Prof. V. “Juggy” Jagannathan

Net-based Technologies for Healthcare: Focus on Java, CORBA, DCOM and XML

Prof. V. “Juggy” Jagannathan
CSEE Department & Concurrent Engineering Research Center West Virginia University & CareFlow|Net, Inc. Prof. K. Srinivas CSEE Department & Concurrent Engineering Research Center West Virginia University

Agenda Objects and the Web Distributed Object Technologies
Internet and Extranets World Wide Web XML Architectural Alternatives Distributed Object Technologies CORBA DCOM Java Technology Java JavaBeans Lotus InfoBus JavaBlend Enterprise Java Beans Healthcare Security Aspects XML in Healthcare Object Healthcare Standards Baptist Case Study

Intranets and Extranets

Internet Internet is the largest network of networks.
These networks share a large number of protocols such as ftp, TCP/IP,NNTP,HTTP, IIOP and many others.

What are Intranets Use Internet technology (such as TCP/IP, NNTP, HTTP) for access to internal corporate data Usually intra-organization Some workflow such as forms routing.

Advantages Use of inexpensive Internet technologies
Client Server Computing with Browser Clients

Facilities Provided Usually Intranets provide facilities for browsing, searching, electronic mail and group collaboration tools such as those provided by current day browsers. Can also be linked to existing organizational databases to graphically retrieve data from backends.

What are Extranets A vast majority of commerce occurs through business-to-business transactions. However the information exchange in these transactions have to be done securely, so that competition is not aware of the details. Extranets allow companies to share sensitive information securely through internet channels producing large cost savings.

Extranets Use Internet technology to perform some transactions through secure public networks.

Examples Secure Access to Trading Partners
Global Ordering (Marshall, Dell) Shipment Tracking(Federal Express, UPS) Product Configuration(Cisco) Concurrent Engineering(Ford, Chrysler)

World Wide Web

The Common Gateway Interface
The purpose of the Common Gateway (CGI) Interface is to allow generation of HTML data from dynamic data sources. With CGI data can come from databases and/or be calculated at the moment the request for the document is made. CGI programs can be written in any language.

Common Gateway Interface (cont)
CGI is the generic interface between the server and server-side 'gateway' programs. CGI specifies how data are sent to the gateway program, and how data can be returned by the gateway program, through the server and back to the browser that originally sent the data. text from

WEB Problems

Static to Dynamic Increase in the number of systems that generate dynamic HTML documents on the fly. Primary mechanism for this is the CGI Leads to performance problems - http bottleneck Harder to integrate Harder to maintain - CGI Scripts KLUDGE

Whatever happened to “Session”
Unidirectional mechanisms geared for publishing rather than transactions. No direct mechanisms to support sessions, transactions support or for event notification

Side Effects Input consistency checking difficult. Javascript can alleviate the problem. Still a kludge. No drag and drop and other familiar controls Frame problem: When dealing with multiple frames, keeping them consistent is not easy.

The obvious conclusion
Web is great for publishing. It simply was not designed to support client-server interactions. But the overriding ease-of-use and ubiquity of access from multiple platforms has resulted in all sorts of unmaintainable kludges being deployed.

Evolution of Web Technologies*
Hyper-text Web Simple Forms Web Object Web JavaBeans/Applets ActiveX Controls Component Coordinators ORB-based interactions via CORBA or DCOM Function Dynamic HTML Scripts Cookies/Session Active Server Pages CORBA plug-ins Web Objects Servlets Forms CGI Tables ISAPI NSAPI URL-Based File Server Interactive Responsiveness * Adapted from Orafali and Harkey, Client Server Programming with Java and CORBA

XML Technology

Emerging Importance of XML
HTML-tagging is display oriented. XML-based content tagging has important uses: data mining role-oriented display customization intelligent searching and other value added elements Wide spread industry support for this new open standard Microsoft Netscape W3C is pushing the standardization efforts Complementary technology to HTML-based web browsers

Requirements best addressed by XML
Customizing front-end applications - easy presentation of what users want to see Data mining - ala altavista-type search Synthesis type applications - combining multiple information sources Electronic commerce-type applications

XML Markup Elements and attributes Entity References Comments
Processing Instructions Marked Sections Document Type Definitions (DTDs)

Elements Bounded by start and end tags Sample markup
<Patient> <FirstName> Frank</FirstName> <LastName> Foster</LastName> </Patient> Patient, LastName, FirstName are all entity tags.

Attributes Name-value pairs included as part of start tags.
Sample markup <APatient patientID=“123” FirstName=“Frank” LastName=“Foster”> <Insurance> Blue Cross </Insurance> <Insurance> HMO </Insurance> </APatient> FirstName and LastName in the example above are attribute declarations.

Document Type Definitions
Allows the expression of constraints on tags Defines sequencing and nesting of tags Defines attributes and values and defaults Allows specification of external file references Four kinds of declarations in XML Element declarations Attribute List declarations Entity declarations notation declarations

DTD Element Declarations
<!Element Patient (FirstName, LastName, Insurance?)> Says that Patient info is composed of FirstName, LastName and optionally Insurance information. <!Element Insurance (#PCDATA)> Says element Insurance is composed of parse-able character data.

DTD Attribute List Declaration
<!ATTLIST Apatient patientID ID #required FirstName CDATA LastName CDATA >

Other aspects of DTD Entity declarations (sort of macro capabilities)
DTDs can be included with the tagged document or referred to externally. Distinction between “well-formed” and “valid” documents Well-formed: satisfy XML markup constraints - no associated DTD. Valid documents: XML markup that adhere to the constraints specified in a DTD.

XML’s evolving family of standards
XML Linking Specification (XLL) Resource Directory Framework (RDF) Style sheets DSSSL - Document Style Semantics and Specification Language CSS Cascading Style sheets XSL XML Style Specification Language Domain Object Model Document Content Descriptors and Schemas

Objects on the Web

World Wide Web and Objects
How to combine Objects and the WWW What are the commercial solutions and directions Java-based ORBs

Aproaches to Combining Objects and the WWW
Web Browser Server HTTP Protocol

Web Server-based interfaces
Server API Web Browser Web Server ORB Clients HTTP Protocol CGI Scripts CORBA IIOP Protocol ORB Servers

Direct Support for IIOP
IOR://xyz Web Browser ORB Server IIOP Protocol

Java-based ORBs Two main players:
Iona’s OrbixWeb Inprise ’s Visibroker IDL to Java mappings have been standardized. Commercial implementations supporting the standardized mapping is being shipped by both Iona and Inprise .

Common Object Request Broker Architecture
Distributed Object Infrastructure

References Robert Orfali, Dan Harkey, “Client/Server Programming with Java and CORBA, Second Edition.” John Wiley and Sons, 1998. Andreas Vogel and Keith Duddy, “Java Programming with CORBA, Second Edition, Advanced Techniques for Building Distributed Applications,” John Wiles and Sons, 1998. John Siegal (written and edited by), “CORBA Fundamentals and Programming,” John Wiley and Sons, 1996.

Outline Overview CORBA 1.1, 2.0, 3.0 IDL and Interface Repository
CORBA services

Background* Not-for-profit company based in United States, with representation in Italy, United Kingdom, Germany, Japan, Australia & India. Founded April 1989. Small staff (35 full time); no internal development. Almost all technical work done by engineers in member companies Almost 800 members (4/98) .. * Viewfoil courtesy OMG:

Worldwide Scope * Andersen APM Alta AITECH AT&T BaaN Bull British Telecom Bankers Trust Data Access Eurocontrol EDS Ericsson FinSiel Fujitsu Genesis HP Harlequin ICL Informix Intel IBM IONA Tech. Microsoft MITRE Netscape Nortel Novell OHRA Insurances Oracle Open Group POSC Sodalia Siemens Nixdorf Software AG Sun Microsystems Sybase Thomson CSF Telecom Italia Telefonica Telia AB TRW Unisys Valtech……. * Viewfoil courtesy OMG:

Adoption Process * RFI (Request for Information) to establish range of commercially available software. RFP (Request for Proposals) to gather explicit descriptions of available software; Architecture Board approves. Letters of Intent to establish corporate direction. Task Force evaluation & recommendation; simultaneous evaluation by Business Committee. Architecture Board consideration for consistency. Board decision based on recommendations from the appropriate Technology Committee & Business Committee. Fast Track Process.. * Viewfoil courtesy OMG:

CORBA Architecture Clients Server Servers Client Requests IDL-based
Java Ada other C C++ Java Ada other C Client Requests IDL-based Service IDL-based ORB

Integration Technology - CORBA
The Common Object Request Broker Architecture is the standard adopted by OMG as a framework to provide common ORB services and interfaces to support portable clients and services. The Object Request Broker (ORB) provides the mechanisms by which clients transparently make requests and receive responses.

CORBA (continued) Advantages offered by CORBA:
architecture independence language independence location independence The standard specifies the Interface Definition Language (IDL) - language used to describe the interfaces that client objects call and object implementations provide.

De-facto Standards and products available*
CORBAdomains - Manufacturing: - Electronic Commerce: - Healthcare: -Telecommunications: - Finance -Transportation - ….. CORBAfacilities - Architecture guide and roadmap - Working on Internet facilities. CORBA applications CORBA 2 (IIOP) - ORBIX - IONA - Obj Broker BEA - VisiBroker Borland - Omni Orb Olivetti - Component Broker IBM CORBAservices - Naming - Security (...ICL) - Transactions (..Bull) - Query Service - Persistence - Lifecycle * Viewfoil courtesy OMG:

The Evolution of CORBA*
Basic ORB, IR, BOA, C Bindings, Naming, Events, Lifecycle etc. CORBA 2.0 (1995) IIOP, Federated IR, C++ Bindings, Transactions, Concurrency, Externalization, Relationships, Query, Licensing, Trader, Security, Collections, Time etc. CORBA 3.0 (1999) Messaging (MOM), Server Portability (POA), Business Objects (JavaBeans), Java Bindings, Objects-by-value, CORBA/DCOM, IIOP Firewall, Workflow, Domain-level Frameworks, Mobile Agents etc. * Adapted from Orafali and Harkey’s Book

ORB services Multiple language bindings - C, C++, Java, Smalltalk, Ada, Cobol Interface Repository stores the interface specifications of all services Transparency of object location

ORB services - Contd Object-oriented - provides for encapsulation, polymorphism and inheritance Can provide security for content and context-sensitive transactions

Client/Server Request Using the ORB 2.0
Object Implementations Client Implementation Repository Dyamic Invoc- ation Client IDL Stubs ORB Inter- face Static Skeletons Dynamic Object Adapter Interface Repository Object Request Broker

Client IDL Stubs Provides local proxies for remote services
Provides for marshaling of parameters into standard formats

Dynamic Invocation Interface
Late binding of method calls Run time discovery of service IDL interface

Interface Repository Runtime database of interfaces of all registered objects Supports the query of, registration of, and update of interfaces of objects mediated by the ORB Repository IDs - uniquely and globally identify interface repository across multivendor ORBs

Server IDL Stubs Also called skeletons
provide static interfaces to each service provided both client side and server side stubs are generated using IDL compilers

Dynamic Skeleton Interface (DSI)
to implement dynamic services or dynamically changing services run-time binding of new services using scripting languages and interpreters to redirect messages to objects for which a compiled idl-interface is not known

Object Adapter responsible for managing a collection of server objects
instantiates server objects when needed and provides them with object IDs called object references registers the classes and instances in the Implementation Repository All CORBA implementations must support a Basic Object Adapter

Implementation Repository
Keeps track of classes and run-time instances of server objects supported by the ORB Allows for mechanisms to support audit trails, trace information and security related infrastructure

Basic Object Adapter Must provide for the following functionality:
An implementation repository Manage instantiation and destruction of objects Manage object references and invoking methods Mechanism to authenticate clients

CORBA 2.0 Interoperability Standard
CORBA 1.1 allowed for portability CORBA 2.0 specifies the Internet Inter-ORB Protocol (IIOP) Public domain IIOPs are now available (from Sun for instance) Every CORBA-compliant ORB must implement IIOP or provide a half bridge to it

ORB-to-ORB Bridging Server Client DII DSI ORB From Vendor A
ORB From Vendor B

IDL and Interface Repository
Interface Definition Language (IDL): fundamental mechanism supported by all ORBs to separate interfaces and implementations Interface Repository is a queriable and updateable runtime information store of interface specification generated from IDL

IDL users Client programmers who want to access the services provided by an object - they need the IDL to determine how to call the services Server programmers who want to extend the service provided - they need the IDL to subclass and provide additional capabilities

IDL Structure Module: groups a collection of class definitions (interfaces) Interface: defines a class; attributes and exceptions Operation: defines a method; the arguments; argument types; in, out or in-out; exceptions; optional context description Data types: basic (short , float, char...) and constructed

IDL Example : type codes
typedef string Date_T; typedef string PersonID_T; typedef string Address_T; typedef char MaritalStatus_T; typedef char Sex_T; typedef long PolicyID_T;

IDL Example: Interfaces
interface FamilyMember; interface Employer; interface InsurancePolicy; interface InsuranceCompany;

IDL Example: Interface definition
interface Demographics: PRObject { readonly attribute PersonID_T personID; attribute string lastName; attribute string firstName; attribute long SSN; attribute Date_T DOB; attribute string birthPlace; attribute MaritalStatus_T maritalStatus; readonly attribute sequence<InsurancePolicy> insurancePolicies; readonly attribute sequence<FamilyMember> familyMembers; readonly attribute sequence<Employer> employers; };

IDL Example: Interface definition
interface InsurancePolicy: PRObject { readonly attribute PolicyID_T policyID; attribute string insuranceType; attribute string carrierProgram; attribute long groupNo; attribute long payorNo; attribute long controlNo; attribute string relationshipToPolicyHolder; readonly attribute Demographics policyHolder; readonly attribute InsuranceCompany insuranceCompany; };

Type Codes represent IDL-defined data types
provide for self-describing data Used by: DII, IIOP, Interface Repositories and any data type

Interface Repository - where used
Run-time type checking on method invocation parameters Connecting multi-vendor ORBs Support dynamic discovery of object interfaces and support for DII Provide for self-describing objects

CORBA 3.0 Trader Service POA Workflow Business Objects Facility
CORBA Component Model CORBA Scripting Language IIOP over firewall Java to IDL mapping Real-time CORBA Asynchronous Messaging Domain-specific frameworks Manufacturing, Transportation, Finance, Healthcare, Telecom, Electronic Commerce and more! See: for a press release on CORBA 3.0 by major vendors for an early 1999 commercial availability.

Trader Service Naming Service is like white pages
Trader is like yellow pages Trader ORB ORB Client “Importer” Server “Exporter” ORB Import Service Export Service Invoke Service

Portable Object Adapter (POA)
To quote Orafali & Harkey: “The POA is simply the BOA done right.” Similar to BOA, POA supports management of: separate process for each method separate process for each object shared process for multiple objects In addition, POA supports the notions of: servants and servant managers (instance managers) transient and persistent servants and instances Essentially addresses scalability and flexibility in server implementations

CORBA/Java Security Reference: Andreas Vogel & Keith Duddy, “Java Programming With CORBA,” Second Edition, John Wiley & Sons, 1998.

Applet Security Issues
Java Virtual Machine for applet execution are restricted in their ability to access local resources - referred to as “applet sandboxing.” Applets are only allowed to communicate with the server they are downloaded from CORBA clients can in principle communicate with any object for which there is an IOR reference. Two approaches have been identified to address applet security restrictions.

Working with Applet Security restrictions
Establish an IIOP gateway which serves as a proxy to the real server Use signed applets Browser Client Applet WWW Server IIOP Gateway Download Applet Server Implementation IIOP IIOP

Firewalls Firewalls restrict and filter network traffic
In a client-server environment, in the general case, there may be a client-side and a server-side firewall involved. Server side Client side

Types of firewalls Origin/Destination Filtering - router-based
filtering based on IP address of target and specific port numbers on that address filtering based on IP addresses of specific set of source machines Gateway firewall A machine with dual network cards - one connects to Internet and the other to Intranet. Only way for packet traffic to bridge the two networks is a protocol-specific bridge that forwards packets to the appropriate applications

Client-side firewalls
Gatekeeper Server Implementation Browser Client Applet HTTP IIOP Client-side Firewall HTTP Tunneling With Gatekeeper Proxy Browser Client-side Firewall Server Implementation Client Applet Port 80 HTTP Gatekeeper Proxy IIOP IIOP Gatekeeper with dual functionality

IIOP over Secure Socket Layer (SSL)
SSL is layered on top of TCP/IP It is the basis for secure electronic commerce over the Web - using Secure HTTP (SHTTP) SSL authentication is based on public key cryptography Authentication is based on digitally signed certificates.

Overview of CORBA Security Service

Goals of a security service
Confidentiality Integrity Accountability Availability

Sample threats to security
An authorized user accessing information they should not A user pretending to be someone else to access information Eavesdropping on others communication Modifying, deleting or maliciously tampering with information

Features of the Security Service
Identification and authentication Authorization and access control Auditing Communications security Non-repudiation Administration of security policy

Security Conformance Levels
Security Level 1 - targeted at securing security-unaware applications. Allows for client authentication, secure communications and method-level access control based on security policies. Security Level 2 - supports all of the above and supports integrity, trust and auditing. Targets security-aware application which may enforce their own policies.

CORBA World Players Netscape (bundle CORBA-clients with their web browser) Oracle has adopted CORBA/Java as their base platform JavaSoft - is layering RMI on top of CORBA IIOP. Sun has also adopted Visibroker as its ORB technology. IBM/Lotus: Adopted base infrastructure is CORBA/Java.

CORBA World Players - Others
Iona Visigenic/Inprise HP Tandem Novell I-Kinetics Expersoft BEA Symantec ParcPlace Penumra Inprise Sybase NetDynamics Vignette Allaire and 800 more!

Distributed Component Object Model (DCOM)*
Microsoft Version of Distributed Object Computing * Material for this tutorial is based on Orafali and Harkey book on Client Server Programming with Java and CORBA and Richard Grimes book on DCOM Programming.

DCOM and CORBA Like CORBA, DCOM adheres to separation of interface from implementation using Microsoft Interface Definition Language (IDL) based on DCE. Not compatible with CORBA IDL. Also provides an additional IDL for OLE automation called Object Definition Language (ODL).

DCOM Unlike CORBA, DCOM does not support multiple inheritance. It supports multiple interfaces and compositional architectures. Like CORBA, DCOM provides both static and dynamic bindings for methods Type Library in DCOM corresponds to Interface Repository in CORBA. DCOM registry corresponds to Implementation Repository.

DCOM Interface DCOM Interface is collection of method calls.
DCOM interface is language neutral Microsoft provides language bindings for Visual C++, Visual Basic, and Visual J++. Inprise ’s Delphi products provide bindings for Pascal.

DCOM Interface To access DCOM interface, clients use pointer to an array of function pointers - called virtual table or vtable. Object User Pointer Internal Data Interface Function Table Implementation of Member Functions Pointers to DCOM Object

DCOM Conventions Plug-in-jack pictorial representation of components.
Interface by convention is named with a letter beginning with capital “I” - e.g. IDispatch At run time, interfaces are known by their Interface Identifier (IID) IID is globally unique (GIID) bit IDs.

DCOM Object Also known as ActiveX object.
DCOM object implements all the interfaces the object supports. Identified by a unique 128-bit Class ID (CLSID) Implements IUnknown interface IUnknown Interface A DCOM Object Interface B Interface C

DCOM Server DCOM servers is a DLL or EXE or a Java Class.
Factory DCOM Object IClassFactory or IClassFactory2 Interfaces IUnknown DCOM servers is a DLL or EXE or a Java Class. Server must provide a class factory for instantiating new objects IClassFactory2 interface needs to be supported if object is instantiated only if a valid license file is present

DCOM Local/Remote Transparency
In-process servers: server DLLs that can be loaded in the same process as the client. Local servers: clients use DCOM’s Lightweight RPC (LRPC) to communicate with server running on a different process space in the same machine. Remote servers: clients use DCE RPC-like mechanisms to make method invocation.

DCOM IUnknown Interface
IUnknown Interface consists of: QueryInterface - for supporting interface negotiations AddRef - to support garbage collection Release - to support life cycle management

DCOM’s Dynamic Invocation Facilities
Create Object OLE Automation Controller OLE Automation Server Get Object Get/Set Properties Invoke Methods DCOM Services MIDL precompiler ITypeLib ODL Spec

Writing a Java Client/Server Application in DCOM
1. Create DCOM IDL 2. Generate GUIDs 3. MIDL Summary.txt 4. JavaTLB Interface Class Proxy Interface 5. Implement Server 8. Implement Client 9. jvc 6. jvc 10. JavaReg 7. JavaReg 11. jview Server Client

DCOM Conclusions DCOM is maturing rapidly
Java support is there, although it is for Microsoft version of Java Biggest differences with CORBA Support limited to Wintel platforms Range of services available limited (CORBA has from Workflow to security to vertical domain standardization efforts Biggest drivers Freely available with Windows NT MTS and MSMQ and other internet Microsoft technologies

Introduction to Programming in Java

Why Java Java is a simple, efficient, secure, portable high-performance programming language. It is similar to C++, easy to learn. It has no pointer arithmetic, no need to free memory which is a serious problem in C/C++. Very compact Runtime.

A Small Java Program class helloworld {
public static void main(String args[ ]) { System.out.println(“Hello World!”); } 5

Compilation Java files are created with extension .java.
java files are compiled using javac (the java compiler) which produces a filename with a .class extension. The .class file contains java bytecodes There are no header files in java. 8

Primitive Types boolean, byte, char, short, int, long, float and double Arrays and Strings are objects in Java Due to garbage collection, no need to free memory which eliminates the errors due to memory leaks etc.

Executing Java Java applications can be executed by the java runtime. i.e an application with a .class file can be run by typing “java <filename.class>“ Applets can be executed by embedding the class in an HTML file with the <applet code = <“classname”><param > </applet> tag. 9

Example Type Declarations
byte intvar; short noofChildren; long WorldPop; float pi; char c; boolean Day;

Declaring Arrays int i[]; //one dimensional array
char ca[][]; //two dimensional array float[] f;// optional placement of square brackets

Array Allocation use the new operator to instantiate the array
i = new i(10);

Control Flow If (expr) statement else statement
for (expr;expr;expr) statement while (expr) statement do statement while (expr); switch (expr) { ... } 11

If Statement if (a < b) { a=b;} else {b = a: }

for Statement a[] = new int[10]; for( int i =0; i< 10; i++) { }
a[i] = 0; }

Classes Single Implementation Inheritance
Multiple Interface Inheritance Runtime Type information available All methods are virtual or Static 12

Class Example Class Computer { void pc() {
System.out.println(“ Iam a PC”) } int processor_speed() { return 100; 13

Class Example (Contd) Class Dec_alpha extends Computer {
int processor_speed() { return 200; } 14

Class Example (Contd) Computer c = new Computer();
Dec_alpha d = new Dec_alpha(); c.pc(); d.pc(); int s1 = c.processor_speed(); int s2 = d.processor_speed(); 15

Interfaces Define an interface that a class must implement.
Interfaces support multiple inheritance, since a class can implement multiple interfaces Java interfaces are similar to IDL interfaces . 16

Interface Example interface Automobile{ void auto_type(); }
Class myclass implements Automobile{ void auto_type() { System.out.println( “ Truck”); 17

Access Modifiers public -- accessible to everyone
protected-- accessible only to its subclasses private -- accessible only to the class Default is access by any class in the same package. 18

Exceptions Exceptions similar to C++ try { int val = sum * count;
if (val > MAXINT) { throw new valTooLargeException; } return val; 19

Exceptions (Contd) catch ( valTooLargeException e) {
System.out.println (“ divide by 0”); return -1; } 20

Multithreading Supports high-performance by preemptive multithreading.
No explicit locking is necessary to ensure mutual exclusion. Synchronized methods automatically ensure mutual exclusion. 21

Native Methods Java allows C/C++ code to be embedded.
Shared libraries can be dynamically loaded . 22

Packages A package is a collection of classes and or interfaces.
A particular package is imported using the import statement. 23

Libraries java.lang contains language types, Threads, Exceptions etc
java.util contains Hash Tables, Vectors, Cache etc java.io contains input/output classes java.awt contains an abstract windowing toolkit for writing user-interfaces and such. java.network contains sockets etc. 24

Recent Java APIs Java Beans is a Component Architecture for Java. It provides an API for creating and assembling java components. JavaBeans is a component model similar to OLE/COM, OpenDoc and LiveConnect. Java Beans will also interoperate with these existing component models

JavaBeans (contd) JavaBeans component model services include
Runtime component publishing and Discovery Event handling persistence Layout Application Builder Support

JDBC (Database Connectivity)
JDBC is a “call level “ SQL interface from Java. This facilitates the execution of SQL statements and return the results. JDBC is an interface level specification. JDBC API is implemented on top of existing SQL level API -- ODBC.

JDBC (Contd) The most important JDBC interfaces are
java.sql.Environment provides support for creating new database connections java.sql.Connection to connect to a particular database java.sql.Statement for executing a SQL statement on a given Connection java.sql.ResultSet to access the resultset for a given SQL statement.

JDBC (Contd.) Furthermore java.sql.Statement has two additional interfaces java.sql.PreparedStatement for executing a pre-compiled SQL statement java.sql.CallableStatement for executing a database stored procedure

JDBC (Contd) A JDBC-ODBC Bridge driver currently sits between the ODBC Drivers (provided by database vendors) and the JDBC API.

Java Security API Provides a security framework for application designers. Provides Authentication, Data Encoding, Data Encryption, Key Management and related security features.

Other Java APIs Java Telephony API Java Wallet Java Server API

Remote Method Invocation
Java facilitates distributed computation through its RMI mechanism. Using RMI it is possible to invoke methods on remote objects. RMI supports object references within a Java VM and across multiple Java VMs. It includes rmigen(similar to rpcgen) which generates the Java as well as Transport classes

Bytecodes The bytecodes consituite the instruction set of the Java Virtual Machine (JVM) which implements the java runtime. It is Architecture neutral, easy to interpret and generate. Register based 39

Security Byte codes are verified by a bytecode verifier.
classes can have digital signatures which can be verified Strongly typed. Null pointer checking Array bounds checking 40

Performance Interpreted code 15--20 times slower than compiled C.
By using Just-in-Time (JIT) compiler, the performance is about the same as C. Small amount of extra overhead for null pointer and array bounds checking. 41

JavaAWT Java provides a package called the Abstract Windowing Toolkit (AWT) for performing windowing and Graphical functions. It is a platform independent Graphical User Interface (GUI) toolkit.

Java AWT It is abstract because it provides an interface between the Java Language and platform specific windowing systems such as Motif, Win32, and others.

Structure of AWT Component Label Button Container Canvas List Panel
Window Checkbox ScrollBar Applet Frame Choice TextComp Dialog

Containers Containers are used to group related components.
The components are laid out inside a container using a layout manager.

LayoutManagers LayoutManager is an abstract class, hence there one can implement their own LayoutManager. BorderLayout, CardLayout, GridLayout, FlowLayout, GridBagLayout are some of the managers that come with the implementation.

Events AWT generates Event Objects form these low-level events.
When a user interacts with a GUI, either through a mouse, a keyboard, audio or a video device, events are generated by the hardware and the Operating System.

Event Delegation Event Sources “fire “ Event Objects.
EventListeners listen to the events.

Event Delegation Events Event Source Event Listener

this and super In object-oriented programming, this is a reference to the object itself. In otherwords the class refers to itself using the this refernce. (similar to this in C++ and self in smalltalk) super refers to the superclass of the current class.

JavaBeans 1

JavaBeans JavaBeans is a software Component model for Java.
Facilitate third party ISVs to create and Ship Java Components that can be composed together by end -users (VB model) 3

JavaBeans JavaBeans provides a platform independent component architecture. Will bridge to ActiveX, OpenDoc and LiveConnect.

JavaBean A JavaBean is a Reusable Software Component that can be manipulated visually in a builder Tool.

Characteristics of a Bean
Support Introspection Support Customization Support Events using simple communication metaphors Support for properties Support for persistence through Java Serialization.

Bean Three important features of a Bean are
the set of properties it exposes the set of methods available externally the set of events it fires.

Events AWT generates Event Objects form these low-level events.
When a user interacts with a GUI, either through a mouse, a keyboard, audio or a video device, events are generated by the hardware and the Operating System.

Distributed Beans Database Server JDBC CORBA SERVER IIOP RMI JAVA

JAR Java Beans are packaged as JAR (Java Archive). (Beans come in a JAR :-)

Pragmatics How does one create a Bean??

Creating Beans Write the component in Java using the JDK 1.1 Event model (Event Delegation model) and implement the appropriate Listeners and add the listeners to the sources. Creating a BeanInfo class is highly recommended. Use Design Patterns for Creating the Java Beans

Design Patterns In very simplistic terms, design patterns are naming conventions. For example, if there is a property named Label, you would have public String getLabel() { } public void setLabel(String labelname) { }

Design Patterns Boolean Properties public boolean isRed() { }
public void setRed( Color red) { }

Design Patterns EventListeners
public void add<ListenerType> (<ListenerType> listener) public void remove<ListenerType> (<ListenerType> listener)

Example addSriniEventListener(SriniEventListener srevt)
removeSriniEventListener(SriniEventListener srevt)

Bean Analysis Introspection Java beans Bean Boxes Design Patterns
Reflection

Introspection Discovers Events, Properties and Methods when the Bean Designer provides a BeanInfo Class

Reflection Reads Events, Properties and Methods using Design Patterns

JAR Files is similar to Zip Archives and may optionally have a MANIFEST file with information describing the contents of the JAR file. JAR files are used to collect class files, serialized objects, images help files and similar resource files.

MANIFEST FILES A JAR file that wants to advertise its contents should have a MANIFESTS file. The MANIFEST file will indicate which of the potential beans in the JAR archive are actual beans. If there is no MANIFEST every potential class is regarded as a bean.

Authentication JAR files can be signed to provide authentication.

Lotus InfoBus

What is Infobus Component Architectures such as JavaBeans provide mechanisms to build reusable software components. But Applications consist of multiple components that need to communicate

Infobus Communication also implies data exchange and information sharing. The data exchange and information sharing can either be done in Java itself or by using Scripting languages such as Tcl/Tk, PERL and others

The Problem ... The problem with scripting or using the programming language itself may result in ad hoc solutions.

What is needed for Component Communication...
A standard for discovering the data to be exchanged. A standard for accessing and representing data. Preferably a dynamic mechanism with possible run-time discovery

Infobus Infobus provides mechanisms for discovery and data access amongst Java components. It works with applets, applications, JavaBeans and other Java Components

What Does Infobus Provide??
Provides standard interfaces to access internal data structures. Ability to provide data to other applications. It provides dynamic change notification

Infobus Standard It is an open, vendor independent, free standard.

Reduces Complexity The infobus provides a mechanism for inter-component communication while hiding the complexity of low-level issues such as synchronization Synchronization based on Rendezvous

Producer Infobus Consumers

Change Notification Producers and Consumers notify changes performed by each other to the shared data. An Event based mechanism. Supports security and access control

More Information Can be found including specs and such at

Java Blend

What is Java Blend Java Blend Integrates Objects in the Java Programming language with Enterprise Objects. Provides a single consistent, coherent object model for enterprise based on the Java object.

Java Blend Jointly developed by JavaSoft and Baan.
Currently the programmer must explicitly convert to and from Java objects and database objects. Current applications are split into Java part and SQL part and both interacting through JDBC or some similar mechanism.

Object-Relational Mapping
Currently done by the programmer. Decomposition of Objects into many tables or build objects from many tables. Mappings between foreign keys and Object references Mappings between field types and SQL types

Object Relational Mapping
Map and or Infer Inheritance Relationships from Foreign keys Perform Transactions and process the results of transactions.

Java Blend Java Blend provides automatic mapping between Java Objects and backend relational database tables. The programmer only deals with Java Objects and is unaware of the SQL. SQL translations, Database representations (relational) are transparent to the programmer.

Advantages Easy access to enterprise relational data from Java Programming Language. No need to know, SQL, DDL and other relational database specific ideas. Significant reduction in application development time.

Java Blend Environment
development environment supports automatic object<--> Relational Mapping. Runtime environment supports Transaction Management Caching Query Processing

Development Process A mapping tool is used to map business objects written in Java to database schema. Queries can be written in OQL (ODMG compliant)

Enterprise Application
Persistent Objects Java Blend Runtime JDBC JVM

Java Blend Runtime Architecture
Transaction Manager Run Time Cache Query Engine

Other Advantages Multiple threads for multiple user transactions
Multiple simultaneous transactions per application Upon commit stores objects in the database Rollback mechanisms

Performance Increases performance by optimistic concurrency control(i.e., does not hold read and write locks on server) Runtime caching Support for stored procedures

EJB and Java Blend Java Blend works with EJB APIs Extremely scalable.

Enterprise Java Beans

What is EJB It is a distributed Software Component Architecture.
It is a Framework for Creating Middleware. EJB is part of the Enterprise Java API

EJB It is a Server side Component model It focuses on Business Logic.

ENTERPRISE JAVABEANS COMPONENTS
HTML JavaBeans Servlets IIOP RMI and other Protocols ENTERPRISE JAVABEANS COMPONENTS Server Platform J T S J M A P I J N D I J I D L J M S J D B C

EJB server E EJB Client EJB Container EJB

Web Server database EJB Container Client Servlet Application Server

EJB Architecture EJB architecture consists of EJB Servers
EJB Containers EJB Clients EJB Auxiliary Systems such as JNDI, JTS and others. 8

The Various Players EJB Providers EJB Server Providers
Provide Enterprise Java Beans (Components) EJB Server Providers Creates and sells EJB servers EJB Container Providers sell EJB containers Usually the server provider will also provide containers 9

The Various Players EJB Application Assemblers
Will enable application building using EJB components, servers and Containers. 10

EJB Servers EJB Servers are similar to CORBA ORBs
It Provides Naming(JNDI) and Transaction Services (JTS) Makes containers visible to clients

EJB Containers Encapsulate the Bean
Client accesses Beans’ methods through the container methods Container methods map to Bean methods Client only knows about container methods.

EJB Clients First discover the services (ala CORBA ) using mechanisms such as JNI Request Bean Services through Container Services.

Types of Enterprise Java Beans
Usually categorized as Session Beans or Entity Beans

Session EJB Is associated with a Single Client.
It is created and destroyed by a client

Entity EJB Are Shared by multiple clients Persistence is supported.

Structure of an EJB Client
First Locate a EJB container using a directory service Allocate a bean Use the bean services Dispose the bean.

EJB Support IBM Oracle Lotus Novell Iona Netscape Inprise
and many many others

Prof. V. “Juggy” Jagannathan

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Prof. V. “Juggy” Jagannathan

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