Java Beans

The JavaBeans specification defines the following types of bean properties:

► Simple: A bean property with a single value whose changes are independent of changes in any other property.

► Indexed: A bean property that supports a range of values instead of a single value.

► Bound: A bean property for which a change to the property results in a notification being sent to some other bean.

► Constrained: A bean property for which a change to the property results in validation by another bean. The other bean may reject the change if it is not appropriate.

Bean properties can also be classified as follows:

► Writable: A bean property that can be changed:

► ► Standard

► ► Expert

► ► Preferred

► Read Only: A bean property that cannot be changed.

► Hidden: A bean property that can be changed. However, these properties are not disclosed with the BeanInfo class

Enterprise JavaBeans (EJB) is an API specification for building scalable, distributed, component-based, multi-tier applications. It leverages and extends the JavaBeans component model to provide a rich object-oriented transactional environment for developers building enterprise applications.

Enterprise JavaBeans (EJB) technology is the basis of Java 2 Platform, Enterprise Edition (J2EE). EJB technology provides the scalable architecture for executing business logic in a distributed computing environment. J2EE makes the life of an enterprise developer easier by combining the EJB component architecture with other enterprise technologies to solutions on the Java platform for seamless development and deployment of server side applications.

► JavaBeans may be visible or nonvisible at runtime.For

example, the visual GUI component may be a button,list

box,graphic or a chart.

An EJB is a nonvisual ,remote object.

► JavaBeans are intended to be local to a single process

and are primarly intended to run on the client side.Although

one can develop server-side JavaBeans,it is far easier to

develop them using the EJB specification instead.

EJB's are remotely executable components or business

objects that can be deployed only on the server.

► JavaBeans is a component technology to create generic

Java components that can be composed together into applets

and applications.

Even though EJB is a component technology,it neither

builds upon nor extends the original JavaBean specification.

► JavaBeans have an external interface called the properties

interface, which allows a builder tool to interpret the

functionality of the bean.

EJBs have a dployement descriptor that describes its

functionality to an external builder tool or IDE

► JavaBeans may have BeanInfo classes,property editors or

customizers

Yes. InfoBus is typically used to communicate among Beans at the client, and it can also be useful for sharing information among components at a single server site. The initial version of InfoBus is not distributed, and is therefore not intended for transmission of data between clients and servers.

A variety of Java communication services, including JDBC, CORBA, and RMI can be used by InfoBus components for access to distributed data. For example, the ESuite Data Access component is a Bean that connects any JDBC compliant data source to the InfoBus. Once the data is on the bus, it can easily be imported by any InfoBus Data Consumer, such as a spreadsheet, chartingcomponent, word processor or data analysis tool.

The InfoBus is a compact Java API which allows cooperating applets or Beans, on a Web page or in any other Java application, to communicate data to one another. The InfoBus architecture enables Beans to be categorized as "data providers" and "data consumers". Data providers are Beans whose primary function is to access data from their native store, such as a DBMS, spreadsheet, flat file, Lotus Notes database etc., and to offer data onto the InfoBus.

Data consumers retrieve data from the bus, for analysis or visual display. This segregation of provider from consumer is extremely powerful in that it enables applications to be independent of their data; for example, a charting Bean need not understand SQL or JDBC in order to access DBMS data.

Of course, a Bean can be both a consumer and provider: for example a spreadsheet may accept data from a DBMS and provide data to a chart Bean.

Enterprise JavaBeans extends the JavaBeans component model to handle the needs of transactional business applications.

JavaBeans is a component model for visual construction of reusable components for the Java platform. Enterprise JavaBeans extends JavaBeans to middle-tier/server side business applications. The extensions that Enterprise JavaBeans adds to JavaBeans include support for transactions, state management, and deployment time attributes.

Although applications deploying the Enterprise JavaBeans architecture are independent from the underlying communication protocol, the Enterprise JavaBeans architecture specifies how communication among components maps into the underlying communication protocols, such as CORBA/IIOP.