配置RamRole實作ECS執行個體的無AK通路，是真的不需要AK麼？

文檔隻配置了如下資訊，

DefaultProfile profile = DefaultProfile.getProfile("");

InstanceProfileCredentialsProvider provider = new InstanceProfileCredentialsProvider(
        "<your-role-name>"
    );
    DefaultAcsClient client = new DefaultAcsClient(profile, provider);
    DescribeInstancesRequest request = new DescribeInstancesRequest();
    try {
        DescribeInstancesResponse response = client.getAcsResponse(request);
    } catch (ClientException e) {
        System.err.println(e.toString());
    }           

但是JAVA後端卻不能通路，這種是否也需要子使用者的access Key呢？