Intercepting Filter Design Pattern
package dp.fcdp;
import java.io.IOException;
import java.util.logging.Logger;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
public class UserAgentFilter implements Filter {
private Logger logger;
private FilterConfig config;
@Override
public void init(FilterConfig config) throws ServletException {
this.config=config;
logger=Logger.getLogger("logfile");
}
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException {
String userAgent=null;
userAgent=((HttpServletRequest) request).getHeader("User-Agent");
logger.info("User Agent : "+userAgent);
if(userAgent.contains("Mozilla")) {
chain.doFilter(request, response);
}else{
RequestDispatcher rd=request.getRequestDispatcher("badBrowser.jsp");
rd.forward(request, response);
}
}
@Override
public void destroy() {
logger=null;
}
}
package dp.fcdp;
import java.io.IOException;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class HomeServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
@Override
protected void service(HttpServletRequest request,HttpServletResponse response)
throws ServletException, IOException{
request.setAttribute("loggedInUser", " john");
RequestDispatcher rd=request.getRequestDispatcher("home.jsp");
rd.forward(request, response);
}
}
home.jsp
<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Home Page</title>
</head>
<body>
<form action="empList.do">
LoggedIn ${loggedInUser}
<input type="hidden" name="token" value="${token}" />
</form>
</body>
</html>
badBrowser.jsp
<%@ page language="java" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Browser not supported</title>
</head>
<body>
<p style="color: red;">Browser not Supported use Firefox </p>
</body>
</html>
web.xml
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://java.sun.com/xml/ns/javaee"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
id="WebApp_ID" version="3.0">
<filter>
<filter-name>UserAgent</filter-name>
<filter-class>dp.fcdp.UserAgentFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>UserAgent</filter-name>
<url-pattern>/*</url-pattern>
<dispatcher>REQUEST</dispatcher>
</filter-mapping>
<servlet>
<servlet-name>HomeServlet</servlet-name>
<servlet-class>dp.fcdp.HomeServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>HomeServlet</servlet-name>
<url-pattern>/home.do</url-pattern>
</servlet-mapping>
</web-app>
index.html
<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Home</title>
</head>
<body>
<a href="/javaT/home.do">Click Here</a>
</body>
</html>
output :
http://localhost:8001/javaT/
LoggedIn john
|