tomcat6.0数据库连接池配置实例(informix)

求大神支持下informix，如何配置tomcat数据库连接池，详细步骤 Tomcat Informix 数据库连接池实例 --------------------编程问答-------------------- 我做的尝试：1，在E:\mywork\apache-tomcat-6.0.32\lib下引入ifxjdbc.jar
2，配置E:\mywork\apache-tomcat-6.0.32\conf下的context.xml，配置如下
<Resource
      name="jdbc/informix"
      type="javax.sql.DataSource"
      driverClassName="com.informix.jdbc.IfxDriver"
      maxIdle="2"
      maxWait="5000"
      username="cbsl"
      password="qqww"
      url="jdbc:informix-sqli://localhost:9021/hn4300car3gdb:informixserver=hn_4300_cb_ids;NEWLOCALE=zh_CN,zh_CN;NEWCODESET=gb18030,8859-1,819;IFX_USE_STRENC=true"
      maxActive="4"/>
3，在web.xml中配置如下<resource-ref>
    <description>Informix DB Connection Pool</description>
    <res-ref-name>jdbc/informix</res-ref-name>
    <res-type>javax.sql.DataSource</res-type>
    <res-auth>Container</res-auth>
    <res-sharing-scope>Shareable</res-sharing-scope>
</resource-ref>

4，test测试数据
  public static void main(String[] args) {
DataSource ds = null;
    try{
    Context initCtx = new InitialContext();
    Context envCtx = (Context) initCtx.lookup("java:comp/env");
    ds = (DataSource) envCtx.lookup("jdbc/informix");
    Connection conn = ds.getConnection();
    Statement stmt = conn.createStatement();
    String strSql = " select psncode,psnname from bd_psndoc";
    ResultSet rs = stmt.executeQuery(strSql);
    ArrayList<Monopolyer> ms= new ArrayList<Monopolyer>();
    while(rs.next()){
     Monopolyer m=new Monopolyer();
     m.setPsncode(rs.getString(1));
     m.setPsnname(rs.getString(2));
     System.out.println(m.getPsncode());
     ms.add(m);
      }
    }
    catch(Exception ex){
     ex.printStackTrace();
    }
}
5，报错----javax.naming.NoInitialContextException: Need to specify class name in environment or system property, or as an applet parameter, or in an application resource file:  java.naming.factory.initial

补充：Java ,  Web 开发