Introducing JavaBeans Identify the features of a JavaBean Create and add a bean to an application Manipulate bean properties using accessor and mutator

Introducing JavaBeans

Identify the features of a JavaBean

Create and add a bean to an application

Manipulate bean properties using accessor and mutator methods


Getting Started

Object

Is a runtime instance of a class

Software components:

Are reusable objects

Pluggable into any software application from any vendor

Examples - Spell-check utility, find and replace utility

JavaBeans

Are reusable and self-contained software components created using Java


Getting Started (Contd.)

JavaBeans – Development Phases:

Construction phase

Involves creation of a JavaBean and its user interface

Build phase

Involves placing the JavaBean into the target container

Execution Phase

Involves execution of the the container application in which the JavaBean is placed



Construction Phase involves creation of the following:

.class files

.mft file

.jar file

Elements of a JavaBean

Properties

Are the private member data contained in a JavaBean



Methods

Are the public member functions used to:

Manipulate bean properties

Expose bean functionality

Events

Are used to communicate changes in bean property values or changes in its state to other beans



The JavaBean Component Specification

Customization

Is the ability of a JavaBean to allow its properties to be changed

Persistence

Is the ability of a bean to save its state

Communication

Is the ability of a bean to inform changes in its attributes to other beans and to the container application



Introspection

Is the ability of a bean to be queried by external applications

Types of JavaBeans

Bean type Description

Control beans Are used to create graphical user interface components

Container beans Are used to hold other Java beans

Invisible Runtime beans

Are used to create components that perform a specific task in the background


Building an Application Using Existing Beans

To identify the software to be used to build and test the components and familiarize yourself with the software by creating an application similar to the one shown below:


Task List

Identify the software to be used to create the application

Identify the beans to be added to the BeanBox window

Add the beans to the BeanBox window

Associate events with the beans

Save and execute the application


Task 1: Identify the software to be used to create the application

Beans Development Kit

Is used as a tool to:

Build bean based applications

Test bean functionality

Contains several example beans

To start BDK

Execute the run.bat file from the command prompt.


Task 1: Identify the software to be used to createthe application (Contd.)

The following windows appear on starting BDK:

Window name Description

ToolBox Contains a list of sample beans supplied with BDK

BeanBox Acts as a form or a container for the beans that make up an application

Properties Displays the properties of the bean currently selected in the BeanBox window

Method Tracer Keeps track of method invocations across beans


Task 1: Identify the software to be used to createthe application (Contd.)

Result:

BDK will be used to test the beans


Task 2: Identify the beans to be added to the BeanBox

Result:

The application uses two beans that are supplied with the BDK software

Juggler bean

Two instances of the OurButton bean


Task 3: Add the beans to the BeanBox window

Task 4: Associate events with the beans

Task 5: Save and execute the application


The Juggler bean is an example of a ____ type of bean.

Which window of BDK is used to change the background color of a bean?

Which window of BDK is used to build a bean application?


Creating Beans and Building Applications

A customer can access his account only after entering the pin number. You need to construct and test the component for the ATM application. The specifications for the component are given below:

It should display the logo of the bank as an animation. You might plug in the login component into the ATM application of any bank. So, the logo should be modifiable according to the ATM application of a particular bank into which the component is plugged in

It should accept the pin number of a customer


Creating Beans and Building Applications (Contd.)

It should contain a method that checks if the pin number entered by a customer is present in the Earnest Bank database. This feature is specific to the Earnest Bank ATM application

After you create the login component, build a sample application and test the functionality of the component. The user interface of the sample login application should look similar to the one shown:


Creating Beans and Building Applications (Contd.)

The user interface of the sample login application should look similar to the one shown:


Task List

Identify the controls to be used

Identify the properties to be exposed by the bean

Identify the methods to be supported by the bean

Create the User Interface of the bean

Add code to expose the bean properties

Code the methods to be supported by the bean

Save and compile the program

Create the .mft file

Create the .jar file


Task List

Load the bean into BDK

Build an application using the bean

Execute the application and verify the functionality of the bean


Task 1: Identify the controls to be used

Result:

The controls to be used are:

A label and text field control for accepting the pin number

A label control for displaying the bank logo


Task 2: Identify the properties to be exposed by the bean

Result:

The logo property should be exposed


Task 3: Identify the methods to be supported bythe bean

Result:

A method named validatePinNo()needs to be coded in the component

Task 4: Create the User Interface of the bean


Task 5: Add code to expose the bean properties

Properties of a Bean:

Are the characteristics of a bean

Are used to change the appearance and behavior of a bean

Example:

Properties that have to be exposed by a spell check utility can be coded as:

private String language;

private String dictionaryPath;


Task 5: Add code to expose the bean properties(Contd.)

Accessor and Mutator Methods

Are used to make the properties of a bean available to the outside world

Are used to ensure the integrity of bean data

get method

Allows the current value of a property to be read

set method

Allows the current value of the property to be changed


Task 6: Code the methods to be supported by the bean

Task 7: Save and compile the program


Task 8: Create the .mft file

The Manifest file:

Is used by the target application to recognize a JavaBean

Is saved with a .mft extension

Contains a list of all class files that make up a JavaBean


Task 9: Create the .jar file

The JAR file:

Is similar to a zip file

Is used to package a JavaBean for distribution

Contains the manifest file and all other files such as the class files and picture files of the bean

Has a .jar extension


Task 10: Load the bean into BDK

Task 11: Build an application using the bean

Task 12: Execute the application and verify thefunctionality of the bean


Creating Beans and Building Applications(try out)

A component needs to be created that accepts the login id and password of a customer. The component should wait for 30 seconds before the user enters the login information. The code for the component is given below. You need to modify the code to do the following:

If the user does not login for the specified time, a login time out message should be displayed

The time out message to be displayed will be specified during the build phase

The component should be pluggable into the ATM application of any bank


An object is a run-time instance of a class. A component is a reusable object that can be embedded into any software application from any vendor. The SpellCheck utility is an example of a component

Beans created using Java takes advantage of all the security and platform independent features of Java

A JavaBean exists in one of the following three phases: the construction phase, the build phase, and the execution phase


As per the JavaBean Component Specification, a simple Java object must support the following five features for it to become a JavaBean:

Properties

Customization

Persistence

Communication

Introspection


You can create three types of beans:

Control beans

Container beans

Invisible run-time beans

A wide variety of application development environments such as Forte For Java, IBM Visual Age, Kawa, Beans Development Kit (BDK) and Symantec Visual Cafe are available in the market that support the creation, building, and testing of Java beans

BDK can be used as build tool to build bean applications or as a testing tool to test the beans for their intended functionality


Execute the run.bat file from the command prompt to start BDK

On starting BDK, the ToolBox palette, the BeanBox window, and the Properties window are displayed

BDK consists of several re-usable sample beans such as the Juggler bean and the OurButton bean

Properties are the characteristics of a bean and are similar to the data members of a class. By changing the properties, you can change the appearance and behavior of a bean

The get and set accessor methods are used to expose the bean properties to external applications


The manifest file contains information about a bean such as the name of the bean and the files present in the .jar file of the bean

JavaBeans are packaged and distributed as .jar files

Documents

Introducing JavaBeans Identify the features of a JavaBean Create and add a bean to an application Manipulate bean properties using accessor and mutator