Ajs 1 b

Legacy Connectivity and Protocols

Pre-assessment Questions
1. Which statement depicts the role of an architect in the post-construction
phase?
a) Focuses on the requirements of the developer
b) Reviews the construction-level designs to analyze the problems
and requests changes
c) Enables a client to migrate the project rollout to the new system
EJB home object
d) Expands the details of the design and refines the design to
converge on the final design

©NIIT Architecting J2EE Solutions Lesson 1B / Slide 1 of 43


1. Consider the statements:
Statement A: Layering is an architectural pattern that breaks up a
complicated system into some modules.
Statement B: Layers are divided based on the functional responsibilities
of the modules.
Identify the correct option.
b) Statement A is true and statement B is false
c) Statement A is false and statement B is true
d) Both, statements A and B, are true
e) Both, statements A and B, are false



1. Consider the statements:
Statement A: Vertical scalability is achieved by adding new servers to
the existing system.
Statement B: Horizontal scalability is achieved by adding memory to the
existing server or by adding more CPUs to the server.
Identify the correct option.
a) Statement A is true and statement B is false
b) Statement A is false and statement B is true
c) Both, statements A and B, are true
d) Both, statements A and B, are false



1. Which J2EE client component makes application deployment a simple
process?
a) Application Client
b) HTML Page
c) Applet
d) Java WebStart

2. Which option is identified as a business component?
a) EJB
b) JSP
c) Servlet
d) Applet



Solutions to Pre-assessment Questions
1. c. Enables a client to migrate the project rollout to the new system
2. c. Both, statements A and B, are true
3. d. Both, statements A and B, are false
4. d. Java WebStart
5. a. EJB



Objectives

In this lesson you will learn to:

• Identify the types of legacy integration
• Examine the various approaches to legacy integration
• Implement legacy connectivity using JNI and JCA
• Identify the features of Different Protocols



Legacy Integration
• Legacy integration is referred to as the integration of J2EE components with a
legacy system.
• Legacy integration allows interconnectivity between different platforms and
programming languages.
• Synchronous Integration:
• Involves circular communication between a J2EE application and the
Enterprise Information System (EIS).
• Provides synchronous communication between a J2EE application and the
EIS, which consists of the request/response interaction model.



Legacy Integration (Contd.)
• Asynchronous Integration
• Involves message-based communication between a J2EE application and
EIS.
• A message in asynchronous communication carries information used
within a single business process of an enterprise or across the business
processes of multiple enterprises.
• The two types of asynchronous communication are:
• Queue-based communication: Involves a message queue that does
not depend on application, which is sending and receiving messages.
Queue-based communication is also known as point-to-point
messaging.
• Publish-subscribe Messaging : Involves a message board, where an
application publishes messages on a specific topic. Subscriber
applications can subscribe to a specific topic and receive all the
published messages on that topic.



Approaches to Legacy Integration
• Different approaches to perform legacy integration are:
• Data level integration
• Integrates a J2EE application with the backend data stores that are
used in an integrated application.
• Includes access to newly developed data stores produced by a legacy
system, for the specific purpose of data access.
• Can be push-based or pull-based.
• Application Interface Integration
• Uses the integration frameworks and application programming
interfaces (APIs) of integrated applications to integrate two
applications.
• Is preferable to other approaches, such as data level integration,
because it is transparent to the integrated application and preserves
data integrity of the application.



Approaches to Legacy Integration
(Contd.)
• Different approaches to perform legacy integration are (Contd.):
• Method Level Integration
• Shares business logic as a collection of methods or operations that
the integrated application can invoke.
• Is useful when each integrated application provides a similar set of
API or functional methods.
• User Interface Level Integration
• Accesses the existing applications through the user interfaces of the
applications.
• Is suitable when you do not have direct access to a database or when
the business logic is embedded in the user interface.



Legacy Connectivity
• Legacy connectivity means connecting a J2EE component with an already
existing application or a library that may have been written in languages other
than Java.
• Some techniques or architectures that provide connectivity to the legacy
applications are:
• Java native interface
• J2EE connector architecture
• Web services



Legacy Connectivity (Contd.)

• Using Java Native Interface
• Used to write the custom code that enables you to integrate new business
logic with a legacy system.
• Programmers use JNI to write Java native methods to handle the
situations when an application cannot be written entirely in Java.
• Enables Java to call native methods and also allows the native methods to
create and manipulate the Java objects.
• A native method can also update the Java objects that are passed to it or
that are created by it.



• Using Java Native Interface (Contd.)
• Legacy program using JNI



• The steps involved in writing native methods for java programs are:
• Write the Java code: Write a Java code to create a class that
declares the native method and includes a main method to call the
native method.
• Compile the Java code: Compile the created Java code using javac
command.
• Create the .h file: You use the javah command with the native
interface flag -jni to generate a header file for the native method.
• Write the native method implementation: Write the C or C++ code
to implement the native method. The name of the native function
consists of the prefix Java_, the package name, the class name,
and the name of the native method. The underscore (_) is used as
the separator between each component name.



• The steps involved in writing native methods for java programs are
(Contd.):
The syntax of the native method declaration is:
JNIEXPORT void JNICALL
Java_PackageName_ClassName_NativeMethodName(JNIEnv *, jobject)
3. Create a shared library: Create a shared library file or a dynamic
link library (DLL) file by compiling the header file and the
implementation (C or C++) file. The command to create the DLL
file is:
CL -FeTemp.dll –LD msg.c
You need to specify the name of the DLL file and the native
language file.
4. Run the program: You can now execute the java program to
perform the desired task.



• The advantage of JNI is:
• It is faster than the other legacy integration approaches.
• The disadvantages of JNI are:
• It cannot connect to all legacy system.
• The existing system needs to run in process.
• It is platform-specific.
• If you want to run the code on multiple platforms, it is difficult to
test and maintain the code.



• Using J2EE Connector Architecture
• J2EE Connector Architecture:
• Defines a standard architecture for connecting a J2EE application
server to EIS.
• Provides a Java solution to the connectivity problem between the
existing EISs and the various application servers.
• Enables Java to call native methods and also allows the native
methods to create and manipulate the Java objects.
• Enables a vendor to provide a standard resource adapter for its EIS.



• Using J2EE Connector Architecture (Contd.)
• The following figure shows the JCA architecture:



• Types of contracts in JCA are:
• System level contracts: Exist between a J2EE application server
and a resource adapter.
• Application level contracts: Exist between an application server
and a J2EE application.



• Three types of system contracts are:
• Connection Management: Describes the agreement a J2EE
container with the resource adapter regarding establishing,
pooling, and closing down connections.
• Transaction Management: Controls transactions in two different
ways by creating distributed transactions and local transactions.
• Security: Enables the application server to connect to an EIS
system via resource adapter using security properties.



• The JCA also defines a CCI for EIS access.
• CCI:
• Defines a client API that is a standard for application components.
• Enables the application components and Enterprise Application
Integration (EAI) frameworks to perform interactions across
heterogeneous EISs using a common client API.
• EAI is the process of creating an integrated framework for linking
different legacy systems, applications, and data sources across an
enterprise.



• The steps for using the CCI API and a connector resource to access a
database are:
• Create a connector module that specifies the resource adapter file.
• Create a connection pool that uses the connector module.
• Create a JNDI context for a session, where the username and
password required to access a database are specified.
• Use the lookup() method to locate the ConnectionFactory for the
resource adapter.
• Use the getConnection() ConnectionFactory method to open a
connection to the database.
• Perform the required operation on the database.
• Close the connection to the database.



• Using Web Services
• Web Services:
• Provide a distributed computing environment for using the
business services of applications.
• Use standard XML protocols and formats, which makes the Web
Services platform independent, language independent, and vendor
independent.
• Provide an approach to integrate to existing systems.
• Provide standard ways to access middle-tier and back-end
services, such as database management systems and transaction
monitors.



• Using Web Services (Contd.)
• The advantage of Web services is that any system that is Internet-
enabled can use Web services without a separate communications
infrastructure, such as Common Object Request Broker Architecture
(CORBA) or Java Message Service (JMS).
• The disadvantage of Web services is that the XML parsing overhead
may decrease the performance of the system.
• The Web service APIs, such as Java API for XML-based RPC (JAX-RPC),
Java API for XML Registries (JAXR), and SOAP (Simple Object Access
Protocol) with Attachments API for Java (SAAJ) provides a standard
Java API for connecting applications and legacy systems.



• Using Web Services (Contd.)
• The JAX APIs can be divided into two categories:
• Document-oriented: Deals with XML documents processing.
• Procedure-oriented: Deals with procedures. Web services use the
procedure-oriented APIs for connecting to legacy systems.
• The procedure-oriented APIs are:
• JAX-RPC: Sends SOAP method calls to remote sites over the
Internet and receives the response.
• SAAJ: Provides messaging in Java applications using resource
factories similar to the Java Messaging Service (JMS). Sends
SOAP messages over the Internet in a standard way.
• JAXR: Provides a standard way to access business registries
and share information.



Demonstration-Implementing Legacy
Integration Using JNI
• Problem Statement
• Homelike Hospital Ltd. research laboratories situated at US is
conducting certain experiments on creating a vaccine. For this
they require that the temperature be mentioned in Celsius. They
are doing a sampling on a base of 15,000 persons per day but
the sample data received till now has the temperature recorded
in Fahrenheit. The Smart Software Developers have earlier
developed a program for converting temperature from
Fahrenheit to Celsius but that program was created using ‘C’, for
Homelike Hospital Ltd. The software that is being used by
Homelike Hospital Ltd at present is Java. Smart Software
Developers have been assigned the responsibility of reusing that
code in the current setup.



Integration Using JNI (Contd.)
• Solution
• To solve the preceding problem, perform the following tasks:
1. Write the Java code.
2. Compile the Java code.
3. Create the .h file.
4. Write the native method implementation.
5. Create a shared library.
6. Run the program.



Integration Using Resource Adapter
• Problem Statement
• ABC Corp. deals in computer hardware products and stores
business information in EIS (PointBase Database). With the
increase in its client base, the management of ABC Corp. has
decided to implement J2EE, for providing the information of
product to its clients over the Internet. The company has
decided to use SQL Server 2000 to store the application data.
The management also wants that earlier information of their
products stored in the PointBase database, should also be
accessible through the J2EE application. The management wants
that the integration with the PointBase database should be done
using JCA resource adapters to ensure that any future change or
upgradation of its database will have minimum effect on the
application.



Integration Using Resource Adapter
(Contd.)
• Solution
• To solve the preceding problem, perform the following tasks:
1. Create JCA administered object.
2. Create a J2EE Web client.
3. Run the Application.



Overview of Protocols
• You need the protocols over which you can connect to some legacy systems.
• Some of the protocols are Hypertext Transfer Protocol (HTTP), HTTP over
secure socket layer (HTTPS), Internet Inter-ORB Protocol (IIOP), and Java
Remote Method Protocol (JRMP).
• HTTP and HTTPS are primarily intended as Web page transport, IIOP and
JRMP are transports for CORBA and RMI respectively.
• You can use IIOP as an alternative transport for RMI and it is the preferred
transport for RMI in an EJB system.



Overview of Protocols (Contd.)
• HTTP
• HyperText Transfer Protocol (HTTP):
• Is based on the request/response model.
• Specifies how messages are transmitted and formatted.
• Defines the actions, Web servers and browsers in response to
various requests from client.
• Is a connectionless and stateless protocol.
• A stateless protocol means that the information from an earlier request
or response is not available to subsequent responses.
• You can add some state between two requests to associate the content
of the two requests.
• You can add state by using cookies, URL rewriting, and HTTPS.



• HTTP (Contd.)
• Some of the request formats used by HTTP are:
• GET: Carries only a URL into the server and the server should
response with the data for the URL. The URL for a GET request is
reflected in the address bar of most browsers.
• POST: Sends information along with the URL when the client sends
a request to the server.
• HEAD: Obtains some information about a Web page without
loading the page. The HEAD method is used to determine whether
a Web page has changed from the last cached page.



• HTTP (Contd.)
• Advantages of HTTP are:
• It possesses simple request and response mechanism.
• It is allowed through firewalls.
• HTTP supports transmission of arbitrary data.
• Disadvantages of HTTP are:
• HTTP is non-transactional protocol.
• It is insecure and inefficient, as it requires too many TCP
connections.



• HTTPS
• HTTP over Secure Socket Layer (SSL) transmits data securely over a
network.
• HTTP over SSL (HTTPS) is a combination of HTTP over a Secure Socket
Layer (SSL) transport.
• HTTPS is a connection-based Web protocol that encrypts and decrypts
user page requests and also the pages returned by the Web servers.
• SSL provides encryption, authentication, and a session for maintaining
state.
• SSL uses a private key to encrypt data transferred over the SSL
connection. The level of encryption and authentication depends on the
capability of the client and the server.



• HTTPS (Contd.)
• Advantages of HTTPS are:
• It is a secure protocol.
• It is allowed through firewalls.
• It is widely supported and deployed protocol.
• Disadvantages of HTTPS are:
• It can process only 10% of the traffic HTTP can process.
• Administration overheads are high in case you are using HTTPS.



• IIOP
• Internet Inter-ORB Protocol (IIOP) enables distributed programs written
in different programming languages to communicate over the Internet.
• IIOP is developed by the Object Management Group (OMG) to
implement CORBA connectivity over a network.
• J2EE uses IIOP in two ways:
• By using the Java Interface Definition Language (Java IDL) APIs.
• By running Remote Method Invocation (RMI) over IIOP.



• IIOP (Contd.)
• The following figure shows the IIOP over the Internet:



• IIOP (Contd.)
• Advantages of IIOP are:
• It supports interoperability. For example, Java clients can call C++
servers and C client can call Java server.
• It is used in legacy integration.
• It is designed for remote object invocation.
• IIOP provides built-in support for security and transactions.
• Disadvantages of IIOP are:
• Firewalls cannot be configured with an IIOP port.
• All method invocations are remote, as a result performance is not
good.
• IIOP supports only remote references.



• JRMP
• Java Remote Method Protocol (JRMP) is a proprietary wire-level protocol
for communication using Java Remote Method Invocation (RMI)
technology.
• JRMP can:
• Invoke methods and pass arguments, return values, and
exceptions over the network.
• Handle objects and JRMP does not restrict argument and return
types to data values.
• JRMP is used to send method invocations and parameters and to return
values and exceptions from one JVM to another.



• JRMP(Contd.)
• JRMP Messages



• JRMP(Contd.)
• Advantages of JRMP are:
• It supports parameter passing by reference or by value.
• It supports distributed garbage collection.
• It provides single multiplexed connection.
• Disadvantages of JRMP are:
• Servers are bound to arbitrary ports.
• HTTP tunneling is limited.
• Performance is low because all method invocations are remote.



Summary
In this lesson, you learned:
• The legacy integration is of two types, synchronous and asynchronous.
• Synchronous integration involves synchronous communication between
a J2EE application and an Enterprise Information System (EIS).
• The synchronous communication between a J2EE application and an EIS
consists of the request/response interaction model.
• Asynchronous integration involves message-based communication
between a J2EE application and EIS.
• Two types of asynchronous communication are queue-based
communication and publish-subscribe messaging.
• There are different approaches to perform legacy integration, such as
data level integration, application interface level integration, method
level integration, and user interface level integration.
• Data level integration integrates the backend data stores, which are
used in the integrated application.



Summary(Contd.)
• Application interface level integration uses the integration frameworks and
application programming interfaces (APIs) of integrated applications to
integrate two applications.
• Method level integration shares business logic as a collection of methods or
operations that the integrated application can invoke.
• User interface level integration accesses existing applications through their
user interfaces.
• Java Native Interface (JNI) is used to write custom code that integrates new
business logic with a legacy system.
• J2EE Connector Architecture (JCA) defines a standard architecture for
connecting a J2EE application server to EIS.
• The Web service APIs, such as JAX-RPC, JAXR, and SAAJ provides a standard
Java API for connecting applications and legacy systems
• Various protocols are required to connect over legacy systems. The protocols
are HTTP, HTTPS, IIOP, and JRMP.


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