Datasheet

13
Chapter 1 ✦ Understanding Java and the J2EE Platform
Standard Service Version App Client Web EJB
SAAJ 1.2 Required Required Required
JAXR 1.0 Required Required Required
JAX-RPC 1.1 Required Required Required
JMX 1.2 Required Required Required
JACC 1.0 Not Required Required Required
Application component APIs
The standard services described in the previous section are used to provide addi-
tional J2EE application-component specifications as Web and server components.
The following is a list of the application component APIs specified in J2EE.
✦ Enterprise JavaBeans (EJB) 2.1 — EJBs are similar to CORBA components
and typically encapsulate business-logic code or data-model code. They exe-
cute within a container, which manages their interactions with other compo-
nents, including resources and security. Three different types of EJBs exist:
• Entity beans
• Message-driven beans
• Session beans, which come in two flavors — either stateless or stateful.
✦ Java Servlet 2.4 — Servlets are classes that reside on the server and are typi-
cally used to respond to incoming requests via HTTP. They are often used to
return the presentation layer to a client.
✦ JavaServer Pages (JSP) 2.0 — JSP pages are very similar to HTML pages,
except that they have embedded Java code. The pages are parsed and exe-
cuted on the server prior to being returned to the requesting client. JSPs can
make use of additional APIs, such as JSP tag extensions, to allow for more
complex logic.
Not all of the preceding APIs will be discussed in this book, as many of them are
fairly straightforward.
Discovering What’s New in J2EE 1.4
Version 1.4 introduces significant improvements in J2EE’s support for Web services
and XML. Until now J2EE lagged behind the recently introduced Microsoft .NET,
which provided extensive support for XML from its initial release in 2000. However,
Note
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