Dear All
I work on a small application with database support. For development I use
the MySQL database which is just doing fine. During testing I experienced a,
in my opinion, strange bug.
I have the following source code:
>>>>>>>>>>>>>>
Connection conn = p_GetConnectionFromPool();
try {
// Try to lock the database connection to have exclusive access for
table locks
synchronized (conn) {
Statement stmt = null;
ResultSet rSet = null;
try {
// Create statement from connection
stmt = conn.createStatement();
// First, read the configured timeout time
rSet = stmt.executeQuery("select v from config where
k='time'");
rSet.next();
String ttl = rSet.getString("v");
rSet.close();
rSet = null;
rSet = stmt.executeQuery("show databases");
while (rSet.next()) {
// Do something in here
}
rSet.close();
} catch (SQLException Ex) {
// Notify about exception
} finally {
// Do some cleanup work
if (rSet != null) {
try { rSet.close(); } catch (SQLException
Ignore) {}
rSet = null;
}
if (stmt != null) {
try { stmt.close(); } catch (SQLException
Ignore) {}
stmt = null;
}
}
}
} finally {
// Place the connection back in the connection pool
if (conn != null) { p_Connections.push(conn); }
}
<<<<<<<<<<<<<<<<<<
Now the problem I encounter:
The first query ("select v from config where k='time'") is executed without
any problems. I can read the returned value and save in 'ttl'. Then, I close
this result set and leave it to the garbage collector. Next, I want to use
the same variable to take the result set of another query ("show databases")
which is executed as well. But then, when I execute "while (rSet.next())" I
get the following exception:
>>>>>>>>>>>>>>>>>>
java.sql.SQLException: Operation not allowed after ResultSet closed
at com.mysql.jdbc.ResultSet.checkClosed(ResultSet.java:4579)
at com.mysql.jdbc.ResultSet.next(ResultSet.java:2423)
at
net.sos.web.services.mapping.CMySQLMappingService$1.run(CMySQLMappingService
.java:323)
at java.lang.Thread.run(Unknown Source)
<<<<<<<<<<<<<<<<<<
"while (rSet.next())" is on line 323 in an anonymous class implementation of
java.lang.Runnable, but I think this is not the reason for the exception.
I use Connection/J in version 3.1.1alpha and MySQL 5.0.0alpha (I have to
because of some features unique to MySQL 5). The JDK I use is 1.4.2_02
I hope someone can help me since I have really no clue why this is
happening. Temporarily I don't close the result set but this would result in
a lot of memory consumption in my system.
Thanks
Bjoern
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