tomcat配置oracel数据库全局jndi数据源

<Resource driverClassName="oracle.jdbc.driver.OracleDriver"
              factory="org.apache.tomcat.jdbc.pool.DataSourceFactory"
              name="jdbc/oracle"
              password="tiger"
              scope="Shareable"
              type="javax.sql.DataSource"
              url="jdbc:oracle:thin:@127.0.0.1:1521:orcl"
              username="scott"/>

    <ResourceLink global="jdbc/oracle" name="jdbc/oracle" type="javax.sql.DataSource"/>

try {
            Context ctx = new InitialContext();

            // 此处要添加的是查找数据源的名字  但是要加前缀java:comp/env
            DataSource ds = (DataSource)ctx.lookup("java:comp/env/jdbc/oracle");
            // 通过数据源获得数据源中的连接
            Connection conn = ds.getConnection();
            String sql = "select * from emp";
            PreparedStatement pstmt = conn.prepareStatement(sql);
            ResultSet rs = pstmt.executeQuery();
            while(rs.next()){
                System.out.println(rs.getString(1));
            }
        } catch (Exception e) {
            e.printStackTrace();
        }