Is there any way to get the hashcode of an InputStream using Guava?

Question

Is there a way to get the HashCode of an InputStream in Java, I am trying to upload a picture using the <p:fileUpload/> from PrimeFaces, converting it into a HashCode and comparing it to another picture.

At the moment I'm trying this:

public void save(FileUploadEvent event) throws IOException {
        HashCode hashCode = null;
        HashCode hashCodeCompare = null;
        hashCode = Files.asByteSource(new File(event.toString())).hash(Hashing.murmur3_128(50));
        hashCodeCompare = Files.asByteSource(new File(FilePathOfFileToCompare)).hash(Hashing.murmur3_128(50));
        boolean hashTrueFalse;
        if(hashCode.equals(hashCodeCompare)) {
            System.out.println("true");
        } else{
            System.out.println("false");
        }

        try (InputStream input = event.getFile().getInputstream()) {
            String imageName = generateFileName() + "." + fileExtensions(event.getFile().getFileName());
            String imageLink = PICTURE_DESTINATION + "\\" + imageName;


            Picture picture = new Picture();
            picture.setPictureUrl(imageLink);
            pictureService.createOrUpdate(picture);

            personForm.getCurrentPersonDTO().setPictureDTO(pictureMapper.toDTO(picture));


        } catch (IOException e) {
            e.printStackTrace();
        }
    }

Is there any way to turn the InputStream into a hashcode?

Answer 1

What you want to do is ByteStreams.copy(input, Funnels.asOutputStream(hasher)) where hasher is acquired from e.g. Hashing.sha256().newHasher(). Then, call hasher.hash() to get the resulting HashCode.