JDBC连接DB2、Oracle、MySQL、PostgreSQL

package   com.terac.util;         import   java.sql.Connection;     import   java.sql.DriverManager;     import   java.sql.ResultSet;     import   java.sql.Statement;         public   class   DBTest   {     public   static   void   main(String[]   args)   {     try   {     String   user   =   "user";     String   password   =   "password";     String   driver   =   "COM.ibm.db2.jdbc.net.DB2Driver";     //"oracle.jdbc.driver.OracleDriver";     //"com.mysql.jdbc.Driver";     //"org.postgresql.Driver";     String   url   =   "jdbc:db2://localhost/a";     //"jdbc:oracle:thin:@localhost:1521:a";     //"jdbc:mysql://localhost/a";     //"jdbc:postgresql://localhost:5740/a";     String   sql   =   "SELECT   current   timestamp   FROM   sysibm.sysdummy1";     //"SELECT   sysdate   FROM   dual";     //"SELECT   now()";     //"SELECT   current_timestamp";     Class.forName(driver).newInstance();     Connection   c   =   DriverManager.getConnection(url,   user,   password);     Statement   stmt   =   c.createStatement();     ResultSet   rs   =   stmt.executeQuery(sql);     while   (rs.next())   {     System.out.println(rs.getString(1));     }     }   catch   (Exception   e)   {     e.printStackTrace();     }     }     }