Building Daemon or Service Apps with Office 365 REST API in Java

Question

I am trying to build a batch job to access Office 365 Mail API. Up on checking the documentation (the concept is very clear), I wasn't able to find a code sample written for Java. I've found this but it relies on the java pom file but I would love to use REST API or Graphi API directly if possible.

Can someone point me on how to get started with building a Daemon service to access Office 365 REST API without users login ?

UPDATE

I've the following code to get the token using AADL library

String tenant="....";
        String authority = "https://login.windows.net/"+tenant+"/oauth2/authorize";
        ExecutorService service=null;
        service= Executors.newFixedThreadPool(1);

        try{

            AuthenticationContext authenticationContext= new AuthenticationContext(authority,false,service);
            String certFile="/mycert2.pfx";
            InputStream pkcs12Cert= new SharedFileInputStream(certFile);

            AsymmetricKeyCredential credential=AsymmetricKeyCredential.create("....",pkcs12Cert,"pass");


            Future<AuthenticationResult> future=authenticationContext.acquireToken("https://outlook.office365.com",credential,null);

            System.out.println("Token Received"+future.get().getAccessToken());
            String token = future.get().getAccessToken();

            HttpGet httpGet = new       HttpGet("https://graph.microsoft.com/v1.0/users");

            httpGet.setHeader("Authorization", "Bearer "+token);


            GraphServices graphServices = new GraphServices();
            ResponseEntity<String> responseEntity;


            //responseEntity = graphServices.getEmails(token); //Throws the same Unauthorized exception 

            HttpClient httpClient= HttpClients.createDefault();

            HttpResponse response=httpClient.execute(httpGet);
//response contains Unauthorized access 
            HttpEntity entity=response.getEntity();

        }
        catch (MalformedURLException e){
            e.printStackTrace();

        }
        catch (Exception e){
            e.printStackTrace();
        }


    }

Here the Unauthorized error from the http.execute method

HttpResponseProxy{HTTP/1.1 401 Unauthorized [Content-Type: application/json; charset=utf-8, Server: Microsoft-IIS/8.5, request-id: 49ca360f-ab4b-42d5-a4b0-9676e4244c21, client-request-id: 49ca360f-ab4b-42d5-a4b0-9676e4244c21, x-ms-ags-diagnostic: {"ServerInfo":{"DataCenter":"West US","Slice":"SliceA","ScaleUnit":"003","Host":"AGSFE_IN_8","ADSiteName":"WST"}}, X-Powered-By: ASP.NET, Date: Tue, 06 Sep 2016 20:43:24 GMT, Content-Length: 244] ResponseEntityProxy{[Content-Type: application/json; charset=utf-8,Content-Length: 244,Chunked: false]}}

eyJ0eXAiOiJKV1QiLCJxcy76FRUlljRV9tb3RXVkpLSHJ3TEJiZF85cyIsImtpZCI6IlliUkFRUlljRV9tb3RXVkpLSHJ3TEJiZF85cyJ9..BKt54345DIfv2WWT4pQ--Nuy-0aHkkht4332r7E4d5mP-EAEKmcQe7y0IPjkYGZTNhyNiG2tVAyb56Gcbessdsfewz_BNoAolTVukxttXc-pFY1_Ol5Adc8T5yio43ixfs88mrVRqZEHsb7c-wjO-otBXocZs8waYXdree83g1JtcnULs7bAGp3VBUhMjuJ2u87363Yq3lfse39_Pt6tRw]

(the token is something similar to this, just changed it to something similar for security)

Answer 1

Java walkthrough here (though for a web app using auth code flow): https://dev.outlook.com/restapi/tutorial/java

There's also this sample that uses client credential flow:

https://github.com/jasonjoh/java-calendar-demo

Answer 2

To authenticate in the daemon or service apps, we can use Client Credentials flow. After we register the app, we would get the secret . Then we can use the request below direct to get the app-only access token:

POST https://login.microsoftonline.com/<tenantId>/oauth2/token HTTP/1.1
Content-Type: application/x-www-form-urlencoded

grant_type=client_credentials
&client_id=<clientId>
&client_secret=<clientSecret>
&resource=https://graph.microsoft.com

And to use the Office 365 access token, we can replace the resource with https://outlook.office.com . Here is a detail document about calling Microsoft Graph in a service or daemon app.