cdi 2.0 deep dive

CDI 2.0 Deep Dive

Mark

Stru

berg • Member Apache Software Foundation

• VP, Apache OpenWebBeans

• CDI expert group member

• Twitter: @struberg• Blog: struberg.wordpress.com

@struberg @thjanssen123CDI 2.0 Deep Dive

http://www.twitter.com/struberg

http://struberg.wordpress.com/

Thor

ben J

anss

en • Independent author and trainer• Senior developer and architect @ Qualitype GmbH

• CDI 2.0 expert group member

• Twitter: @thjanssen123• Blog: www.thoughts-on-java.org


https://twitter.com/thjanssen123

http://www.thoughts-on-java.org/

CDI? What‘s that?


Wha

t isC

DI?

• Contexts and Dependency Injection for JavaTM 2.0 (JSR 365)

• Provides

• Contexts

• Dependency Injection

• Events

• Interceptors and decorators

• Extensions


Hist

oryo

fCDI

• CDI 1.0 (Java EE 6) December 2009

• CDI 1.1 (Java EE 7) June 2013

• CDI 1.2 April 2014

• CDI 2.0 Start September 2014

• CDI 2.0 Early Draft Release 2015

• CDI 2.0 Release 1st half of 2016

• CDI 2.1 Start after 2.0 Release


CDI 2.0


CDI 2

.0• Work on CDI 2.0 is still in progress

• No final decision yet

• Everything might change


Main

Topi

cs• Improve the event system

• Bootstrapping for Java SE

• Modularity

• Improve AOP

• Enhance SPI and Contexts

• Support Java 8 features


Main

Topi

cs• Defined by

• Existing entries in Jira

• Requirements by other specs

• Input from former expert group members

• Community survey


Comm

unity

Sur

vey • June 2014

• 260 participants

• 20 features to rate

• Asynchronous events

• Bootstrapping outside of Java EE

• AOP for produced or custom beans

• Observer ordering


Events


Even

ts• One of the bigger topics in CDI 2.0

• High demand by community

• Features

• Asynchronous events

• Ordering of events


Sync

hron

ousE

vent

s • Fire a synchronous event

@Inject

Event<UserEvent> userEvent;

…

userEvent.fire (new UserEvent(…));

• Observe a synchronous event

public void handleUserEvent(@Observes UserEvent e)

{…}

Asyn

chro

nous

Even

ts • Fire an asynchronous event

@Inject

Event<UserEvent> userEvent;

…

userEvent.fireAsync(new UserEvent(…));

• Observe an asynchronous event

public void handleUserEvent(@ObserveAsync UserEvent e) {…}

Asyn

chro

nous

Even

ts • Result and exception handling

event.fireAsync(new UserEvent(…))

.whenComplete((event, throwable) -> {

if (throwable != null) {

logger.error(“Error during processing of

UserEvent” +

throwable.getMessage());

} else {

logger.info(“Processing successful”);

}

});


Asyn

chro

nous

Even

ts • What could possibly go wrong?

• Thread executor group might get blocked by slow observers

• Mutable non-threadsafe payloade.g. visitor pattern with ArrayList in event payload

• @SessionScoped doesn‘t get propagated between threads

• @RequestScoped doesn‘t get propagated between threadse.g. @Inject Principal currentUser


Asyn

chro

nous

Even

ts • What could possibly go wrong?

• ThreadLocals of all kind don‘t get propagatede.g. log4j MappedDiagnosticContext

• Transactions don‘t get propagatedTransactionSynchronisationRegistry is basically a ThreadLocal

• New EntityManager and @PersistenceContext for each thread

• @Observes(during=TransactionPhase.AFTER_SUCCESS)

• Each async observer gets ist own transaction!


Asyn

chro

nous

Even

ts • All these problems are caused by multi-threading behaviorin Java EE and not CDI specific

• Very same problems occure with EJB @Asynchronousand Concurrency-Utils for Java EE


Asyn

chro

nous

Even

ts • Introduces new, asynchronous kind of events

• CompletionStage fireAsync(U event)

• @ObservesAsync

Event method @Observes notified @ObservesAsyncnotified

fire() Yes No

fireAsync() No Yes

Orde

ringo

fEve

nts • Define the order of event observers

public void handleUserEvent(

@Observe @Priority(1000) UserEvent e) {…}

• Call smallest priority first

• Uses default priority if not defined

• Order undefined for Observer with same priority


Bootstrapping


Boot

stra

pping

• Define a standard way to boot the CDI container in Java SE

• Already part of Weld and Open Web Beans

• First API proposed in EDR 1


Boot

stra

pping

• API proposal in EDR1

public static void main(String... args) {

try(CDI<Object> cdi =

CDI.getCDIProvider().initialize()) {

// start the container,

// retrieve a bean and do work with it

MyBean myBean = cdi.select(MyBean.class).get();

myBean.doWork();

}

// shuts down automatically after

// the try with resources block.

}

https://docs.jboss.org/cdi/spec/2.0.EDR1/cdi-spec.html#bootstrap-se


https://docs.jboss.org/cdi/spec/2.0.EDR1/cdi-spec.html#bootstrap-se

Boot

stra

pping

• API currently under discussion

• Context control not defined yet

• Bean discovery mode still under discussion

• Provide an option to choose implementation


CdiC

trlCd

iCon

taine

r • Allows to boot embedded EE containers with a vendorindependent API

• Implementations for:• Apache OpenWebBeans• JBoss Weld• JBoss WildFly in the making• Apache OpenEJB (TomEE embedded)

• add your own

• Simply replace the impl jar to switch!


CdiC

trl-C

onta

iner B

oots

trap • Very usable for unit tests, batches or other standalone Java

processes:

CdiContainer cdiContainer =

CdiContainerLoader.getCdiContainer();

cdiContainer.boot();

cdiContainer.getContextControl().startContexts();

…

cdiContainer.shutdown();


CdiC

trl-C

onte

xtCo

ntro

l• Also usable in EE containers

• Usage:@Inject ContextControl ctxCtrl;

• Allows to attach dummy RequestContext, SessionContextetc to the current Thread.

• Usable for Quartz extensions or any other async work


AOP


AOP

• Work on AOP improvements just started

• Topics

• Improve handling of UnproxyableResolutionException

• Interceptors and Decorators on produced and custom beans

• Support AOP on inner calls


Clas

s Pro

xies

• No Java SE support so far!

• All done in a container depending own way

• Most times uses bytecode libraries like javassist, ASM, cglib, bcel or serp

• Create a sub-class of the given type

• Override all public methods


Unpr

oxyA

ble?

• CDI throws an UnproxyAbleResolutionException for all classes which have

• No default constructor

• final, non-static and non-private methodse.g. ConcurrentHashMap

www.thoughts-on-java.org

Subc

lassP

roxy

Exam

ple1

/2 • The business class

@SessionScoped

public class User {

private String name;

public String getName() {

return name;

}

}


Subc

lassP

roxy

Exam

ple2

/2 public class User$$Proxy extends User {

@Override

public String getName() {

return getInstance().getName();

}

private T getInstance() {

beanManager.getContext().get(...);

}

}


Allow

Prox

ying

• Proposed solution

• Annotation @AllowProxying

• beans.xml <allowProxying>

Allow

Prox

ying

• Proposed solution 1

• Annotation @AllowProxying

Public class Owner {

@Produces

@RequestScoped

@TenantA

@AllowProxying

ConcurrentHashMap createConfigBase() {…}

}


Allow

Prox

ying

• Proposed solution

• beans.xml <allowProxying>

<allowProxying>

<class>java.util.concurrent.ConcurrentHashMap</class>

</allowProxying>

Inte

rcep

tors

on Pr

oduc

ers • Long discussions…

• Probably solvable by introducing javax.proxy.ProxyFactory?

• Like java.lang.reflect.Proxy but with subclassingsee DeltaSpike PartialBean


Java 8


Java

8• Java 8 was released after Java EE 7

• Support for Java 8 features

• All new APIs will use Java 8

• Changes of existing APIs are still under discussion


Java

8• Asynchronous events

fireAsync methods return new CompletionStage

public CompletionStage fireAsync(U event);

public CompletionStage fireAsync(U event,

Executor executor);

Java

8• Repeatable qualifiers and interceptor bindings

• Proposed by RI Weld, not specified so far

@Produces

@Language(„english“)

@Language(„german“)

public Translator createTranslator() { … }


Get in touch


Geti

n tou

ch• Website: http://www.cdi-spec.org

• Blog: http://www.cdi-spec.org/news/

• Twitter: @cdispec

• Mailing list: https://lists.jboss.org/mailman/listinfo/cdi-dev

• JIRA: https://issues.jboss.org/


http://www.cdi-spec.org/

http://www.cdi-spec.org/news/

https://twitter.com/cdispec

https://lists.jboss.org/mailman/listinfo/cdi-dev

https://issues.jboss.org/

Geti

n tou

chMark StrubergTwitter: @strubergBlog: struberg.wordpress.com

Thorben JanssenTwitter: @thjanssen123Blog: www.thoughts-on-java.org


http://www.twitter.com/struberg

http://struberg.wordpress.com/

https://twitter.com/thjanssen123

http://www.thoughts-on-java.org/

Reso

urce

s• CDI website:

http://www.cdi-spec.org• JSR 365 – CDI 2.0:

https://jcp.org/en/jsr/detail?id=365• CDI 2.0 EDR1:

https://docs.jboss.org/cdi/spec/2.0.EDR1/cdi-spec.html• The path to CDI 2.0 by Antoine Sabot-Durand:

https://www.youtube.com/watch?v=RynnZPsQdxMhttp://de.slideshare.net/antoinesd/the-path-to-cdi-20

• Blog Weld – CDI reference implementation: http://weld.cdi-spec.org/news/

• Apache OpenWebBeans:http://openwebbeans.apache.org


http://www.cdi-spec.org/

https://jcp.org/en/jsr/detail?id=365

https://docs.jboss.org/cdi/spec/2.0.EDR1/cdi-spec.html

https://www.youtube.com/watch?v=RynnZPsQdxM

http://de.slideshare.net/antoinesd/the-path-to-cdi-20

http://weld.cdi-spec.org/news/

http://openwebbeans.apache.org/