Init parameters:
Init parameters refer to the initialization parameters of a servlet or filter. <init-param> attribute is used to define an init parameter. <init-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.
ServletConfig interface:
The ServletConfig interface is used to access the init parameters.
Methods of ServletConfig interface:
1. getInitParameter(String name): Returns the value of the specified parameter if the parameter exists otherwise returns null.
Syntax:
public String getInitParameter(String name)
2. getInitParameterNames(): Returns the names of init parameters as Enumeration if servlet has init parameters otherwise returns an empty Enumeration.
Syntax:
public Enumeration getInitParameterNames()
3. getServletContext():Returns an instance of ServletContext.
Syntax:
public ServletContext getServletContext()
4. getServletName(): Returns the name of the servlet.
Syntax:
public String getServletName()
Example:
InitParamExample.java
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; /** * This class is used to show the use of init parameters. * @author W3schools360 */ public class InitParamExample extends HttpServlet { private static final long serialVersionUID = 1L; //no-argument constructor public InitParamExample() { } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); //get ServletConfig object. ServletConfig config=getServletConfig(); //get init parameter from ServletConfig object. String appUser = config.getInitParameter("appUser"); out.print("Application User: " + appUser + ""); out.close(); } }
web.xml
<!--?xml version="1.0" encoding="UTF-8"?--> <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemalocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5"> <servlet> <servlet-name>InitParamExample</servlet-name> <servlet-class> com.w3schools.business.InitParamExample </servlet-class> <init-param> <param-name>appUser</param-name> <param-value>jai</param-value> </init-param> </servlet> <servlet-mapping> <servlet-name>InitParamExample</servlet-name> <url-pattern>/InitParamExample</url-pattern> </servlet-mapping> </web-app>