从输出流中获取输入流 [英] Get an input stream from an output stream

问题描述

我有一个在输出流(ByteArrayOutputStream)中给我数据的组件，我需要将其写入SQL数据库的blob字段中而不创建临时缓冲区，因此需要获取输入流.

I have a component that's given me data in an output stream (ByteArrayOutputStream) and I need to write this into a blob field of a SQL database without creating temp buffers hence the need to get an input stream.

基于答案此处和

Based on answers here and here I came up the following method to get an input stream from an output stream:

private PipedInputStream getInputStream(ByteArrayOutputStream outputStream) throws InterruptedException
{
    PipedInputStream pipedInStream = new PipedInputStream();
    Thread copyThread = new Thread(new CopyStreamHelper(outputStream, pipedInStream));
    copyThread.start();
    // Wait for copy to complete
    copyThread.join();
    return pipedInStream;
}

class CopyStreamHelper implements Runnable
{
    private ByteArrayOutputStream outStream;
    private PipedInputStream pipedInStream;

    public CopyStreamHelper (ByteArrayOutputStream _outStream, PipedInputStream _pipedInStream)
    {
        outStream = _outStream;
        pipedInStream = _pipedInStream;
    }

    public void run()
    {
        PipedOutputStream pipedOutStream = null;
        try
        {
            // write the original OutputStream to the PipedOutputStream
            pipedOutStream = new PipedOutputStream(pipedInStream);
            outStream.writeTo(pipedOutStream);
        }
        catch (IOException e) 
        {
            // logging and exception handling should go here
        }
        finally
        {
            IOUtils.closeQuietly(pipedOutStream);
        }
    }
}

请注意，输出流已经包含写入的数据，并且可以运行1-2 MB. 但是，无论尝试在两个单独的线程中还是在同一线程中执行此操作，我都会发现总是PipedInputStream挂在以下位置:

Please note that the output stream already contains the written data and it can run up to 1-2 MB. However regardless of trying to do this in two separate threads or the same thread I am finding that always PipedInputStream hangs at the following:

Object.wait(long) line: not available [native method]   
PipedInputStream.awaitSpace() line: not available   

推荐答案

您正在使解决方案过于复杂

You are overcomplicating the solution

ByteArrayOutputStream baos = ...;
byte[] data = baos.toByteArray();
return new ByteArrayInputStream(data);

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