Servlet Config Interface

• An object of ServletConfig is created by the web container for each servlet.
• This object can be used to get configuration information from web.xml file.
•  If the configuration information is modified from the web.xml file, we don't need to change the servlet.

Methods of Servlet Config Interface

1. public String getInitParameter(String name):Returns the parameter value for the specified parameter name.
2. public Enumeration getInitParameterNames():Returns an enumeration of all the initialization parameter names.
3. public String getServletName():Returns the name of the servlet.
4. public ServletContext getServletContext():Returns an object of ServletContext.

Syntax to Call the methods of ServletConfig interface

ServletConfig config=getServletConfig();  

Syntax to provide the initialization parameter for a servlet

The init-param sub-element of servlet is used to specify the initialization parameter for a servlet.

<web-app> 
  <servlet> 
    ...... 
     
    <init-param> 
      <param-name>parametername</param-name> 
      <param-value>parametervalue</param-value> 
    </init-param> 
    ...... 
  </servlet> 
</web-app>

 Example of ServletConfig to get initialization parameter

In this example, we are getting all the initialization parameter from the web.xml file and printing this information in the servlet.

DemoServlet.java

    import java.io.*; 
    import javax.servlet.*; 
    import javax.servlet.http.*; 
     
    public class DemoServlet extends HttpServlet { 
    public void doGet(HttpServletRequest request, HttpServletResponse response) 
        throws ServletException, IOException { 
     
        response.setContentType("text/html"); 
        PrintWriter out = response.getWriter(); 
         
        ServletConfig config=getServletConfig(); 
        String driver=config.getInitParameter("driver"); 
        out.print("Driver is: "+driver); 
             
        out.close(); 
        } 
     
    }  

Web.xml

<web-app> 
     
    <servlet> 
    <servlet-name>DemoServlet</servlet-name> 
    <servlet-class>DemoServlet</servlet-class> 
     
    <init-param> 
    <param-name>driver</param-name> 
    <param-value>sun.jdbc.odbc.JdbcOdbcDriver</param-value> 
    </init-param> 
     
    </servlet> 
     
    <servlet-mapping> 
    <servlet-name>DemoServlet</servlet-name> 
    <url-pattern>/servlet1</url-pattern> 
    </servlet-mapping> 
     
    </web-app>

Example of ServletConfig to get all the initialization parameters

In this example, we are getting all the initialization parameter from the web.xml file and printing this information in the servlet.

DemoServlet.java

    import java.io.IOException; 
    import java.io.PrintWriter; 
    import java.util.Enumeration; 
     
    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 DemoServlet extends HttpServlet { 
    public void doGet(HttpServletRequest request, HttpServletResponse response) 
            throws ServletException, IOException { 
     
        response.setContentType("text/html"); 
        PrintWriter out = response.getWriter(); 
         
        ServletConfig config=getServletConfig(); 
        Enumeration<String> e=config.getInitParameterNames(); 
             
        String str=""; 
        while(e.hasMoreElements()){ 
        str=e.nextElement(); 
        out.print("<br>Name: "+str); 
        out.print(" value: "+config.getInitParameter(str)); 
        } 
             
        out.close(); 
    } 
     
    }

Web.xml

<web-app> 
     
    <servlet> 
    <servlet-name>DemoServlet</servlet-name> 
    <servlet-class>DemoServlet</servlet-class> 
     
    <init-param> 
    <param-name>username</param-name> 
    <param-value>system</param-value> 
    </init-param> 
     
    <init-param> 
    <param-name>password</param-name> 
    <param-value>oracle</param-value> 
    </init-param> 
     
    </servlet> 
     
    <servlet-mapping> 
    <servlet-name>DemoServlet</servlet-name> 
    <url-pattern>/servlet1</url-pattern> 
    </servlet-mapping> 
     
    </web-app>