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tushar panda

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Posts: 133

posted 8 years ago

this is what i got when i tried to pass servlet data to the same servlet.

output at browser :

servlet code :

is there a error in transferring the data from the servlet to itself

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Bear Bibeault

Author and ninkuma
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posted 8 years ago

Not a Tomcat question. Moved to the Servlets forum.

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Bear Bibeault

Author and ninkuma
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posted 8 years ago

Here's the important part:

java.lang.NullPointerException
auction.doPost(auction.java:21)

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tushar panda

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Posts: 133

posted 8 years ago

Bear Bibeault wrote:
auction.doPost(auction.java:21)

line 21 is :
if(itemid.trim().equals(""))

and i don't think there is an error here

entire code is :

import java.io.* ;
import javax.servlet.* ;
import javax.servlet.http.* ;
import java.lang.String ;

public class auction extends HttpServlet{
public void doPost(HttpServletRequest req,HttpServletResponse res)throws IOException,ServletException{
res.setContentType("text/html");
PrintWriter out = res.getWriter();

out.println("<HTML>");
out.println("<HEAD><TITLE>My Auction Site</TITLE></HEAD>");
out.println("<BODY BGCOLOR=\"#ACACAC\">\n");
out.println("<FORM  METHOD='POST'>");

String itemid = req.getParameter("itemid");
String itemname = req.getParameter("itemname");
String email = req.getParameter("email");

if(itemid.trim().equals(""))
{ itemid="";
  out.println("ItemID  :"+"<INPUT TYPE='TEXT' NAME='itemid' VALUE=''><BR>");
}

else
{ out.println("ItemID  :"+itemid+"<BR>");
}

if(itemname.trim().equals(""))
{ itemname="";
  out.println("ItemName  :<INPUT TYPE='TEXT' NAME='itemname' VALUE=''><BR>");
}

else
{ out.println("ItemName  :"+itemname+"<BR>");
}

if(email.trim().equals(""))
{ email="";
  out.println("Email  :<INPUT TYPE='TEXT' NAME='email' VALUE=''><BR>");
}

else
{ out.println("Email  :"+email+"<BR>");
}

if((itemid.trim().equals(""))||(itemname.trim().equals(""))||(email.trim().equals("")))
{out.println("<INPUT TYPE='SUBMIT' NAME='SUBMIT' VALUE='SUBMIT'>");
}

else
{out.println("Congratulations : Details submitted sucessfully");
}

out.println("</FORM>");
out.println("</BODY>");
out.println("</HTML>");

}
}

my purpose of writing this program is to transfer form data to servlet and if any data is not filled ,it is asked again to do so,
but the problem is i am unable

to transfer the servlet data to the same servlet .

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Charbel Keyrouz

Ranch Hand

Posts: 46

posted 8 years ago

are you sure that the itemid is not null?

You should change your tests to take into consideration the null values.

tushar panda

Ranch Hand

Posts: 133

posted 8 years ago

Charbel Keyrouz wrote:are you sure that the itemid is not null?

You should change your tests to take into consideration the null values.

yeah i took null and got the result , but what't the difference between null and blank("")

cheers
Tushar

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salvin francis

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Posts: 1563

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posted 8 years ago

There is a huge difference between both.

Think of strings as an object.

so "", is also an Object in memory. it has properties such as length, etc.

now lets look at null, Its a Black hole, not even light can accept it.

a null is a reference thats initialised to nothing [pardon my non technical grammer here]
rather it "refers" to nothing.

consider the diff between:

and

and

I agree. Here's the better link: Salvin.in

It is sorta covered in the JavaRanch Style Guide.

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