io.methvin.watcher.hashing

Interface FileHasher

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.

@FunctionalInterface
public interface FileHasher

A function to convert a Path to a hash code used to check if the file content is changed. This is called by DirectoryWatcher after checking that the path exists and is not a directory. Therefore this hasher can generally assume that those two things are true.

By default, this hasher may throw an IOException, which will be treated as a `null` hash by the watcher, meaning the associated event will be ignored. If you want to handle that exception you can catch/rethrow it.

Field Summary

Fields

Modifier and Type	Field and Description
static FileHasher	DEFAULT_FILE_HASHER The default file hasher instance, which uses Murmur3.
static FileHasher	LAST_MODIFIED_TIME A file hasher that returns the last modified time provided by the OS.

Method Summary

Modifier and Type	Method and Description
FileHash	hash(java.nio.file.Path path)

Field Detail

DEFAULT_FILE_HASHER

static final FileHasher DEFAULT_FILE_HASHER

The default file hasher instance, which uses Murmur3.

LAST_MODIFIED_TIME

static final FileHasher LAST_MODIFIED_TIME

A file hasher that returns the last modified time provided by the OS.

This only works reliably on certain file systems and JDKs that support at least millisecond-level precision.

Method Detail

hash

FileHash hash(java.nio.file.Path path)
       throws java.io.IOException

Throws:

java.io.IOException