Find the Public IP of all my EC2 instances using Java?

Question

I am trying to get the Public IP of all my Amazon Ec2 instances using the Java SDK. I have been searching through the documentation and found that I need to use a DescribeInstanceRequest, DescribeInstanceResult and a Filter to achieve my purpose.

However, I do not understand how to complete the circle. The DescribeInstanceResult does not seem to have what I need and I do not know how to effectively print the instance IPs that I want.

So far, this is my code:

public List<String> getPublicIPs(){
        DescribeInstancesRequest request =  new DescribeInstancesRequest();
        request.setInstanceIds(instanceIds);

        List<Filter> filters = new LinkedList<Filter>();
        filters.add(new Filter("ip-address"));
        request.setFilters(filters);


        DescribeInstancesResult result = ec2.describeInstances(request);

        //what now!?
        return null;
    }

How do I complete it? What am I missing?

Answer 1

The problem were the filters. Apparently using them is a bad decision and there is no point whatsoever in doing so.

Solution:

    /**
     * Returns a list with the public IPs of all the active instances, which are
     * returned by the {@link #getActiveInstances()} method.
     * 
     * @return  a list with the public IPs of all the active instances.
     * @see     #getActiveInstances()
     * */
    public List<String> getPublicIPs(){
        List<String> publicIpsList = new LinkedList<String>();

        //if there are no active instances, we return immediately to avoid extra 
        //computations.
        if(!areAnyActive())
            return publicIpsList;

        DescribeInstancesRequest request =  new DescribeInstancesRequest();
        request.setInstanceIds(instanceIds);

        DescribeInstancesResult result = ec2.describeInstances(request);
        List<Reservation> reservations = result.getReservations();

        List<Instance> instances;
        for(Reservation res : reservations){
            instances = res.getInstances();
            for(Instance ins : instances){
                LOG.info("PublicIP from " + ins.getImageId() + " is " + ins.getPublicIpAddress());
                publicIpsList.add(ins.getPublicIpAddress());
            }
        }

        return publicIpsList;
    }

Answer 2

The below codes just explain the idea and have not gone through the compiler.

DescribeInstancesResult result= ec2.describeInstances(request);
List <Reservation> list  = result.getReservations();

for (Reservation res:list) {
     List <Instance> instanceList= res.getInstances();

     for (Instance instance:instanceList){

             System.out.println("Instance Public IP :" + instance.getPublicIpAddress());

     }     
}

Answer 3

Refer the following code that fetches the public IP of instances.

public void fetchInstancePublicIP(){
    DescribeInstancesRequest request = new DescribeInstancesRequest().withInstanceIds(instanceIDs);
    DescribeInstancesResult result= ec2.describeInstances(request);
    List <Reservation> list  = result.getReservations();

    for (Reservation res:list) {
         List <Instance> instanceList= res.getInstances();

         for (Instance instance:instanceList){

                 System.out.println("Instance Public IP :" + instance.getPublicIpAddress());
                 System.out.println("Instance Public DNS :" + instance.getPublicDnsName());
                 System.out.println("Instance State :" + instance.getState());
                 System.out.println("Instance TAGS :" + instance.getTags());
         }     
    }
}