ServletContext
Defines a set of methods that a servlet uses to communicate
with its servlet container, for example, to get the MIME type of a file,
dispatch requests, or write to a log file.
There is one context per "web application" per Java
Virtual Machine. (A "web application" is a collection of servlets and
content installed under a specific subset of the server's URL namespace such as
/catalog and possibly installed via a .war file.)
In the case of a web application marked "distributed" in its deployment descriptor, there will be one context
instance for each virtual machine. In this situation, the context cannot be
used as a location to share global information (because the information won't
be truly global). Use an external resource like a database instead.
The ServletContext object is contained within the ServletConfig
object, which the Web server provides the servlet when the servlet is
initialized.
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<context-param>
<param-name>filepath</param-name>
<param-value>/text.txt</param-value>
</context-param>
<listener>
<listener-class>feeder.init</listener-class>
</listener>
<servlet>
<servlet-name>display</servlet-name>
<servlet-class>view.display</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>display</servlet-name>
<url-pattern>/display</url-pattern>
</servlet-mapping>
<session-config>
<session-timeout>
30
</session-timeout>
</session-config>
<welcome-file-list>
<welcome-file>display</welcome-file>
</welcome-file-list>
</web-app>
text.txt
This is sample TEXT.
ABC your line.
Now this config shows multiple lines that are stored on the single file.
view.Display class
package view;
import java.io.*;
import java.net.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class display extends HttpServlet
{
private int i;
protected void processRequest(HttpServletRequest request, HttpServletResponse
response)
throws ServletException, IOException
{
response.setContentType("text/html;charset=UTF-8");
PrintWriter out = response.getWriter();
try
{
ServletContext c=getServletContext();
int i1=2;
String s = c.getAttribute("i1").toString();
i1=Integer.valueOf(s);
out.println("<html>");
out.println("<head>");
out.println("<title>Display Text</title>");
out.println("</head>");
out.println("<body>");
for(i=0;i<i1;i++)
{
String val=(String) c.getAttribute("s["+i+"]");
out.println(val);
out.println("<br />");
}
out.println("</body>");
out.println("</html>");
}
finally
{
out.close();
}
}
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
processRequest(request, response);
}
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
processRequest(request, response);
}
public String getServletInfo() {
return "Short description";
}
}
feeder.init class
package feeder;
import java.io.*;
import javax.servlet.*;
public class init implements ServletContextListener
{
public void contextInitialized(ServletContextEvent arg0)
{
try
{
ServletContext c = arg0.getServletContext();
String value = c.getInitParameter("filepath");
InputStream i;
BufferedReader br;
i = c.getResourceAsStream(value);
br = new BufferedReader(new InputStreamReader(i));
String line;
int i1=0;
while ((line=br.readLine()) != null)
{
c.setAttribute("s["+i1+"]",line);
i1++;
}
c.setAttribute("i1",i1);
}
catch (IOException ex) {}
}
public void contextDestroyed(ServletContextEvent arg0)
{
throw new UnsupportedOperationException("Not supported yet.");
}
}
