急！急！急！急！急！急！jxl导出Excel问题，NullPointerException

Question

javaexcel数据异常

Answer 1

异常信息如下：
java.lang.NullPointerException
        at jxl.write.biff.File.write(File.java:133)
        at jxl.write.biff.WritableWorkbookImpl.write(WritableWorkbookImpl.java:6
04)
        at com.extrapackage.exportExcel.exportDetailExcel.writeDetailExcel(expor
tDetailExcel.java:89)
        at org.apache.jsp.others.excelTest_jsp._jspService(excelTest_jsp.java:86
)
        at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper
.java:432)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:3
90)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(Appl
icationFilterChain.java:305)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationF
ilterChain.java:210)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperV
alve.java:222)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextV
alve.java:123)
        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(Authentica
torBase.java:472)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.j
ava:171)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.j
ava:99)
        at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:
936)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineVal
ve.java:118)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.jav
a:407)
        at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp
11Processor.java:1004)
        at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(
AbstractProtocol.java:589)
        at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoin
t.java:1822)
        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExec
utor.java:886)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor
.java:908)
        at java.lang.Thread.run(Thread.java:619)
java.lang.RuntimeException: java.lang.NullPointerException
        at jxl.write.biff.File.write(File.java:147)
        at jxl.write.biff.WritableWorkbookImpl.write(WritableWorkbookImpl.java:6
04)
        at com.extrapackage.exportExcel.exportDetailExcel.writeDetailExcel(expor
tDetailExcel.java:89)
        at org.apache.jsp.others.excelTest_jsp._jspService(excelTest_jsp.java:86
)
        at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper
.java:432)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:3
90)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(Appl
icationFilterChain.java:305)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationF
ilterChain.java:210)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperV
alve.java:222)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextV
alve.java:123)
        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(Authentica
torBase.java:472)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.j
ava:171)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.j
ava:99)
        at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:
936)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineVal
ve.java:118)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.jav
a:407)
        at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp
11Processor.java:1004)
        at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(
AbstractProtocol.java:589)
        at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoin
t.java:1822)
        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExec
utor.java:886)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor
.java:908)
        at java.lang.Thread.run(Thread.java:619)
Caused by: java.lang.NullPointerException
        at jxl.write.biff.File.write(File.java:133)
        ... 25 more

Answer 2

DEBUG看看吧，空指针异常还是比较好找的

Answer 3

writeHead()方法里写完头部就把book关闭了。下面当然空，没写完你关什么。