Servlet Context

ServletContext is a interface which helps us to communicate with the servlet container. There is only one ServletContext for the entire web application and the components of the web application can share it. The information in the ServletContext will be common to all the components. Remember that each servlet will have its own ServletConfig. The ServetContext is created by the container when the web application is deployed and after that only the context is available to each servlet in the web application.

Web application initialization:

1. First of all the web container reads the deployment descriptor file and then creates a name/value pair for each <context-param> tag.
2. After creating the name/value pair it creates a new instance of ServletContext.
3. Its the responsibility of the Container to give the reference of the ServletContext to the context init parameters.
4. The servlet and jsp which are part of the same web application can have the access of the ServletContext.

The Context init parameters are available to the entire web application not just to the single servlet like servlet init parameters.

How can we do the mapping of the Context init parameters in web.xml

<servlet>
  <servlet-name>Mapping</servlet-name>
  <servlet-class>ContextMapping</servlet-class>
</servlet>

<context-param>
  <param-name>Email</param-name>
  <param-value>[email protected]</param-value>
</context-param>

In the servlet code we will write this as

ServletContext context = getServletContext();
pw.println(context.getInitParameter("Email");