java程序独自运行正确，用jsp调用就出错_Java相关

java程序单独运行正确，用jsp调用就出错
本人编写了一段java类程序，功能是将html网页保存为pdf格式，这个java类单独运行结果是正确的。但是如果把这段代码加入jsp中，让jsp页面调用，结果就出错，请各位大侠帮忙看一下。。。谢谢啦
JSP代码为：
<%@ page language="java" import="java.util.*" pageEncoding="ISO-8859-1"%>
<%@ page import="format.conversion.HtmlToPdf" %>

<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">

    <title>My JSP 'index.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">

  </head>

  <body>
    This is my JSP page. <br>
  </body>
  <%
   HtmlToPdf htp=new HtmlToPdf();
   htp.go();
   %>
</html>

java类代码为：
package format.conversion;

import java.io.File;
import java.io.FileOutputStream;
import java.io.OutputStream;

import javax.swing.JFileChooser;
import javax.swing.filechooser.FileFilter;

import org.xhtmlrenderer.pdf.ITextFontResolver;
import org.xhtmlrenderer.pdf.ITextRenderer;

import com.lowagie.text.pdf.BaseFont;

public class HtmlToPdf {
        public static void main(String[] args){
         try{
         HtmlToPdf tt=new HtmlToPdf();
             tt.go();
             System.out.println("pdf保存成功");
         }catch(Exception ex){
         System.out.println("pdf保存失败");
         ex.printStackTrace();
         }
         System.exit(0);

        }

        public void go()throws Exception{
         String inputFile = "WebRoot/Report.html";
            String url = new File(inputFile).toURI().toURL().toString();

            JFileChooser fileSave=new JFileChooser(".");
            fileSave.showSaveDialog(null);
            File file=fileSave.getSelectedFile();

            String outputFile =file.toString();
            String url1=new File(outputFile).toURI().toURL().toString();
            System.out.println(url);
            System.out.println(url1);
            OutputStream os = new FileOutputStream(outputFile);
            ITextRenderer renderer = new ITextRenderer();
            renderer.setDocument(url);

            ITextFontResolver fontResolver = renderer.getFontResolver();
            fontResolver.addFont("C:/Windows/Fonts/SIMSUN.TTC", BaseFont.IDENTITY_H, BaseFont.NOT_EMBEDDED);

            renderer.layout();
            renderer.createPDF(os);