用户在 Grails 中取消了文件下载答案

【问题标题】：User cancelled file download in Grails用户在 Grails 中取消了文件下载
【发布时间】：2013-08-01 04:57:08
【问题描述】：

如何正确处理取消的文件下载？有问题的文件是一个相当大的 zip 文件，需要很长时间才能构建，因此用户有足够的时间点击下载对话框窗口上的“取消”按钮。

当它发生时，会发生一个令人讨厌的异常（见下文），这是意料之中的，因为客户端破坏了管道。但是怎么清理呢？在哪里/什么是捕获异常的正确方法，以便tomcat日志不会被它们乱扔？

谢谢。

下载代码本身就是教科书中的标准代码：

import java.util.zip.ZipEntry
import java.util.zip.ZipOutputStream

def getZipFile(params) {   
  response.setHeader("Expires", "0");
  response.setHeader("Cache-Control", "must-revalidate, post-check=0, pre-check=0");
  response.setHeader("Pragma", "public");
  response.setHeader("Content-Disposition", "attachment; filename=\"filename.zip\"");
  response.contentType = "application/zip"

  def zos = new ZipOutputStream(response.outputStream)
  zos = functionThatCreatesTheZipFile(zos, params) // this takes some time
  zos.close()
}

例外：

rfpmgr [2013-05-01 10:14:32.337] ERROR: web.errors.GrailsExceptionResolver IOException occurred when processing request: [GET] /rfpManager/report/downloadZipFile
Stacktrace follows:
java.io.IOException
at java.util.zip.ZipOutputStream.writeBytes(ZipOutputStream.java:617)
at java.util.zip.ZipOutputStream.writeCEN(ZipOutputStream.java:501)
at java.util.zip.ZipOutputStream.finish(ZipOutputStream.java:348)
at java.util.zip.DeflaterOutputStream.close(DeflaterOutputStream.java:238)
at java.util.zip.ZipOutputStream.close(ZipOutputStream.java:360)
at gov.usgs.eventManager.ZipService.getZipFile(ZipService.groovy:32)
at gov.usgs.eventManager.ReportController$_closure18.doCall(ReportController.groovy:738)
at gov.usgs.jdt.josso.spring.JOSSOProcessingFilter.doFilter(JOSSOProcessingFilter.java:144)
at gov.usgs.jdt.josso.agent.GenericServletSSOAgentFilter.doFilter(GenericServletSSOAgentFilter.java:431)
at java.lang.Thread.run(Thread.java:722)
rfpmgr [2013-05-01 10:14:32.354] ERROR: web.errors.GrailsExceptionResolver IllegalStateException occurred when processing request: [GET] /rfpManager/report/downloadZipFile
getOutputStream() has already been called for this response. Stacktrace follows:
org.codehaus.groovy.grails.web.pages.exceptions.GroovyPagesException: Error processing GroovyPageView: getOutputStream() has already been called for this response
at gov.usgs.jdt.josso.spring.JOSSOProcessingFilter.doFilter(JOSSOProcessingFilter.java:144)
at gov.usgs.jdt.josso.agent.GenericServletSSOAgentFilter.doFilter(GenericServletSSOAgentFilter.java:431)
at java.lang.Thread.run(Thread.java:722)
Caused by: java.lang.IllegalStateException: getOutputStream() has already been called for this response
at gsp_rfpManager_errorserrors_gsp.run(gsp_rfpManager_errorserrors_gsp.groovy:17)
... 3 more

【问题讨论】：

标签： grails

【解决方案1】：

这似乎工作得很好：

import java.util.zip.ZipEntry
import java.util.zip.ZipOutputStream
import org.apache.catalina.connector.ClientAbortException

def getZipFile(params) {   
  response.setHeader("Expires", "0");
  response.setHeader("Cache-Control", "must-revalidate, post-check=0, pre-check=0");
  response.setHeader("Pragma", "public");
  response.setHeader("Content-Disposition", "attachment; filename=\"filename.zip\"");
  response.contentType = "application/zip"

  try {
    def zos = new ZipOutputStream(response.outputStream)
    zos = functionThatCreatesTheZipFile(zos, params) // this takes some time
    zos.close()
  }
  catch (ClientAbortException ex) {
    println "user aborted download"
  }
}

【讨论】：

所以我不必在我的路径中包含 tomcat 我捕获了 IOException

【解决方案2】：

我可以看到：

原因：java.lang.IllegalStateException：getOutputStream() 已为此响应调用

这对于 Grails 控制器在直接渲染事物时很常见。解决方案：

render ( file: <InputStream>, contentType: 'image/jpeg')
//or
render ( file: <byte[]>, contentType: 'image/jpeg')
//or
GrailsWebRequest webRequest = 
             (GrailsWebRequest) RequestContextHolder.currentRequestAttributes()
webRequest.setRenderView(false)

这应该会有所帮助。

【讨论】：