jsp错误原因？？？
exception
org.apache.jasper.JasperException: Exception in JSP: /Ex1_5.jsp:33
30: String sideA=request.getParameter("a");
31: String sideB=request.getParameter("b");
32: String sideC=request.getParameter("c");
33: double a1=Double.parseDouble(sideA);
34: double b1=Double.parseDouble(sideB);
35: double c1=Double.parseDouble(sideC);
36:
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:489)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:411)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:308)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:259)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
[解决办法]
你这是数据提交到本页，然后计算
第一次进这个页面，肯定没有获得任何数据了
所以你要判断的
<%
String sideA=request.getParameter("a");
String sideB=request.getParameter("b");
String sideC=request.getParameter("c");
if(!(sideA==null||sideB==null||sideC==null)){
//这里还要对非数字的判断，建议将参数转换放到方法里面
double a1=Double.parseDouble(sideA);
double b1=Double.parseDouble(sideB);
double c1=Double.parseDouble(sideC);
%>
<h2>求面积结果为：</h2>
<%= mianji(a1,b1,c1) %>
<%}%>
[解决办法]
