如何根据spring couchbase文档中的字段值来派生过期值

@Document
public class Document {

    @Id
    private String id;

    @Field
    private Date expirationDate;

    // 其他字段和方法省略...
    
    // getter和setter方法省略...
}

public class CustomMutationSpecification implements MutationSpecification {

    @Override
    public <T> CasMutateMeta mutate(T document, CasMutateMeta casMutateMeta) {
        if (document instanceof Document) {
            Document doc = (Document) document;
            // 根据expirationDate计算过期时间，这里假设过期时间是从当前时间开始算的
            long expirationTime = doc.getExpirationDate().getTime() - System.currentTimeMillis();
            // 设置过期时间
            casMutateMeta.setExpiry(Duration.of(expirationTime, TimeUnit.MILLISECONDS));
        }
        return casMutateMeta;
    }
}

@Autowired
private CouchbaseRepository<Document, String> repository;

public void saveDocument(Document document) {
    repository.upsert(document, new CustomMutationSpecification());
}