为什么这个异常FileItemStream $ ItemSkippedException？

Question

在gwt Web应用程序中.我必须发送一个文件和一些附加的参数.

在ServerSide上

try {

        ServletFileUpload upload = new ServletFileUpload();

        FileItemIterator iterator = upload.getItemIterator(request);

        while (iterator.hasNext()) {
            FileItemStream item = iterator.next();


            if (item.isFormField()) {

                String fieldName=item.getFieldName();
                String fieldValue = Streams.asString(item.openStream());
                System.out.println(" chk  " +fieldName +"  =  "+ fieldValue);
            } else {
                stream = item.openStream();
                fileName = item.getName();
                mimetype = item.getContentType();
                int c;
                while ((c = stream.read()) != -1) { 
                  System.out.print((char) c); 
                    }
            }
        }
    }catch (Exception e) {
        // TODO: handle exception
        e.printStackTrace();
    }
    System.out.println("out of try");
    ByteArrayOutputStream output = new ByteArrayOutputStream();
    int nRead;
    while ((nRead = stream.read(buffer, 0, buffer.length)) != -1) {
        System.out.println("lenth111" +nRead);
        output.write(buffer, 0, nRead);
    }
    System.out.println("lenth" +nRead);
    output.flush();

使用此代码,我可以读取流.并且还在控制台上"打印出来"也打印出来

最后,while ((nRead = stream.read(buffer, 0, buffer.length)) != -1) 我得到了一个警告

警告:/ UploadFileServlet:org.apache.commons.fileupload.FileItemStream $ ItemSkippedException.

如何解决这个问题呢.？？

Answer 1

回答有点迟,但我遇到了同样的问题.

为什么会出现异常:ItemSkippedException的JavaDocs解释了一下:

如果在创建FileItemStream的迭代器上调用Iterator.hasNext()之后尝试从FileIream读取数据,则会抛出此异常(FileItemStream.openStream()返回).

您正在使用while循环外部的InputStream 流导致该问题,因为调用了另一个迭代,该迭代将关闭(跳过)您尝试读取的文件InputStream.

解决方案:在while循环中使用InputStream.如果在处理文件之前需要所有表单字段,请确保在客户端以正确的顺序设置它.首先是所有字段,最后是文件.例如,使用JavaScript FormData:

var fd = new window.FormData();

fd.append("param1", param1);
fd.append("param2", param2);

// file must be last parameter to append
fd.append("file", file);

在服务器端:

FileItemIterator iter = upload.getItemIterator(request);
while (iter.hasNext()) {
    FileItemStream item = iter.next();
    InputStream stream = item.openStream();

    // the order of items is given by client, first form-fields, last file stream
    if (item.isFormField()) {
        String name = item.getFieldName();
        String value = Streams.asString(stream);
        // here we get the param1 and param2
    } else {
        String filename = item.getName();
        String mimetype = item.getContentType();

        ByteArrayOutputStream output = new ByteArrayOutputStream();
        int nRead;
        while ((nRead = stream.read(buffer, 0, buffer.length)) != -1) {
            System.out.println("lenth111" +nRead);
            output.write(buffer, 0, nRead);
        }
        System.out.println("lenth" +nRead);
        output.flush(); 
    }
}