今天在用struts2就行文件下載時出現如下錯誤：

Servlet.service() for servlet default threw exception java.lang.IllegalArgumentException: Can not find a java.io.InputStream with the name [imageStream] in the invocation stack.
Check the <param name="inputName"> tag specified for this action. at org.apache.struts2.dispatcher.StreamResult.doExecute(StreamResult.java:189) at org.apache.struts2.dispatcher.StrutsResultSupport.execute(StrutsResultSupport.java:178) at com.opensymphony.xwork2.DefaultActionInvocation.executeResult(DefaultActionInvocation.java:348) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:253) at com.best.top.validate.TopInterceptor.intercept(TopInterceptor.java:47) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:224) at com.opensymphony.xwork2.DefaultActionInvocation$2.doProfiling(DefaultActionInvocation.java:223) at com.opensymphony.xwork2.util.profiling.UtilTimerStack.profile(UtilTimerStack.java:455) at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:221) at org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:50) at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:504) at org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:419)

說實話這個提示真有誤導人的嫌疑，剛開始還以為是名稱不對，估計一般人看到這個提示都這樣想。然后查看StreamResult的源代碼才發現是因為InputStream為null的緣故，汗一個。看下源碼：

if (inputStream == null) { // Find the inputstream from the invocation variable stack inputStream = (InputStream) invocation.getStack().findValue(conditionalParse(inputName, invocation)); } if (inputStream == null) { String msg = ("Can not find a java.io.InputStream with the name [" + inputName + "] in the invocation stack. " + "Check the <param name=\"inputName\"> tag specified for this action."); LOG.error(msg); throw new IllegalArgumentException(msg); }

大家如果也碰到此類問題,直接打印

InputStream in=ServletActionContext.getServletContext().getResourceAsStream(realPath); System.out.println(in);

如果打印為NULL的話,恭喜您,問題得以解決,問題的原因是這個流的realPath路徑錯誤,還沒明白的往下看,怪呀,我的配置應該沒錯呀

頁面上:

<a href="fileDownload.action?fileName=<s:property value ="imageName" />">下載此圖片</a>

struts.xml中：

<!-- 文件下載，支持中文附件名 --><action name="fileDownload"class="com.test.action.filedown.FileDownloadAction"><result name="success" type="stream"><!-- 動態文件下載的，事先并不知道未來的文件類型，那么我們可以把它的值設置成為：application/octet-stream;charset=ISO8859-1 ，注意一定要加入charset，否則某些時候會導致下載的文件出錯； --><param name="contentType">application/octet-stream;charset=ISO8859-1</param><param name="contentDisposition">attachment;filename="${downloadFileName}"</param><!-- 使用經過轉碼的文件名作為下載文件名，downloadFileName屬性對應action類中的方法 getDownloadFileName() 其中特殊的代碼就是${downloadFileName}，它的效果相當于運行的時候將action對象的屬性的取值動態的填充在${}中間的部分，我們可以認為它等價于＋action. getDownloadFileName()。 --><param name="inputName">inputStream</param><param name="bufferSize">4096</param></result></action>

action中：

private String fileName;// 初始的通過param指定的文件名屬性 set get/** 文件名 轉換編碼 防止中文亂碼*/ public String getDownloadFileName() {String fileName=ServletActionContext.getRequest().getParameter("fileName");String downFileName = fileName;try {downFileName = new String(downFileName.getBytes(), "ISO8859-1");} catch (Exception e) {e.printStackTrace();}return downFileName; } //下載的流 public InputStream getInputStream() {String name=this.getDownloadFileName(); // String realPath=ServletActionContext.getServletContext().getRealPath("/uploadImages")+ "/"+name; 路徑錯誤String realPath="/uploadImages/"+name;InputStream in=ServletActionContext.getServletContext().getResourceAsStream(realPath);if(null==in){System.out.println("Can not find a java.io.InputStream with the name [inputStream] in the invocation stack. Check the <param name=\"inputName\"> tag specified for this action.檢查action中文件下載路徑是否正確."); }return ServletActionContext.getServletContext().getResourceAsStream(realPath); }@Override public String execute() throws Exception {return SUCCESS; }

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轉載于:https://www.cnblogs.com/longshiyVip/p/4958668.html

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