How to generate Signature in AWS from Java

Question

When I invoke API endpoints from REST client, I got error by concerning with Signature.

Request:

Host: https://xxx.execute-ap

Answer 1

You can use classes from aws-java-sdk-core: https://github.com/aws/aws-sdk-java/tree/master/aws-java-sdk-core

More specifically, Request, Aws4Signer and a few other ones:

//Instantiate the request
Request request = new DefaultRequest("es"); //Request to ElasticSearch
request.setHttpMethod(HttpMethodName.GET);
request.setEndpoint(URI.create("http://..."));

//Sign it...
AWS4Signer signer = new AWS4Signer();
signer.setRegionName("...");
signer.setServiceName(request.getServiceName());
signer.sign(request, new AwsCredentialsFromSystem());

//Execute it and get the response...
Response rsp = new AmazonHttpClient(new ClientConfiguration())
    .requestExecutionBuilder()
    .executionContext(new ExecutionContext(true))
    .request(request)
    .errorResponseHandler(new SimpleAwsErrorHandler())
    .execute(new SimpleResponseHandler());

If you want a cleaner design, you can use the Decorator pattern to compose some elegant classes and hide the above mess. An example for that here: http://www.amihaiemil.com/2017/02/18/decorators-with-tunnels.html