Develop enterprise beans

 

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Overview

There are two basic approaches to selecting tools for developing enterprise beans:

• Use an IDE to automatically generate significant parts of the enterprise bean code and contain integrated tools for packaging and testing enterprise beans.

• If you have decided to develop enterprise beans without an IDE, we need at least an ASCII text editor. We can also use a Java development tool that does not support enterprise bean development. We can then use tools available in the Java SDK and in WAS to assemble, test, and deploy the beans.

The following steps primarily support the second approach, development without an IDE.

 

Procedure

1. If necessary, migrate any pre-existing code to the required version of the EJB specification.

2. Write and compile the components of the enterprise bean.

   • At a minimum, an EJB 1.1 session bean requires a bean class, a home interface, and a remote interface. An EJB 1.1 entity bean requires...
     • bean class
     • primary-key class
     • home interface
     • remote interface

   • At a minimum, an EJB 2.x session bean requires...
     • bean class
     • home or local home interface
     • remote or local interface

     An EJB 2.x entity bean requires...

     • bean class
     • primary-key class
     • remote home or local home interface
     • remote or local interface

     The types of interfaces go together: If you implement a local interface, define a local home interface as well.

     Optionally, the primary-key class can be unknown.

   • A message-driven bean requires only a bean class.

3. For each entity bean, complete work to handle persistence operations.

   • Create a database schema for the entity bean's persistent data.

     • For entity beans with CMP, store the bean's persistent data in one of the supported databases. The Application Service Toolkit automatically generates SQL code for creating database tables for CMP entity beans. If your CMP beans require complex database mappings, it is recommended that you use the IBM Rational Application Developer product to generate code for the database tables.

     • For entity beans with BMP, one can create the database and database table by using the database tools or use an existing database and database table.

   • (CMP entity beans for EJB 2.x only) Define finder queries with EJB Query Language (EJB QL).

     With EJB QL, you define finders in terms of CMP fields and container-managed relationships, as follows:

     • Public finders are visible in the bean's home interface. Implemented in the bean class, they return only remote interfaces and collection types.

     • Private finders, expressed as SELECT statements, are used only within the bean class. They can return both local and remote interfaces, dependent values, other CMP field types, and collection types.

   • (CMP entity beans for EJB 1.1 only: an IBM extension) Create a finder helper interface for each CMP entity bean that contains specialized finder methods (other than the findByPrimaryKey method).

     The following logic is required for each finder method (other than the findByPrimaryKey method) contained in the home interface of an entity bean with CMP:

     • The logic must be defined in a public interface named NameBeanFinderHelper, where Name is the name of the enterprise bean (for example, AccountBeanFinderHelper).

     • The logic must be contained in a String constant named findMethodName WhereClause, where findMethodName is the name of the finder method. The String constant can contain zero or more question marks (?) that are replaced from left to right with the value of the finder method's arguments when that method is called.

 

What to do next

Assemble the beans in one or more EJB modules.

 

See also

Develop read-only entity beans
Migrate enterprise bean code to the supported specification
WebSphere extensions to the Enterprise JavaBeans specification
Best practices for develop enterprise beans
Unknown primary-key class
Configure a Timer Service
Timer service for Enterprise JavaBeans 2.1
Web service support
Bind Web modules to virtual hosts
Bind EJB and resource references
Define data sources for entity beans

 

See Also

Enterprise beans
Concurrency control

 

Related Tasks

Developing applications that use JNDI

 

See Also

Enterprise beans: Resources for learning

 

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