jsp连接oracle出现的问题

     今天第一次使用oracle数据库来做东西。可是却遇到了麻烦！具体连接数据库的代码是在网上看的。     连接代码如下：
     <%
      Class.forName("oracle.jdbc.driver.OracleDriver").newInstance(); 
      String url="jdbc:oracle:thin:@localhost:1521:scott"; 
      //这个scott是数据库名字吗？我没建库，用的就是Scott，是这样子的吗 ？
      String user="scott"; 
      String password="tiger"; 
      Connection conn= DriverManager.getConnection(url,user,password); 
      Statement stmt=conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE); 
      String sql="select * from emp"; 
      //scott里面有emp这张表。
      ResultSet rs=stmt.executeQuery(sql); 
      while(rs.next()) {
      %> 
        您的第一个字段内容为：<%=rs.getString(1)%> 
        您的第二个字段内容为：<%=rs.getString(2)%> 
     <%
     }
     %> 
        <%out.print("数据库操作成功，恭喜你");%>         <%
           rs.close(); 
           stmt.close(); 
           conn.close(); 
        %> 
     连接时出现如下错误：     严重: Servlet.service() for servlet jsp threw exception
           java.sql.SQLException: Listener refused the connection with the following error:
           ORA-12505, TNS:listener does not currently know of SID given in connect descriptor
           The Connection descriptor used by the client was:
           localhost:1521:scott at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:125)
at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:280)
at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:319)
at oracle.jdbc.driver.PhysicalConnection.<init>(PhysicalConnection.java:344)
at oracle.jdbc.driver.T4CConnection.<init>(T4CConnection.java:148)
at oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:32)
at oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:545)
at java.sql.DriverManager.getConnection(DriverManager.java:582)
at java.sql.DriverManager.getConnection(DriverManager.java:185)
at org.apache.jsp.testoracle_jsp._jspService(testoracle_jsp.java:72)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Thread.java:619)
   麻烦大家给看看时怎么回事。。谢谢啦！！！