如何在 Java 中制作 InputStream 的深层副本
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How to make a deep copy of an InputStream in Java
提问by Spredzy
I would like to know how to make a deep copy of an InputStream.
我想知道如何制作InputStream.
I know that it can be done with IOUtils packages, but I would like to avoid them if possible. Does anyone know an alternate way?
我知道它可以用 IOUtils 包来完成，但我想尽可能避免它们。有谁知道另一种方法？
回答by Peter Knego
InputStream is abstract and does not expose (neither do its children) internal data objects. So the only way to "deep copy" the InputStream is to create ByteArrayOutputStream and after doing read() on InputStream, write() this data to ByteArrayOutputStream. Then do:
InputStream 是抽象的并且不公开（也不公开其子代）内部数据对象。因此，“深度复制” InputStream 的唯一方法是创建 ByteArrayOutputStream，然后在 InputStream 上执行 read() 之后，将此数据写入 ByteArrayOutputStream。然后做：
newStream = new ByteArrayInputStream(byteArrayOutputStream.toArray());
If you are using mark()on your InputStream then indeed you can not reverse this. This makes your stream "consumed".
如果您mark()在 InputStream上使用，那么您确实无法扭转这一点。这会使您的流“消耗”。
To "reuse" your InputStream avoid using mark() and then at the end of reading call reset(). You will be then reading from beginning of the stream.
要“重用”您的 InputStream，请避免使用 mark()，然后在阅读结束时调用 reset()。然后，您将从流的开头开始阅读。
Edited:
编辑：
BTW, IOUtils uses this simple code snippet to copy InputStream:
顺便说一句，IOUtils 使用这个简单的代码片段来复制 InputStream：
public static int copy(InputStream input, OutputStream output) throws IOException{
byte[] buffer = new byte[DEFAULT_BUFFER_SIZE];
int count = 0;
int n = 0;
while (-1 != (n = input.read(buffer))) {
output.write(buffer, 0, n);
count += n;
}
return count;
}
Read more: http://kickjava.com/src/org/apache/commons/io/CopyUtils.java.htm#ixzz13ymaCX9m
阅读更多：http: //kickjava.com/src/org/apache/commons/io/CopyUtils.java.htm#ixzz13ymaCX9m
