Kenneth SaksSenior Staff EngineerSUN Microsystems

Enterprise JavaBeansTM

(EJBTM) 3.1

2

Agenda

• Background• Proposed Functionality• Summary• Q & A

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EJB 3.0 Specification (JSR 220)

• Features> Simplified EJB API> Java Platform Persistence API

• Focus on ease-of-use> Annotations > Intelligent defaults> Fewer classes needed

• Very well received within the community> But... more work is needed

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EJB 3.1 Specification

• Goals> Continued focus on ease-of-use> New features

• JSR (Java Specification Request) 318> Launched in August 2007

– Java Persistence API will evolve separately ( JSR 317 )

> Early Draft February 2008 > Public Draft October 2008

• Caveat – APIs still subject to change

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Agenda

• Introduction• Proposed Functionality • Summary• Q & A

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Ease of Use Improvements

• Optional Local Business Interfaces• Simplified Packaging• EJB “Lite” • Portable Global JNDI Names• Simplified Unit Testing

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Session Bean with Local Business Interface

<<interface>com.acme.Hello

String sayHello()

com.acme.HelloBean

public String sayHello() { ... }

@EJB private Hello h;

...

h.sayHello();

HelloBean Client

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Optional Local Business Interfaces

• Sometimes local business interface isn't needed• Better to completely remove interface from

developer's view than to generate it• Result : “no-interface” view

> Just a bean class> public bean class methods exposed to client> Same behavior and client programming model

as Local view– Client acquires an EJB component reference instead

of calling new()

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Session Bean with “No-interface” View@Statelesspublic class HelloBean {

public String sayHello(String msg) { return “Hello “ + msg; }

}

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No-interface View Client

@EJB HelloBean h;

...

h.sayHello(“bob”);

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Web/EJB Application in JavaTM EE Platform 5

foo.ear

WEB-INF/web.xmlWEB-INF/classes/ com/acme/FooServlet.classWEB-INF/classes com/acme/Foo.class

foo_web.war

com/acme/FooBean.classcom/acme/Foo.class

foo_ejb.jar

foo.ear

lib/foo_common.jar

com/acme/Foo.class

WEB-INF/web.xmlWEB-INF/classes/ com/acme/FooServlet.class

foo_web.war

com/acme/FooBean.class

foo_ejb.jar

OR

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foo.war

WEB-INF/classes/ com/acme/FooServlet.class

WEB-INF/classes/ com/acme/FooBean.class

Web/EJB Application in JavaTM EE Platform 6

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Simplified Packaging

• Goal is to remove an artificial packaging restriction> Not to create a new flavor of EJB component

• EJB component behavior is independent of packaging> One exception : module-level vs. component-level

environment

• No new restrictions placed on .war > Deploy .war stand-alone OR within an .ear

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EJB “Lite”

• Small subset of EJB 3.1 API for use in Web Profile• Broaden the availability of EJB technology

> Without losing portability

• Same exact Lite application can be deployed to Web Profile and Full Profile > Thanks to simplified .war packaging

• Open issue : whether Web Profile will require EJB Lite

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“Lite” vs. Full Functionality

Lite • Local Session Beans• Annotations / ejb-

jar.xml• CMT / BMT• Declarative Security• Interceptors

• (Also requires JPA 2.0 API / JTA 1.1 API )

Full = Lite + the following:• Message Driven Beans• EJB Web Service

Endpoints• RMI-IIOP

Interoperability• 2.x / 3.x Remote view• 2.x Local view• Timer Service• CMP / BMP

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Session Bean Exposing a Remote View@Stateless@Remote(Hello.class)public class HelloBean implements Hello {

public String sayHello(String msg) { return “Hello “ + msg; }

}

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Remote Clients

// Remote client in a Java EE container@EJB Hello hello;

// Remote client in a Java SE environmentHello hello = (Hello) new InitialContext().lookup(???);

Question : How does the caller find the target EJB component?

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Problems with “Global” JNDI Names

• Not portable> Global JNDI namespace is not defined in Java EE

platform specification > Vendor-specific configuration needed for each

deployment

• No standard syntax> Can names contain : “.”, “_”, “/” ?

• Not clear which resources have them> Local interfaces?

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Portable Global JNDI Names

“java:global[/<app-name>]/<module-name>/<bean-name>”

// Client in a Java EE container@EJB(mappedName= ”java:global/hello/HelloBean”) Hello hello;

// Client in a Java SE environmentHello hello = (Hello) new InitialContext() lookup(“java:global/hello/HelloBean”);

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EJB Component Testing

• It's too hard to test EJB components, especially the Local view > Forced to go through Remote facade or Web tier> Separate JVM™ instances needed for server and client

• Support for running in Java SE exists, but...> Not present in all implementations> No standard API for bootstrapping, component discovery,

shutdown etc.

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Example: No-interface Stateless Session Bean

@Statelesspublic class BankBean {

@PersistenceContext EntityManager accountDB;

public String createAccount(AccountDetails d) { ... }

public void removeAccount(String accountID) { ... }

}

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Example: Embeddable APIpublic class BankTester {

public static void main(String[] args) { EJBContainer container = EJBContainer.createEJBContainer();

// Acquire EJB component reference BankBean bank = (BankBean)container.getContext(). lookup(“java:global/bank/BankBean”);

testBank(bank); ... container.close(); }

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Example : Embeddable API (cont.)

% java -classpath bankClient.jar : bank.jar : javaee.jar : <vendor_rt>.jar com.acme.BankTester

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Embeddable API

• Execute enterprise beans in a Java SE environment• “Single application” model• Same EJB component behavior / lifecycle as

server-side> CMT, injection, threading guarantees, etc.

• Only EJB “Lite” functionality required to be available

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New Features

• Singletons• Application startup / shutdown callbacks• Calendar-based timer expressions• Automatic timer creation• Simple Asynchrony

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Singletons

• New session bean component type> One singleton bean instance per application per JVM> Provides easy sharing of state within application> Designed for instance-level concurrent access

• Lots in common with stateless / stateful beans> Client views (No-interface , Local, Remote, Web Service) > CMT / BMT> Container services: timer service, injection, etc.> Method authorization

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Simple Singleton

@Singletonpublic class SharedBean {

private SharedData shared;

@PostConstruct private void init() { shared = ...; }

public int getXYZ() { return shared.xyz; }

}

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Singleton Client

@Stateless public class FooBean {

@EJB private SharedBean shared;

public void foo() { int xyz = shared.getXYZ(); ... }

}

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Singleton Concurrency Options

• Single threaded (default)> Container serializes concurrent requests

• Container Managed Concurrency> Concurrency via method-level locking metadata

– Read lock (Shared): allow any number of concurrent accesses

– Write lock (Exclusive) : ensure single-threaded access

> Container blocks invocations until they can proceed– ...or until app-specified timeout is reached

• Bean Managed Concurrency > Like Java Servlet API threading model

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Read-Only Singleton with Container Managed Concurrency

@Singletonpublic class SharedBean {

private SharedData shared;

@Lock(READ) public int getXYZ() { return shared.xyz; }

...}

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Read-Mostly Singleton with Container Managed Concurrency

@Singleton@Lock(READ)public class SharedBean {

private SharedData shared;

public int getXYZ() { return shared.xyz; }

@Lock(WRITE) public void update(...) { // update shared data ... }

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Concurrent Access Timeouts

@Singletonpublic class SharedBean {

private SharedData shared;

@Lock(READ) @AccessTimeout(1000) public int getXYZ() { return shared.xyz; }

@Lock(WRITE) public void update(...) { // update shared data }

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Read-Mostly Singleton with Bean Managed Concurrency

@Singleton@ConcurrencyManagement(BEAN)public class SharedBean {

private SharedData shared;

synchronized public int getXYZ() { return shared.xyz; }

synchronized public void update(...) { // update shared data ... }

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Startup / Shutdown Callbacks

@Singleton@Startuppublic class StartupBean {

@PostConstruct private void onStartup() { ... }

@PreDestroy private void onShutdown() { ... }

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Timer Service Features

• Calendar-based timeout expressions • Automatic timer creation• Non-persistent timers

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Calendar Based Timeouts

• “Cron”-like semantics with improved syntax• Usable with automatic or programmatic timers • Named attributes

> second, minute, hour ( default = “0” )> dayOfMonth, month, dayOfWeek, year (default = “*”)

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Calendar Based Timeouts

// The last Thursday in November at 2 p.m.(hour=”14”, dayOfMonth=”Last Thu”, month=”Nov”)

// Every weekday morning at 3:15 a.m.(minute=”15”, hour=”3”, dayOfWeek=”Mon-Fri”)

// Every five minutes (minute=”*/5”, hour=”*”)

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Expression Attribute Syntax

• Single value : minute = “30”• List : month = “Jan, Jul, Dec”• Range : dayOfWeek = “Mon-Fri”• Wildcard : hour = “*”• Increment : minute = “*/10”

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Automatic Timer Creation

• Container creates timer automatically upon deployment

• Logically equivalent to one createTimer() invocation• Each automatic timer can have its own timeout

callback method

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Automatic Timer Creation

@Stateless public class BankBean { @PersistenceContext EntityManager accountDB; @Resource javax.mail.Session mailSession;

// Callback the 1st of each month at 8 a.m.

@Schedule(hour=”8”, dayOfMonth=”1”) void sendMonthlyBankStatements() { ... }

}

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Non-persistent Timers

• Timers without persistent delivery guarantee • Only live for duration JVM instance• Good fit for Singleton cache updates• Better performance for fine-grained timeouts

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Non-Persistent Timer Example

@Singleton public class CacheBean {

private Cache cache;

@Schedule(minute=”*/5”,hour=”*”,persistent=false) private void updateCache() { ... }

...

}

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Simple Asynchrony

• Different styles> Local concurrency

– E.g : break large piece of work into independent tasks

> Async RPC

• Too difficult with existing APIs> JMS API – complex API / lots of configuration> Threads – not well integrated with component model

• Approach : integrate asynchronous support directly into session bean components

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Simple Local Concurrent Computation

@Stateless public class DocBean {

@Resource SessionContext ctx;

public void processDocument(Document document) { DocBean me = ctx.getBusinessObject(DocBean.class); me.doAnalysisA(document); me.doAnalysisB(document); }

@Asynchronous public void doAnalysisA(Document d) {...} @Asynchronous public void doAnalysisB(Document d) {...}

}

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Asynchronous Operation Results -- Client@EJB Processor processor;

Task task = new Task(...);

Future<int> computeTask = processor.compute(task);

...

int result = computeTask.get();

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@Asynchronous on Bean Class

@Stateless public class ProcessorBean implements Processor {

@PersistenceContext EntityManager db;

@Asynchronous public Future<int> compute(Task t) { // perform computation int result = ...;

return new javax.ejb.AsyncResult<int>(result); }

}

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@Asynchronous on Interface

public interface Processor {

@Asynchronous public Future<int> compute(Task t);

}

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@Asynchronous on Interface

@Stateless @Local(Processor.class)public class ProcessorBean {

@PersistenceContext EntityManager db;

public int compute(Task t) { // perform computation int result = ...;

return result; }

}

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Async Behavior

• Transactions> No transaction propagation from caller to callee

• Method authorization> Works the same as for synchronous invocations

• Exceptions> Exception thrown from target invocation available via

Future<V>.get()

• SessionContext.isCancelled() allows bean to check for cancellation during processing

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Agenda

• Introduction• Proposed Functionality• Summary• Q & A

51

Summary

• EJB 3.1 Specification (JSR 318)• Part of Java EETM Platform 6• Goals

> Ease-of-use> New Features

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For More Information

• JSR 318 Home : http://jcp.org/en/jsr/detail?id=318> Send comments to jsr-318-comments@jcp.org

• Blog : http://blogs.sun.com/kensaks/• Reference Implementation : GlassFish project V3

> http://glassfish.dev.java.net> ejb@glassfish.dev.java.net

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Agenda

• Introduction• Proposed Functionality• Summary• Q & A

Kenneth SaksSenior Staff EngineerSUN Microsystems

Enterprise JavaBeansTM

(EJBTM) 3.1