Tomcat error: 500 The server encountered an internal error that prevented it from fulfilling this request

Background:
I use JDK1.8 and tomcat8.0, but I encounter the following two problems


then I made a new tomcat, and its version is as follows:

and it succeeded…..

The reason: Tomcat version is higher than JDK version

In addition, I have problems with my code
here is the error code:

<%@ page contentType="text/html;charset=UTF-8" %>
<%@ taglib tagdir="/WEB-INF/tags" prefix="computer"%>
<html>
The three values entered a,b,c (representing the three sides of a triangle or the upper base, lower base and height of a trapezoid);
<body color=cyan>
        <form action="" method=get name=form> 
        <%--Get parameters to submit to yourself--%>
        <table>
        <tr><td>Enter value a: </td>
            <td><input type="text" name="a"></td>
        </tr>
        <tr><td>input value b: </td>
            <td><input type="text" name="b"></td>
        </tr>
        <tr><td>input value c: </td>
            <td><input type="text" name="c"></td>
        </tr>
        </table>
        <input type="radio" name="r" value="triangle">stands for triangle
        <input type="radio" name="r" value="lader">stands for trapezoid
        <br>
        <input type="submit" name="submit" value="submit" name=submit>stands for submit button
        </form>
        <% String a=request.getParameter("a");
           String b=request.getParameter("b");
           String c=request.getParameter("c");
           String cd=request.getParameter("r");
           if(a==null||b==null||c==null){
              a="0";
              b="0";
              c="0";
              cd="0";
                      
           }
           if(a.length()>0&&b.length()>0&&c.length()>0){
        %>
           <computer:Getarea numberA="<%=a%>" numberB="<%=b%>"
                             numberC="<%=c%>" condition="<%=cd%>"/>
           
           
           <br><%= message%>
           <br><%= area %>
        
        <% }
        %>
        </body>
        </html>

The reason for the error is that there are two more spaces. The error report is the same
here is the correct code:

<%@ page contentType="text/html;charset=UTF-8" %>
<%@ taglib tagdir="/WEB-INF/tags" prefix="computer"%>
<html>
The three values entered a,b,c (representing the three sides of a triangle or the upper base, lower base and height of a trapezoid);
<body color=cyan>
        <form action="" method=get name=form> 
        <%--Get parameters to submit to yourself--%>
        <table>
        <tr><td>Enter value a: </td>
            <td><input type="text" name="a"></td>
        </tr>
        <tr><td>input value b: </td>
            <td><input type="text" name="b"></td>
        </tr>
        <tr><td>input value c: </td>
            <td><input type="text" name="c"></td>
        </tr>
        </table>
        <input type="radio" name="r" value="triangle">stands for triangle
        <input type="radio" name="r" value="lader">stands for trapezoid
        <br>
        <input type="submit" name="submit" value="submit" name=submit>stands for submit button
        </form>
        <% String a=request.getParameter("a");
           String b=request.getParameter("b");
           String c=request.getParameter("c");
           String cd=request.getParameter("r");
           if(a==null||b==null||c==null){
              a="0";
              b="0";
              c="0";
              cd="0";
                      
           }
           if(a.length()>0&&b.length()>0&&c.length()>0){
        %>
           <computer:Getarea numberA="<%=a%>" numberB="<%=b%>"
                             numberC="<%=c%>" condition="<%=cd%>"/>
           
           
           <br><%=message%>
           <br><%=area %>
        
        <% }
        %>
        </body>
        </html>

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