reason for java.sql.SQLException: Closed Connection

[Steve Jiang]

I have the following code , which works fine normally. We found a exception for "java.sql.SQLException: Closed Connection" in a demo site recently. I don't understand why connection is closed , and what could be the reason.

In demo site, it happens everytime, so it looks like not other thread to close the connection.


Could anyone point me the possible reason for "java.sql.SQLException: Closed Connection" in this case?

        if (m_conn == null))
          return null;
        
        PreparedStatement stmt = null;
        ResultSet result = null;
        try
        {
Line 805:          stmt = m_conn.prepareStatement( "select value from v$osstat where stat_name = 'NUM_CPU_CORES'");  // throw "Closed Connection" exception in this line
          result = stmt.executeQuery();
          

2010-09-07 06:44:37,411logp.251 - java.sql.SQLException: Closed Connection
java.sql.SQLException: Closed Connection
at oracle.jdbc.driver.SQLStateMapping.newSQLException(SQLStateMapping.java:70)
at oracle.jdbc.driver.DatabaseError.newSQLException(DatabaseError.java:133)
at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:199)
at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:263)
at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:271)
at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:445)
at oracle.jdbc.driver.PhysicalConnection.prepareStatement(PhysicalConnection.java:3127)
at oracle.jdbc.driver.PhysicalConnection.prepareStatement(PhysicalConnection.java:3042)
at sysman.util.jdbc.ConnectionWrapper.prepareStatement(ConnectionWrapper.java:577)
at sysman.emo.util.ValueResolver.getCpuCores(ValueResolver.java:805)

[Sandeep Sanaboyina]

You are getting a Closed Connection exception because by line 805, your connection object m_conn is getting closed.

It won't be possible to tell why it is getting closed with the code you have provided.

Instead of using

if (m_conn == null))   
          return null; 

use

if (m_conn == null))   
          return null; 
if (m_conn.isClosed())
          return null;

That should stop the application from throwing the exception. But, to find out why the connection is closed, you will have to dig in some more ito your code.

[Steve Jiang]

Thanks for the reply. Since the demo site is using shiphome, we can't add the debugger for it. But in development env, we haven't met this case before. That make me very curious how the connection could be closed .

[David Newton]

Someone might be closing it. As mentioned, with the code provided, there's no way to know.