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If you want to use Weld in another environment, you will need to provide certain information to Weld via the integration SPI. In this Appendix we will briefly discuss the steps needed.
If you just want to use managed beans, and not take advantage of enterprise services (EE resource injection, CDI injection into EE component classes, transactional events, support for CDI services in EJBs) and non-flat deployments, then the generic servlet support provided by the "Weld: Servlets" extension will be sufficient, and will work in any container supporting the Servlet API.
All SPIs and APIs described have extensive JavaDoc, which spell out the detailed contract between the container and Weld.
The Weld SPI is located in the weld-spi module, and packaged as weld-spi.jar. Some SPIs are optional, and should only be implemented if you need to override the default behavior; others are required.
All interfaces in the SPI support the decorator pattern and provide a Forwarding class located in the helpers sub package. Additional, commonly used, utility classes, and standard implementations are also located in the helpers sub package.
Weld supports multiple environments. An environment is defined by an implementation of the Environment interface. A number of standard environments are built in, and described by the Environments enumeration. Different environments require different services to be present (for example a Servlet container doesn't require transaction, EJB or JPA services). By default an EE environment is assumed, but you can adjust the environment by calling bootstrap.setEnvironment().
Weld uses a generic-typed service registry to allow services to be registered. All services implement the Service interface. The service registry allows services to be added and retrieved.
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 Deployment Archives (BDAs)—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 of Bean Deployment Archives in its deployment structure SPI. Each deployment exposes the BDAs which it contains; each BDA may also reference other which it can access. Together, the transitive closure of this graph forms the beans which are deployed in the application.
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.
In a strict container, each BDA might have to explicitly specify which other BDAs it can access. However many containers will allow an easy mechanism to make BDAs bi-directionally accessible (such as a library directory). In this case, it is allowable (and reasonable) to describe all such archives as a single, 'virtual' BeanDeploymentArchive.
A container, might, for example, use a flat accessibility structure for the application. In this case, a single BeanDeploymentArchive would be attached to the Deployment.
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.parseBeansXml(URL). Weld can also parse multiple beans.xml files, merging them to become a single data-structure. This can be achieved by calling Bootstrap.parseBeansXml(Iterable<URL>).
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.
In practice, you can regard the deployment structure represented by Deployment, and the virtual BDA graph as a mirror of the classloader structure for a deployment. If a class can from BDA X can be loaded by another in BDA Y, it is accessible, and therefore BDA Y's accessible BDAs should include BDA X.
To specify the directly accessible BDAs, the container should provide an implementation of BeanDeploymentArchive.getBeanDeploymentArchives().
Weld allows the container to describe a circular graph, and will convert a graph to a tree as part of the deployment process.
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.
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 第 A.1.8 节 “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 第 A.1.4 节 “EJB services”, 第 A.1.7 节 “Resource Services” and 第 A.1.5 节 “JPA services”.
CDI only provides annotation-based EE resource injection; if you wish to provide deployment descriptor (e.g. ejb-jar.xml) injection, you must use 第 A.1.8 节 “Injection 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.
If you use a non-EE environment then you may implement any of the EE service SPIs, and Weld will provide the associated functionality. There is no need to implement those services you don't need!
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.
EJBResolutionServices.resolveEjb(InjectionPoint ij) allows the resolution of @EJB (for injection into managed beans). This service is not required if the implementation of 第 A.1.8 节 “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 第 A.1.8 节 “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.
任何 javax.transaction.Synchronization 实现必须传递给 registerSynchronization() 方法，SPI实现应该立刻将同步注册到EJB使用的JTA事务管理器。
为了更容易的决定对于请求线程来说一个事务在当前是否是活动的，我们可以使用isTransactionActive() 方法。SPI实现应该查询EJB使用的同一个JTA事务管理器。
The resolution of @Resource (for injection into managed beans) is delegated to the container. You must provide an implementation of ResourceServices which provides these operations. This service is not required if the implementation of 第 A.1.8 节 “Injection Services” takes care of @Resource 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.
In order to obtain the default ValidatorFactory for the application deployment, the container should provide an implementation of ValidationServices.
When a client makes a request to an application which uses Weld, the request may be addressed at any of the BDAs in the application deployment. To allow Weld to correctly service the request, it needs to know which BDA the request is addressed at. Where possible, Weld will provide some context, but use of these by the integrator is optional.
Most Servlet contains use a classloader-per-war, this may provide a good way to identify the BDA in use for web requests.
When Weld needs to identify the BDA, it will use one of these services, depending on what is servicing the request:
ServletServices.getBeanDeploymentArchive(ServletContext ctx)Identify the war in use. The ServletContext is provided for additional context.
Weld uses a map like structure to store bean instances - org.jboss.weld.context.api.BeanStore. You may find org.jboss.weld.context.api.helpers.ConcurrentHashMapBeanStore useful.
Weld expects the Application Server or other container to provide the storage for each application's context. The org.jboss.weld.context.api.BeanStore should be implemented to provide an application scoped storage.
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 Boostrap), tell it about the services in use, and then request the container start.
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.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.spi.ResourceLoader.
There are a number of requirements that Weld places on the container for correct functioning that fall outside implementation of APIs.
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.WeldListener as a Servlet listener, either automatically, or through user configuration, for each CDI application which uses Servlet.
You must ensure that WeldListener.contextInitialized() is called after beans are deployed is complete (Bootstrap.deployBeans() has been called).
If you are integrating Weld into a JSF environment you must register org.jboss.weld.jsf.WeldPhaseListener as a phase listener.
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.
There are a number of ways you can obtain the bean manager for the module. You could call Bootstrap.getManager(), passing in the BDA for this module. Alternatively, you could use the injection into Java EE component classes, or look up the bean manager in JNDI.
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.
Weld only supports JSF 1.2 and above.
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.
There are a number of ways you can obtain the bean manager for the module. You could call Bootstrap.getManager(), passing in the BDA for this module. Alternatively, you could use the injection into Java EE component classes, or look up the bean manager in JNDI.
If you are integrating Weld into an EJB environment you must register the aroundInvoke method of org.jboss.weld.ejb.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 3.1 environment, you should register this as an around-timeout interceptor as well.
你必须为所有的EJB在栈中将SessionBeanInterceptor 注册为一个最内部的拦截器。
weld-core.jar 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)
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(); 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<?> ejbDescriptor = beanManager.getEjbDescriptor(ejbName); // Get an the Bean object Bean<?> bean = beanManager.getBean(ejbDescriptor); // Create the injection target InjectionTarget it = deploymentBeanManager.createInjectionTarget(ejbDescriptor); // Per instance required, create the creational context CreationalContext<?> cc = deploymentBeanManager.createCreationalContext(bean); // 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(); cc.release();