新手求教~将servlet从数据库中读取到的数据在JSP中输出

严重: Servlet.service() for servlet jsp threw exception

java.lang.NullPointerException

	at org.apache.jsp.view.regist_005fclass_jsp._jspService(regist_005fclass_jsp.java:111)

	at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)

	at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)

	at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:393)

	at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)

	at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)

	at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)

	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:175)

	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:263)

	at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844)

	at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:584)

	at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)

	at java.lang.Thread.run(Thread.java:745)

if ("toTeacherList".equalsIgnoreCase(operName)) {

       List<UserInfo> List_teacher = infoDao.getTeacherInfo();

		for(int i=0;i<List_teacher.size();i++){    

			System.out.println(List_teacher.get(i));

			}

			request.setAttribute("List_teacher", List_teacher);

			request.getRequestDispatcher("/view/regist_class.jsp").forward(request, response);

<%

	List<UserInfo> teacherList = (List<UserInfo>)request.getAttribute("List_teacher");

 %>

<select name="teacher">

<%

for (UserInfo info : teacherList) {

%>

<option value="<%=info.getUsername()%>"><%=info.getUsername()%></option>

<%

}

%>

</select>