package org.superbiz.stateless.basic;

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
import javax.ejb.Stateless;
import javax.interceptor.AroundInvoke;
import javax.interceptor.InvocationContext;

@Stateless
public class CalculatorBean {

    @PostConstruct
    public void postConstruct() {
        ExecutionChannel.getInstance().notifyObservers("postConstruct");
    }

    @PreDestroy
    public void preDestroy() {
        ExecutionChannel.getInstance().notifyObservers("preDestroy");
    }

    @AroundInvoke
    public Object intercept(InvocationContext ctx) throws Exception {
        ExecutionChannel.getInstance().notifyObservers(ctx.getMethod().getName());
        return ctx.proceed();
    }

    public int add(int a, int b) {
        return a + b;
    }

    public int subtract(int a, int b) {
        return a - b;
    }

    public int multiply(int a, int b) {
        return a * b;
    }

    public int divide(int a, int b) {
        return a / b;
    }

    public int remainder(int a, int b) {
        return a % b;
    }

}

package org.superbiz.counter;

import java.util.ArrayList;
import java.util.List;

public class ExecutionChannel {
    private static final ExecutionChannel INSTANCE = new ExecutionChannel();

    private final List<ExecutionObserver> observers = new ArrayList<ExecutionObserver>();

    public static ExecutionChannel getInstance() {
        return INSTANCE;
    }

    public void addObserver(ExecutionObserver observer) {
        this.observers.add(observer);
    }

    public void notifyObservers(Object value) {
        for (ExecutionObserver observer : this.observers) {
            observer.onExecution(value);
        }
    }
}

package org.superbiz.counter;

public interface ExecutionObserver {

    void onExecution(Object value);

}

package org.superbiz.stateless.basic;

import org.junit.Assert;
import org.junit.Test;

import javax.ejb.embeddable.EJBContainer;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;

public class CalculatorTest implements ExecutionObserver {
    private static final String JNDI = "java:global/simple-stateless-callbacks/CalculatorBean";

    private List<Object> received = new ArrayList<Object>();

    public Context getContext() throws NamingException {
        final Properties p = new Properties();
        p.put(Context.INITIAL_CONTEXT_FACTORY, "org.apache.openejb.core.LocalInitialContextFactory");
        return new InitialContext(p);

    }

    @Test
    public void test() throws Exception {
        ExecutionChannel.getInstance().addObserver(this);

        final EJBContainer container = EJBContainer.createEJBContainer();

        {
            final CalculatorBean calculator = (CalculatorBean) getContext().lookup(JNDI);

            Assert.assertEquals(10, calculator.add(4, 6));

            //the bean is constructed only when it is used for the first time
            Assert.assertEquals("postConstruct", this.received.remove(0));
            Assert.assertEquals("add", this.received.remove(0));

            Assert.assertEquals(-2, calculator.subtract(4, 6));
            Assert.assertEquals("subtract", this.received.remove(0));

            Assert.assertEquals(24, calculator.multiply(4, 6));
            Assert.assertEquals("multiply", this.received.remove(0));

            Assert.assertEquals(2, calculator.divide(12, 6));
            Assert.assertEquals("divide", this.received.remove(0));

            Assert.assertEquals(4, calculator.remainder(46, 6));
            Assert.assertEquals("remainder", this.received.remove(0));
        }

        {
            final CalculatorBean calculator = (CalculatorBean) getContext().lookup(JNDI);

            Assert.assertEquals(10, calculator.add(4, 6));
            Assert.assertEquals("add", this.received.remove(0));

        }

        container.close();
        Assert.assertEquals("preDestroy", this.received.remove(0));
        Assert.assertTrue(this.received.isEmpty());
    }

    @Override
    public void onExecution(Object value) {
        System.out.println("Test step -> " + value);
        this.received.add(value);
    }
}