Convert InputStream to byte array in Java
如何将整个InputStream读入字节数组？
You can use Apache Commons IO to handle this and similar tasks.
The IOUtils type has a static method to read an InputStream and return a byte[] .
InputStream is;
byte[] bytes = IOUtils.toByteArray(is);
Internally this creates a ByteArrayOutputStream and copies the bytes to the output, then calls toByteArray() . It handles large files by copying the bytes in blocks of 4KiB.
You need to read each byte from your InputStream and write it to a ByteArrayOutputStream . You can then retrieve the underlying byte array by calling toByteArray() ; eg
InputStream is = ...
ByteArrayOutputStream buffer = new ByteArrayOutputStream();
int nRead;
byte[] data = new byte[16384];
while ((nRead = is.read(data, 0, data.length)) != -1) {
buffer.write(data, 0, nRead);
}
buffer.flush();
return buffer.toByteArray();
Finally, after twenty years, there's a simple solution without the need for a 3rd party library, thanks to Java 9:
InputStream is;
…
byte[] array = is.readAllBytes();
Note also the convenience methods readNBytes(byte[] b, int off, int len) and transferTo(OutputStream) addressing recurring needs.
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