jsp 出现：org.apache.jasper.JasperException: Unable to compile class for JSP:

数据库连接 我用的是Dao（Database Access Object）用jsp写网页调用数据库老是出现以下错误：

HTTP Status 500 -

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException: Unable to compile class for JSP:

An error occurred at line: 41 in the jsp file: /index.jsp
Dao cannot be resolved
38:   			<li><label class="inputfeature">Structure:</label><select name="structure" class="inputcontent">
39:   			<%
40:   				//ResultSet rs=Dao.getStructure();
41:   				out.println("<p>"+(String)Dao.getStructure().get(1)+"</p>");
42:   				int i=1;
43:   				//while(rs.next()){
44:

Stacktrace:
org.apache.jasper.compiler.DefaultErrorHandler.javacError(DefaultErrorHandler.java:102)
org.apache.jasper.compiler.ErrorDispatcher.javacError(ErrorDispatcher.java:331)
org.apache.jasper.compiler.JDTCompiler.generateClass(JDTCompiler.java:457)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:378)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:353)
org.apache.jasper.compiler.Compiler.compile(Compiler.java:340)
org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:646)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:357)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
javax.servlet.http.HttpServlet.service(HttpServlet.java:722)

note The full stack trace of the root cause is available in the Apache Tomcat/7.0.23 logs.

Apache Tomcat/7.0.23

弄了好久才解决，自建的类不能放在默认包里，应该新建包来存放