Java Beans

A property editor is a tool for customizing a particular property type. Property editors are activated in the Properties window. This window determines a property's type, searches for a relevant property editor, and displays the property's current value in a relevant way.

Write the SimpleBean code. Put it in a file named SimpleBean.java, in the directory of your choice. Here's the code:

import java.awt.Color;

import java.beans.XMLDecoder;

import javax.swing.JLabel;

import java.io.Serializable;

public class SimpleBean extends JLabel

implements Serializable {

public SimpleBean() {

setText( "Hello world!" );

setOpaque( true );

setBackground( Color.RED );

setForeground( Color.YELLOW );

setVerticalAlignment( CENTER );

setHorizontalAlignment( CENTER );

}

}

Use the Externalizable interface when you need complete control over your bean's serialization (for example, when writing and reading a specific file format).

To use the Externalizable interface you need to implement two methods: readExternal and writeExternal. Classes that implement Externalizable must have a no-argument constructor.

A bean has the property of persistence when its properties, fields, and state information are saved to and retrieved from storage. Component models provide a mechanism for persistence that enables the state of components to be stored in a non-volatile place for later retrieval.

Usually this is because of a mistake in the JAR file being loaded. In the meantime, typical errors include:

► The MANIFEST file uses classes using the wrong file separator ("/" should be used in all platforms).

► The MANIFEST file refers to classes in a package but the actual .class files are not really in that package.

A coalition of industry leaders in component development worked with JavaSoft to create the JavaBeans specification, which was released to the Internet for public comments on September 4, 1996. The "frozen" JavaBeans specification combines the work of Apple, Borland, IBM, JustSystem, Microsoft, Netscape, Rogue Wave, SunSoft and Symantec and many, many others... We're very pleased to see the tools community swiftly embracing JavaBeans by announcing support for JavaBeans in their visual application builder tools.

Java Beans are usual Java classes which adhere to certain coding conventions:

► Implements java.io.Serializable interface

► Provides no argument constructor

► Provides getter and setter methods for accessing it's properties.

JavaBeans does not add any security features to the Java platform. Rather, JavaBeans components have full access to the broad range of security features that are part of the Java platform. JavaBeans components can be used to build a range of different kinds of solutions from full-fledged Java desktop applications to web-based Applets.

The complete set of JavaBeans APIs are core to Java 2, hence any platform that is fully compatible with Java 2 implicitly supports JavaBeans. Thus, JavaBeans support will be available as soon as this platform/operating system vendor supports Java 2.

JavaBeans brings the extraordinary power of the Java platform to component development, offering the ideal environment for a developer who wants to extend the concept of reusable component development beyond one platform and one architecture to embrace every platform and every architecture in the industry.

JavaBeans is a complete component model. It supports the standard component architecture features of properties, events, methods, and persistence. In addition, JavaBeans provides support for introspection (to allow automatic analysis of a JavaBeanscomponent) and customization (to make it easy to configure a JavaBeans component).

A reference to an entity that is substituted for the reference when the XML document is parsed. It can reference a predefined entity such as < or reference one that is defined in the DTD. In the XML data, the reference could be to an entity that is defined in the local subset of the DTD or to an external XML file (an external entity). The DTD can also carve out a segment of DTD specifications and give it a name so that it can be reused (included) at multiple points in the DTD by defining a parameter entity.

Developers are turning to creating components rather than monolithic applications to free themselves from slow, expensive application development, and to build up a portable, reusable code base. This enables developers to quickly attack new market opportunities, new joint development opportunities, and new ways to sell smaller packages of software.

The JFC (Java Foundation Classes) is based upon the AWT (Abstract Windowing Toolkit), which has been part of the Java platform from the beginning. JFC effectively adds a richer set of visual elements for building JavaBeans components and applications. See the JFC web site for more information.

An application developer who produces enterprise bean classes, remote and Interview Questions - Home interfaces, and deployment descriptor files, and packages them in an EJB JAR file.

A distinct, individual item that can be included in an XML document by referencing it. Such an entity reference can name an entity as small as a character (for example, <, which references the less-than symbol or left angle bracket, <). An entity reference can also reference an entire document, an external entity, or a collection of DTD definitions.

Yes. A large number of companies, both large and small, have announced their plans to deliver JavaBeans-based products.