java当中JDBC当中请给出一个Oracle DataSource and SingleTon例子

Oracle DataSource and SingleTon：　
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import oracle.jdbc.pool.OracleDataSource;
import java.sql.Connection;
import java.sql.*;

public class OracleSingletonDataSource {
  static private OracleDataSource ods;
  private OracleSingletonDataSource() {
    try{
        ods = new OracleDataSource();
        ods.setURL("jdbc:oracle:thin:@localhost:1521:qixy");
        ods.setUser("scott");
        ods.setPassword("tiger");
            }catch(Exception e){
            e.printStackTrace();
            }
  }
  public static Connection getConnection() throws Exception {
    if (ods==null)
       {
           new OracleSingletonDataSource();
          // ods.getConnection();

      }
      Connection con =null;
      try {
          con = ods.getConnection();
      } catch (SQLException ex) {
        ex.printStackTrace();
      }
       return  con;
      }

}




测试程序：

import java.sql.*;
public class testOracleSingletonDataSource {

  public static void main(String args[]) {
    Connection con;
    Statement stm = null;
ResultSet rs = null;
    try {
/* DatabaseConnection's "static private OracleDataSource ods;" is always in the memory once it is created becasue it is static..*/
con = OracleSingletonDataSource.getConnection();
stm = con.createStatement();
rs = stm.executeQuery("select ename from emp");
  while(rs.next())
  {
        String name=rs.getString("ename");
        System.out.println(name);

  }
  rs.close();
  stm.close();
  con.close();
}

    catch (Exception e) {
      e.printStackTrace();
    }

//    System.out.println("the following is the second time ");

  }
}