1、错误描述
java.lang.NumberFormatException: empty Stringat sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1020)at java.lang.Double.parseDouble(Double.java:540)service.impl.BillServiceImpl.exportBillExcel(BillServiceImpl.java:301)at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)at java.lang.reflect.Method.invoke(Method.java:606)at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:317)at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:190)at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157)at org.springframework.aop.framework.adapter.AfterReturningAdviceInterceptor.invoke(AfterReturningAdviceInterceptor.java:52)at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92)at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:207)at com.sun.proxy.$Proxy46.exportBillExcel(Unknown Source)controller.BillController.exportBillExcel(ArrivalBillController.java:159)at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)at java.lang.reflect.Method.invoke(Method.java:606)at org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:215)at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:132)at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:749)at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:689)at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:83)at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:938)at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:870)at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:961)at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:852)at javax.servlet.http.HttpServlet.service(HttpServlet.java:620)at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:837)at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)at filter.TranscationFilter.doFilter(TranscationFilter.java:32)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)at filter.ContentFilter.doFilter(ContentFilter.java:57)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)at org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:61)at org.apache.shiro.web.servlet.AdviceFilter.executeChain(AdviceFilter.java:108)at org.apache.shiro.web.servlet.AdviceFilter.doFilterInternal(AdviceFilter.java:137)at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)at org.apache.shiro.web.servlet.ProxiedFilterChain.doFilter(ProxiedFilterChain.java:66)at org.apache.shiro.web.servlet.AbstractShiroFilter.executeChain(AbstractShiroFilter.java:449)at org.apache.shiro.web.servlet.AbstractShiroFilter$1.call(AbstractShiroFilter.java:365)at org.apache.shiro.subject.support.SubjectCallable.doCall(SubjectCallable.java:90)at org.apache.shiro.subject.support.SubjectCallable.call(SubjectCallable.java:83)at org.apache.shiro.subject.support.DelegatingSubject.execute(DelegatingSubject.java:383)at org.apache.shiro.web.servlet.AbstractShiroFilter.doFilterInternal(AbstractShiroFilter.java:362)at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:344)at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:261)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1070)at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:611)at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)at java.lang.Thread.run(Thread.java:745)2、错误原因double result = 0;for(int i=0;i<data.size();i++){Map<String,Object> map=(Map<String, Object>) data.get(i);HSSFRow datarow = sheet.createRow(i+1); HSSFCell c8 = datarow.createCell(8);HSSFRichTextString t8 = new HSSFRichTextString(map.get("result")+"");c8.setCellValue(t8);result += Double.parseDouble(t8.toString());} 在将字符串强制转换成double时，，数据库查询的result字段值为空字符串，而强制转换成double类型的值不能为null或“”，这样就导致报错
3、解决办法
将强制转换前判断result是否为空字符串（null已经在SQL语句中判断）：
result += Double.parseDouble("".equals(t8.toString())?"0.00":t8.toString());
注意：这里字符串为空，用equals方法而不是用“==”
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