The Internet Phenomenon - Secure Java: For Web Application Development - page 12

Figure 1.5 provides a high-level perspective of these Java technologies that help in creating Web
and enterprise applications.

1.3.1 Applets

Applets are special Java applications. Applets are application programs that use the client's Web
browser to provide a user interface to the client to access and transact for information over the
Web and Internet. Unlike the normal Java applications, the life cycles of applets are governed and
taken care of by the browsers in which they run.

1.3.2 Java Servlet

Servlets are the server-side component of Java Platform, Enterprise Edition. A servlet is a special
Java class that extends the capabilities of servers that host applications that are accessed by way
of a request-response oriented programming model. Servlets are created to respond to any type
of request. However, they are commonly used to extend the applications hosted by Web servers.
hese applications are usually referred to as Web applications . For instance, a servlet can be used to
perform a very simple task such as getting a text input from an online form and printing it back
to the screen using HTML page and format. Another servlet can be used to perform more serious
and transaction-oriented operations such as the data persistence operation to a ile or database, on
the other hand.

Business Logic Tier

Presentation Tier

Client Tier

Message
Driven
Beans

Entity
Beans

Session
Beans

JSP

Servlet

Filter

HTTP/HTTPS

Applet

J2SE

J2SE

J2SE

HTTP/HTTPS

Application Client

EAI Tier

Application
Client

EIS

J2SE

Figure 1.5 the Java Platform, enterprise edition technologies Big Picture.