我在开发阶段,在那里我有两个模块,从一个我得到输出作为一个OutputStream和第二个,它只接受InputStream。你知道如何将OutputStream转换为InputStream(反之亦然,我的意思是真的这样),我将能够连接这两个部分吗?
谢谢
我在开发阶段,在那里我有两个模块,从一个我得到输出作为一个OutputStream和第二个,它只接受InputStream。你知道如何将OutputStream转换为InputStream(反之亦然,我的意思是真的这样),我将能够连接这两个部分吗?
谢谢
当前回答
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.
其他回答
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……
由于输入和输出流只是起点和终点,解决方案是将数据临时存储在字节数组中。因此,您必须创建中间ByteArrayOutputStream,从中创建字节[],用作新ByteArrayInputStream的输入。
public void doTwoThingsWithStream(InputStream inStream, OutputStream outStream){
//create temporary bayte array output stream
ByteArrayOutputStream baos = new ByteArrayOutputStream();
doFirstThing(inStream, baos);
//create input stream from baos
InputStream isFromFirstData = new ByteArrayInputStream(baos.toByteArray());
doSecondThing(isFromFirstData, outStream);
}
希望能有所帮助。
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.
正如一些人已经回答的那样,没有有效的方法来“转换”一个OutputStream到一个InputStream。解决这类问题的技巧是将所有需要OutputStream的代码执行到它自己的线程中。通过使用管道流,我们可以将数据从创建的线程传输到InputStream中。
使用示例:
public static InputStream downloadFileAsStream(final String uriString) throws IOException {
final InputStream inputStream = runInOwnThreadWithPipedStreams((outputStream) -> {
try {
downloadUriToStream(uriString, outputStream);
} catch (final Exception e) {
LOGGER.error("Download of uri '{}' has failed", uriString, e);
}
});
return inputStream;
}
辅助功能:
public static InputStream runInOwnThreadWithPipedStreams(
final Consumer<OutputStream> outputStreamConsumer) throws IOException {
final PipedInputStream inputStream = new PipedInputStream();
final PipedOutputStream outputStream = new PipedOutputStream(inputStream);
new Thread(new Runnable() {
public void run() {
try {
outputStreamConsumer.accept(outputStream);
} finally {
try {
outputStream.close();
} catch (final IOException e) {
LOGGER.error("Closing outputStream has failed. ", e);
}
}
}
}).start();
return inputStream;
}
单元测试:
@Test
void testRunInOwnThreadWithPipedStreams() throws IOException {
final InputStream inputStream = LoadFileUtil.runInOwnThreadWithPipedStreams((OutputStream outputStream) -> {
try {
IOUtils.copy(IOUtils.toInputStream("Hello World", StandardCharsets.UTF_8), outputStream);
} catch (final IOException e) {
LoggerFactory.getLogger(LoadFileUtilTest.class).error(e.getMessage(), e);
}
});
final String actualResult = IOUtils.toString(inputStream, StandardCharsets.UTF_8);
Assertions.assertEquals("Hello World", actualResult);
}
库io-extras可能很有用。例如,如果你想使用GZIPOutputStream gzip一个InputStream,并且你希望它同步发生(使用默认的缓冲区大小8192):
InputStream is = ...
InputStream gz = IOUtil.pipe(is, o -> new GZIPOutputStream(o));
请注意,该库具有100%的单元测试覆盖率(当然,这是值得的!),并且位于Maven Central上。Maven依赖项是:
<dependency>
<groupId>com.github.davidmoten</groupId>
<artifactId>io-extras</artifactId>
<version>0.1</version>
</dependency>
一定要查看更新的版本。