Example of authenticating user using filter

Example of authenticating user using filter

Let's see the simple example of authenticating user using filter.

Here, we have created 4 files:

• index.html
• MyFilter.java
• AdminServlet.java
• web.xml

index.html

1.     <form action="servlet1">  

2.     Name:<input type="text" name="name"/><br/>  

3.     Password:<input type="password" name="password"/><br/>  

4.       

5.     <input type="submit" value="login">  

6.       

7.     </form>  

---

MyFilter.java

1.     import java.io.IOException;  

2.     import java.io.PrintWriter;  

3.     import javax.servlet.*;  

4.       

5.     public class MyFilter implements Filter{  

6.       

7.     public void init(FilterConfig arg0) throws ServletException {}  

8.           

9.     public void doFilter(ServletRequest req, ServletResponse resp,  

10.           FilterChain chain) throws IOException, ServletException {  

11.             

12.       PrintWriter out=resp.getWriter();  

13.             

14.       String password=req.getParameter("password");  

15.       if(password.equals("admin")){  

16.       chain.doFilter(req, resp);//sends request to next resource  

17.       }  

18.       else{  

19.       out.print("username or password error!");  

20.       RequestDispatcher rd=req.getRequestDispatcher("index.html");  

21.       rd.include(req, resp);  

22.       }  

23.             

24.   }  

25.       public void destroy() {}  

26.     

27.   }  

---

AdminServlet.java

1.     import java.io.IOException;  

2.     import java.io.PrintWriter;  

3.       

4.     import javax.servlet.ServletException;  

5.     import javax.servlet.http.*;  

6.       

7.     public class AdminServlet extends HttpServlet {  

8.     public void doGet(HttpServletRequest request, HttpServletResponse response)  

9.             throws ServletException, IOException {  

10.     

11.           response.setContentType("text/html");  

12.           PrintWriter out = response.getWriter();  

13.             

14.           out.print("welcome ADMIN");  

15.           out.close();  

16.       }  

17.   }  

---

web.xml

1.     <web-app>  

2.      <servlet>  

3.         <servlet-name>AdminServlet</servlet-name>  

4.         <servlet-class>AdminServlet</servlet-class>  

5.       </servlet>  

6.       

7.       <servlet-mapping>  

8.         <servlet-name>AdminServlet</servlet-name>  

9.         <url-pattern>/servlet1</url-pattern>  

10.     </servlet-mapping>  

11.       

12.    <filter>  

13.     <filter-name>f1</filter-name>  

14.     <filter-class>MyFilter</filter-class>  

15.     </filter>  

16.     <filter-mapping>  

17.     <filter-name>f1</filter-name>  

18.     <url-pattern>/servlet1</url-pattern>  

19.     </filter-mapping>  

20.       

21.   </web-app>  

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