ServletConfig:
Here let us see how to use ServletConfig interface
in java servlet….
ServletConfig is one of the pre-defined interface.
ServletConfig object is used for developing flexible servlets.
ServletConfig object exist one per servlet program.
An object of ServletConfig created by the container during its initialization
phase.
An object of ServletConfig is available to the servlet during its execution,
once the servlet execution is completed, automatically ServletConfig interface
object will be removed by the container.
An object of ServletConfig interface contains <init-param> details at
web.xml, of a particular servlet.
The moment when we are using an object of ServletConfig, we need to configure
the web.xml by writing <init-param> tag under <servlet> tag of
web.xml.
When ever compiler executes init() mehod then the ServletConfig will be
created in general.
An object of ServletConfig contain the <init-param> data in the form of
key,value pairs, here the keys represents init param names and values are its
values, which are represented in the web.xml file
How to Get ServletConfig Object into Servelt:
An object of ServletConfig can be obtained in 2 ways, they are…
Way 1:
ServletConfig conf = getServletConfig();
In the above statement, we are directly calling getServletConfig() method as it
is available in Servlet interface, inherited into GenericServlet and defined and
further inherited into HttpServlet and later inherited into our own servlet
class.
Way 2:
ServletConfig object will be available in init() method of the servlet.
public void init(ServletConfig config)
{
// …………………
}
So finally we are able to create ServletConfig object in our servlet
class, then how to get the data from that object… ?
How to Retrieve Data from ServletConfig Interface Object:
In order to retrieve the data of the ServletConfig we have two methods, which
are present in ServletConfig interface..
public String getInitParameter(“param name”);
public Enumeration getInitParameterNames();
I am not going to explain about these methods, these are similar to ‘Retrieve
Client Input Data in Servlet‘ but here we are retrieving values from web.xml
that’s it.
Example of ServletConfig:
Directory Structure:
Servlet on servlet config
settings
bulid
src
r4r.in
on servlet config.java
web content
META-INF
WEB-INF
lib
web.xml
classpath
project
Files Required:
index.html
OnServletConfig.java
web.xml
index.html:
|
<font face="verdana" size="2px"> <form action="onSCG" method="post"> Example on ServletConfig<br> <input type="submit" value="Calculate Sum"> </form> </font> |
OnServletConfig.java:
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package r4r.in; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletConfig; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class OnServletConfig extends HttpServlet { protected void doPost(HttpServletRequest req,HttpServletResponse res)throws ServletException,IOException { PrintWriter pw=res.getWriter(); res.setContentType("text/html"); ServletConfig conf=getServletConfig(); String s1=conf.getInitParameter("n1"); String s2=conf.getInitParameter("n2"); pw.println("n1 value is " +s1+ " and n2 is " +s2); pw.close(); } } web.xml <web-app> <servlet> <servlet-name>onServletConfig</servlet-name> <servlet-class>r4r.OnServletConfig</servlet-class> <init-param> <param-name> n1 </param-name> <param-value> 100 </param-value> </init-param> <init-param> <param-name> n2 </param-name> <param-value> 200 </param-value> </init-param> </servlet> <servlet-mapping> <servlet-name>onServletConfig</servlet-name> <url-pattern>/onSCG</url-pattern> </servlet-mapping> <welcome-file-list> <welcome-file>index.html</welcome-file> </welcome-file-list> </web-app> |