JAVA SERVLET
Introduction to
javax.servlet and Client-Server Intraction
The javax.servlet package
provides interfaces and classes for writing servlets. The
architecture of the package is described below.
The Servlet Interface
The central abstraction in the Servlet
API is the Servlet interface. All servlets implement this
interface, either directly or, more commonly, by extending a class that
implements it such as HttpServlet
The Servlet interface declares, but does not
implement, methods that manage the servlet and its communications with
clients. Servlet writers provide some or all of these methods when
developing a servlet.
Client Interaction
When a servlet accepts a call from a
client, it receives two objects:
A ServletRequest, which encapsulates the communication from the
client to the server.
A ServletResponse, which encapsulates the communication from the servlet
back to the client.
ServletRequest and ServletResponse are interfaces defined by
the javax.servlet package.
The ServletRequest Interface,The ServletRequest interface
allows the servlet access to:
Information such as the names of the parameters passed in by the client,
the protocol (scheme) being used by the client, and the names of the
remote host that made the request and the server that received it.
The input stream, ServletInputStream. Servlets use the input stream
to get data from clients that use application protocols such as the HTTP
POST and PUT methods.
Interfaces that extend ServletRequest interface allow the servlet
to retrieve more protocol-specific data. For example, the HttpServletRequestinterface
contains methods for accessing HTTP-specific header information.
The ServletResponse Interface, The ServletResponse interface
gives the servlet methods for replying to the client. It:
Allows the servlet to set the content length and
MIME type of the reply.
Provides an output stream, ServletOutputStream, and a Writer
through which the servlet can send the reply data. Interfaces that
extend the ServletResponse interface give the servlet more
protocol-specific capabilities. For example, the HttpServletResponseinterface
contains methods that allow the servlet to manipulate HTTP-specific
header information.
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