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.
发表评论

此博客中的热门博文

JPA 2.1: Attribute Converter

JPA 2.1: Attribute Converter If you are using Hibernate, and want a customized type is supported in your Entity class, you could have to write a custom Hibernate Type. JPA 2.1 brings a new feature named attribute converter, which can help you convert your custom class type to JPA supported type. Create an Entity Reuse thePostentity class as example. @Entity @Table(name="POSTS") public class Post implements Serializable { private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name="ID") private Long id; @Column(name="TITLE") private String title; @Column(name="BODY") private String body; @Temporal(javax.persistence.TemporalType.DATE) @Column(name="CREATED") private Date created; @Column(name="TAGS") private List<String> tags=new ArrayList<>(); } Create an attribute converter In this example…

Auditing with Hibernate Envers

Auditing with Hibernate Envers The approaches provided in JPA lifecyle hook and Spring Data auditing only track the creation and last modification info of an Entity, but all the modification history are not tracked. Hibernate Envers fills the blank table. Since Hibernate 3.5, Envers is part of Hibernate core project. Configuration Configure Hibernate Envers in your project is very simple, just need to addhibernate-enversas project dependency. <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-envers</artifactId> </dependency> Done. No need extra Event listeners configuration as the early version. Basic Usage Hibernate Envers provides a simple@Auditedannotation, you can place it on an Entity class or property of an Entity. @Audited private String description; If@Auditedannotation is placed on a property, this property can be tracked.

Spring Data Mongo: bridge MongoDB and Spring

Spring Data Mongo: bridge MongoDB and SpringMongoDBis one of the most popular NoSQL products, Spring Data Mongo(Maven archetype id is spring-data-mongodb) tries to provides a simple approach to access MongoDB. Configuration Add the following code fragments in your Spring configuration. <!-- Mongo config --> <mongo:db-factory id="mongoDbFactory" host="localhost" port="27017" dbname="conference-db" /> <bean id="mongoTemplate" class="org.springframework.data.mongodb.core.MongoTemplate"> <constructor-arg ref="mongoDbFactory" /> </bean> <mongo:repositories base-package="com.hantsylabs.example.spring.mongo" /> Firstly, declare aDbFactorywhich is responsible for connecting to the MongoDB server. Then, register theMongoTemplateobject which envelop the data operations on MongoDB. Lastly addmongo:repositorieswith an essentialbase-packageattribute, Spring will discovery your d…