Example of ServletConfig in Java Servlet

Let us see why/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 objct 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

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

package java4s;

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>java4s.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>

Output

You Might Also Like

• How to Connect Servlet to the Database with Example
• Difference between ServletConfig and ServletContext in Java
• Example of ServletContext in Java
• Understanding ServletConfig and ServletContext
• Example on getParameterValues() method of Servlet Request

::. About the Author .::
		Sivateja Kandula - Java/J2EE Full Stack Developer Founder of Java4s - Get It Yourself, A popular Java/J2EE Programming Blog, Love Java and UI frameworks. You can sign-up for the Email Newsletter for your daily dose of Java tutorials.