Spring：已经为此响应调用了 getOutputStream()

Question

我知道还有很多其他帖子处理同样的错误，但所有这些帖子要么是关于 JSP/GSP 页面的，要么是出于任何其他原因对我来说不是很有帮助。我正在使用带有 Thymeleaf 的 Spring MVC。以下函数用于下载文件。

@RequestMapping(value = "/test/download/*", method = RequestMethod.GET)
public String getFile(HttpServletResponse response)
{

    ServletOutputStream stream = null;
    try
    {
        stream = response.getOutputStream();

        MultipartFile f = test.getFile();

        InputStream is = f.getInputStream();
        IOUtils.copy(is, stream);
        response.flushBuffer();

        stream.flush();
        stream.close();

    } catch(Exception ex)
    {

    }

    return "test";

}

它确实有效，所以问题不大，但在控制台中，我总是收到以下错误：

2014-01-10T09:28:09.053+0100  SEVERE  Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception  [Request processing failed; nested exception is java.lang.IllegalStateException: getOutputStream() has already been called for this response] with root cause
java.lang.IllegalStateException: getOutputStream() has already been called for this response
at org.apache.catalina.connector.Response.getWriter(Response.java:638)
at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:214)
at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:105)
at javax.servlet.ServletResponseWrapper.getWriter(ServletResponseWrapper.java:105)
at org.springframework.security.web.context.SaveContextOnUpdateOrErrorResponseWrapper.getWriter(SaveContextOnUpdateOrErrorResponseWrapper.java:125)
at org.thymeleaf.spring3.view.ThymeleafView.renderFragment(ThymeleafView.java:335)
at org.thymeleaf.spring3.view.ThymeleafView.render(ThymeleafView.java:190)
[...]

据我所知，getOutputStream()只被调用一次。此外，整个函数被一个try-catch-block包围。所以我想知道，这个错误是从哪里来的？

Answer 1

如果您返回“test”，则是在使用响应 outputStream 返回二进制文件后，指示您的控制器将您发送到某个视图。以下是您应该如何管理此问题的想法：

从弹簧控制器下载文件