Delete table records using checkbox in jsp

**debasisdas** · Mar 5 '09, 07:22 AM

Question moved to Java forum.

**r035198x** · Mar 5 '09, 08:08 AM

1.) Use code tags when posting code.
2.) Move all that database connection code away from the JSP into some utility class or servlet. JSPs are for displaying data only.
3.) Check whether c[] is null or not before you try to do anything with it.

**chaarmann** · Mar 5 '09, 08:18 AM

1.) Please list line number of your error.
2.) Please change your program in a way that you check for EVERY possible value of the called functions first! For example:

Your code:

Code:

String c[]= request.getParameterValues("chbox");
out.println(c[0]);

Change to:

Code:

String c[]= request.getParameterValues("chbox");
if (c != null && c.length != 0) out.println(c[0]);
else out.println("Something went wrong! I tried to access a non-existing array or the first element of an existing array that is not there!");

**JosAH** · Mar 5 '09, 09:26 AM

Originally posted by debasisdas

Question moved to Java forum.

Trash belongs in the trash bin, thank you.

kind regards,

Jos

**ramprakashjava** · Mar 6 '09, 08:34 AM

Originally posted by chaarmann

1.) Please list line number of your error.
2.) Please change your program in a way that you check for EVERY possible value of the called functions first! For example:

Your code:

Code:

String c[]= request.getParameterValues("chbox");
out.println(c[0]);

Change to:

Code:

String c[]= request.getParameterValues("chbox");
if (c != null && c.length != 0) out.println(c[0]);
else out.println("Something went wrong! I tried to access a non-existing array or the first element of an existing array that is not there!");

/* here i listed line number of error*/
java.lang.NullP ointerException
org.apache.jsp. deletepage_jsp. _jspService(del etepage_jsp.jav a:57)
org.apache.jasp er.runtime.Http JspBase.service (HttpJspBase.ja va:94)
javax.servlet.h ttp.HttpServlet .service(HttpSe rvlet.java:802)
org.apache.jasp er.servlet.JspS ervletWrapper.s ervice(JspServl etWrapper.java: 324)
org.apache.jasp er.servlet.JspS ervlet.serviceJ spFile(JspServl et.java:292)
org.apache.jasp er.servlet.JspS ervlet.service( JspServlet.java :236)
javax.servlet.h ttp.HttpServlet .service(HttpSe rvlet.java:802)

**r035198x** · Mar 6 '09, 08:44 AM

Did you make the code changes suggested?

**chaarmann** · Mar 6 '09, 09:01 AM

Originally posted by ramprakashjava

/* here i listed line number of error*/
java.lang.NullP ointerException
org.apache.jsp. deletepage_jsp. _jspService(del etepage_jsp.jav a:57)
org.apache.jasp er.runtime.Http JspBase.service (HttpJspBase.ja va:94)
javax.servlet.h ttp.HttpServlet .service(HttpSe rvlet.java:802)

that's a beginning, but not enough. You should be aware that every jsp-page is converted to java and stored in Apaches "work" directory. The line number listed above references to the line inside this java file and not to a line number in the original jsp.
In your case, your file "deletepage.jsp " is converted to "deletepage_jsp .java". The error is in line 57 of "deletepage_jsp .java" that you can find in "work" directory.

Please just grab the line number 57 from it and list it here.

**ramprakashjava** · Mar 6 '09, 01:34 PM

s i grabbed it that line is
out.println(c[0]);

**r035198x** · Mar 6 '09, 01:41 PM

This is turning out to be a rather pointless thread. Did you make all the suggested code changes?
There is no point in posting suggestions if you are just ignoring them.

**ramprakashjava** · Mar 6 '09, 01:47 PM

here i eclosed few lines thats plz check it

out.write("\r\n ");
out.write("<htm l>\r\n");
out.write("<hea d>\r\n");
out.write("<tit le>Delete page</title>\r\n");
out.write("\r\n ");
out.write("</head>\r\n");
out.write("\r\n ");
out.write("<bod y>\r\n");
out.write(" \r\n");
out.write("\r\n ");
out.write(" ");

String c[]= request.getPara meterValues("ch box");
out.println(c[0]);

Connection con = null;
Statement stmt = null;

try
{

Class.forName(" com.mysql.jdbc. Driver");
con = DriverManager.g etConnection("j dbc:mysql://localhost:3306/ram","root","ad min");
stmt = con.createState ment();
for(String s:c)

**r035198x** · Mar 6 '09, 01:52 PM

Read the replies that have already been posted. Why are you ignoring them?

**chaarmann** · Mar 9 '09, 10:33 AM

Originally posted by ramprakashjava

s i grabbed it that line is
out.println(c[0]);

Ok, so you know that it's crashing because the array c[] is null or empty.
If you have checkboxes and you don't check them, the values are not passed, so the array that you want to get is null.
So c[]=request.getPar ameterValues("c hbox"); gives you exactly that null array in this case.

You cannot access an array that's not there. (i.e. that is null)
You cannot access the first element of an array if the array has no elements. (i.e. accessing c[0])
That's what I mean with:
You have to care about ALL possible values a function might return in your code. I mean every function, especially including the function request.getPara meterValues().

So please apply my code changes listed above. I will list them again here:

Code:

String c[]= request.getParameterValues("chbox"); 
if (c != null && c.length != 0) out.println(c[0]); 
else out.println("Something went wrong! I tried to access a non-existing array or the first element of an existing array that is not there!");

(and write the rest of the code in your program accordingly)

Then your program will work bugfree.

**r035198x** · Mar 10 '09, 08:37 AM

A relevant read.

Delete table records using checkbox in jsp

Delete table records using checkbox in jsp

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment