Question

Recently, I have been facing a problem with throwing exception in JDBC topic.

I synchronized Connection object by using 2 synchronized methods: getConnection() and releaseConnection(). Then another method which removes a row from database as follow:

public void removeItem(int itemID) throws ItemNotFound {
    PreparedStatement ps = null;
    String query = "DELETE * FROM Student.Book WHERE id = ?";
    getConnection();
    try {
      ps = con.prepareStatement(query);
      ps.setInt(1, bookID);
      ps.executeUpdate();
    } catch (SQLException sqle) {
      this.close(null, null, ps);  // method to close PreparedStatement and ResultSet
      releaseConnection();
      throw new BookNotFoundException("Book not found!");
    } finally {
      this.close(null, null, ps);
      releaseConnection();
    }
}

Everything works well if no exception occurs. In case exception occurs, in catch block after releaseConnection() method, throw new BookNotFoundException(“Book not found!”) hangs up!! If i comment releaseConnection() method then it throws normally?

Answer 1

You’re releasing the connection twice. The finally block will always run, even if a catch block runs. My guess is it’s doing the throw, then running the finally block, which tries to release the connection a second time. I’m not sure how you implemented releaseConnection(), but if that blocks when the connection has already been released then this would explain the problem.

I think if you just remove the close and releaseConnection from the catch block it should work fine.