在编写导出功能使用action请求，在处理导出异常时期望跳转异常页，Controller中的方法返回类型String的url
在处理完逻辑导出文件后后台控制台出现
WARN [org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver] (default task-22) Handling of [org.springframework.http.converter.HttpMessageNotWritableException] resulted in Exception: java.lang.IllegalStateException: UT010019: Response already commited
and
ERROR [io.undertow.request] (default task-22) UT005023: Exception handling request to /snq-admin/data/exportDataDetail.do: org.springframework.web.util.NestedServletException: Request processing failed; nested exception is org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: UT010029: Stream is closed; nested exception is java.io.IOException: UT010029: Stream is closed
Caused by: org.springframework.http.converter.HttpMessageNotWritableException: Could not write JSON: UT010029: Stream is closed; nested exception is java.io.IOException: UT010029: Stream is closed
Caused by: java.io.IOException: UT010029: Stream is closed
在写入文件时调用requestOutputStream.write()方法已将response发出，再在Controller中return时被认为是再发送一次，因而会报错，解决这个问题只需返回null即可。
Action请求后台出现Response already commited异常解决方法
原文：https://www.cnblogs.com/seedling/p/10011551.html