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PWB519 Accessing Third-Party Enterprise JavaBeans Servers from PowerBuilder 9.0

Jim O’NeilPrincipal Technical Support EngineerSybase, Inc. (Concord, MA)[email protected]

Accessing Third-Party EJB Servers

Agenda Overview of the Enterprise JavaBeans (EJB) Model PowerBuilder EJB client implementation Coding a PowerBuilder EJB client application Deploying PowerBuilder NVOs to EJB servers Additional resources

Overview of the Enterprise JavaBeans Model

EJB is Sun’s J2EE transactional, vendor-neutral, enterprise component architecture providing

Modeling of business entities and synchronous and asynchronous processes Persistence via explicit code (bean-managed) or via services of the EJB server

(container-managed) Vendor neutrality and interoperability XML driven deployment and configuration

Core Concepts


EJB types Session beans model processes

Stateless EJBs are reusable and ‘single-task’ oriented Stateful EJBs remain associated with a client and are disposed when

client is through Entity beans model objects that persist, often in the form of records in a

database Message-driven beans respond to asynchronous requests from the Java

Message Service (JMS)

Core Concepts

business method

createfindByPrimaryKey


J2EE ServerClient Application

homeinterface stub

EJB Home

Implementation class

ancillary Java classes

remoteinterface stub

EJB Object

return value

lookupInitial

Context

Java Message Service

Message-driven bean

onMessage

JNDI Service

topic/queue

External messagingclient applications

messages

EnterpriseInformation

System

Representative Enterprise JavaBeans Server and Client Application


Java Naming and Directory Interface (JNDI) Provides a standardized way of accessing resources in a distributed environment Protocol and naming service agnostic

DNS NDIS LDAP X.500

Implemented by the javax.naming package and three other packages below it javax.naming.InitialContext is the entry point to the EJB Server

bind – associates a name with an object lookup – finds an object given the name

Interfaces and Classes


Home interface Provides remote client-view of methods affecting the EJB lifecycle Extends javax.ejb.EJBHome Can include business methods that are not specific to a given EJB instance Lacking for message-driven beans since they have no client-view



Component interface Provides remote client-side view of bean’s business methods Extends javax.ejb.EJBObject thus providing methods to obtain access to

Home interface and Primary Key classes and to test for equality between EJB instances

Lacking for message-driven beans since they have no client-view



Implementation class Implements one of the extensions of the javax.ejb.EnterpriseBean class

which provide lifecycle notification methods (e.g., ejbPassivate) javax.ejb.EntityBean javax.ejb.SessionBean javax.ejb.MessageDrivenBean

Class in which EJB developer codes the business methods defined in the bean’s component interface(s)



Primary key class Applicable only to entity beans Uniquely differentiates one instance from the other instances sharing the same

EJBHome Class must be a legal value type in RMI-IIOP

Implements java.io.Serializable Does not implement java.rmi.remote



Exceptions System exceptions are unchecked and propagate to the client as

java.rmi.RemoteException Application exceptions are checked and propagate to the client as a descendant of

java.lang.Exception EJB-specific exceptions include FinderException, CreateException,

RemoveException (all in javax.ejb package) Business method exceptions are at the discretion of the EJB developer



Other interfaces and classes Local interfaces used for access within server context (e.g., intercomponent calls,

servlet invocation) javax.ejb.EJBLocalHome javax.ejb.EJBLocalObject

Interfaces for serializing EJB references HomeHandle - reference to EJBHome Handle - reference to EJBObject

EJBMetaData interface provides mechanism to gather information about the bean Reference to EJBHome object Home, component interface and primary key classes Functions to determine bean type


PowerBuilder EJB Client Implementation

Feature overview Uses Java Native Interface (JNI) for interoperability Supports 1.0, 1.1, and 2.0 EJBs Supports client-managed transactions Supports system and application exception handling Supplemented by EJB Proxy Generator

PowerBuilder IDE EJB2PB90 command line utility

Architecture Overview


Implementation overview Built using the PowerBuilder Native Interface (PBNI) which allows developers to

Extend core features of PowerBuilder via custom C++ classes, and Access PowerBuilder objects from other languages like C++, VisualBasic, and

Delphi Three PBNI classes are exposed in the PBEJBCLIENT90.PBD

JavaVM EJBConnection EJBTransaction

EJBLocator Java class, which wraps javax.naming.InitialContext, is contained in PBEJBCLIENT90.JAR

PowerBuilder proxy objects represent all other Java classes and interfaces required for a given EJB

JDK required for development, JRE for runtime – PowerBuilder installs Sun JDK 1.4 by default to ease configuration issues



JavaVM object Loads and initializes Java VM inside of the PowerBuilder process Supported by configurable PowerBuilder ‘JVM Service’ which handles all JDK/JRE

needs in PowerBuilder environment JDBC Connectivity EJB Client Functionality JSP Deployment XSL-FO

Be aware… Once Java VM is loaded, for whatever reason, by PowerBuilder, you cannot

modify its environment, classpath, etc.; use return value of CreateJavaVM to determine if Java VM was actually loaded or already resident

Debug option for CreateJavaVM method is not available for JDK 1.4 Methods exist for determining the actual class for a returned interface,

downcasting classes, determining interfaces implemented by classes, etc.



PowerBuilder JVM Service configuration JDK and JRE Location can be specified in System Options dialog

JVM properties and CLASSPATH entries are in the registry Design-time: \\HKLM\Sybase\PowerBuilder\9.0\Java\PBIDEConfig

• PBJVMConfig• PBJVMProps• PBSysClasspath

Run-time: \\HKLM\Sybase\PowerBuilder\9.0\Java\PBRTConfig• PBJVMConfig• PBJVMProps


PowerBuilder EJB Client ImplementationArchitecture Overview

EJBConnection object Analog of the PowerBuilder Connection object Serves as a PowerBuilder façade to the InitialContext class within the

PBEJBCLIENT90.JAR file

ConnectToServer - sets initialContext

DisconnectServer - closes initialContext Lookup - returns EJBHome reference given JNDI name

GetEJBTransaction - returns reference enabling client-managed transactions

CreateJavaInstance – create a Java class within client Java VM

Be aware…

Properties array argument to ConnectToServer is the only ‘vendor-specific’ requirement; PowerBuilder doesn’t ‘know’ what EJB server you are using

CreateJavaInstance is used to create a Java class on the client – you don’t need an EJB server at all to do this!


EJBTransaction object Populated by GetEJBTransaction method of the EJBConnection object Wraps javax.transaction.UserTransaction and so provides methods for

initiating, coordinating, and completing a transaction from a client application Begin GetStatus Commit SetRollbackOnly Rollback SetTransactionTimeout

Be aware… Not all EJB servers support client-managed transactions Best practices have a session bean on the server controlling the transaction


EJBLocator Java class Single Java class residing in PBEJBCLIENT90.JAR:

com.sybase.powerbuilder.ejb.EJBLocator Four methods, all wrapped by the EJBConnection PBNI object Required for deployed applications

JAR is included in CLASSPATH managed by JVM Service with the assumption that it is located relative to the PBJVM90.DLL


PowerBuilder proxy objects Used to delegate requests to and from the underlying Java classes Inherited from Nonvisualobject or Exception class like other PowerBuilder proxies Generated using javap command in JDK

EJB Client Proxy wizard / project in PowerBuilder development environment EJB2PB90 stand-alone utility

Includes Public methods defined on its associated Java class Public class variables in PowerBuilder 9.0.1 and later

To avoid conflicts with PowerBuilder reserved words, names may be decorated Proxy name prefix “java_”, for example, java_integer Method name postfix ”_j”, for example, and_j

Java methods that return arrays will return any in PowerBuilder Proxies are also supported by a PowerBuilder mapping structure that correlates the

PowerBuilder proxy name to the underlying Java class name


Sample source for a PowerBuilder proxy object

$PBExportHeader$ejbobject.srx

$PBExportComments$Proxy imported from EJB via EJB Proxy generator.

global type EJBObject from Remote

end type

type variables

protected:

string EJBObject_javaname= "javax.ejb.EJBObject"

end variables

forward prototypes

public:

function EJBHome getEJBHome() throws RemoteException alias for

"getEJBHome,()Ljavax/ejb/EJBHome;"

function any getPrimaryKey() throws RemoteException alias for

"getPrimaryKey,()Ljava/lang/Object;"

subroutine remove() throws RemoteException, RemoveException alias for "remove,()V"

function Handle getHandle() throws RemoteException alias for "getHandle,()Ljavax/ejb/Handle;”

function boolean isIdentical( EJBObject EJBObject_1) throws RemoteException alias for

"isIdentical,(Ljavax/ejb/EJBObject;)Z"

end prototypes

Coding a PowerBuilder EJB Client Application

Setting up your environment Adding the EJB client implementation to your target Generating proxies

Basic client coding steps Advanced topics


Adding the EJB Client implementation to your target Include PBEJBCLIENT90.PBD in your target’s library list

Setting Up Your Environment


Generating proxies Use EJB Client Proxy Wizard


EJB home interface name must be same as remote interface name followed by ‘Home’


Generating proxies Use EJB2PB90.EXE, a completely stand-alone utility, and import resulting files

into PowerBuilder target

Syntax: ejb2pb90 [-classpath pathlist] EJBName [prefix]

Output includes Various .srx files – the proxy objects ejbproxies.txt – listing the .srx files produced ejbproxies.err – containing the diagnostic message in the event an error

occurs while the proxies are generated $EJBName$_ejb_pb_mapping.srs – the mapping structure



Basic client coding steps Initialize the Java VM Connect to the EJB Server Lookup an EJB Invoke methods on the EJB Disconnect from the EJB Server


Initialize the Java VM

TRY

g_JavaVM = CREATE JavaVM

CHOOSE CASE g_JavaVM.CreateJavaVM(is_ClassPath, false)

CASE 0

// JVM just loaded

CASE 1

// JVM was already loaded, is_ClassPath ignored

CASE -1

// failure, likely due to not finding JVM.DLL

CASE -2

// failure, do to not finding EJBLocator class

END CHOOSE

CATCH (PBXRuntimeError prte)

// catch any exception raised in PBNI extension

END TRY

Basic Client Coding Steps


Connect to the EJB Server

TRY

g_EJBConn = CREATE EJBConnection

// set initial context properties

ls_props[1] = "javax.naming.Context.INITIAL_CONTEXT_FACTORY=" + &

"com.sybase.ejb.InitialContextFactory"

ls_props[2] = "javax.naming.Context.PROVIDER_URL=iiop://localhost:9000"

ls_props[3] = "javax.naming.Context.SECURITY_PRINCIPAL=jagadmin"

ls_props[4] = "javax.naming.Context.SECURITY_CREDENTIALS="

// connect to EJB server

g_EJBConn.connectToServer(ls_props)

CATCH (NamingException ne)

// naming exception may occur when initial context class not found


// catch any exception raised in PBNI extension

END TRY



Lookup an EJB

TRY

g_HelloHome = g_EJBConn.lookup("HelloHome", "PB9/Hello", "pb9.HelloHome")

g_hello = g_helloHome.create()


// raised if EJB not located

CATCH (CreateException ce)

// raised if problem in instantiating EJB

CATCH (RemoteException re)

// raised whenever there is a unchecked exception on server


// raised whenever there is an exception in the PBNI extension

END TRY



Invoke methods on the EJB

TRY

MessageBox("Hello", g_hello.sayHello()

CATCH (YourCustomException yce)

// handle user-defined exception raised by EJB, for example, an exception

// indicating that an account lacks sufficient funds for withdrawal

CATCH (RemoteException re)

// raised whenever there is a unchecked exception on server



END TRY



Disconnect from the EJB server

TRY

g_EJBConn.disconnectServer()


// naming exception is unlikely here, but could be thrown by underlying

// Java InitialContext object



END TRY


As in many distributed processing scenarios, disconnecting a client does NOTautomatically free server resources, such as stateful EJBs that the client was using.


Advanced topics java.lang.Object references Using interfaces and casting Client-managed transactions Creating proxies for stand-alone Java classes


java.lang.Object references• Many EJB methods will return java.lang.Object references or expect them as

parameters• PowerBuilder will treat a java.lang.Object reference as a PowerBuilder any

variable within the method prototype• The mapping structure created when generating proxies is consulted at run-time to

map the underlying Java class to an appropriate proxy

Advanced Topics

global type Hello_ejb_pb_mapping from structure

string item1 = "java.rmi.Remote:Remote"

string item2 = "java.io.Serializable:Serializable"

string item3 = "java.io.IOException:IOException"

string item4 = "java.io.OutputStream:OutputStream"

string item5 = "java.io.FilterOutputStream:FilterOutputStream"

string item6 = "java.io.UnsupportedEncodingException:UnsupportedEncodingException"

string item7 = "java.io.PrintStream:PrintStream"

…


Using interfaces and casting• Additional JavaVM object methods extend your capabilities

GetActualClass – determines the actual Java class name when provided a PowerBuilder proxy object that represents a Java interface

GetSuperClass – determines the Java class that is the ancestor of the Java class or interface represented by the PowerBuilder proxy object

GetInterfaces – returns list of Java interfaces implemented by the Java class represented by the given PowerBuilder proxy object

DynamicCast – casts a PowerBuilder proxy object to another object – typically used to downcast a Java reference, use cautiously since invalid casts can cause instability

Advanced Topics


Using interfaces and casting – an example

Collection px_Collection

Vector px_Vector

Stack px_Stack

TRY

px_ListMgr = px_ListMgrHome.create()

px_Collection = px_ListMgr.getList(as_listType)

CHOOSE CASE g_JavaVM.GetActualClass(px_Collection)

CASE "java.util.Stack"

px_Stack = g_JavaVM.DynamicCast(px_Collection, "Stack")

DO WHILE TRUE

this.processItem(px_Stack.pop())

LOOP

CASE "java.util.Vector“

px_Vector = g_JavaVM.DynamicCast(px_Collection, “Vector”)

FOR i TO px_Vector.size()

this.processItem(px_Vector.elementAt(i))

NEXT

...

Advanced Topics


Client-managed transactions• The EJBTransaction object in the PBNI implementation has a direct

correspondence to javax.transaction.UserTransaction Begin - starts a transaction Commit - commits the current transaction SetRollbackOnly - marks the current transaction as doomed SetTransactionTimeout - sets the amount of time a transaction can be in

progress before it is rolled back. GetStatus - returns the status of the current transaction

Not all EJB servers support this and even if they do, best practices discourage its use

Advanced Topics


Client-managed transactions – an example

EJBConnection connEJBTransaction trans

conn = create EJBConnectionTRY

conn.connectToServer(is_props)trans = conn.getEJBTransaction() trans.Begin()

// Create a component and call methods to be// executed within the transaction

trans.Commit()

CATCH (Exception e)

trans.Rollback()

END TRY

Advanced Topics


Creating proxies for stand-alone Java classes• You can use the EJB client implementation to call Java classes on the client as

well!• Create ‘dummy’ home and remote interface Java classes and reference the

desired Java class as a method argument or return value• Generate proxies for this ‘pseudo’ EJB and the proxies for the referenced classes

will be automatically generated• Now use the CreateJavaInstance method of the EJBConnection object to

create instances of your Java class on the client (you can do this without issuing a ConnectToServer)

Advanced Topics

public interface DummyHome {}

Dummy Home interface Java code Dummy Home interface Java code

public interface Dummy{ public abstract void foo(com.your.JavaClass x);}

Deploying PowerBuilder NVOs to EJB Servers

Sunlly Group’s PBridge (http://www.sunlly.com) Since PowerBuilder 7, you can use PowerBuilder NVOs natively in EAServer and

have them interoperate with EJB components and Java clients Sunlly PBridge’s offering will allow you to deploy your PowerBuilder components

into other application servers such as WebLogic and WebSphere Built on PBNI architecture offered by PowerBuilder 9 Currently in beta and supporting

BEA WebLogic IBM WebSphere Sun J2EE reference implementation

Visit them at TechWave!

Deploying PowerBuilder NVOs to EJB ServersSunlly PBridge – Client Deployment Interface


InitialContext classes and default URLs for major EJB servers

Additional Resources

Server INITIAL_CONTEXT_FACTORY Class PROVIDER_URL (default)

Sybase EAServer com.sybase.ejb.InitialContextFactory iiop://server:9000

BEA WebLogic Server

weblogic.jndi.WLInitialContextFactory t3://server:7001

IBM WebSphere Application Server

com.ibm.websphere.naming.WsnInitialContextFactory

iiop://server:900 (v. 4)

Iiop://server:2809 (v. 5)

Sun ONE com.sun.jndi.cosnaming.CNCtxFactory iiop://server:9010

Oracle9iAS com.evermind.server.ApplicationClientInitialContextFactory

ormi://server:23791/application

Jboss org.jnp.interfaces.NamingContextFactory jnp://server:1099


Learning more about the EJB client feature PowerBuilder Extension Reference in product documentation set EJB specification (http://java.sun.com/products/ejb/docs.html)

3rd party J2EE server web sites BEA Systems WebLogic Server (http://www.bea.com/framework.jsp?

CNT=index.htm&FP=/content/products/platform/) Jboss (http://www.jboss.org) IBM WebSphere Application Server (http://www.ibm.com/websphere) Oracle9iAS (http://http://www.oracle.com/ip/deploy/ias/)

SAMS Publishing PowerBuilder: Internet and Distributed Application Development (http://www.pb9book.com)

Sybase Developer Network (http://sdn.sybase.com) Technical document: “Accessing 3rd Party EJB Servers from PowerBuilder 9”

(http://www.sybase.com/detail?id=1024977) CodeXchange…

Additional Resources

SDN Presents CodeXchange

New SDN feature enables community collaboration Download samples created by Sybase Leverage contributions of others to exploit PBNI (i.e. PBNI CommonDialog,

PBNI OLEObject utilities) Contribute your own code or start your own collaborative project with input

from other PowerBuilder experts

Any SDN member can participate Log in using your MySybase account via SDN

Join the collaboration already underway http://powerbuilder.codexchange.sybase.com or via SDN at

www.sybase.com/developer

SDN & CodeXchange at TechWave Technology Boardwalk Sybase Booth Theater

Share PowerBuilder 9 Code and Tools


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