MalformedStreamException：流意外结束

Question

给定：

byteString 是

-----------------------------149742642616556
Content-Disposition: form-data; name="file"; filename="test.txt"
Content-Type: text/plain

test
-----------------------------149742642616556--

然后这段代码（未优化）：

Pattern pattern = Pattern.compile(BOUNDARY_PATTERN); // "(?m)\A-+\d+$"
Matcher matcher = pattern.matcher(byteString);
String boundary = null;
while (matcher.find()) {
    boundary = matcher.group();
    contentType = "multipart/form-data; boundary=" + boundary;
}
LOG.info("Content Type = " + contentType);

@SuppressWarnings("deprecation")
org.apache.commons.fileupload.MultipartStream multipartStream =
        new org.apache.commons.fileupload.MultipartStream(new ByteArrayInputStream(byteString.getBytes()), boundary.getBytes());
ByteArrayOutputStream bos = new ByteArrayOutputStream();
multipartStream.readBodyData(bos); // throw error
byte[] byteBody = bos.toByteArray();

引发此错误：

org.apache.commons.fileupload.MultipartStream$MalformedStreamException: Stream ended unexpectedly
    at org.apache.commons.fileupload.MultipartStream$ItemInputStream.makeAvailable(MultipartStream.java:1005)
    at org.apache.commons.fileupload.MultipartStream$ItemInputStream.read(MultipartStream.java:903)
    at java.io.InputStream.read(InputStream.java:101)
    at org.apache.commons.fileupload.util.Streams.copy(Streams.java:100)
    at org.apache.commons.fileupload.util.Streams.copy(Streams.java:70)
    at org.apache.commons.fileupload.MultipartStream.readBodyData(MultipartStream.java:593)

这里可能有什么问题？我将不胜感激。

Answer 1

这个问题似乎是由于错误的行尾和检索边界的方式造成的。 根据 RFC2046 quote taken from a SO answer:

The Content-Type field for multipart entities requires one parameter, "boundary". The boundary delimiter line is then defined as a line consisting entirely of two hyphen characters ("-", decimal value 45) followed by the boundary parameter value from the Content-Type header field, optional linear whitespace, and a terminating CRLF.

问题正好出在两点上：行尾类型和边界参数值前面的两个连字符。

行尾

由于您的代码没有准确显示 byteString 的值，我尝试了 LF (\n) 和 CRLF (\r\n) 行尾看看会发生什么。

当 错误的 行尾 - 即不是 CRLF - 就在之前时，问题似乎重现了最后一个边界，如下图：

String byteString=
    "-----------------------------149742642616556\r\n" +
    "Content-Disposition: form-data; name=\"file\"; filename=\"test.txt\"\r\n" +
    "Content-Type: text/plain; charset=UTF-8\r\n" +
    "\r\n" +
    "test\r\n" + // <-- only \n here lead to a MalformedStreamException
    "-----------------------------149742642616556--\r\n";

听起来 MultipartStream 无法解析边界的开头，因为它没有捕获上一行的右行尾 (CRLF)。 所以，我用的是 LF 终结符，你应该用 CRLF 替换它们。

边界格式

RFC 指出边界 delimiter 是两个连字符 + 边界参数 + CRLF。您的正则表达式不仅捕获边界参数值，还包括两个连字符。所以我替换了这部分：

// capturing group = boundary parameter value
String regexp="(?m)\A--(-*\d+)$";
// [...]
while (matcher.find()) {
    boundary = matcher.group(1);
    // [...]
}

工作代码

可作为 MCVE 运行

您将在下面找到的代码可以在没有 Tomcat 的控制台中运行。只需要commons-fileupload-1.3.3-bin.tar.gz and commons-io-2.6-bin.tar.gz。

为了查看 MultipartStream 解析的内容，我在 readBodyData() 调用中暂时将 bos 替换为 System.out（如评论中所述）。

编译：

javac Test.java -classpath ./commons-fileupload-1.3.3-bin/commons-fileupload-1.3.3.jar

到运行:

java -classpath ./commons-fileupload-1.3.3-bin/commons-fileupload-1.3.3.jar:./commons-io-2.6/commons-io-2.6.jar:. Test

代码本身

import java.util.regex.*;
import java.io.*;
import org.apache.commons.fileupload.*;

public class Test {
    public final static void main(String[] argv) {
    String byteString=
        "-----------------------------149742642616556\r\n" +
        "Content-Disposition: form-data; name=\"file\"; filename=\"test.txt\"\r\n" +
        "Content-Type: text/plain; charset=UTF-8\r\n" +
        "\r\n" +
        "test\r\n" + // <-- only \n here lead to a MalformedStreamException
        "-----------------------------149742642616556--\r\n";

    String regexp="(?m)\A--(-*\d+)$"; // edited regexp to catch the right boundary

    Pattern pattern = Pattern.compile(regexp);
    Matcher matcher = pattern.matcher(byteString);
    String boundary = null;
    String contentType=null;
    while (matcher.find()) {
        boundary = matcher.group(1);
        contentType = "multipart/form-data; boundary=\"" + boundary + "\"";
    }

    System.out.println("boundary = \"" + boundary + "\"");

    @SuppressWarnings("deprecation")
        org.apache.commons.fileupload.MultipartStream multipartStream =
        new org.apache.commons.fileupload.MultipartStream
        (new ByteArrayInputStream(byteString.getBytes()), boundary.getBytes());
     ByteArrayOutputStream bos = new ByteArrayOutputStream();

    try {
        // Use the commented line instead the following one
        // To see what the multipartStream is reading (for debug)
        // multipartStream.readBodyData(System.out);
        multipartStream.readBodyData(bos);
    } catch (MultipartStream.MalformedStreamException e) {
        System.out.println("Malformed Exception " + e.getMessage());
    } catch (IOException e) {
        System.out.println(e.getMessage());
    }
    byte[] byteBody = bos.toByteArray();

    // Displaying the body read
    for(byte c : byteBody) {
        System.out.format("%c", c);
    }
    System.out.println();
    }
}

输出：

boundary = "---------------------------149742642616556"
-----------------------------149742642616556
Content-Disposition: form-data; name="file"; filename="test.txt"
Content-Type: text/plain; charset=UTF-8

test

Answer 2

经过一些调试，我发现MultipartStream是在边界上添加\r\n--作为前缀，因为我在内容的开头没有换行我得到了MultipartStream.MalformedStreamException("Stream ended unexpectedly") 异常，因为找不到边界。

可能是因为 commons-fileupload 版本较旧，或者因为我正在从 curl

发送的 HTTP PUT 请求中读取多部分内容

tl;dr

如果到目前为止没有其他帮助，请在您的内容开头添加一个 换行符。

MalformedStreamException：流意外结束

MalformedStreamException: Stream ended unexpectedly

java

apache

multipartform-data

java-8

行尾

边界格式

工作代码

可作为 MCVE 运行

代码本身

输出：

tl;dr