Java bean gives null pointerexception

Posted on 2003-11-01
Last Modified: 2010-04-01
   I know this is really very very funny.At times my java bean application works and at times it give an exception of null pointer.
I think my problem is that maybe i am not using the get  properly,

I mean, when i use set i use:

<jsp:useBean id="vol" class="com.dhal.volun" scope="session"/>
<jsp:setProperty name="vol" property="*"/>

But i use the getters such as:

Do i need to write something maybe to use it, for example,


coz, when i look at work folder for the jas_jsp files it seems as if vol is null.

But if write
username gets printed so i am surprise which is null.

Question by:Jasbir21
  • 5
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LVL 14

Expert Comment

Comment Utility
the is nothing wrong of the code that u have posted. the problem is in somewhere else, post the full stack trace of you exception.

Author Comment

Comment Utility

When  i looked at the line 250,it is about this line

The java code for query that i use is....

   connection = DriverManager.getConnection(connectionURL, "", "");
   String myquery="select * from account where username='Jasbir22'";

   String query="select * from volunteer where username='Jasbir22'";

    .......//its is alot here


   catch(SQLException ex ) {  ex.printStackTrace() ; }

   catch( ClassNotFoundException ex ){  ex.printStackTrace() ; }


LVL 14

Accepted Solution

kennethxu earned 60 total points
Comment Utility
rs.getString(2) is giving you null.

make sure password is the column number 2 and it is not null for user Jasbir22.
BTW, I'd suggest you to use column name instead of possition, since position might change if you add new columns to database.

Author Comment

Comment Utility
   I don't understand something, does it mean that a column value cannot be null because if its it would give a null pointer,
sometimes, a user would need not enter a column, soit is null

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Author Comment

Comment Utility
when i type describle table,

i get

So, i guess it is at column 2 ????

How do i do it the column name way

LVL 15

Assisted Solution

dualsoul earned 40 total points
Comment Utility
>So, i guess it is at column 2 ????
columns are counted from ResultSet, not DB schema, but in your it's the same, because you retrive all columns.

>How do i do it the column name way
just use overloading methods in ResultSet:
    String s=rs.getString("password");


Author Comment

Comment Utility
When you say column are counted from Resultset,

how are they are counted...

LVL 14

Expert Comment

Comment Utility
>> When you say column are counted from Resultset.
that's the order in your select statment. it's same if you use select *, but if you use select password, username from..., then the order is password, username.

>> does it mean that a column value cannot be null
NO, the problem is that you are doing a trim(), so if the rs.getString() returns null, you are doing s = null.trim(), of course, you get NPE.
for those columns that could be null in database, you should always use
String s = rs.getString("columnname");
if( s != null ) s=s.trim();

Author Comment

Comment Utility
......I have been spending days to find out what my problem, and you guys in experts - exchange solved in seconds.Thank you so much....


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