TCP/IP Tutorial and Technical Overview - IBM Redbooks

HTTP-Based
Client
Java
Application
HTTP
Figure 16-5 The Enterprise JavaBeans environment
Remote Method Invocation (RMI)
RMI is a standard protocol for communication between Java objects residing on
different computers. RMI provides a way for client and server applications to
invoke methods across a distributed network of clients and servers running the
JVM. You can invoke methods on the remote RMI object as you do on a local
Java object. RMI is cross-platform, but not cross-language (Java only).
Sun Microsystems, with IBM and others, developed a more portable version of
RMI, which uses the Object Management Group’s (OMG) Internet Inter-ORB
Protocol. IIOP is necessary for Java 2 Platform, Enterprise Edition (J2EE)
deployments to be interoperable with CORBA systems.
Types of EJBs
There are two types of Enterprise JavaBeans (EJB):
► Entity EJBs
They encapsulate permanent data, which is stored in a data source such as a
database or a file system, and associated methods to manipulate that data. In
most cases, an entity bean must be accessed in some transactional manner.
Instances of an entity bean are unique and they can be accessed by multiple
users. For example, information about a bank account can be encapsulated
in an entity bean. An account entity bean might contain an account ID, an
account type (checking or savings), a balance variable, and methods to
manipulate these variables.
620 TCP/IP Tutorial and Technical Overview
Web
Server
EJB Server
Servlet or JSP
RMI/IIOP
Data Source