Ajs 2 a

UML Diagrams And Design Patterns

Pre-assessment Questions
1. Identify the correct statement for synchronous integration.
a) Request invocation thread of the application does not block the
processing of the application
b) Supports loose coupling of applications
c) Sends message to a request invocation thread and continues
d) Supports the request/response interaction model

©NIIT Architecting J2EE Solutions Lesson 2A / Slide 1 of 51


1. Consider the statements:
Statement A: Queue-based communication involves a message sender
sending a message to a message queue that is responsible for processing the
message.
Statement B: Queue-based communication involves a message sender
sending a message to a message queue that is responsible for dispatching
the message to a receiver.
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.



• Which level of integration uses the integration frameworks and application
programming interfaces to integrate two applications?
a) Data level
b) Application interface level
c) Method level
d) User interface level



1. Being a System Analyst, you are responsible for integrating a J2EE
application with a legacy system. You need to integrate the J2EE application
and legacy system using their similar functional methods. Which option
enables you to perform the specified task?
a) User interface level integration
b) Data level integration
c) Method level integration
d) Application interface level integration
2. Which technique defines a standard architecture for connecting a J2EE
application server with different enterprise information system?
a) Java native interface
b) CORBA
c) Web services
d) J2EE Connector Architecture



Solutions to Pre-assessment Questions:

1. d. Supports the request/response interaction model
2. b. Statement A is false and statement B is true
3. b. Application interface level
4. c. Method level integration
5. d. J2EE Connector Architecture



Objectives
In this lesson, you will learn to:

• Model J2EE applications using UML diagrams
• Identify the need for design patterns
• Use creational design patterns



Modeling J2EE Applications Using UML

• Case study:
• NewTech Inc. is a retail bookstore that sells books of different categories
such as science & technology, medicine, astronomy, novels, and children
books.
• As a part of its expansion plan, NewTech Inc. wants to go online and
create an Online Bookstore System to attract customers from all over the
globe.
• Consider that NewTech Inc. names it online system as Online Bookstore
System. The Website of the Online Bookstore System should list the books
according to the categories that the books belong to.
• The users of the Website should be able to browse through a catalog of
books that is made available to them on the Website. Each book selected
by the user should be listed in the user’s shopping cart.



(Contd.)
• Case study (Contd.):
• The Website of the retail bookstore should support two kinds of users:
registered and unregistered. The Website should allow the unregistered
user to browse through the online retail bookstore and view the details of
the books.
• In addition, the unregistered users should be allowed to add books to their
shopping cart. However, only the registered users should be allowed to
make an online purchase.
• Moreover, the registered users should have a different view of the retail
bookstore, which includes informational messages customized to their
interests.
• The Website of NewTech Inc. should also sell books to its various retail
stores. The company has an enormous market following and therefore, the
Website of the company should be scalable enough to support large
number of page hits per day.



(Contd.)
• The UML Diagrams that can be used to represent the structure and design of
an enterprise application are:
• Use case diagrams
• Class diagrams
• Package diagrams
• Sequence diagrams
• Collaboration diagrams
• State diagrams
• Activity diagrams
• Component diagrams
• Deployment diagrams



(Contd.)
• Using Use Case Diagram
• Depicts the various operations that a system performs.
• Contains use cases, actors, and their relationships.
• Elements of a Use Case Diagram are:
• Use Cases: Describe the behavior of a given system in textual
format.
• Actors: Represent the coherent set of roles that the users of a given
system play while interacting with the use cases.



(Contd.)
• Using Use Case Diagram (Contd.)
• Elements of a Use Case Diagram are (Contd.):
• Relationships: Represents the interaction between the actors and the
use cases. The two types of relationships are:
• Extend: Indicates that an existing use case is extended by
additional behavior to obtain another use case.
• Include: Indicates that the functions of one use case are
included in the functions of the other.
• System boundary: Defines the limits of the given system.



(Contd.)
• Analyzing the Use Cases and Actors
• Use Case diagram for the Online Shopping System:



(Contd.)
• A use case specification document includes information, such as:
• Actors: Specifies the participants of use cases.
• Pre-conditions: Specifies the prerequisites to be met.
• Post-conditions: Specifies the actions to be performed.
• Basic flow: Lists the basic events that will occur when a use case is
executed.
• Alternative flows: Lists the subsidiary events that occurs in use case.
• Special Requirements: Specifies the success and failure scenarios of
business rules for the basic and alternative flows of events.
• Use case relationships: Specifies the relationships that exist between
the various use cases.



(Contd.)
• Using Class Diagram
• Represents the static design view of a system.
• Includes a set of classes and interfaces along with the collaborations and
relationships among the classes and interfaces.
• The three types of classes that realize the behavior specified in the use
case are:
• Boundary class: Represents the interface between the actors and the
given system.
• Control class: Represents the use case logic and coordinates with
other classes in the given system.
• Entity class: Manages the information that a given system requires to
provide a specific functionality.



(Contd.)
• Using Class Diagram (Contd.)
• Elements of a Class Diagram are:
• Class: Represents an entity of a given system that provides an
encapsulated implementation of business functionality for a given
system.
• Interface: Represents an entity of a given system that provides only
the declaration of implementing business functionality.
• Relation: Defines a logical connection between classes and interfaces
of a given system.



(Contd.)
• Using Class Diagram (Contd.)
• Class diagram for the Online Shopping System:



(Contd.)
• Using Package Diagram
• Represents the grouping of related boundary, control, and entity classes of
a given system.
• Is similar to namespaces such that you can store classes with the same
name in two different packages.
• Elements of a Package Diagram are:
• Packages: Refer to the grouping of similar elements. In J2EE
environment, you group the classes with similar function in a
package.
• Relationships: Define a logical connection between various packages
in a given system.



(Contd.)
• Using Package Diagram (Contd.)
• Package diagram for the Online Bookstore System:



(Contd.)
• Using Sequence Diagram
• Represents the interaction between the objects of a system in the form of
messages in a sequence by time.
• Depicts the dynamic behaviour of a given system.
• Elements of a Sequence Diagram are:
• Objects: Refer to an instance of a class.
• Messages: Refer to the interaction between the various objects in the
sequence diagram.



(Contd.)
• Using Sequence Diagram (Contd.)
• User login session sequence diagram for the Online BookStore System:



(Contd.)
• Using Collaboration Diagram
• Represents the interaction between objects of a system in the form of
messages.
• Elements of a Collaboration Diagram are:
• Objects: Refer to an instance of a class.
• Messages: Refer to the interaction between the various objects as
arrows in the collaboration diagram. .
• Relations: Refer to the line associated with the objects of a given
system.



(Contd.)
• Using Collaboration Diagram (Contd.)
• User login session collaboration diagram for the Online BookStore System:



(Contd.)
• Using State Diagram
• Shows how the object of a system reacts when an event occurs.
• Depicts the business flow of an object of a given system.
• Elements of a State Diagram are:
• Initial state: Refers to the first activity in a flow and is represented by
a solid circle.
• State: Refers to the state of an object at a specific instance of time.
• Transition: Refers to the transition from one state to another and is
represented by an arrow.
• Event/Action: Refers to a user- or system-generated action that
causes a transition to occur.
• Final state: Refers to the last activity in a flow and is represented by
a bull’s eye symbol.



(Contd.)
• Using State Diagram (Contd.)
• User login session state diagram for the Online BookStore System:



(Contd.)
• Using Activity Diagram
• Represents the dynamic view of a system that depicts the flow of control
of objects from one activity to another.
• Represents the business and operational workflows of a given system.
• Elements of an Activity Diagram are:
• Initial Activity: Refers to the first activity in a flow and is represented
by a solid circle.
• Activity: Refers to an action in a flow and is represented with a
rectangle with rounded corners.
• Decisions: Refers to the business logic where a decision is taken.
• Final Activity: Refers to the last activity in a flow and is represented
by a bull’s eye symbol.



(Contd.)
• Using Activity Diagram (Contd.)
• Order processing activity diagram for the Online BookStore System:



(Contd.)
• Using Component Diagram
• Represents the grouping of packages and other components of a system
along with their relationship with each other.
• Represents the implementation of a given system.
• Elements of a Component Diagram are:
• Components: Refer to the entities that interact with each other in a
given system.
• Class/Interface/Object: Represents entities of a given system that
forms a part of the component.
• Relation/Association: Defines a logical connection between various
components of a given system.



(Contd.)
• Using Component Diagram (Contd.)
• Order processing component diagram for the Online BookStore System:



(Contd.)
• Using Deployment Diagram
• Represents the configuration of run-time processing nodes and the
components that reside on the node.
• Provides a complete deployment environment for the given system, which
is easy to comprehend.
• Elements of a Deployment Diagram are:
• Nodes: Represent the elements that provide an execution
environment for the various components of a given system.
• Relation: Represents the interconnection between various nodes of a
given system.



(Contd.)
• Using Deployment Diagram (Contd.)
• The deployment diagram for the Online BookStore System:



Creating a UML Diagram
• Problem Statement
• MetalTech US Engineering Inc. has an online product information system
for its product designers. The product designers are located in different
parts of country. The products are identified as metallic and non-metallic
products. The information about a product includes attributes, such as
product_id, product_name, product_type, and product_picture. A
collection of assembled products form an assembly, which is identified by
the attributes, assembly_id, and assembly_name. In the product
information system, the part forming an assembly is known as Bill of
Material (BOM). While creating the BOM, the product designer at the
server end can add and remove the product parts from an assembly, as
the structure of assemblies change frequently. Draw the use case
diagram, class diagram, and sequence diagram for modeling the online
product information system.



Creating a UML Diagram (Contd.)

• Solution
1. Identify use cases.
2. Identify actors.
3. Draw use case diagram.
4. Draw class diagram.
5. Draw sequence diagram.



Overview of Patterns

• Patterns
• Is a proven solution to a problem in a given context.
• Is first verified several times in the real-world systems to be actually
called a pattern.
• Promotes reuse of software concepts and technologies, which make you
work faster and efficiently.



Overview of Patterns (Contd.)
• About GoF’s Design Patterns
• The four elements of GoF’s design patterns are:
• Pattern name: Identifies a pattern.
• Problem: Describes when to apply a pattern and the context in which
to apply the pattern.
• Solution: Describes a pattern as a template, which can be applied to
different contexts.
• Consequences: Describes the pros and cons in applying the pattern in
a certain context.



• About GoF’s Design Patterns (Contd.)
• The advantages of using design patterns are:
• Allows reusing the experience of predecessors.
• Communicates the knowledge gained from experience.
• Establishes common terminology for problems.
• Provides solutions to real-world problems.
• Captures knowledge and documenting best practices for a domain.
• Documents the decision along with the rationale that leads to the
solution.
• Describes the circumstances, influences, and the resolution of a
solution.
• Facilitates design modifications, documentation, and
understandability of a software system.



• Types of GoF’s Design Patterns
• The three types of design patterns are:
• Creational design patterns: Provide techniques for creating objects
• Structural design patterns: Describe the composition of objects and
their organization.
• Behavioral design patterns: Provide guidelines for enabling
communication among objects of a given system.



• Creational Design Patterns
• Supports the creation of class instances.
• Allows instances of classes to be created, without the need to identify the
class type by having the subclass of the class create the objects.
• Hides the details of the class to be instantiated from the calling class, by
using an abstract class.



Creational Design Pattern
• Abstract Factory Pattern
• Provides an interface to create families of related or dependent classes
without declaring their concrete classes.
• Consists of an abstract class along with a couple of subclasses that provide
the implementations of the abstract class.
• Allows the clients to use the classes only through their abstract classes.
• Advantages of using abstract factory pattern are:
• Isolates the implementation of concrete classes from the user.
• Enables easy exchange of families of objects.
• Ensures consistency among the families of objects.



Creational Design Pattern (Contd.)
• Builder Pattern
• Separates the construction of a complex object from its representation to
enable the same construction process to create different objects.
• Allows a client object to create a complex object by specifying only its type
and content.
• Defines an interface to create an object, but allows the subclass to decide
which class to instantiate for the creation of an object.
• Enables you to:
• Change the internal representation of an object.
• Separate the code of construction from the code of representation.
• Control the construction process.



• Builder Pattern (Contd.)
• Object diagram depicting builder pattern:



• Factory Method Pattern
• Defines an interface to create an object but allows the subclasses to
decide the class to be instantiated.
• Helps construct individual objects for a specific purpose by deferring the
instantiation to subclasses.
• Enables addition of new classes without the need to modify the code, as
the new class only needs to implement an interface.



• Factory Method Pattern (Contd.)
• Object diagram depicting factory method pattern:



• Prototype Pattern
• Provides a way to dynamically select the instantiation of an object and to
return a clone of a prototypical object.
• Is used when it is time-consuming to instantiate a highly complex class.
• The advantages of using prototype pattern are:
• Enables run-time addition or removal of objects.
• Hides the concrete product classes from the client.



• Prototype Pattern (Contd.)
• Object diagram depicting prototype pattern:



• Singleton Pattern
• Ensures that a class has only a single instance and provides a global point
of access to it.
• Ensures all the objects that use the instance of the class use the same
instance.
• Is used when exactly a single instance of a class should exist.



• Singleton Pattern (Contd.)
• The advantages of using singleton pattern are:
• Controls the access to the single instance of a class.
• Lessens the use of namespaces.
• Enables refinement of class operations and representation.
• Allows variable number of class instances to exist.
• Object diagram depicting singleton pattern:



Identifying Creational Design Patterns
• Problem Statement:
• In the online product information system of Mastery Mechanics
Engineering Inc., the product designer needs to brief the developer the
kind of patterns that he/she can implement while developing the code so
as to optimize the code. Identify the various creational patterns that can
be applied to the above case study.



Identifying Creational Design Patterns
(Contd.)
• Solution
1. Identify the Builder design pattern.
2. Identify the Factory Method design pattern.
3. Identify the Prototype pattern.
4. Identify the Singleton pattern.



Summary
In this lesson, you learned:
• The structure and design of an enterprise application can be represented by
identifying the elements and analyzing the following nine UML diagrams:
• Use case diagram: Depicts the various operations that a system
performs.
• Class diagram: Depicts the static design view of a system. It includes a
set of classes and interfaces along with the collaborations and
relationships among the classes and interfaces.
• Package diagram: Depicts the grouping of related classes and interfaces
of a given system.
• Sequence diagram: Depicts the interaction between the objects of a
system in the form of messages in a sequence by time.
• Collaboration diagram: Depicts the interaction between objects of a
system in the form of messages.
• State diagram: Depicts how the object of a system reacts when an event
occurs.


Summary (Contd.)
• Activity diagram: Depicts the dynamic view of a system, showing the
flow of control of the objects from one activity to another.
• Component diagram: Depicts the grouping of packages and other
components of a system, and their relationship with each other.
• Deployment diagram: Depicts a deployment diagram that represents
the configuration of the run-time processing nodes and the components
that reside on the node.
• Patterns are defined as proven solutions to problems in a given context.
• The important elements of the GoF’s design patterns are pattern name,
problem, solution, and consequences.
• The advantages of using the design patterns in providing solutions to the
real-world problems.
• The GoF’s design patterns are categorized into three types, based on their
purpose and scope:



Summary (Contd.)

• The GoF’s design patterns are categorized into three types, based on their
purpose and scope:
• Creational Design Patterns
• Structural Design Patterns
• Behavioral Design Patterns
• The creational design patterns provide the techniques for creating objects.
These patterns make a system independent of how the objects are created,
composed, and represented.
• The structural design patterns describe the composition and organization of
the objects.
• The behavioral design patterns provide the guidelines for enabling
communication among various objects of a given system.
• The various types of creational design patterns are abstract factory, builder,
factory method, prototype, and singleton patterns.


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