转帖 谢谢
今天在用struts2实现文件下载时出现如下错误:
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)
说实话这个提示真有误导人的嫌疑,刚开始还以为是名称不对,估计一般人看到这个提示都这样想。然后查看StreamResult的源代码才发现是因为InputStream为null的缘故,汗一个。看下源码:
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);
}
原因:
流 为空,路径一定要为 相对路径("/download") 服务器中的, 若为实际路径如 "D:/tomcat/webApp/download" 则会报此异常
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