Spring boot image cannot identify dockerized elasticsearch hostname

I made a web application that is configured like this: Springboot (elastic beanstalk) + elasticsearch (elastic beasntalk) + postgres(aws RDS).

The connection between Springboot and aws RDS is running fine, but the problem comes with elasticsearch connection. It is a communication between dockerized containers within elastic beanstalk.

The Springboot configures elasticsearch as below.

@Value(value = "${elasticsearch.host}")
    String elasticSearchHost;

 public Client client() throws Exception {

        Settings settings = Settings.builder()
                .put("cluster.name", "elasticsearch")
                .build();

        return new PreBuiltTransportClient(settings)
                .addTransportAddress(new TransportAddress(InetAddress.getByName(elasticSearchHost), 9300));
    }

and from application.properties, I have the following value configured.

elasticsearch.host=localhost

Here is my Dockerrun.aws.json file.

{
  "AWSEBDockerrunVersion": 2,
  "containerDefinitions": [
    {
      "name": "elasticsearchmyapp",
      "image": "me/elasticsearch",
      "hostname": "elasticsearchmyapp",
      "essential": false,
      "portMappings": [
        {
          "hostPort": 9300,
          "containerPort": 9300
        }
      ],
      "memory": 1024
    },
    {
      "name": "myapp",
      "image": "me/myapp",
      "hostname": "myapp",
      "essential": true,
      "portMappings": [
        {
          "hostPort": 80,
          "containerPort": 8081
        }
      ],
      "environment": [
        {
          "name": "ELASTICSEARCH_HOST",
          "value": "elasticsearchmyapp"
        }
      ],
      "links": ["elasticsearchmyapp"],
      "memory": 1024
    }
  ]
}

Here is my logic

1. I set environment variable of the Springboot container in the "environment" part.
2. Because environment variable has higher priority than application.properties inside the jar, the Spring boot will refer to environment value "elasticsearchmyapp"
3. Once elasticsearchmyapp is identified, the docker DNS will translate the key 'elasticsearchmyapp' to a proper URL for elasticsearch container.

But it hopeless fails every time I deploy. Saying the hostname is not identified. How can I resolve this issue?