Java Servlet Programming and application of the second

The development environment required to write a servlet

The basic environment required for servlet development is JSDK and a Web server that supports the servlet.

1.JSDK (Java Servlet Development Kit)

JSDK contains the Java class libraries and related documentation needed to compile the servlet application. For users who are developing with Java 1.1, JSDK must be installed. JSDK has been integrated into the Java 1.2 beta, and if you are developing with Java 1.2 or later, you do not have to install JSDK.

JSDK can be downloaded at JavaSoft Company's site for free, with the address: http://www.sun.com/software/jwebserver/redirect.html

2. Web server with servlet support

The servlet needs to run on a Web server that supports a servlet. The Web server that currently supports the servlet, JSWDK1.0.1 of Sun Corporation. If the existing Web server does not support a servlet, you can leverage the server additions (add-ons) of some third-party vendors to enable the Web server to support the servlet, which is the Live software company (http:// Www.livesoftware.com provides a product called JRun that enables Microsoft IIS and Netscape Web server to support the servlet by installing the appropriate version of JRun.

The process of developing a servlet

Here's a simple servlet example to illustrate the process of developing a servlet.

1. Writing servlet code

The Java Servlet API is a standard Java Extender package that contains two Package:javax.servlet and Javax.servlet.http. For developers who want to develop custom based protocols, the classes and interfaces in the Javax.servlet package should be used, and developers interacting with the client only with HTTP protocols need to be developed using the classes and interfaces in the Javax.servlet.http package.

The following is a servlet's program code (REQUESTINFOEXAMPLE.JAVA):

Import java.io.*;
Import java.servlet.*;
Import javax.servlet.*;
public class Requestinfoexample extends HttpServlet {
public void doget (HttpServletRequest request, httpservletresponse response)
Throws IOException, Servletexception
{
Response.setcontenttype ("text/html");
PrintWriter out = Response.getwriter ();
Out.println ("");
Out.println ("");
Out.println ("");
Out.println ("Request information Example");
Out.println ("");
Out.println ("");
Out.println ("

Request information Example

");
Out.println ("Method:" + Request.getmethod ());
Out.println ("Request URI:" + Request.getrequesturi ());
Out.println ("Protocol:" + request.getprotocol ());
Out.println ("PathInfo:" + request.getpathinfo ());
Out.println ("Remote Address:" + request.getremoteaddr ());
Out.println ("");
Out.println ("");
}
public void DoPost (HttpServletRequest request, HttpServletResponse Res)
Throws IOException, Servletexception
{
Doget (request, response);
}
}

The servlet implements the following functionality: When a user accesses the servlet through a browser, the servlet returns an HTML page to the client browser: