Oracle JDBC UCP和Java

Question

I'm wondering if anyone can shed some light on this topic, as I have been racking my brain for days and can't quite understand why this does not work. I have three classes main , RetrieveDBVersion , GetOracleConnection I've been doing some testing with oracle JDBC, UCP and Java 1.7. According to the Oracle documentation, If I use connection pooling the connection will be returned to the pool as soon as I close the connection, Invalidate it and set it to null See Here . So I decided to give it a whirl and see if it would perform just like the documentation says it should. In my Main application I have a simple loop which makes a connection 200 times by calling RetrieveDBVersion . RetrieveDBVersion is simply performing a query and returning the driver version. My loop works fine until I hit the magic number of 68 and then I receive an error which states

java.sql.SQLException: Exception occurred while getting connection:  
oracle.ucp.UniversalConnectionPoolException:    
Cannot get Connection from Datasource: java.sql.SQLException: 
Listener refused the connection with the following error:
ORA-12516, TNS:listener could not find available handler with matching protocol stack

These are the detail of the 3 methods. These methods are not in a server environment. They are simply calling a local oracle express database and I'm running them from my desktop. Why would I keep getting this error? If I'm returning the connections back to the pool?

1. Main

    import com.jam.DB.JDBCVersion; import static java.lang.System.out; public class MainApp { public static void main(String[] args) { String myMainJDBCVar; try{ for(int i=1; i<200; i++ ) { myMainJDBCVar= JDBCVersion.RetrieveDBVersion(); out.println(myMainJDBCVar + " " + i); } out.println("this is Done!"); } catch (Exception e) { System.out.println(e.getMessage()); } } } 

2. RetrieveDBVersion

     import java.sql.*; import oracle.ucp.jdbc.ValidConnection; public class JDBCVersion { public static String DBVersion; public static String RetrieveDBVersion()throws SQLException { Connection conn = JDBCConnection.GetOracleConnection("test"); try { DatabaseMetaData meta = conn.getMetaData(); //get driver info System.out.println("JDBC driver version is " + meta.getDriverMajorVersion()); DBVersion = meta.getDriverVersion(); } catch (SQLException e) { e.printStackTrace(); DBVersion = e.getMessage(); } finally { System.out.println("hit the finally clause"); ((ValidConnection) conn).setInvalid(); conn.close(); conn=null; } return DBVersion; } 

3. GetOracleConnection

     import oracle.ucp.jdbc.PoolDataSource; import oracle.ucp.jdbc.PoolDataSourceFactory; import java.sql.*; public class JDBCConnection { public static Connection GetOracleConnection(String Enviroment) throws SQLException{ PoolDataSource pds = PoolDataSourceFactory.getPoolDataSource(); Connection conn = null; //ora.defaultConnection(); try { pds.setConnectionFactoryClassName("oracle.jdbc.pool.OracleDataSource"); pds.setURL("jdbc:oracle:thin:@//localhost:1521/xe"); pds.setUser("system"); //pds.setInitialPoolSize(5); pds.setPassword("xxx"); pds.setMaxStatements(10); conn = pds.getConnection(); return conn; } catch(Exception e){ e.printStackTrace(); } return conn; } 

Answer 1

So after careful though and getting a little extra help from the Oracle forum. I finally understand why the above referenced code is giving the error message that I'm receiving. See Here For Response Because I'm setting the data source everytime the loop goes around, I'm essentially creating more than one pool. The way to do this, is create one pool and than pull connections from that pool. New code to replace the GetOracleConnection I created a singleton class for datasource and in code I simply retrieve the connection from the data source like such

Connection conn = Database.getInstance().GetPoolSource().getConnection();

package com.jam.DB;

import oracle.ucp.jdbc.PoolDataSource;
import oracle.ucp.jdbc.PoolDataSourceFactory;

public class Database {

private static Database dbIsntance;
private static PoolDataSource pds;

private Database() {
    // private constructor //
}

public static Database getInstance() {
    if (dbIsntance == null) {
        dbIsntance = new Database();
    }
    return dbIsntance;
}

public PoolDataSource GetPoolSource() {

    if (pds == null) {
        pds = PoolDataSourceFactory.getPoolDataSource();

        try {

            pds.setConnectionFactoryClassName("oracle.jdbc.pool.OracleDataSource");
            pds.setURL("jdbc:oracle:thin:@//localhost:1521/xe");
            pds.setUser("system");
            pds.setPassword("xxxx");
            pds.setMaxStatements(15);
            return pds;

        } catch (Exception e) {

        }
        return pds;
    }

    return pds;

  }
}