should be used, and the integrator should implement the Section A.1.4, “EJB services”, Section A.1.7, “Resource Services” and Section A.1.5, “JPA services”.

If the container performs EE resource injection, the injected resources must be serializable. If EE resource injection is provided by Weld, the resolved resource must be serializable.

Weld registers resource injection points with EjbInjectionServices, JpaInjectionServices, ResourceInjectionServices and JaxwsInjectionServices implementations upfront (at bootstrap). This allows validation of resource injection points to be performed at boot time rather than runtime. For each resource injection point Weld obtains a ResourceReferenceFactory which it then uses at runtime for creating resource references.

public interface ResourceReferenceFactory<T> {

    ResourceReference<T> createResource();

}

A ResourceReference provides access to the resource reference to be injected. Furthermore, ResourceReference allows resource to be release once the bean that received resource injection is destroyed.

public interface ResourceReference<T> {

    T getInstance();

    void release();

}

EJB services are split between two interfaces which are both per-BDA.

EjbServices is used to resolve local EJBs used to back session beans, and must always be provided in an EE environment. EjbServices.resolveEjb(EjbDescriptor ejbDescriptor) returns a wrapper—SessionObjectReference—around the EJB reference. This wrapper allows Weld to request a reference that implements the given business interface, and, in the case of SFSBs, both request the removal of the EJB from the container and query whether the EJB has been previously removed.

EjbInjectionServices.registerEjbInjectionPoint(InjectionPoint injectionPoint) registers an @EJB injection point (on a managed bean) and returns a ResourceReferenceFactory as explained above. This service is not required if the implementation of Section A.1.9, “Injection Services” takes care of @EJB injection.

Just as EJB resolution is delegated to the container, resolution of @PersistenceContext for injection into managed beans (with the InjectionPoint provided), is delegated to the container.

To allow JPA integration, the JpaServices interface should be implemented. This service is not required if the implementation of Section A.1.9, “Injection Services” takes care of @PersistenceContext injection.

Weld delegates JTA activities to the container. The SPI provides a couple hooks to easily achieve this with the TransactionServices interface.

Any javax.transaction.Synchronization implementation may be passed to the registerSynchronization() method and the SPI implementation should immediately register the synchronization with the JTA transaction manager used for the EJBs.

To make it easier to determine whether or not a transaction is currently active for the requesting thread, the isTransactionActive() method can be used. The SPI implementation should query the same JTA transaction manager used for the EJBs.

The resolution of @Resource (for injection into managed beans) is delegated to the container. You must provide an implementation of ResourceInjectionServices which provides these operations. This service is not required if the implementation of Section A.1.9, “Injection Services” takes care of @Resource injection.

The resolution of @WebServiceRef (for injection into managed beans) is delegated to the container. An integrator must provide an implementation of JaxwsInjectionServices. This service is not required if the implementation of Section A.1.9, “Injection Services” takes care of @WebServiceRef injection.

An integrator may wish to use InjectionServices to provide additional field or method injection over-and-above that provided by Weld. An integration into a Java EE environment may use InjectionServices to provide EE resource injection for managed beans.

InjectionServices provides a very simple contract, the InjectionServices.aroundInject(InjectionContext ic); interceptor will be called for every instance that CDI injects, whether it is a contextual instance, or a non-contextual instance injected by InjectionTarget.inject().

The InjectionContext can be used to discover additional information about the injection being performed, including the target being injected. ic.proceed() should be called to perform CDI-style injection, and call initializer methods.

In order to obtain the Principal representing the current caller identity, the container should provide an implementation of SecurityServices.

The org.jboss.weld.bootstrap.api.Bootstrap interface defines the initialization for Weld, bean deployment and bean validation. To boot Weld, you must create an instance of org.jboss.weld.bootstrap.WeldBeansBootstrap (which implements Bootstrap), tell it about the services in use, and then request the container start.

public interface Bootstrap {

    public Bootstrap startContainer(Environment environment, Deployment deployment);

    public Bootstrap startInitialization();

    public Bootstrap deployBeans();

    public Bootstrap validateBeans();

    public Bootstrap endInitialization();

    public void shutdown();

    public WeldManager getManager(BeanDeploymentArchive beanDeploymentArchive);

    public BeansXml parse(URL url);

    public BeansXml parse(Iterable<URL> urls);

    public BeansXml parse(Iterable<URL> urls, boolean removeDuplicates);

    public Iterable<Metadata<Extension>> loadExtensions(ClassLoader classLoader);

}

The bootstrap is split into phases, container initialization, bean deployment, bean validation and shutdown. Initialization will create a manager, and add the built-in contexts, and examine the deployment structure. Bean deployment will deploy any beans (defined using annotations, programmatically, or built in). Bean validation will validate all beans.

To initialize the container, you call Bootstrap.startInitialization(). Before calling startInitialization(), you must register any services required by the environment. You can do this by calling, for example, bootstrap.getManager().getServices().add(JpaServices.class, new MyJpaServices()). You must also provide the application context bean store.

Having called startInitialization(), the Manager for each BDA can be obtained by calling Bootstrap.getManager(BeanDeploymentArchive bda).

To deploy the discovered beans, call Bootstrap.deployBeans().

To validate the deployed beans, call Bootstrap.validateBeans().

To place the container into a state where it can service requests, call Bootstrap.endInitialization()

To shutdown the container you call Bootstrap.shutdown(). This allows the container to perform any cleanup operations needed.

Weld needs to load classes and resources from the classpath at various times. By default, they are loaded from the Thread Context ClassLoader if available, if not the same classloader that was used to load Weld, however this may not be correct for some environments. If this is case, you can implement org.jboss.weld.resources.spi.ResourceLoader.

import org.jboss.weld.bootstrap.api.Service;


public interface ResourceLoader extends Service {

    public Class<?> classForName(String name);

    public URL getResource(String name);

    public Collection<URL> getResources(String name);

}

The optional AnnotationDiscovery service has been deprecated and is not used by Weld since Weld 2.2. Integrators are encouraged to implement ClassFileServices instead.

Integrators with bytecode-scanning capabilities may implement an optional ClassFileServices service.

Bytecode-scanning is used by some application servers to speed up deployment. Compared to loading a class using ClassLoader, bytecode-scanning allows to obtain only a subset of the Java class file metadata (e.g. annotations, class hierarchy, etc.) which is usually loaded much faster. This allows the container to scan all classes initially by a bytecode scanner and then use this limited information to decide which classes need to be fully loaded using ClassLoader. Jandex is an example of a bytecode-scanning utility.

ClassFileServices may be used by an integrator to provide container’s bytecode-scanning capabilities to Weld. If present, Weld will try to use the service to avoid loading of classes that do not need to be loaded. These are classes that:

This usually yields improved bootstrap performance especially in large deployments with a lot of classes in explicit bean archives.

public interface ClassFileServices extends BootstrapService {

    ClassFileInfo getClassFileInfo(String className);

}

public interface ClassFileInfo {

    String getClassName();

    String getSuperclassName();

    boolean isAnnotationDeclared(Class<? extends Annotation> annotationType);

    boolean containsAnnotation(Class<? extends Annotation> annotationType);

    int getModifiers();

    boolean hasCdiConstructor();

    boolean isAssignableFrom(Class<?> javaClass);

    boolean isAssignableTo(Class<?> javaClass);

    boolean isVetoed();

    boolean isTopLevelClass();

See the JavaDoc for more details.

The standard way for an integrator to provide Service implementations is via the deployment structure. Alternatively, services may be registered using the ServiceLoader mechanism. This is useful e.g. for a library running in weld-servlet environment. Such library may provide TransactionServices implementation which would not otherwise be provided by weld-servlet.

A service implementation should be listed in a file named META-INF/services/org.jboss.weld.bootstrap.api.Service

A service implementation can override another service implementation. The priority of a service implementation is determined from the javax.annotation.Priority annotation. Service implementations with higher priority have precedence. A service implementation that does not define priority explicitly is given implicit priority of 4500.

If you are integrating Weld into an environment that supports deployment of multiple applications, you must enable, automatically, or through user configuration, classloader isolation for each CDI application.

If you are integrating Weld into a Servlet environment you must register org.jboss.weld.servlet.WeldInitialListener and org.jboss.weld.servlet.WeldTerminalListener as Servlet listeners, either automatically, or through user configuration, for each CDI application which uses Servlet.

You must ensure that WeldListener is called before any other application-defined listener is called and that WeldTerminalListener is called only after all application-defined listeners have been called.

You must ensure that WeldListener.contextInitialized() is called after beans are deployed is complete (Bootstrap.deployBeans() has been called).

A CDI implementation is required to provide a Servlet filter named “CDI Conversation Filter”. The filter may be mapped by an application in the web descriptor. That allows application to place another filter around the CDI filter for dealing with exceptions.

Weld provides this filter with a fully qualified class name of`org.jboss.weld.servlet.ConversationFilter`.

If the application contains a filter mapping for a filter named “CDI Conversation Filter”, the integrator is required to register org.jboss.weld.servlet.ConversationFilter as a filter with “CDI Conversation Filter” as its filter name. If no such mapping exists in the application, the integrator is not required to register the filter. In that case, WeldListener will take care of conversation context activation/deactivation at the beginning of HTTP request processing.

If you are integrating Weld into a JSF environment you must register org.jboss.weld.el.WeldELContextListener as an EL Context listener.

If you are integrating Weld into a JSF environment you must register org.jboss.weld.jsf.ConversationAwareViewHandler as a delegating view handler.

If you are integrating Weld into a JSF environment you must obtain the bean manager for the module and then call BeanManager.wrapExpressionFactory(), passing Application.getExpressionFactory() as the argument. The wrapped expression factory must be used in all EL expression evaluations performed by JSF in this web application.

If you are integrating Weld into a JSF environment you must obtain the bean manager for the module and then call BeanManager.getELResolver(), The returned EL resolver should be registered with JSF for this web application.

If you are integrating Weld into a JSF environment you must register org.jboss.weld.servlet.ConversationPropagationFilter as a Servlet listener, either automatically, or through user configuration, for each CDI application which uses JSF. This filter can be registered for all Servlet deployment safely.

If you are integrating Weld into a JSP environment you must register org.jboss.weld.el.WeldELContextListener as an EL Context listener.

If you are integrating Weld into a JSP environment you must obtain the bean manager for the module and then call BeanManager.wrapExpressionFactory(), passing Application.getExpressionFactory() as the argument. The wrapped expression factory must be used in all EL expression evaluations performed by JSP.

If you are integrating Weld into a JSP environment you must obtain the bean manager for the module and then call BeanManager.getELResolver(), The returned EL resolver should be registered with JSP for this web application.

org.jboss.weld.ejb.SessionBeanInterceptor takes care of activating the request scope around EJB method invocations in a non-servlet environment, such as message-driven bean invocation, @Asynchronous invocation or @Timeout. If you are integrating Weld into an EJB environment you must register the aroundInvoke method of SessionBeanInterceptor as a EJB around-invoke interceptor for all EJBs in the application, either automatically, or through user configuration, for each CDI application which uses enterprise beans.

If you are running in a EJB 3.2 environment, you should register this as an around-timeout interceptor as well.

In addition, since CDI 1.1 the aroundInvoke method of SessionBeanInterceptor should be invoked around @PostConstruct callbacks of EJBs.

Weld can reside on an isolated classloader, or on a shared classloader. If you choose to use an isolated classloader, the default SingletonProvider, IsolatedStaticSingletonProvider, can be used. If you choose to use a shared classloader, then you will need to choose another strategy.

You can provide your own implementation of Singleton and SingletonProvider and register it for use using SingletonProvider.initialize(SingletonProvider provider).

Weld also provides an implementation of Thread Context Classloader per application strategy, via the TCCLSingletonProvider.

You should bind the bean manager for the bean deployment archive into JNDI at java:comp/BeanManager. The type should be javax.enterprise.inject.spi.BeanManager. To obtain the correct bean manager for the bean deployment archive, you may call bootstrap.getBeanManager(beanDeploymentArchive)

CDI 1.1 provides a simplified approach to accessing the BeanManager / CDI container from components that do not support injection. This is done by the CDI class API. The integrating part can either use org.jboss.weld.AbstractCDI or org.jboss.weld.SimpleCDI provided by Weld core and register it using javax.enterprise.inject.spi.CDIProvider file that is visible to the CDI API classes or use the CDI.setCDIProvider(CDIProvider provider) method method early in the deployment.

Alternatively, an integrating part may provide a specialized implementation such as the one provided by WildFly integration.

The CDI specification requires the container to provide injection into non-contextual resources for all Java EE component classes. Weld delegates this responsibility to the container. This can be achieved using the CDI defined InjectionTarget SPI. Furthermore, you must perform this operation on the correct bean manager for the bean deployment archive containing the EE component class.

The CDI specification also requires that a ProcessInjectionTarget event is fired for every Java EE component class. Furthermore, if an observer calls ProcessInjectionTarget.setInjectionTarget() the container must use the specified injection target to perform injection.

To help the integrator, Weld provides WeldManager.fireProcessInjectionTarget() which returns the InjectionTarget to use.

// Fire ProcessInjectionTarget, returning the InjectionTarget

// to use

InjectionTarget it = weldBeanManager.fireProcessInjectionTarget(clazz);


// Per instance required, create the creational context

CreationalContext<?> cc = beanManager.createCreationalContext(null);


// Produce the instance, performing any constructor injection required

Object instance = it.produce();


// Perform injection and call initializers

it.inject(instance, cc);


// Call the post-construct callback

it.postConstruct(instance);


// Call the pre-destroy callback

it.preDestroy(instance);


// Clean up the instance

it.dispose(instance);

cc.release();

The container may intersperse other operations between these calls. Further, the integrator may choose to implement any of these calls in another manner, assuming the contract is fulfilled.

When performing injections on EJBs you must use the Weld-defined SPI, WeldManager. Furthermore, you must perform this operation on the correct bean manager for the bean deployment archive containing the EJB.

// Obtain the EjbDescriptor for the EJB

// You may choose to use this utility method to get the descriptor

EjbDescriptor<T> ejbDescriptor = beanManager.<T>getEjbDescriptor(ejbName);


// Get an the Bean object

Bean<T> bean = beanManager.getBean(ejbDescriptor);


// Create the injection target

InjectionTarget<T> it = beanManager.createInjectionTarget(ejbDescriptor);


// Per instance required, create the creational context

WeldCreationalContext<T> cc = beanManager.createCreationalContext(bean);


// register an AroundConstructCallback if needed

cc.setConstructorInterceptionSuppressed(true);

cc.registerAroundConstructCallback(new AroundConstructCallback<T>() {

    public T aroundConstruct(ConstructionHandle<T> handle, AnnotatedConstructor<T> constructor, Object[] parameters,

            Map<String, Object> data) throws Exception {

        // TODO: invoke @AroundConstruct interceptors

        return handle.proceed(parameters, data);

    }

});


// Produce the instance, performing any constructor injection required

T instance = it.produce(cc);


// Perform injection and call initializers

it.inject(instance, cc);


// You may choose to have CDI call the post construct and pre destroy

// lifecycle callbacks

// Call the post-construct callback

it.postConstruct(instance);


// Call the pre-destroy callback

it.preDestroy(instance);


// Clean up the instance

it.dispose(instance);

cc.release();

Weld implements support for constructor call interception and invokes interceptors that are associated with the particular component either using an interceptor binding or the @Interceptors annotation.

This can be suppressed by calling WeldCreationalContext.setConstructorInterceptionSuppressed(true)

In addition, an integrator may register a callback in which it performs additional operations around the constructor call. This way an integrator may for example implement support for additional interceptors (e.g. those bound using the deployment descriptor).

See AroundConstructCallback and WeldCreationalContext.registerAroundConstructCallback() for more details.

Optionally, an integrator may register the following Probe Development Tool components in order to enable its functionality. Note that these components should only be registered if the development mode is enabled - see also Section 21.1, “How to enable the development mode”.

All the changes are documented in this external migration document.