Servlet context parameters and ServletContext interface

Context parameters:

Context parameters refer to the initialization parameters for all servlets of an application. <context-param> attribute is used to define a context parameter. <context-param> attribute has two main sub attributes <param-name> and <param-value>. The <param-name> contains the name of the parameter and <param-value> contains the value of the parameter.

ServletContext interface:

The servletContext interface is used to access the context parameters.

Commonly used methods of ServletContext interface:

1. getInitParameter(String name): Returns the value of the specified parameter if the parameter exists otherwise returns null.

public String getInitParameter(String name)

2. getInitParameterNames(): Returns the names of context parameters as Enumeration if the servlet has context parameters otherwise returns an empty Enumeration.

public Enumeration getInitParameterNames()

3. setAttribute(String name, Object object): Binds the specified object to the specified attribute name and puts this attribute in the application scope.

public void setAttribute(String name,Object object)

4. getAttribute(String name): Returns the specified attribute if exists otherwise returns null.

public Object getAttribute(String name)

5. removeAttribute(String name): Removes the specified attribute.

public void removeAttribute(String name)


import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

 * This class is used to show the use of context parameters.
 * @author W3schools360
public class ContextParamExample extends HttpServlet {
   private static final long serialVersionUID = 1L;
   //no-argument constructor.
    public ContextParamExample() {

    protected void doGet(HttpServletRequest request, 
		HttpServletResponse response)
	              throws ServletException, IOException {
    	PrintWriter out = response.getWriter();
    	//get ServletContext object.
    	ServletContext context=getServletContext();  
    	//get context parameter from ServletContext object.
    	String appUser = context.getInitParameter("appUser");
    	out.print("Application User: " + appUser + "");



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