安装x-pack 
bin/elasticsearch-plugin install x-pack

修改elasticsearch.yml配置，新增（如果有，不用新增）
http.cors.enabled: true
http.cors.allow-origin: "*"
http.cors.allow-headers: Authorization
xpack.security.enabled: true

重启elasticsearch
./bin/elasticsearch -d

创建新的superuser：admin用户，设置密码
curl -X POST "http://elastic:changeme@ip:9200/_xpack/security/user/admin?pretty" -d '{
"password":"123456",
"roles":["superuser" ],
"metadata":{"intelligence":7}
}'

失效原superuser：elastic
curl -X PUT "http://admin:123456@ip:9200/_xpack/security/user/elastic/_disable?pretty"

java代码修改
引入x-pack-transport.jar包（版本号与elasticsearch对应）：

<dependency>
    <groupId>org.elasticsearch.client</groupId>
    <artifactId>x-pack-transport</artifactId>
    <version>5.6.1</version>
</dependency>

Settings settings = Settings.builder()
        .put("cluster.name", clusterName)
        .put("client.transport.sniff", true)
        // 设置xpack权限用户
        .put("xpack.security.user", userName + ":" + password)
        .build();
        
 Client client = new PreBuiltXPackTransportClient(settings)
        .addTransportAddress(new InetSocketTransportAddress(InetAddress.getByName(clusterHost), clusterPort));

注：参考中，加了ssl部分的，并未使用及验证，有需要可以借鉴

参考：

Setting Up User Authentication | X-Pack for the Elastic Stack [5.6] | Elastic 

Java Client and Security | X-Pack for the Elastic Stack [5.6] | Elastic 

Built-in Roles | X-Pack for the Elastic Stack [5.6] | Elastic

Elasticsearch密码设置及其后续问题解决_这个名字还中的博客-CSDN博客_elasticsearch设置密码

Elasticsearch+X-pack和Java Transport方式连接_AllenAlbert的博客-CSDN博客_x-pack-transport