java.lang.NullPointerException：没有设置FileItemFactory

Question

在试图使用流式API实现fileUpload时，我得到如下所述的错误： 当我从the Streaming API网页收集“传统FileItemFactory完全被忽略”时，我想知道我做错了什么。所以我决定的基本方法如下：

/** 
* 
* @param 
* @return 
*/ 
public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException { 

    // Check that we have a file upload request 
    boolean isMultipart = ServletFileUpload.isMultipartContent(request); 

    if (isMultipart) { 

     ServletFileUpload upload = new ServletFileUpload();     // Create a new file upload handler 

      // Parse the request 
      try { 
Line 39 -->   List items = upload.parseRequest(request);      // FileItem 
      Iterator iter = items.iterator(); 
      while (iter.hasNext()) { 
       FileItemStream item = (FileItemStream) iter.next(); 

       if (!item.isFormField()) { 
        this.processFITSFile(item); 
       } 
      } 
     } catch (FileUploadException e) { 
      // TODO Auto-generated catch block 
      e.printStackTrace(); 
     }  
    } 
} 

但是，这会导致下面的错误：

SEVERE: Servlet.service() for servlet FitsFileProcessorServlet threw exception 
java.lang.NullPointerException: No FileItemFactory has been set. 
    at org.apache.commons.fileupload.FileUploadBase.parseRequest(FileUploadBase.java:353) 
    at org.apache.commons.fileupload.servlet.ServletFileUpload.parseRequest(ServletFileUpload.java:126) 
    at controller.FITSFileProcessor.doPost(FITSFileProcessor.java:39) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:637) 
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717) 
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) 
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) 
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233) 
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191) 
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128) 
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) 
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) 
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293) 
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849) 
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583) 
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454) 
    at java.lang.Thread.run(Unknown Source) 

Answer 1

new ServletFileUpload()创建一个未初始化的实例。其文档说：

构造此类的未初始化实例 。在 试图解析请求之前，工厂必须配置为 ，使用 setFileItemFactory（）。

因此，您需要使用setFileItemFactory()或使用其他构造函数，它将工厂作为参数。像这样：

// Create a factory for disk-based file items 
FileItemFactory factory = new DiskFileItemFactory(); 

// Create a new file upload handler 
ServletFileUpload upload = new ServletFileUpload(factory); 

有关更多信息，请参阅the documentation。这个例子也是从那里开始的。

或者，你可以使用streaming API，但你需要获得不同的迭代器：

ServletFileUpload upload = new ServletFileUpload(); 
FileItemIterator iter = upload.getItemIterator(request); 
while (iter.hasNext()) { 
    FileItemStream item = iter.next(); 
    ... 
}