java - JSTL fn :length() Function with byte[]

Question

这是我的 Spring Web 模型- View - Controller (MVC) 框架中 JSP 文件中的代码。 Spring Web模型- View - Controller (MVC)框架的版本是3.2.8，部署在WebLogic Server版本:12.1.2.0.0中。我使用的是jSTL-1.2

<c:if test="${not empty form.attachment}">
${fn:length(form.attachment.bytes.length)}
</c:if>

哪里

private MultipartFile attachment;

但是我有这个错误:

java.lang.NumberFormatException: For input string: "length"
        at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
        at java.lang.Integer.parseInt(Integer.java:492)
        at java.lang.Integer.parseInt(Integer.java:527)
        at javax.el.ArrayELResolver.toInteger(ArrayELResolver.java:378)
        at javax.el.ArrayELResolver.getValue(ArrayELResolver.java:198)
        at javax.el.CompositeELResolver.getValue(CompositeELResolver.java:188)
        at com.sun.el.parser.AstValue.getValue(AstValue.java:138)
        at com.sun.el.parser.AstValue.getValue(AstValue.java:183)
        at com.sun.el.parser.AstFunction.getValue(AstFunction.java:122)
        at com.sun.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:224)
        at weblogic.servlet.jsp.ELHelper.evaluate(ELHelper.java:32)
        at jsp_servlet._web_45_inf._jsp._manage.__managecompanybody._jsp__tag2(__managecompanybody.java:952)
        at jsp_servlet._web_45_inf._jsp._manage.__managecompanybody._jspService(__managecompanybody.java:252)
        at weblogic.servlet.jsp.JspBase.service(JspBase.java:34)
        at weblogic.servlet.internal.StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:280)
        at weblogic.servlet.internal.StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:254)
        at weblogic.servlet.internal.StubSecurityHelper.invokeServlet(StubSecurityHelper.java:136)
        at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:341)
        at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:238)
        at weblogic.servlet.internal.RequestDispatcherImpl.invokeServlet(RequestDispatcherImpl.java:573)
        at weblogic.servlet.internal.RequestDispatcherImpl.include(RequestDispatcherImpl.java:480)
        at weblogic.servlet.jsp.PageContextImpl.include(PageContextImpl.java:162)
        at jsp_servlet._web_45_inf._jsp._manage.__managebody._jspService(__managebody.java:1048)
        at weblogic.servlet.jsp.JspBase.service(JspBase.java:34)
        at weblogic.servlet.internal.StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:280)
        at weblogic.servlet.internal.StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:254)
        at weblogic.servlet.internal.StubSecurityHelper.invokeServlet(StubSecurityHelper.java:136)
        at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:341)
        at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:238)
        at weblogic.servlet.internal.RequestDispatcherImpl.invokeServlet(RequestDispatcherImpl.java:573)
        at weblogic.servlet.internal.RequestDispatcherImpl.include(RequestDispatcherImpl.java:480)
        at org.apache.taglibs.standard.tag.common.core.ImportSupport.acquireString(ImportSupport.java:347)
        at org.apache.taglibs.standard.tag.common.core.ImportSupport.doEndTag(ImportSupport.java:204)
        at jsp_servlet._web_45_inf._jsp._template.__template._jsp__tag2(__template.java:365)
        at jsp_servlet._web_45_inf._jsp._template.__template._jspService(__template.java:247)
        at weblogic.servlet.jsp.JspBase.service(JspBase.java:34)
        at weblogic.servlet.internal.StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:280)
        at weblogic.servlet.internal.StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:254)
        at weblogic.servlet.internal.StubSecurityHelper.invokeServlet(StubSecurityHelper.java:136)
        at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:341)
        at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:238)
        at weblogic.servlet.internal.RequestDispatcherImpl.invokeServlet(RequestDispatcherImpl.java:573)
        at weblogic.servlet.internal.RequestDispatcherImpl.forward(RequestDispatcherImpl.java:272)
        at org.springframework.web.servlet.view.InternalResourceView.renderMergedOutputModel(InternalResourceView.java:238)
        at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:264)
        at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1208)
        at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:992)
        at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:939)
        at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
        at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:953)
        at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:855)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:751)
        at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:829)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:844)
        at weblogic.servlet.internal.StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:280)
        at weblogic.servlet.internal.StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:254)
        at weblogic.servlet.internal.StubSecurityHelper.invokeServlet(StubSecurityHelper.java:136)
        at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:341)
        at weblogic.servlet.internal.TailFilter.doFilter(TailFilter.java:25)
        at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:79)
        at cpm.tdk.iot.taglib.datagrid.export.ExcelExportFilter.doFilter(ExcelExportFilter.java:39)
        at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:79)
        at cpm.tdk.iot.filter.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:27)
        at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:79)
        at cpm.tdk.iot.filter.EventDispatcherFilter.doFilter(EventDispatcherFilter.java:38)
        at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:79)
        at cpm.tdk.iot.filter.RequestUrlFilter.doFilter(RequestUrlFilter.java:31)
        at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:79)
        at cpm.tdk.iot.support.context.DevicesSecurityFilter.doFilter(DevicesSecurityFilter.java:82)
        at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:79)
        at weblogic.servlet.internal.RequestEventsFilter.doFilter(RequestEventsFilter.java:27)
        at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:79)
        at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.wrapRun(WebAppServletContext.java:3367)
        at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.run(WebAppServletContext.java:3333)
        at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:321)
        at weblogic.security.service.SecurityManager.runAs(SecurityManager.java:120)
        at weblogic.servlet.provider.WlsSubjectHandle.run(WlsSubjectHandle.java:57)
        at weblogic.servlet.internal.WebAppServletContext.doSecuredExecute(WebAppServletContext.java:2220)
        at weblogic.servlet.internal.WebAppServletContext.securedExecute(WebAppServletContext.java:2146)
        at weblogic.servlet.internal.WebAppServletContext.execute(WebAppServletContext.java:2124)
        at weblogic.servlet.internal.ServletRequestImpl.run(ServletRequestImpl.java:1564)
        at weblogic.servlet.provider.ContainerSupportProviderImpl$WlsRequestExecutor.run(ContainerSupportProviderImpl.java:254)
        at weblogic.work.ExecuteThread.execute(ExecuteThread.java:295)
        at weblogic.work.ExecuteThread.run(ExecuteThread.java:254)

Answer 1

您需要更改:

fn:length(form.attachment.bytes.length)

致:

fn:length(form.attachment.bytes)

您希望 fn:length 获取字节数组的长度，而不是 length 的长度。