What is serialVersionUID?

[RC]

import javax.servlet.*;
import javax.servlet.http.*;

public class MyClass extends HttpServlet {
.....
}

warning: [serial] serializable class MyClass has no definition of
^
serialVersionUID
public class MyClass extends HttpServlet {

What is this warning message mean?
How do I get rid it?

Thank Q very much in advance!

P.S. I know a warning message is NOT an error, but
someday, sometime may be cause run time failure.

 

[Ingo R. Homann]

Hi,

import javax.servlet.*;
import javax.servlet.http.*;

public class MyClass extends HttpServlet {
....
}

warning: [serial] serializable class MyClass has no definition of
^
serialVersionUID
public class MyClass extends HttpServlet {

What is this warning message mean?

You need a serialVersionId, if your class implements "Serializable".
HttpServlet does so, and so you need such an id. (It is used, if the
Servlet-Context is relaunched and your sessions should be made
persistant / restored. If you do not need this feature, you do not need
a serialVersionId.)

How do I get rid it?

There is some switch to disable the warning (e.g. in Eclipse...)

P.S. I know a warning message is NOT an error, but
someday, sometime may be cause run time failure.

Yes, its better not to ignore warnings (although that's not possible
with Java5 :-()

Ciao,
ingo

 

[blaine]

You'll need to add a serialVersionUID to your class eg:

public class MyClass extends HttpServlet{
public static final long serialVersionUID = 1L;

public MyClass(){
}
}

 

[Skip]

You'll need to add a serialVersionUID to your class eg:

public class MyClass extends HttpServlet{
public static final long serialVersionUID = 1L;

public MyClass(){
}
}

That static field may be private too.

 

[Bryce]

Hi,

import javax.servlet.*;
import javax.servlet.http.*;

public class MyClass extends HttpServlet {
....
}

warning: [serial] serializable class MyClass has no definition of
^
serialVersionUID
public class MyClass extends HttpServlet {

What is this warning message mean?

You need a serialVersionId, if your class implements "Serializable".
HttpServlet does so, and so you need such an id. (It is used, if the
Servlet-Context is relaunched and your sessions should be made
persistant / restored. If you do not need this feature, you do not need
a serialVersionId.)

How do I get rid it?

There is some switch to disable the warning (e.g. in Eclipse...)

P.S. I know a warning message is NOT an error, but
someday, sometime may be cause run time failure.

Yes, its better not to ignore warnings (although that's not possible
with Java5 :-()

Added note:

If you are using Eclipse, it can generate the id for you. Click on the
yellow lightbulb.

 

[Roedy Green]

serialVersionUID

see http://mindprod.com/jgloss/serialization.html

--
Bush crime family lost/embezzled $3 trillion from Pentagon.
Complicit Bush-friendly media keeps mum. Rumsfeld confesses on video.
http://www.infowars.com/articles/us/mckinney_grills_rumsfeld.htm

Canadian Mind Products, Roedy Green.
See http://mindprod.com/iraq.html photos of Bush's war crimes

 

[Roedy Green]

serialVersionUID
public class MyClass extends HttpServlet {

What is this warning message mean?
How do I get rid it?

see http://mindprod.com/jgloss/serialization.html