Would singleton database connection affect performance in a weblogic clustered environment? - database

Question

I have a Java EE struts web application using a singleton database connection. In the past, there is only one weblogic server, but now, there are two weblogic servers in a cluster.
Session replication have been tested to be working in this cluster. The web application consist of a few links that will open up different forms for the user to fill in. Each form has a dynamic dropdownlist that will populate some values depending on which form is clicked. These dropdownlist values are retrieved from the oracle database.
One unique issue is that the first form that is clicked, might took around 2-5 seconds, and the second form clicked could take forever to load or more than 5 mins. I have checked the codes and happened to know that the issue lies when an attempt to call the one instance of the db connection. Could this be a deadlock?
public static synchronized DataSingleton getDataSingleton()
throws ApplicationException {
if (myDataSingleton == null) {
myDataSingleton = new DataSingleton();
}
return myDataSingleton;
}
Any help in explaining such a scenario would be appreciated.
Thank you
A sample read operation calling Singleton
String sql = "...";
DataSingleton myDataSingleton = DataSingleton.getDataSingleton();
conn = myDataSingleton.getConnection();
try {
PreparedStatement pstmt = conn.prepareStatement(sql);
try {
pstmt.setString(1, userId);
ResultSet rs = pstmt.executeQuery();
try {
while (rs.next()) {
String group = rs.getString("mygroup");
}
} catch (SQLException rsEx) {
throw rsEx;
} finally {
rs.close();
}
} catch (SQLException psEx) {
throw psEx;
} finally {
pstmt.close();
}
} catch (SQLException connEx) {
throw connEx;
} finally {
conn.close();
}
The Singleton class
/**
* Private Constructor looking up for Server's Datasource through JNDI
*/
private DataSingleton() throws ApplicationException {
try {
Context ctx = new InitialContext();
SystemConstant mySystemConstant = SystemConstant
.getSystemConstant();
String fullJndiPath = mySystemConstant.getFullJndiPath();
ds = (DataSource) ctx.lookup(fullJndiPath);
} catch (NamingException ne) {
throw new ApplicationException(ne);
}
}
/**
* Singleton: To obtain only 1 instance throughout the system
*
* #return DataSingleton
*/
public static synchronized DataSingleton getDataSingleton()
throws ApplicationException {
if (myDataSingleton == null) {
myDataSingleton = new DataSingleton();
}
return myDataSingleton;
}
/**
* Fetching SQL Connection through Datasource
*
*/
public Connection getConnection() throws ApplicationException {
Connection conn = null;
try {
if (ds == null) {
}
conn = ds.getConnection();
} catch (SQLException sqlE) {
throw new ApplicationException(sqlE);
}
return conn;
}

Answer 1

It sounds like you may not be committing the transaction at the end of your use of the connection.
What's in DataSingleton - is it a database connection? Allowing multiple threads to access the same database connection is not going to work, for example once you have more than one user. Why don't you use a database connection pool, for example a DataSource?