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.
Syntax:
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.
Syntax:
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.
Syntax:
public void setAttribute(String name,Object object)
4. getAttribute(String name): Returns the specified attribute if exists otherwise returns null.
Syntax:
public Object getAttribute(String name)
5. removeAttribute(String name): Removes the specified attribute.
Syntax:
public void removeAttribute(String name)
Example:
ContextParamExample.java
import java.io.IOException;
import java.io.PrintWriter;
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.
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 {
response.setContentType("text/html");
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 + "");
import java.io.IOException;
import java.io.PrintWriter;
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 {
response.setContentType("text/html");
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 + "");
out.close();
}
}
import java.io.IOException;
import java.io.PrintWriter;
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 {
response.setContentType("text/html");
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 + "");
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-name>ContextParamExample</servlet-name>
com.w3schools.business.ContextParamExample
<param-name>appUser</param-name>
<param-value>jai</param-value>
<servlet-name>ContextParamExample</servlet-name>
<url-pattern>/ContextParamExample</url-pattern>
<!--?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>ContextParamExample</servlet-name>
<servlet-class>
com.w3schools.business.ContextParamExample
</servlet-class>
</servlet>
<context-param>
<param-name>appUser</param-name>
<param-value>jai</param-value>
</context-param>
<servlet-mapping>
<servlet-name>ContextParamExample</servlet-name>
<url-pattern>/ContextParamExample</url-pattern>
</servlet-mapping>
</web-app>
<!--?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>ContextParamExample</servlet-name>
<servlet-class>
com.w3schools.business.ContextParamExample
</servlet-class>
</servlet>
<context-param>
<param-name>appUser</param-name>
<param-value>jai</param-value>
</context-param>
<servlet-mapping>
<servlet-name>ContextParamExample</servlet-name>
<url-pattern>/ContextParamExample</url-pattern>
</servlet-mapping>
</web-app>