example code for hidden form field

Hidden Form Field

Hidden Form Field a hidden (invisible) textfield is used for maintaining the state of an user.

we store the information in the hidden field and get it from another servlet. This approach is better if we have to submit form in all the pages and we don't want to depend on the browser. 

1.    <input type="hidden" name="user" value="bschandel">  

user is the hidden field name and bschandel is the hidden field value.

Examples of using Hidden Form Field

In this examples, We are storing the name of the user in a hidden textfield and getting that value from another servlet. 

index.html

1.    <form action="servlet1">  

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

3.    <input type="submit" value="go"/>  

4.    </form>  

<form action="servlet1"> Name:<input type="text" name="userName"/><br/> <input type="submit" value="go"/> </form>

FirstServlet.java

1.    import java.io.*;  

2.    import javax.servlet.*;  

3.    import javax.servlet.http.*;  

4.      

5.    public class FirstServlet extends HttpServlet {  

6.    public void doGet(HttpServletRequest request, HttpServletResponse response){  

7.            try{  

8.      

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

10.         PrintWriter out = response.getWriter();  

11.           

12.         String n=request.getParameter("userName");  

13.         out.print("Welcome "+n);  

14.           

15.         //creating form that have invisible textfield  

16.         out.print("<form action='servlet2'>");  

17.         out.print("<input type='hidden' name='uname' value='"+n+"'>");  

18.         out.print("<input type='submit' value='go'>");  

19.         out.print("</form>");  

20.         out.close();  

21.   

22.                 }catch(Exception e){System.out.println(e);}  

23.     }  

24.   

25. }  

import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class FirstServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response){ try{ response.setContentType("text/html"); PrintWriter out = response.getWriter(); String n=request.getParameter("userName"); out.print("Welcome "+n); //creating form that have invisible textfield out.print("<form action='servlet2'> "); out.print("<input type='hidden' name='uname' value='"+n+"'>"); out.print("<input type='submit' value='go'>"); out.print("</form> "); out.close(); }catch(Exception e){System.out.println(e);} } }

SecondServlet.java

1.    import java.io.*;  

2.    import javax.servlet.*;  

3.    import javax.servlet.http.*;  

4.    public class SecondServlet extends HttpServlet {  

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

6.            try{  

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

8.            PrintWriter out = response.getWriter();  

9.              

10.         //Getting the value from the hidden field  

11.         String n=request.getParameter("uname");  

12.         out.print("Hello "+n);  

13.   

14.         out.close();  

15.                 }catch(Exception e){System.out.println(e);}  

16.     }  

17. }  

import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class SecondServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) try{ response.setContentType("text/html"); PrintWriter out = response.getWriter(); //Getting the value from the hidden field String n=request.getParameter("uname"); out.print("Hello "+n); out.close(); }catch(Exception e){System.out.println(e);} } }

web.xml

1.    <web-app>  

2.      

3.    <servlet>  

4.    <servlet-name>s1</servlet-name>  

5.    <servlet-class>FirstServlet</servlet-class>  

6.    </servlet>  

7.      

8.    <servlet-mapping>  

9.    <servlet-name>s1</servlet-name>  

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

11. </servlet-mapping>  

12.   

13. <servlet>  

14. <servlet-name>s2</servlet-name>  

15. <servlet-class>SecondServlet</servlet-class>  

16. </servlet>  

17.   

18. <servlet-mapping>  

19. <servlet-name>s2</servlet-name>  

20. <url-pattern>/servlet2</url-pattern>  

21. </servlet-mapping>  

22.   

23. </web-app>  

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