Jakarta CDI - After Intermediate Lab 2

In this lab, we will explore the CDI interceptor, creating a timer for methods.

1. Create a Timed annotation

1. Create a new package called audited in the expert.os.labs.persistence.cid package
2. Create an interface called Timed in the expert.os.labs.persistence.cid.audited package
3. Annotate the interface as @interface
4. Add the following annotations:
   • @InterceptorBinding from the jakarta.interceptor package
   • @Target({METHOD, TYPE})
     • the @Target is from the java.lang.annotation package
     • the METHOD and TYPE is from the java.lang.annotation.ElementType package
   • @Retention(RUNTIME)
     • the @Retention is from the java.lang.annotation package
     • the RUNTIME is from the java.lang.annotation.ElementType package

Solution

Click to see...

import jakarta.interceptor.InterceptorBinding;

import java.lang.annotation.Retention;
import java.lang.annotation.Target;

import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.ElementType.TYPE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

@InterceptorBinding
@Target({METHOD, TYPE})
@Retention(RUNTIME)
public @interface Timed {
}

2. Create the TimedInterceptor Class

Steps

1. Create a class called TimedInterceptor in the expert.os.labs.persistence.cid.audited package
2. Add the following annotations:
   • @Timed
   • @Interceptor from the jakarta.interceptor package
   • @Priority(Interceptor.Priority.APPLICATION) from the jakarta.annotation package
     • the Interceptor is from the jakarta.interceptor package
3. Define a private attribute Logger from the java.util.logging package
4. Create a method called timer that will return an Object
   • it has a parameter InvocationContext from the jakarta.interceptor package
5. Annotate the method with @AroundInvoke from the jakarta.interceptor package
6. In the timer() method, add:
   • the current time into a variable using the System.currentTimeMillis()
   • the next interceptor using ctx.proceed();, associating it to an object
   • the time slapsed into a variale (System.currentTimeMillis() - start)
   • the information about the time slapsed into a String showing it using ctx.getTarget().getClass(), ctx.getMethod(), end
   • Log the content of the information using the logger
   • return the information

Solution

Click to see...

import jakarta.annotation.Priority;
import jakarta.interceptor.AroundInvoke;
import jakarta.interceptor.Interceptor;
import jakarta.interceptor.InvocationContext;

import java.util.logging.Logger;

@Timed
@Interceptor
@Priority(Interceptor.Priority.APPLICATION)
public class TimedInterceptor {

    private static final Logger LOGGER = Logger.getLogger(TimedInterceptor.class.getName());

    @AroundInvoke
    public Object timer(InvocationContext ctx) throws Exception {
        long start = System.currentTimeMillis();
        Object result = ctx.proceed();
        long end = System.currentTimeMillis() - start;

        String message = String.format("Time to execute the class %s, the method %s is %d milliseconds",
            ctx.getTarget().getClass(), ctx.getMethod(), end);
        LOGGER.info(message);

        return result;
    }
}

3. Create the FastSupplier Class

Steps

1. Create a class FastSupplier in the in the expert.os.labs.persistence.cid.audited package
2. Implement the Supplier<String>
3. Annotate the method get() with @Timed
4. Return any String

Solution

Click to see...

import java.util.function.Supplier;

public class FastSupplier implements Supplier<String> {

    @Timed
    @Override
    public String get() {
        return "The Fast supplier result";
    }
}

4. Create the SlowSupplier Class

Steps

1. Create a class SlowSupplier in the in the expert.os.labs.persistence.cid.audited package
2. Implement the Supplier<String>
3. Annotate the method get() with @Timed

4. Add the following code to the method

   try {
       TimeUnit.MILLISECONDS.sleep(200L);
   } catch (InterruptedException e) {
       //TODO it is only a sample, don't do it on production :)
       throw  new RuntimeException(e);
   }
   return "The slow result";
   

Solution

Click to see...

import java.util.concurrent.TimeUnit;
import java.util.function.Supplier;

public class SlowSupplier implements Supplier<String> {

    @Timed
    @Override
    public String get() {
        try {
            TimeUnit.MILLISECONDS.sleep(200L);
        } catch (InterruptedException e) {
            //TODO it is only a sample, don't do it on production :)
            throw  new RuntimeException(e);
        }
        return "The slow result";
    }
}

5. Create the app class

Steps

1. Create a class called AppInterceptor in the expert.os.labs.persistence.cid package

2. Add a main method

   public static void main(String[] args) {
   }
   

3. Set up a try-with-resources block, inside the main method, to manage the Jakarta EE SeContainer that is responsible for dependency injection and managing resources

   try (SeContainer container = SeContainerInitializer.newInstance().initialize()) {     
   }
   

4. Obtain the value of the FastSupplier through the container instance

5. Obtain the value of the SlowSupplier through the container instance
6. Printout both results

Expected results

• The following output

  INFO: Time to execute the class class expert.os.labs.persistence.cdi.audited.FastSupplier$Proxy$_$$_WeldSubclass, the method public java.lang.String expert.os.labs.persistence.cdi.audited.FastSupplier.get() is 0 milliseconds
  The result: The Fast supplier result
  
  INFO: Time to execute the class class expert.os.labs.persistence.cdi.audited.SlowSupplier$Proxy$_$$_WeldSubclass, the method public java.lang.
  
  String expert.os.labs.persistence.cdi.audited.SlowSupplier.get() is 203 milliseconds
  The result: The slow result    
  

Solution

Click to see...

import expert.os.labs.persistence.cdi.audited.FastSupplier;
import expert.os.labs.persistence.cdi.audited.SlowSupplier;
import jakarta.enterprise.inject.se.SeContainer;
import jakarta.enterprise.inject.se.SeContainerInitializer;

import java.util.function.Supplier;

public class AppInterceptor {

    public static void main(String[] args) {
        try (SeContainer container = SeContainerInitializer.newInstance().initialize()) {
            Supplier<String> fastSupplier = container.select(FastSupplier.class).get();
            Supplier<String> slowSupplier = container.select(SlowSupplier.class).get();

            System.out.println("The result: " + fastSupplier.get());
            System.out.println("The result: " + slowSupplier.get());
        }
    }
}