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());
}</code></pre>                

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？