从JAVA API获取Amazon EC2实例的公共DNS

Question

我已成功通过 JAVA API 启动、停止和检查之前创建的 EC2 实例的状态。但是，我很难获取此实例的公共 DNS 地址。由于我使用 StartInstancesRequest 启动实例并使用 StartInstancesResponse 获取响应，因此我无法检索实际的 Instance 对象。我的起始代码如下所示，它可以工作：

BasicAWSCredentials oAWSCredentials = new BasicAWSCredentials(sAccessKey, sSecretKey);
AmazonEC2 ec2 = new AmazonEC2Client(oAWSCredentials);
ec2.setEndpoint("https://eu-west-1.ec2.amazonaws.com");
List<String> instanceIDs = new ArrayList<String>();
instanceIDs.add("i-XXXXXXX");

StartInstancesRequest startInstancesRequest = new StartInstancesRequest(instanceIDs);
try {
        StartInstancesResult response = ec2.startInstances(startInstancesRequest);
        System.out.println("Sent! "+response.toString());
    }catch (AmazonServiceException ex){
        System.out.println(ex.toString());
        return false;
    }catch(AmazonClientException ex){
        System.out.println(ex.toString());
        return false;
    }

此外，通过 JSch 连接到此实例的任何帮助都将受到赞赏。

Answer 1

这是一个可以解决问题的方法。在调用此方法之前最好检查实例是否处于运行状态。

String getInstancePublicDnsName(String instanceId) {
    DescribeInstancesResult describeInstancesRequest = ec2.describeInstances();
    List<Reservation> reservations = describeInstancesRequest.getReservations();
    Set<Instance> allInstances = new HashSet<Instance>();
    for (Reservation reservation : reservations) {
      for (Instance instance : reservation.getInstances()) {
        if (instance.getInstanceId().equals(instanceId))
          return instance.getPublicDnsName();
      }
    }
    return null;
}

Answer 2

现在，您可以在使用 describeInstances 时使用过滤器，这样您就不必提取所有实例的信息。

private String GetDNS(String aInstanceId)
{
  DescribeInstancesRequest request = new DescribeInstancesRequest();
  request.withInstanceIds(aInstanceId);
  DescribeInstancesResult result = amazonEC2.describeInstances(request);

  for (Reservation reservations : result.getReservations())
  {
    for (Instance instance : reservations.getInstances())
    {
      if (instance.getInstanceId().equals(aInstanceId))
      {
        return instance.getPublicDnsName();
      }
    }
  }

  return null;
}

使用aws-java-sdk-1.9.35.jar。