跳至主要内容

CDI 2.0: Configurators APIs and Intercept Producers

Configurators APIs and Intercept Producers

In CDI 2.0, it is possible to add Interceptor to a producer programmaticially.
For example, there is a POJO.
public class Greeter {

    public Greeter() {
    }

    public void say(String name) {
        System.out.println("Hi, " + name);
    }
}
We want to count the number of calling the method.
Create a Counted quilifier and CountedInterceptor interceptor class.
@Inherited
@InterceptorBinding
@Retention(RUNTIME)
@Target({METHOD, TYPE})
public @interface Counted {

    public static final class Literal extends AnnotationLiteral<Counted> implements Counted {

        public static final Literal INSTANCE = new Literal();

        private static final long serialVersionUID = 1L;

    }
}
@Interceptor
@Counted
public class CountedInterceptor {

    @Inject
    Logger LOG;

    @Inject
    Counter counter;

    @AroundConstruct
    public void aroundConstructed(InvocationContext ctx) throws Exception {
        LOG.log(Level.INFO, "invoke constructor:" + ctx.getConstructor() + ", arguments:" + ctx.getContextData());
        Object o = ctx.proceed();
        counter.increase();
    }

    @AroundInvoke
    public Object aroundInvoked(InvocationContext ctx) throws Exception {
        LOG.log(Level.INFO, "invoke method:" + ctx.getMethod() + ", paraemters:" + ctx.getParameters());
        Object o = ctx.proceed();
        counter.increase();

        return o;
    }

}
The counting service is done by Counter.
@ApplicationScoped
public class Counter {
    
    private int count = 0;
    
    @Inject
    Logger LOG;
    
    public void increase() {        
        count++;
        LOG.log(Level.INFO, "current counter:" + count);
    }
    
    public int getCount() {
        return count;
    }
    
}
Now put all together.
@ApplicationScoped
public class GreeterProducer {

    @Produces
    public Greeter producesGreeter(InterceptionFactory<Greeter> factory) {
        factory.configure().add(Counted.Literal.INSTANCE);
        return factory.createInterceptedInstance(new Greeter());
    }

}
Verify it works as expected.
@Test()
public void testGreeter() {
 assertNotNull(greeter);

 LOG.log(Level.INFO, "counter.getCount()::" + counter.getCount());
 //assertTrue(1 == counter.getCount());
 greeter.say("CDI 2.0");
 LOG.log(Level.INFO, "counter.getCount() after called Greeter.say()::" + counter.getCount());
 assertTrue(1 == counter.getCount());
}
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 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.
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-we…

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 &…