阻塞式和异步式客户端

ElasticsearchTransport transport = ...

// Synchronous blocking client
ElasticsearchClient client = new ElasticsearchClient(transport);

if (client.exists(b -> b.index("products").id("foo")).value()) {
    logger.info("product exists");
}

// Asynchronous non-blocking client
ElasticsearchAsyncClient asyncClient =
    new ElasticsearchAsyncClient(transport);

asyncClient
    .exists(b -> b.index("products").id("foo"))
    .whenComplete((response, exception) -> {
        if (exception != null) {
            logger.error("Failed to index", exception);
        } else {
            logger.info("Product exists");
        }
    });