跳至主要内容

CDI 2.0: Fire events asynchronously

Fire events asynchronously

CDI 2.0 add the capability of firing an CDI event asynchronously, this will free the client from long-awaited blocking rquest.
Create a simple backing bean.
@ViewScoped
@Named("eventBean")
public class EventBean implements Serializable {

    private static final Logger LOG = Logger.getLogger(EventBean.class.getName());

    @Inject
    Event<Message> event;

    private String message;
    
    private String notification;

    public String getMessage() {
        return message;
    }

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

    public String getNotification() {
        return notification;
    }

    public void setNotification(String notification) {
        this.notification = notification;
    }
    
   
    public void fireEvent() {
        LOG.log(Level.INFO, "fire event async...");
        event.fireAsync(new Message(this.message))
                .thenAccept((m) -> this.setNotification(m+ " was sent")); 
    }

    public void fireEventOptions() {
        LOG.log(Level.INFO, "fire event async...");
        event.fireAsync(
                new Message(this.message),
                NotificationOptions.builder()
                        .set("weld.async.notification.timeout", 1000)
                        .build()
        );
    }
}
CDI 2.0 added two methods to fire a CDI event asynchronously, fireAsync will return a CompletionStage, it could be used in further steps, fireAsync has a varient which an extra NotificationOptions argument.
@ApplicationScoped
public class EventHandler implements Serializable {

    public static final Logger LOG = Logger.getLogger(EventHandler.class.getName());

    public void onMessage(@ObservesAsync Message message) {
        LOG.log(Level.INFO, "observes event:{0}", message);
    }
}
In the EventHandler, use @ObservesAsync to observe the incoming event.
Grab the source codes from my github account, and have a try.

评论

此博客中的热门博文

Build a Reactive application with Angular 5 and Spring Boot 2.0

I have created a post to describe Reactive programming supports in Spring 5 and its subprojects, all codes of this article are updated the latest Spring 5 RELEASE, check spring-reactive-sample under my Github account.
In this post, I will create a simple blog system, including:
A user can sign in and sign out.An authenticated user can create a post.An authenticated user can update a post.Only the user who has ADMIN role can delete a post.All users(including anonymous users) can view post list and post details.An authenticated user can add his comments to a certain post. The backend will be built with the latest Spring 5 reactive stack, including:
Spring Boot 2.0, at the moment the latest version is 2.0.0.M7Spring Data MongoDB supports reactive operations for MongoDBSpring Session adds reactive support for WebSessionSpring Security 5 aligns with Spring 5 reactive stack The frontend is an Angular based SPA and it will be generated by Angular CLI.
The source code is hosted on Github, …

Activating CDI in JSF 2.3

Activating CDI in JSF 2.3 When I upgraed 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.
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-w…

JSF 2.3:Websocket support

Websocket support One of the most attractive features is JSF 2.3 added native websocket support, it means you can write real-time applications with JSF and no need extra effort.
To enable websocket support, you have to add javax.faces.ENABLE_WEBSOCKET_ENDPOINT in web.xml.
<context-param> <param-name>javax.faces.ENABLE_WEBSOCKET_ENDPOINT</param-name> <param-value>true</param-value> </context-param> Hello Websocket Let's start with a simple example.
@ViewScoped@Named("helloBean") publicclassHelloBeanimplementsSerializable { privatestaticfinalLoggerLOG=Logger.getLogger(HelloBean.class.getName()); @Inject@PushPushContext helloChannel; String message; publicvoidsendMessage() { LOG.log(Level.INFO, "send push message"); this.sendPushMessage("hello"); } privatevoidsendPushMessage(Objectmessage) { helloChannel.send(""+ message +" at &…