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JavaBeans Components
To understand JavaBeans…
 Proficient experience with the Java language
required
 Knowledge of classes and interfaces
 Object-Oriented development and design
 Simple Java GUI application programming
using AWT
 Exposure to Java’s Delegation Event-Handling
Model
JavaBeans Overview
 Software Components
 JavaBeans Definition
 The JavaBeans API
 Applying JavaBeans
 The Basic Structure of a Bean
Software Components
 Discrete, Reusable Software standard
 Microsoft’s ActiveX
 Distributed Network Environment
 Cross-platform
 Must be controlled dynamically
 Assembled to form applications
 Interoperablility standards
The Component Model
 Introspection - Discovery and Registration
 Event Handling
 Persistence
 Visual Presentation - Layout
 Application Builder Support
Introspection
 Discovery of Component at Run Time
 Late Binding
 Expose Component Functionality
 Component is Isolated, yet Usable
Event Handling
 Alert to Internal Change
 Component Interactivity
 Listeners
Persistence
 Saving State
 Storage and Retrieval
 Uniform Persistence Mechanism needed
Visual Presentation - Layout
 Dynamic Property Control
 Physical Layout
 Component Interaction and Spatial
Requirement
 Container/Component Behavior
Application Builder Support
 Graphical application builders
 Toolboxes and Palettes
 Editing Properties
 Components must Expose properties and
behaviors
JavaBean Definition
 What is a Bean?
 The JavaBeans specification states:
A JavaBean is a reusable software
component that can be manipulated visually
in a builder tool.
JavaBeans Benefits and
Features
 Simple and Compact
 Portable
 Leverage Strengths of Java Platform
 Application Builder Support
 Flexible Build-Time Component Editors
 Distributed Computing Support
JavaBeans and Java
 Java: “Write once, Run Anywhere”
 JavaBeans mission statement: “….Reuse
Everywhere”
 Java provides no component model
 JavaBeans specifies framework for reusability
and interoperability for components
 Java integration requires code-level knowledge
 JavaBeans integration requires visual editor
JavaBeans API
 Property Management
 Event Handling
 Introspection
 Persistence
 Application Builder Support
 Customization
 Multithreading
Property Management
 Accessor Methods
 Indexed Properties
 Bound Properties
 Constrained Properties
Event Handling
 Event Sources
 Unicast
 Multicast
 Event Listeners
 Event Objects
 Event Adapters
Introspection
 Reflection
 Design Patterns
 Explicit Bean Information
 Introspector
Persistence
 Storage and Retrieval
 Java Object Serialization
 Bean controlled persistence
Application Builder Support
 Edit and Manipulate Beans
 Bundled with Bean Separately
 Property Sheets
 Property Editors
 Customizers
Multithreading
 Relies on conventional Java Programming
techniques
 synchronized keyword
 Make sure Beans are thread-safe
Where and How Beans are
Used
 Web Pages
 Liven up static HTML
 Interactivity
 Applications
 Application Builder Tool
 Handwritten Code
 Bridge Technology
Structure of a JavaBean
 Data
 Methods
 Events
JavaBean
Data
Methods
Events
JavaBeans and the Interface
JavaBean
Interface A
Data
Public
Methods
Interface B
What Constitutes a Bean?
 Class must be instantiable
 Class must have a default constructor (not
officially required by spec, but by most builder
tools)
 Class must be serializable
 Implement Serializable, Externalizable
 Class must follow JavaBeans naming
conventions (sometimes called design patterns)
 Class must use delegation event model
Constructing a Bean
 “Must be instantiable” requirement
 Not abstract
 Not an interface
 “Default constructor” requirement
 Application builder tools
 Persistence
Serialization
 Representation as a series of bytes
 Storage to non-volatile location
 Implement Serializable Interface
 Implement Externalizable Interface
JavaBeans Design
Patterns
 Naming conventions for automatic
Introspection
 Example: Property named Height
public int getHeight();
public void setHeight(int h);
 Patterns for Event Registration
Delegation Event Model
 Introduced in Java 1.1 AWT
 Most Java AWT Components are Beans
 Simple
 Graphical
 Reusable
 JFC Swing Components are JavaBean
compliant
A Simple Bean
public class FirstBean implements java.io.Serializable
{
protected int theValue;
public FirstBean()
{
}
public void setMyValue( int n )
{
theValue = n;
}
public int getMyValue()
{
return theValue;
}
}
Visual Development
Environments
 Developer can focus on Business Application
 Connect Components Visually
 Code-Generation Engine
 Stability
 Ease of Generation
 Knowledge of Underlying Language Helpful
Visual Programming
 NetBeans
 JBuilder
 VisualAge for Java
 Eclipse
 JDeveloper
Security and JavaBeans
 Same security model as Java
 Beans are treated like applets
 Untrusted applet -> Untrusted Bean
 Trusted applet -> Trusted Bean
 Program for Untrusted Environments
Summary
 JavaBeans satisfies the requirements of a
discrete, reusable component model
 Visual and Non-Visual JavaBeans can be
developed and used in diverse development
environments
 Java Classes can become JavaBeans by
adhering to some minimum standards
 Java’s Security Model transfers directly to
JavaBeans