本来版本7.4.0不行，最后换了个版本7.15.1就可以了，但又出现以下问题了：

@Bean
    public ElasticsearchClient elasticsearchClient() {
//        RestClient client = RestClient.builder(new HttpHost("localhost", 9200,"http")).build();

        RestClient client = RestClient.builder(new HttpHost("192.168.101.128", 9200, "http"))
                .setDefaultHeaders(new Header[]{
                        new BasicHeader("Content-type", "application/json"),
                        new BasicHeader("X-Elastic-Product", "Elasticsearch")
                }).build();
        ElasticsearchTransport transport = new RestClientTransport(client, new JacksonJsonpMapper());
        return new ElasticsearchClient(transport);


    }

"Elasticsearch built-in security features are not enabled. Without authentication, your cluster could be accessible to anyone. See https://www.elastic.co/guide/en/elasticsearch/reference/7.13/security-minimal-setup.html to enable security."  

elasticsearch.yml配置：xpack.security.enabled: false