/
Eager.java
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/
Eager.java
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/*
* Copyright 2017 OmniFaces
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
* an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
* specific language governing permissions and limitations under the License.
*/
package org.omnifaces.cdi;
import static java.lang.annotation.ElementType.TYPE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
import javax.enterprise.context.ApplicationScoped;
import javax.enterprise.context.RequestScoped;
import javax.enterprise.context.SessionScoped;
import javax.enterprise.util.Nonbinding;
import javax.faces.context.FacesContext;
import javax.faces.event.PhaseId;
import javax.faces.webapp.FacesServlet;
import javax.servlet.ServletContext;
import javax.servlet.ServletRequestListener;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionListener;
import org.omnifaces.cdi.eager.EagerBeansFilter;
import org.omnifaces.cdi.eager.EagerBeansPhaseListener;
import org.omnifaces.cdi.eager.EagerBeansRepository;
import org.omnifaces.cdi.eager.EagerBeansWebListener;
import org.omnifaces.cdi.eager.EagerExtension;
/**
* <p>
* The CDI annotation <code>@</code>{@link Eager} specifies that a scoped bean is to be eagerly instantiated.
* <p>
* JSF's own native managed beans are being deprecated in favor of CDI managed beans. One feature that those native JSF
* managed beans had that's not directly available for CDI managed beans is the ability to eagerly instantiate
* application scoped beans.
* <p>
* OmniFaces fills this void and even goes one step further by introducing the <code>@Eager</code> annotation
* that can be applied to <code>@RequestScoped</code>, <code>@ViewScoped</code>,
* <code>@SessionScoped</code> and <code>@ApplicationScoped</code> beans. This causes these beans to be instantiated
* automatically at the start of each such scope instead of on demand when a bean is first referenced.
* <p>
* In case of <code>@RequestScoped</code> and <code>@ViewScoped</code> beans instantiation happens per request URI / view
* and an extra attribute is required for specifying this.
*
* <h3>Supported scopes</h3>
*
* <p>
* Currently supported scopes:
* <ol>
* <li> CDI {@link RequestScoped}
* <li> CDI {@link javax.faces.view.ViewScoped}
* <li> OmniFaces {@link ViewScoped}
* <li> CDI {@link SessionScoped}
* <li> CDI {@link ApplicationScoped}
* </ol>
*
* <h3>Usage</h3>
*
* <p>
* E.g.
* The following bean will be instantiated during application's startup:
* <pre>
* @Eager
* @ApplicationScoped
* public class MyEagerApplicationScopedBean {
*
* @PostConstruct
* public void init() {
* System.out.println("Application scoped init!");
* }
* }
* </pre>
* <p>
* <em>Note: you can also use the stereotype <code>@</code>{@link Startup} for this instead.</em>
* <p>
* The following bean will be instantiated whenever a session is created:
* <pre>
* @Eager
* @SessionScoped
* public class MyEagerSessionScopedBean implements Serializable {
*
* private static final long serialVersionUID = 1L;
*
* @PostConstruct
* public void init() {
* System.out.println("Session scoped init!");
* }
* }
* </pre>
* <p>
* The following bean will be instantiated whenever the URI <code>/components/cache</code> (relatively to the
* application root) is requested, i.e. when an app is deployed to <code>/myapp</code> at localhost this will correspond to
* a URL like <code>http://localhost:8080/myapp/components/cache</code>:
* <pre>
* @Eager(requestURI = "/components/cache")
* @RequestScoped
* public class MyEagerRequestScopedBean {
*
* @PostConstruct
* public void init() {
* System.out.println("/components/cache requested");
* }
* }
* </pre>
*
* <h3><code>FacesContext</code> in <code>@PostConstruct</code></h3>
*
* <p>
* When using <code>@Eager</code> or <code>@Eager(requestURI)</code>, be aware that the {@link FacesContext} is
* <strong>not</strong> available in the <code>@PostConstruct</code>. Reason is, the {@link FacesServlet} isn't
* invoked yet at the moment <code>@Eager</code> bean is constructed. Only in <code>@Eager(viewId)</code>, the
* {@link FacesContext} is available in the <code>@PostConstruct</code>.
* <p>
* In case you need information from {@link HttpServletRequest}, {@link HttpSession} and/or {@link ServletContext}, then
* you can just <code>@Inject</code> it right away. Also, all other CDI managed beans are available the usual way
* via <code>@Inject</code>, as long as they do also not depend on {@link FacesContext} in their
* <code>@PostConstruct</code>.
*
* <h3>Compatibility</h3>
*
* <p>
* In some (older) containers, most notably GlassFish 3, the CDI request scope is not available in a {@link ServletRequestListener}
* (this is actually not spec complicant, as CDI demands this scope to be active then, but it is what it is).
* <p>
* Additionally in some containers, most notably GlassFish 3 again, instantiating session scoped beans from a {@link HttpSessionListener}
* will corrupt "something" in the container. The instantiating of the beans will succeed, but if the session is later accessed an
* exception like the following will be thrown:
*
* <pre>
* java.lang.IllegalArgumentException: Should never reach here
* at org.apache.catalina.connector.SessionTracker.track(SessionTracker.java:168)
* at org.apache.catalina.connector.Request.doGetSession(Request.java:2939)
* at org.apache.catalina.connector.Request.getSession(Request.java:2583)
* at org.apache.catalina.connector.RequestFacade.getSession(RequestFacade.java:920)
* at javax.servlet.http.HttpServletRequestWrapper.getSession(HttpServletRequestWrapper.java:259)
* at com.sun.faces.context.ExternalContextImpl.getSession(ExternalContextImpl.java:155)
* at javax.faces.context.ExternalContextWrapper.getSession(ExternalContextWrapper.java:396)
* at javax.faces.context.ExternalContextWrapper.getSession(ExternalContextWrapper.java:396)
* ...
* </pre>
*
* If any or both of those problems occur, a filter needs to be installed instead in <code>web.xml</code> as follows:
*
* <pre>
* <filter>
* <filter-name>eagerBeansFilter</filter-name>
* <filter-class>org.omnifaces.cdi.eager.EagerBeansFilter</filter-class>
* </filter>
* <filter-mapping>
* <filter-name>eagerBeansFilter</filter-name>
* <url-pattern>/*</url-pattern>
* </filter-mapping>
*</pre>
*
* <p>
* Note that the {@link EagerBeansFilter} will automatically disable the {@link EagerBeansWebListener}.
*
*
* @since 1.8
* @author Arjan Tijms
* @see EagerExtension
* @see EagerBeansRepository
* @see EagerBeansPhaseListener
* @see EagerBeansWebListener
* @see EagerBeansFilter
*
*/
@Documented
@Retention(RUNTIME)
@Target(TYPE)
public @interface Eager {
/**
* (Required when combined with {@link RequestScoped}) The URI (relative to the root of the web app) for which a
* request scoped bean should be instantiated. When this attribute is specified the bean will be instantiated very
* early during request processing, namely just before the first Servlet Filter is invoked, but after a SAM.
* <p>
* JSF services will not be available (yet) when the bean is instantiated this way.
* <p>
* If both this attribute and {@link Eager#viewId()} is specified, this attribute takes precedence for {@link RequestScoped}.
* This attribute <b>can not</b> be used for <code>ViewScoped</code> beans.
*
* @return The request URI relative to the context root.
*/
@Nonbinding
String requestURI() default "";
/**
* (Required when combined with {@link RequestScoped} or <code>ViewScoped</code>) The id of the view for which a request or view scoped bean
* should be instantiated. When this attribute is specified the bean will be instantiated during invocation of the
* {@link FacesServlet}, namely right after the RESTORE_VIEW phase (see {@link PhaseId#RESTORE_VIEW}).
*
* <p>
* JSF services are available when the bean is instantiated this way.
*
* <p>
* If both this attribute and {@link Eager#requestURI()} is specified and the scope is {@link RequestScoped}, the
* <code>requestURI</code> attribute takes precedence. If the scope is <code>ViewScoped</code> <code>requestURI</code> is ignored and only
* this attribute is considered.
*
* @return The view ID.
*/
@Nonbinding
String viewId() default "";
}