JSP问题，请大家看看是什么意思，哪里出错了？

org.apache.jasper.JasperException: An exception occurred processing JSP page /teacher.jsp at line 37

34: //设置最大化允许上传的文件大小
35: myUpload.setFilePath("D:\\workspace\\xielinfeng\\excels");
36: //获取要上传的文件名
37: fileName=myUpload.getFileName();
38: //保存上传的文件
39: myUpload.saveFile(fileName);
40: //判断文件是否上传成功

Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:515)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:426)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
root cause

java.lang.NullPointerException
com.upload.FileUpload.getFileName(FileUpload.java:101)
org.apache.jsp.teacher_jsp._jspService(teacher_jsp.java:96)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:384)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)

note The full stack trace of the root cause is available in the Apache Tomcat/6.0.10 logs.
101行是：int firstIndex=fileStr.indexOf("filename=\"");