I'm programming applets & servlets on Tomcat and MySQL with my desktop (PIII500 - Win2000 - 512Mo).

- jakarta-tomcat-4.1.27-LE-jdk14
- mysql-4.0.14b
- j2sdk1.4.2
- mysql-connector-java-3.0.9-stable
- Tomcat DBCP (collections-2.1 dbcp-1.0 pool-1.0.1)

But ! I can not have stable behaviour with ResultSet :

- Sometimes all records are returned. Fine !!!
- Sometimes, 0 (Zero) record is returned. Too bad !
- Sometimes, some (but not all) records are returned. Bad !

And, When all records are not returned, one of the two following exception types is raised :

java.sql.SQLException: Operation not allowed after ResultSet closed
at com.mysql.jdbc.ResultSet.checkClosed(ResultSet.jav a:3601)
at com.mysql.jdbc.ResultSet.checkRowPos(ResultSet.jav a:3614)
....

OR

java.lang.NullPointerException
at com.mysql.jdbc.ResultSet.checkRowPos(ResultSet.jav a:3625)
at com.mysql.jdbc.ResultSet.getString(ResultSet.java: 1772)
at org.apache.commons.dbcp.DelegatingResultSet.getStr ing(DelegatingResultSet.java:137)
....

What my application does :

- Inserting rows in a table (strings, dates, integers).
- And the, selecting table in a Resultset for gettind data
- I use ResultSet.getString() for getting all fields.

Database Pooling configuration in server.xml file :

<parameter>
<name>maxActive</name>
<value>10</value>
</parameter>

<parameter>
<name>maxIdle</name>
<value>0</value>
</parameter>

<parameter>
<name>maxWait</name>
<value>15000</value>
</parameter>

What I DO NOT suspect :

- Having not closed connection, statement or cursor.
- Doing some computation with null variables.

Thanks in advance for your help.

Toum.

I think that there is some thing really wrong in your code (for example you do not test your querry result, if the connection is still avaible ...)

Thanks Olivier for your reply.

Do you mean I have to put the code inside the "try" in a loop and let it run until I get a valid Resultset ? Do you know how I could make sure my Resultset is valid. I could test if (t_rs != null) of course. What if t_rs is not null but is valid only for the first records (obtained by t_rs.next()) ?

In my case, It seems that the t_rs is not null, but something wrong happenned when the next is called.

protected void executeSelect(String str)
{
try
{
if (ds != null)
{
t_conn = ds.getConnection();
if (t_conn != null)
{
t_stm =t_conn.prepareStatement(str);
if (t_stm != null)
{
t_rs = t_stm.executeQuery();
}
}
}
}
catch (Exception e)
{
}
}