开始引用大佬 p-j-meisch 的解释：
About spring-data-elasticsearch:

when using ElasticsearchTemplate, you are using the TransportClient.
when using ElasticsearchRestTemplate you are using the RestClient (available in 3.2.0).
when using a default ElasticsearchRepository you are using the TransportClient.
when using a custom repository extending for example SimpleElasticsearchRepository like shown below you are using the RestClient.

解决的主要问题
1、将TransportClient替换为RestClient 
2、将ElasticsearchTemplate替换为ElasticsearchRestTemplate；

一、pom.xml修改
<!--        <dependency>-->
<!--            <groupId>org.springframework.boot</groupId>-->
<!--            <artifactId>spring-boot-starter-data-elasticsearch</artifactId>-->
<!--        </dependency>-->
        <dependency>
            <groupId>org.springframework.data</groupId>
            <artifactId>spring-data-elasticsearch</artifactId>
            <!-- need 3.2.0 for REST client-->
            <exclusions>
                <exclusion>
                    <groupId>org.elasticsearch.client</groupId>
                    <artifactId>elasticsearch-rest-high-level-client</artifactId>
                </exclusion>
                <exclusion>
                    <groupId>org.elasticsearch</groupId>
                    <artifactId>elasticsearch</artifactId>
                </exclusion>
                <exclusion>
                    <groupId>org.elasticsearch.client</groupId>
                    <artifactId>elasticsearch-rest-client</artifactId>
                </exclusion>
            </exclusions>
            <version>3.2.0.M2</version>
        </dependency>
       <dependency>
            <groupId>org.elasticsearch.client</groupId>
            <artifactId>elasticsearch-rest-high-level-client</artifactId>
            <version>6.8.1</version>
        </dependency>
        <dependency>
            <groupId>org.elasticsearch.client</groupId>
            <artifactId>elasticsearch-rest-client</artifactId>
            <version>6.8.1</version>
        </dependency>
        <dependency>
            <groupId>org.elasticsearch</groupId>
            <artifactId>elasticsearch</artifactId>
            <version>6.8.1</version>
        </dependency>
将原来的spring-boot-starter-data-elasticsearch 修改为spring-data-elasticsearch，由于我们的es是6.8.1版本，我将对应的一些客户端jar版本也替换为6.8.1版本。
二、启动类增加@EnableElasticsearchRepositories
@EnableElasticsearchRepositories
public class DocServerApplication {
    public static void main(String[] args) {
        System.setProperty("es.set.netty.runtime.available.processors", "false");
        SpringApplication.run(DocServerApplication.class, args);
    }
}
三、application.yml增加es配置
es:
  cluster:
    name: my-application
  user: elastic
  password: elastic
  url: 192.168.170.31
  port: 9200
四、项目注入ES 将ElasticsearchRestTemplate 指定为elasticsearchTemplate，支持原来的jpa功能

import org.apache.http.HttpHost;
import org.apache.http.auth.AuthScope;
import org.apache.http.auth.UsernamePasswordCredentials;
import org.apache.http.client.CredentialsProvider;
import org.apache.http.impl.client.BasicCredentialsProvider;
import org.apache.http.impl.nio.client.HttpAsyncClientBuilder;
import org.elasticsearch.client.RestClient;
import org.elasticsearch.client.RestClientBuilder;
import org.elasticsearch.client.RestHighLevelClient;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.elasticsearch.config.AbstractElasticsearchConfiguration;
import org.springframework.data.elasticsearch.core.ElasticsearchRestTemplate;
import javax.annotation.PostConstruct;

/**
 * 项目注入ES
 */
@Configuration
@ConditionalOnClass(RestHighLevelClient.class)
public class ElasticSearchConfig  extends AbstractElasticsearchConfiguration {
    @PostConstruct
    void init() {
        System.setProperty("es.set.netty.runtime.available.processors", "false");
    }



    @Value("${es.cluster.name:#{null}}")
    private String name;
    @Value("${es.user:#{null}}")
    private String user;
    @Value("${es.password:#{null}}")
    private String password;
    @Value("${es.url:#{null}}")
    private String url;
    @Value("${es.port:#{null}}")
    private int port;


    @Override
    @Bean("restHighLevelClient")
    public RestHighLevelClient elasticsearchClient() {
            final CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
            /*设置账号密码*/
            credentialsProvider.setCredentials(AuthScope.ANY,new UsernamePasswordCredentials(user, password));
            /*创建rest client对象*/
            RestClientBuilder builder = RestClient.builder(new HttpHost(url,port))
                    .setHttpClientConfigCallback(new RestClientBuilder.HttpClientConfigCallback() {
                        @Override
                        public HttpAsyncClientBuilder customizeHttpClient(HttpAsyncClientBuilder httpAsyncClientBuilder) {
                            return httpAsyncClientBuilder.setDefaultCredentialsProvider(credentialsProvider);
                        }
                    });
            RestHighLevelClient client = new RestHighLevelClient(builder);
        return client;
    }



    @Bean("elasticsearchTemplate")
    ElasticsearchRestTemplate elasticsearchRestTemplate(@Qualifier("restHighLevelClient") RestHighLevelClient client) {
        return new ElasticsearchRestTemplate(client);
    }

}