Copy InputStream, abort operation if size exceeds limit

Question

I tried to copy an InputStream to a File, and abort the copy if the size of InputStream is greater than 1MB. In Java7, I wrote code as below:

public void cop         


        

Answer 1

My personal choice is an InputStream wrapper that counts bytes as it reads them:

public class LimitedSizeInputStream extends InputStream {

    private final InputStream original;
    private final long maxSize;
    private long total;

    public LimitedSizeInputStream(InputStream original, long maxSize) {
        this.original = original;
        this.maxSize = maxSize;
    }

    @Override
    public int read() throws IOException {
        int i = original.read();
        if (i>=0) incrementCounter(1);
        return i;
    }

    @Override
    public int read(byte b[]) throws IOException {
        return read(b, 0, b.length);
    }

    @Override
    public int read(byte b[], int off, int len) throws IOException {
        int i = original.read(b, off, len);
        if (i>=0) incrementCounter(i);
        return i;
    }

    private void incrementCounter(int size) throws IOException {
        total += size;
        if (total>maxSize) throw new IOException("InputStream exceeded maximum size in bytes.");
    }

}

I like this approach because it is transparent, it is re-usable with all input streams and it works well with other libraries. For example copying files up to 4KB with Apache Commons:

InputStream in = new LimitedSizeInputStream(new FileInputStream("from.txt"), 4096);
OutputStream out = new FileOutputStream("to.txt");
IOUtils.copy(in, out);

PS: The main difference of the implementation above with BoundedInputStream is that BoundedInputStream does not throw an exception when the limit is exceeded (it just closes the stream)