Jasperreport：JSP做报表出现的问题

hhlong 2005-06-13 05:28:25

请问：

　　有如下JSP页面，运行的时候会报如下面的错误，其实也不应该叫错误吧，
因为，在控制台没有相应的出错信息提示啊，还是就是如果我们＂忽略＂那个错误的
情况下，该JSP页面就运行正常，唉．找了好多资料也不知道到底错在哪里，请高手帮忙说明一下．

环境：eclipse3.0+jasperreports-0.6.8.jar+jdk1.4.1
下面的：keepwatch.jasper文件是在iReport5.0下编译过的

---------------------------------------------------------------
<%@ page session="false" %>
<%@ page import="net.sf.jasperreports.engine.*" %>
<%@ page import="com.longer.db.*"%>
<%@ page import="java.sql.*"%>
<%@ page import="javax.sql.*"%>
<%@ page import="java.util.*" %>
<%@ page import="java.io.*" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title></title>
<%
Connection conn = new DBManager().getConnection();
System.out.println("---------conn-------------");

//装载jasper文件
File file = new File(application.getRealPath("/keepwatch.jasper"));
System.out.println("---------File-------------");

　　　　Map parameters = new HashMap();
parameters.put("myDate", "");

　　　　System.out.println("---------Jasper begin-------------");
JasperRunManager.runReportToHtmlFile(file.getPath(),parameters,conn);
System.out.println("---------Jasper End-------------");

response.sendRedirect("/webTest/keepwatch.html");
%>
</head>
<body>
</body>
</html>

　　　　　　　　　　　　　Exception
－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－－
Thread [http-8080-Processor25] (Suspended (exception NullPointerException))
keepWatch(JRCalculator).evaluate(JRExpression) line: 466
keepWatch(JRCalculator).calculateVariables() line: 147
JRVerticalFiller.fillDetail() line: 576
JRVerticalFiller.fillReportStart() line: 210
JRVerticalFiller.fillReport() line: 118
JRVerticalFiller(JRBaseFiller).fill(Map, JRDataSource) line: 622
JRVerticalFiller(JRBaseFiller).fill(Map, Connection) line: 489
JRFiller.fillReport(JasperReport, Map, Connection) line: 76
JasperFillManager.fillReport(JasperReport, Map, Connection) line: 247
JasperRunManager.runReportToHtmlFile(String, Map, Connection) line: 296
createWatcherReport_jsp._jspService(HttpServletRequest, HttpServletResponse) line: 42
createWatcherReport_jsp(HttpJspBase).service(HttpServletRequest, HttpServletResponse) line: 94
createWatcherReport_jsp(HttpServlet).service(ServletRequest, ServletResponse) line: 802
JspServletWrapper.service(HttpServletRequest, HttpServletResponse, boolean) line: 324
JspServlet.serviceJspFile(HttpServletRequest, HttpServletResponse, String, Throwable, boolean) line: 292
JspServlet.service(HttpServletRequest, HttpServletResponse) line: 236
JspServlet(HttpServlet).service(ServletRequest, ServletResponse) line: 802
ApplicationFilterChain.internalDoFilter(ServletRequest, ServletResponse) line: 252
ApplicationFilterChain.doFilter(ServletRequest, ServletResponse) line: 173
StandardWrapperValve.invoke(Request, Response, ValveContext) line: 214
StandardValveContext.invokeNext(Request, Response) line: 104
StandardPipeline.invoke(Request, Response) line: 520
StandardContextValve.invokeInternal(Wrapper, Request, Response) line: 198
StandardContextValve.invoke(Request, Response, ValveContext) line: 152
StandardValveContext.invokeNext(Request, Response) line: 104
StandardPipeline.invoke(Request, Response) line: 520
StandardHostValve.invoke(Request, Response, ValveContext) line: 137
StandardValveContext.invokeNext(Request, Response) line: 104
ErrorReportValve.invoke(Request, Response, ValveContext) line: 118
StandardValveContext.invokeNext(Request, Response) line: 102
StandardPipeline.invoke(Request, Response) line: 520
StandardEngineValve.invoke(Request, Response, ValveContext) line: 109
StandardValveContext.invokeNext(Request, Response) line: 104
StandardPipeline.invoke(Request, Response) line: 520
StandardEngine(ContainerBase).invoke(Request, Response) line: 929
CoyoteAdapter.service(Request, Response) line: 160
Http11Processor.process(InputStream, OutputStream) line: 799
Http11Protocol$Http11ConnectionHandler.processConnection(TcpConnection, Object[]) line: 705
TcpWorkerThread.runIt(Object[]) line: 577
ThreadPool$ControlRunnable.run() line: 684
ThreadWithAttributes(Thread).run() line: 534

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