Examples of java.nio.file.attribute.UserDefinedFileAttributeView

java.nio.file.attribute.UserDefinedFileAttributeView
A file attribute view that provides a view of a file's user-defined attributes, sometimes known as extended attributes. User-defined file attributes are used to store metadata with a file that is not meaningful to the file system. It is primarily intended for file system implementations that support such a capability directly but may be emulated. The details of such emulation are highly implementation specific and therefore not specified.
This {@code FileAttributeView} provides a view of a file's user-definedattributes as a set of name/value pairs, where the attribute name is represented by a {@code String}. An implementation may require to encode and decode from the platform or file system representation when accessing the attribute. The value has opaque content. This attribute view defines the {@link #read read} and {@link #write write} methods to read the value intoor write from a {@link ByteBuffer}. This {@code FileAttributeView} is notintended for use where the size of an attribute value is larger than {@link Integer#MAX_VALUE}.
User-defined attributes may be used in some implementations to store security related attributes so consequently, in the case of the default provider at least, all methods that access user-defined attributes require the {@code RuntimePermission("accessUserDefinedAttributes")} permission when asecurity manager is installed.
The {@link java.nio.file.FileStore#supportsFileAttributeView supportsFileAttributeView} method may be used to test if a specific {@link java.nio.file.FileStore FileStore} supports the storage of user-definedattributes.
Where dynamic access to file attributes is required, the {@link java.nio.file.Files#getAttribute getAttribute} method may be used to readthe attribute value. The attribute value is returned as a byte array (byte[]). The {@link java.nio.file.Files#setAttribute setAttribute} method may be usedto write the value of a user-defined attribute from a buffer (as if by invoking the {@link #write write} method), or byte array (byte[]). @since 1.7

         HashCode hashCode = null;
         Date expires = null;
         ImmutableMap.Builder<String, String> userMetadata = ImmutableMap.builder();


         if (getFileStore(file.toPath()).supportsFileAttributeView(UserDefinedFileAttributeView.class)) {
            UserDefinedFileAttributeView view = getFileAttributeView(path, UserDefinedFileAttributeView.class);
            Set<String> attributes = ImmutableSet.copyOf(view.list());


            contentDisposition = readStringAttributeIfPresent(view, attributes, XATTR_CONTENT_DISPOSITION);
            contentEncoding = readStringAttributeIfPresent(view, attributes, XATTR_CONTENT_ENCODING);
            contentLanguage = readStringAttributeIfPresent(view, attributes, XATTR_CONTENT_LANGUAGE);
            contentType = readStringAttributeIfPresent(view, attributes, XATTR_CONTENT_TYPE);
            if (attributes.contains(XATTR_CONTENT_MD5)) {
               ByteBuffer buf = ByteBuffer.allocate(view.size(XATTR_CONTENT_MD5));
               view.read(XATTR_CONTENT_MD5, buf);
               hashCode = HashCode.fromBytes(buf.array());
            }
            if (attributes.contains(XATTR_EXPIRES)) {
               ByteBuffer buf = ByteBuffer.allocate(view.size(XATTR_EXPIRES));
               view.read(XATTR_EXPIRES, buf);
               buf.flip();
               expires = new Date(buf.asLongBuffer().get());
            }
            for (String attribute : attributes) {
               if (!attribute.startsWith(XATTR_USER_METADATA_PREFIX)) {

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                  " expected: " + expectedHashCode);
         }
         payload.getContentMetadata().setContentMD5(actualHashCode);


         if (getFileStore(outputPath).supportsFileAttributeView(UserDefinedFileAttributeView.class)) {
            UserDefinedFileAttributeView view = getFileAttributeView(outputPath, UserDefinedFileAttributeView.class);
            view.write(XATTR_CONTENT_MD5, ByteBuffer.wrap(actualHashCode.asBytes()));
            writeStringAttributeIfPresent(view, XATTR_CONTENT_DISPOSITION, metadata.getContentDisposition());
            writeStringAttributeIfPresent(view, XATTR_CONTENT_ENCODING, metadata.getContentEncoding());
            writeStringAttributeIfPresent(view, XATTR_CONTENT_LANGUAGE, metadata.getContentLanguage());
            writeStringAttributeIfPresent(view, XATTR_CONTENT_TYPE, metadata.getContentType());
            Date expires = metadata.getExpires();
            if (expires != null) {
               ByteBuffer buf = ByteBuffer.allocate(Longs.BYTES).putLong(expires.getTime());
               buf.flip();
               view.write(XATTR_EXPIRES, buf);
            }
            for (Map.Entry<String, String> entry : blob.getMetadata().getUserMetadata().entrySet()) {
               writeStringAttributeIfPresent(view, XATTR_USER_METADATA_PREFIX + entry.getKey(), entry.getValue());
            }
         }

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