DOM解析XML出现异常

DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); 
//通过文档构建器工厂获取一个文档构建器
 DocumentBuilder builder = factory.newDocumentBuilder();
//通过文档构建器获取一个文档
Document document = builder.parse(inputStream);
我执行最后一条语句的时候 为什么报
java.lang.StringIndexOutOfBoundsException这个异常呢
我获取的input流是从servlet中 获取来的 
这是servlet中的 代码
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException { response.setContentType("application/xml");
    PrintWriter out = response.getWriter();
    out.println("<?xml version=1.0 encoding=UTF-8>");
    out.println("<teleList>");
    out.println("<persons>");
    out.println("  <name></name>");
    out.println("  <tel>15806029022</tel>");
    out.println("</persons>");
    out.println("<persons>");
    out.println("  <name>xiaozhang</name>");
    out.println("  <tel>13506932567</tel>");
    out.println("</teleList>");
    out.flush();
    out.close();
        
      }