Filter is used for pre-processing of requests and post-processing of responses.
Filter Api- it’s a part of servlet api, filter interface can be found in javax.servlet package.
Life cycle-
1- init
2- dofilter
3- destroy
Filterchain interface- its used to invoke other filters in the chain.
Example 11- Web app to show pre-processing text before request is handled by servlet and post-processing text after response is generated by servlet.
output-
Project Structure-
3 files-
1-index.html(inside WebContent)
2-Firstfil.java(inside pacage=’ab’)
3-FirstServ.java(inside pacage=’ab’)
4-SecFil.java(inside pacage=’ab’)
5-web.xml(inside WEB-INF)
1-index.html
Insert title here
2-Firstfil.java(filter)
package ab;
import java.io.*;
import javax.servlet.*;
public class Firstfil implements Filter {
public void destroy() {
// TODO Auto-generated method stub
}
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
String fs=request.getParameter("name");
System.out.println("first filter "+fs);
chain.doFilter(request, response);
System.out.println("after first filter chain-dofilter");
}
public void init(FilterConfig fConfig) throws ServletException {
// TODO Auto-generated method stub
}
}
3-FirstServ.java(servlet)
package ab;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class FirstServ extends HttpServlet {
private static final long serialVersionUID = 1L;
public FirstServ() {
super();
// TODO Auto-generated constructor stub
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String fs=request.getParameter("name");
response.getWriter().print(fs);
System.out.println("first servlet "+fs);
// pass the request along the filter chain
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request, response);
}
}
4-SecFil.java(filter)
package ab;
import java.io.*;
import javax.servlet.*;
public class SecFil implements Filter {
public void destroy() {
// TODO Auto-generated method stub
}
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
// TODO Auto-generated method stub
String fs=request.getParameter("name");
System.out.println("second filter "+fs);
// pass the request along the filter chain
chain.doFilter(request, response);
System.out.println("after second filter chain-dofilter");
}
public void init(FilterConfig fConfig) throws ServletException {
// TODO Auto-generated method stub
}
}
5-web.xml
Filters index.html index.htm index.jsp default.html default.htm default.jsp a ab.Firstfil a /FirstServ b ab.FirstServ b /FirstServ c ab.SecFil c /FirstServ
