Java Client连接Elastic Cloud报错连接拒绝，求正确连接方案

我按照Elastic官方文档尝试用Java Client连接Elastic Cloud上的ES实例，但一直失败。使用的主机名是https://myinstance-xx.europe-west1.gcp.cloud.es.io，配置代码如下：

private String hostName = "https://myinstance-xx.es.europe-west1.gcp.cloud.es.io";
private String username = "username";
private String password = "pass";
@Bean
public ElasticsearchClient client() {
    final CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
    credentialsProvider.setCredentials(AuthScope.ANY,
            new UsernamePasswordCredentials(username, password));
    RestClientBuilder builder = RestClient.builder(new HttpHost(hostName, 9200))
            .setHttpClientConfigCallback(httpClientBuilder ->
                    httpClientBuilder.setDefaultCredentialsProvider(credentialsProvider));
    // Create the low-level client
    RestClient restClient = builder.build();
    // Create the transport with a Jackson mapper
    ElasticsearchTransport transport = new RestClientTransport(restClient, new JacksonJsonpMapper());
    // And create the API client
    return new ElasticsearchClient(transport);
}

运行时抛出异常：

java.net.ConnectException: Connection refused

请问通过Java Client连接Elastic Cloud上ES实例的正确方式是什么？

你的代码存在两个核心问题：

• HttpHost构造错误：传入的hostName包含https://前缀，HttpHost会将整个字符串当作主机名解析，导致无法正确识别目标地址；同时Elastic Cloud的ES实例默认使用443端口而非9200。
• 缺少SSL配置：Elastic Cloud实例强制使用HTTPS协议，必须配置SSL上下文以信任云端证书。

正确的配置代码如下：

private String hostName = "myinstance-xx.europe-west1.gcp.cloud.es.io"; // 移除https://前缀
private String username = "username";
private String password = "pass";

@Bean
public ElasticsearchClient client() {
    final CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
    credentialsProvider.setCredentials(AuthScope.ANY,
            new UsernamePasswordCredentials(username, password));

    RestClientBuilder builder = RestClient.builder(new HttpHost(hostName, 443, "https"))
            .setHttpClientConfigCallback(httpClientBuilder ->
                    httpClientBuilder.setDefaultCredentialsProvider(credentialsProvider)
                            // 配置SSL上下文，此处为默认信任（生产环境建议导入指定CA证书）
                            .setSSLContext(SSLContext.getDefault()));

    RestClient restClient = builder.build();
    ElasticsearchTransport transport = new RestClientTransport(restClient, new JacksonJsonpMapper());
    return new ElasticsearchClient(transport);
}

额外注意事项：

• 生产环境中，请勿使用SSLContext.getDefault()，应将Elastic Cloud控制台提供的CA证书导入到项目的信任库中，再构建安全的SSL上下文，避免潜在的安全风险。
• 确认主机名、用户名、密码与Elastic Cloud控制台中实例的配置完全一致，主机名务必不要包含协议前缀。

内容的提问来源于stack exchange，提问作者Ala A.