Activating CDI in JSF 2.3

When I upgraded my Java EE 7 sample to the newest Java EE 8, the first thing confused me is the CDI beans are not recoganized in Facelects template in a JSF 2.3 based web applicaiton, which is working in the development version, but in the final release version, they are always resolved as null. I filed an issue on Mojarra and discussed it with the developers from communities and the JSF experts.
According to the content of README, In a JSF 2.3 application, to activate CDI support, declaring a 2.3 versioned faces-config.xml and adding javax.faces.ENABLE_CDI_RESOLVER_CHAIN in web.xml is not enough, you have to declare @FacesConfig annotated class to enable CDI.
Here is the steps I created a workable JSF 2.3 applicatoin in Java EE 8.

1. Create a Java web application, this can be done easily by NetBeans IDE, or generated by Maven archetype, for exmaple.
   

   $ mvn archetype:generate -DgroupId=com.example
   -DartifactId=demo
   -DarchetypeArtifactId=maven-archetype-webapp
   -DinteractiveMode=false 
   

2. Add javaee-api in project dependencies.
   

   <properties>
     <version.javaee-api>8.0</version.javaee-api>
     ...// other properties
   </properties>
   <dependencyManagement>
     <dependencies>
      <dependency>
       <groupId>javax</groupId>
       <artifactId>javaee-api</artifactId>
       <version>${version.javaee-api}</version>
       <scope>provided</scope>
      </dependency>
      ...//other dependencies
      </dependencies>  
   </dependencyManagement>
   <dependencies>
      <dependency>
      <groupId>javax</groupId>
      <artifactId>javaee-api</artifactId>
      </dependency>
      ...//other dependencies
   </dependencies>

3. Add a faces-config.xml into WEB-INF folder, it is optional in JSF 2.3. ​
   

   <?xml version='1.0' encoding='UTF-8'?>
   <faces-config xmlns="http://xmlns.jcp.org/xml/ns/javaee"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-facesconfig_2_3.xsd"
      version="2.3">
   </faces-config>

4. Declare a beans.xml, CDI is enabled by default in Java EE 7, so it is optional.
   

   <?xml version="1.0" encoding="UTF-8"?>
   <beans xmlns="http://xmlns.jcp.org/xml/ns/javaee"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/beans_2_0.xsd"
       bean-discovery-mode="all" 
       version="2.0">
   </beans>

5. Add web.xml. It is not required by JSF, but you can customize the application by some properties.
   

   <?xml version="1.0" encoding="UTF-8"?>
   <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
      version="4.0">
    <context-param>
     <param-name>javax.faces.FACELETS_REFRESH_PERIOD</param-name>
     <param-value>0</param-value>
    </context-param>
   
    <context-param>
     <param-name>javax.faces.PROJECT_STAGE</param-name>
     <param-value>Development</param-value>
    </context-param>
   
    <context-param>
     <param-name>javax.faces.validator.ENABLE_VALIDATE_WHOLE_BEAN</param-name>
     <param-value>true</param-value>
    </context-param>
   
    <context-param>
     <param-name>javax.faces.ENABLE_WEBSOCKET_ENDPOINT</param-name>
     <param-value>true</param-value>
    </context-param> 
   
    <!--    <context-param>
     <param-name>javax.faces.DISABLE_FACESSERVLET_TO_XHTML</param-name>
     <param-value>true</param-name>
    </context-param>-->
   </web-app>

   JSF 2.3 provides some options to activate the new features added in 2.3.
   
   • ENABLE_VALIDATE_WHOLE_BEAN is used to enable class level Bean validation
   • ENABLE_WEBSOCKET_ENDPOINT is used to enable websocket support
   • DISABLE_FACESSERVLET_TO_XHTML will disable JSF servelt mapping to *.xhtml. By default, JSF Servlet will serve *.xhtml.
6. Declare a @FacesConfig annotated class to activate CDI in JSF 2.3.
   

   @FacesConfig(
   // Activates CDI build-in beans
   version = JSF_2_3 
   )
   public class ConfigurationBean {
   
   }

   Open the source code of FacesConfig, you will know it is a standard CDI Qualifier.
   

   @Qualifier
   @Target(TYPE)
   @Retention(RUNTIME)
   public @interface FacesConfig {
   
    public static enum Version {
   
     /**
      * <p class="changed_added_2_3">This value indicates CDI should be used
      * for EL resolution as well as enabling JSF CDI injection, as specified
      * in Section 5.6.3 "CDI for EL Resolution" and Section 5.9 "CDI Integration".</p>
      */
     JSF_2_3
   
    }
   
    /**
     * <p class="changed_added_2_3">The value of this attribute indicates that
     * features corresponding to this version must be enabled for this application.</p>
     * @return the spec version for which the features must be enabled.
     */
    @Nonbinding Version version() default Version.JSF_2_3;
   
   }

Done.
Another issue about JSF 2.3 still confused me and other developers, as the codes shown above, we use all bean-discovery-mode in the beans.xml. If we switch to annotated here, we have to add @FacesConfig to every CDI backing beans, it is unreasonable.
Create a simple sample to verify if it works.
Firstly create a simple backing bean to say hello to JSF.

@Named
@RequestScoped
public class HelloBean {

    private String message;

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }

    public void sayHi() {
        this.message = this.message+ " received at " + LocalDateTime.now();
    }

    @Override
    public int hashCode() {
        int hash = 7;
        hash = 13 * hash + Objects.hashCode(this.message);
        return hash;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }
        if (obj == null) {
            return false;
        }
        if (getClass() != obj.getClass()) {
            return false;
        }
        final HelloBean other = (HelloBean) obj;
        if (!Objects.equals(this.message, other.message)) {
            return false;
        }
        return true;
    }

}

And template will accept user input and show the message.

<!DOCTYPE html>
<html lang="en"
      xmlns="http://www.w3.org/1999/xhtml"
      xmlns:h="http://xmlns.jcp.org/jsf/html"
      xmlns:jsf="http://xmlns.jcp.org/jsf">
    <h:head/>

    <h:messages />

    <h:body>
        <p>
            Hello JSF 2.3 with CDI activation
        </p>

        <form jsf:id="form">
            <p>
                <strong>Welcome to JSF 2.3 world: </strong> 
                <div>#{helloBean.message}</div>
            </p>
            <p>
                <strong>Message: </strong> 
                <div><input type="text" jsf:id="message" jsf:value="#{helloBean.message}"></input></div>
            </p>
            <p>
                <input type="submit" value="Say Hi to JSF" jsf:action="#{helloBean.sayHi()}" />
            </p>
        </form>

    </h:body>

</html>

Grab the source codes from my github account.