Java Beans

The most common reason for a "java.lang.ClassFormatError: Duplicate name" error is that a .class file in the JAR contains a class whose class name is different from the expected name. So for example if you have a file called "a/B.class" and it contains a class called "B" or "a.X" instead of the class "a.B" then you will get this error.

Themost common causes for this problem are either forgetting to include a "package a;" statement or having a "package" statement with the wrong name.

Because of the fact, that 99% of all messages is spam. It is recommended to post on JavaBeans forum, which is inspected by Sun engineers on a regular basis.

A component architecture for the development and deployment of object-oriented, distributed, enterprise-level applications. Applications written using the Enterprise JavaBeans architecture are scalable, transactional, and secure.

The applications that constitute an enterprise's existing system for handling companywide information. These applications provide an information infrastructure for an enterprise. An enterpriseinformation system offers a well-defined set of services to its clients. These services are exposed to clients as local or remote interfaces or both. Examples of enterprise information systems include enterprise resource planning systems, mainframe transaction processing systems, and legacy database systems.

Defines the queries for the finder and select methods of an entity bean having container-managed persistence. A subset of SQL92, EJB QL has extensions that allow navigation over the relationships defined in an entity bean's abstract schema.

Software that provides services to an EJB container. For example, an EJB container typically relies on a transaction manager that is part of the EJBserver to perform the two-phase commit across all the participating resource managers. The J2EE architecture assumes that an EJB container is hosted by an EJBserver from the same vendor, so it does not specify the contract between these two entities. An EJB server can host one or more EJB containers.

An object that provides the life-cycle operations (create, remove, find) for an enterprise bean. The class for the EJB Home object is generated by the container's deployment tools. The EJB Home object implements the enterprise bean's Home interface. The client references an EJB Home object to perform life-cycle operations on an EJB object. The client uses JNDI to locate an EJB Home object.

An enterprise bean that represents persistent data maintained in a database. An entity bean can manage its own persistence or can delegate this function to its container. An entity bean is identified by a primary key. If the container in which an entity bean is hosted crashes, the entity bean, its primary key, and any remote references survive the crash.

An object whose class implements the enterprise bean's remote interface. A client never references an enterprise bean instance directly. A client always references an EJB object. The class of an EJB object is generated by a container's deployment tools.

A vendor that supplies an EJB container. An object that allows an enterprise bean to invoke services provided by the container and to obtain the information about the caller of a client-invoked method.

A container that implements the EJB component contract of the J2EE architecture. This contract specifies a runtime environment for enterprise beans that includes security, concurrency, life-cycle management, transactions, deployment, naming, and other services. An EJB container is provided by an EJB or J2EE server.

Three ways to control serilization in java beans:

1.Automatic serialization, implemented by the Serializable interface. The Java serialization software serializes the entire object, except transient and static fields.

2.Customized serialization. Selectively exclude fields you do not want serialized by marking with the transient (or static) modifier.

3.Customized file format, implemented by the Externalizable interface and its two methods. Beans are written in a specific file format.

Introspection is the automatic process of analyzing a bean's design patterns to reveal the bean's properties, events, and methods.

Any class is serializable as long as that class or a parent class implements the java.io.Serializable interface. Examples of serializable classes include Component, String, Date, Vector, and Hashtable.

The InfoBus specification extends JavaBeans by providing a set of enhanced interfaces to share and exchange dynamic data.

Glasgow - the code name for add-ins to the JavaBeans specification. It contains following specifications:

► The Extensible Runtime Containment and Services Protocol

► The Drag and Drop Subsystem for the Java Foundation Classes

► The JavaBeans Activation Framework

To create the title property as a bound property for the MyBean component in the NetBeans GUI Builder, perform the following sequence of operations:

► Right-click the Bean Patterns node in the MyBean class hierarchy.

► Select Add|Property from the pop-up menu.

► Fill the New Property Pattern form as shown on the following figure and click OK.

Yes, under the usual terms of the JDK license. The specification and technology preview are available in our products archive.