老帖子，但可能会帮助别人，使用这种方式:

OutputStream out = new ByteArrayOutputStream();
...
out.write();
...
ObjectInputStream ois = new ObjectInputStream(new ByteArrayInputStream(out.toString().getBytes()));

输出流是将数据写入其中的流。如果某个模块公开了一个OutputStream，则期望在另一端有一些内容正在读取。

另一方面，公开InputStream的内容表明您将需要侦听此流，并且将有您可以读取的数据。

因此，可以将InputStream连接到OutputStream

InputStream----read——> intermediateBytes[n] ----write----> OutputStream

正如有人提到的，这就是IOUtils的copy()方法让您做的事情。相反的方向是没有意义的。希望这能让你们理解

更新:

当然，我越想这一点，就越能看出这实际上是一个要求。我知道有些评论提到了管道输入/输出流，但还有另一种可能性。

如果公开的输出流是bybyterayoutputstream，那么您总是可以通过调用toByteArray()方法来获得完整的内容。然后，您可以使用ByteArrayInputStream子类创建输入流包装器。这两个是伪流，它们基本上都只是包装一个字节数组。因此，以这种方式使用流在技术上是可行的，但对我来说还是很奇怪……

你需要一个中间类来缓冲。每次调用InputStream.read(byte[]…)时，缓冲类将用从OutputStream.write(byte[]…)传入的下一个块填充传入的字节数组。由于块的大小可能不相同，适配器类需要存储一定数量的块，直到它有足够的容量填满读缓冲区和/或能够存储任何缓冲区溢出。

这篇文章很好地分解了解决这个问题的几种不同方法:

http://blog.ostermiller.org/convert-java-outputstream-inputstream

easystream开源库直接支持将OutputStream转换为InputStream: http://io-tools.sourceforge.net/easystream/tutorial/tutorial.html

// create conversion
final OutputStreamToInputStream<Void> out = new OutputStreamToInputStream<Void>() {
    @Override
    protected Void doRead(final InputStream in) throws Exception {
           LibraryClass2.processDataFromInputStream(in);
           return null;
        }
    };
try {   
     LibraryClass1.writeDataToTheOutputStream(out);
} finally {
     // don't miss the close (or a thread would not terminate correctly).
     out.close();
}

他们还列出了其他选项:http://io-tools.sourceforge.net/easystream/outputstream_to_inputstream/implementations.html

Write the data the data into a memory buffer (ByteArrayOutputStream) get the byteArray and read it again with a ByteArrayInputStream. This is the best approach if you're sure your data fits into memory. Copy your data to a temporary file and read it back. Use pipes: this is the best approach both for memory usage and speed (you can take full advantage of the multi-core processors) and also the standard solution offered by Sun. Use InputStreamFromOutputStream and OutputStreamToInputStream from the easystream library.

ByteArrayOutputStream buffer = (ByteArrayOutputStream) aOutputStream;
byte[] bytes = buffer.toByteArray();
InputStream inputStream = new ByteArrayInputStream(bytes);

Though you cannot convert an OutputStream to an InputStream, java provides a way using PipedOutputStream and PipedInputStream that you can have data written to a PipedOutputStream to become available through an associated PipedInputStream. Sometime back I faced a similar situation when dealing with third party libraries that required an InputStream instance to be passed to them instead of an OutputStream instance. The way I fixed this issue is to use the PipedInputStream and PipedOutputStream. By the way they are tricky to use and you must use multithreading to achieve what you want. I recently published an implementation on github which you can use. Here is the link . You can go through the wiki to understand how to use it.