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Using rest api of azure devops

I want to fetch data from the rest api of Azure Devops using Java.But not sure how to establish the connection.May be personal acces token will help,but how to use the token in Code for establishing the connection between code and azure devops? An example from anyone will be very helpful.
A code example will be very helpfull

If I am understanding you correctly, you are trying to call azure APIs, and those API need authorization token?
For example this azure API to send data into Azure queue : https://learn.microsoft.com/en-us/rest/api/servicebus/send-message-to-queue
It needs some payload and Authorization in request header !!
If my Understanding is correct, than from java you need to use any rest client or HTTP client to call the REST API and you need to pass the Authorization token in the request header
For calling a Rest API in java with passing header below is an example:
MultiValueMap<String, String> map= new LinkedMultiValueMap<>();
map.add("Authorization", "Bearer <Azure AD JWT token>"); // set your token here
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_JSON); //someother http headers you want to set
HttpEntity<MultiValueMap<String, String>> request = new HttpEntity<>(map, headers);
RestTemplate restTemplate = new RestTemplate();
String azure_url = "https://azure_url"; // your azure devops REST URL
ResponseEntity<String> response = restTemplate.postForEntity(azure_url, request , String.class);

A small example with httpclient:
static String ServiceUrl = "https://dev.azure.com/<your_org>/";
static String TeamProjectName = "your_team_project_name";
static String UrlEndGetWorkItemById = "/_apis/wit/workitems/";
static Integer WorkItemId = 1208;
static String PAT = "your_pat";
String AuthStr = ":" + PAT;
Base64 base64 = new Base64();
String encodedPAT = new String(base64.encode(AuthStr.getBytes()));
URL url = new URL(ServiceUrl + TeamProjectName + UrlEndGetWorkItemById + WorkItemId.toString());
HttpURLConnection con = (HttpURLConnection) url.openConnection();
con.setRequestProperty("Authorization", "Basic " + encodedPAT);
con.setRequestMethod("GET");
int status = con.getResponseCode();
Link to the file: ResApiMain.java

You can the use java client library for azure devops rest api. This will take the overload of encoding your personal access token and indeed supports OAuth authentication.
It is been actively developed and used in production.
Source code - https://github.com/hkarthik7/azure-devops-java-sdk
Documentation - https://azure-devops-java-sdk-docs.readthedocs.io/en/latest/?badge=latest
A quick example:
public class Main {
public static void main(String[] args) {
String organisation = "myOrganisationName";
String personalAccessToken = "accessToken";
String projectName = "myProject";
// Connect Azure DevOps API with organisation name and personal access token.
var webApi = new AzDClientApi(organisation, project, personalAccessToken);
// call the respective API with created webApi client connection object;
var core = webApi.getCoreApi();
var wit = webApi.getWorkItemTrackingApi();
try {
// get the list of projects
core.getProjects();
// get a workitem
wit.getWorkItem(15);
// Get a work item and optionally expand the field
wit.getWorkItem(15, WorkItemExpand.ALL);
} catch (AzDException e1) {
e1.printStackTrace();
}
}
}
The library has support to most of the APIs and you can view the documentation and examples folder in the github repo to know how to get the most out of it.

Basic Authentication for JAVA Application using OkHttp

First I wanted to authenticate my java application using OkHttp and then after authentication the response returns a session ID(key) that I wanted to use in subsequent API calls. below is the code that I am using to achieve this.
String url = "my application url";
String username = "xxx";
String password = "zzz";
String userpass = username + ":" + password;
String basicAuth = "Basic :" + new String(Base64.getEncoder().encode(userpass.getBytes()));
OkHttpClient client = new OkHttpClient();
Response response ;
Request request = new Request.Builder()
.url(url)
.addHeader("Authorization", basicAuth)
.build();
response = client.newCall(request).execute();
if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
System.out.println(response.body().string());
but its throwing an error saying
{"responseStatus":"FAILURE","responseMessage":"Request method 'GET' not supported","errorCodes":null,"errors":[{"type":"METHOD_NOT_SUPPORTED","message":"Request method 'GET' not supported"}],"errorType":"GENERAL"}
can someone please help me to solve this. or if any have any other idea to authenticate a java application using okhttp then please suggest...

You should use the helper classes to avoid most of the logic for username and password.
https://github.com/square/okhttp/blob/master/samples/guide/src/main/java/okhttp3/recipes/Authenticate.java
String credential = Credentials.basic("jesse", "password1");
return response.request().newBuilder()
.header("Authorization", credential)
.build();
Assuming this API is POST and not GET also follow
https://github.com/square/okhttp/blob/master/samples/guide/src/main/java/okhttp3/recipes/PostString.java
Request request = new Request.Builder()
.url("https://api.github.com/markdown/raw")
.post(RequestBody.create(postBody, MEDIA_TYPE_MARKDOWN))
.build();

You had it all right already. Just a small fix needed:
String basicAuth = "Basic " + new String(Base64.getEncoder().encode(userpass.getBytes()));
i.e you just need to remove extra ':' as it's already taken care of in .addHeader("Authorization", basicAuth) part.

Consuming a StreamingResponseBody with Spring

I've got a simple web-service that stream a file using a StreamingResponseBody.
The definition looks like this:
#GetMapping("/files/{filename}")
public ResponseEntity<StreamingResponseBody> download(#PathVariable String filename) {
...
StreamingResponseBody responseBody = out -> {
...
}
HttpHeaders httpHeaders = new HttpHeaders();
httpHeaders.setContentLength(byteArray.length);
return new ResponseEntity(responseBody, httpHeaders, HttpStatus.OK);
}
It works well, but now, I need to consume it in a client application.
I'm using spring to consume it, but I can't find a way to read the stream and write it to a file as it flows...
I tryied using feign but it seems it doesn't support it.
I tryied using restTemplate but I can't make it work...
Does spring support streaming client side ?
Does anybody know how to do this ?
Perhaps using pure java API ?
Thanks a lot for your help !

You can use Apache Http Client (org.apache.httpcomponents:httpclient:4.5.12):
URI uri = new URIBuilder()
.setScheme(scheme)
.setHost(host)
.setPort(port)
.setPath(url)
.build();
HttpUriRequest request = RequestBuilder.get(uri).build();
try (CloseableHttpClient httpClient = HttpClients.createDefault();
CloseableHttpResponse httpResponse = httpClient.execute(request);
InputStream inputStream = httpResponse.getEntity().getContent()) {
// Do with stream whatever you want, for example put it to File using FileOutputStream and 'inputStream' above.
}

Logging into Content Navigator from external application

I'm trying to access a PluginService on Content Navigator from my Java Application (Event Action Handler in FileNet P8). The application uses the JAXRS logon service to receive the security_token from the Content Navigator server. However, if I try to call the PluginService I get a response that my login has expired.
I'm able to get the security token, as described in this code block:
URL logonUrl = new URL("http://icn-host:9081/jaxrs/logon"
+ "?userid=user"
+ "&password=password"
+ "&desktop=admin"
+ "&contextPath=%2Fnavigator");
HttpURLConnection logonConnection = (HttpURLConnection)logonUrl.openConnection();
logonConnection.setRequestMethod("POST");
logonConnection.setRequestProperty("Content-Type",
"application/x-www-form-urlencoded");
logonConnection.setDoOutput(true);
InputStream logonResponse = logonConnection.getInputStream();
String responseText = IOUtils.toString(logonResponse, "UTF-8")
.replaceFirst("^\\{}&&", "");
JSONObject responseJson = JSONObject.parse(responseText);
return (String)responseJson.get("security_token");
But when I try to make another request, I get an error response:
URL requestUrl = new URL("http://icn-host:9081/plugin.do"
+ "?plugin=myPlugin&action=myPluginService&myRequestProps=foobar");
HttpURLConnection requestConnection =
(HttpURLConnection)requestUrl.openConnection();
requestConnection.setRequestMethod("GET");
String securityToken = getSecurityToken(); // calls above code
requestConnection.setRequestProperty("security_token", securityToken);
equestConnection.setDoOutput(true);
InputStream responseStream = requestConnection.getInputStream();
String responseText = IOUtils.toString(responseStream, "UTF-8")
.replaceFirst("^\\{}&&", "");
log.info("response was: " + responseText);
I always get the following response:
{
"messagesEncoded":true,
"errors": [
{
"adminResponse":null,
"moreInformation":null,
"explanation":"Your session expired because of inactivity.",
"number":"1003",
"userResponse":"Log in again.",
"text":"Your session expired."
}
]
}
I've also tried to set the cookies, but no success.
java.net.CookieManager cookieManager = new java.net.CookieManager();
Map<String, List<String>> headerFields = logonConnection.getHeaderFields();
List<String> cookiesHeader = headerFields.get("Set-Cookie");
if (cookiesHeader != null) {
for (String cookie : cookiesHeader) {
cookieManager.getCookieStore().add(null, HttpCookie.parse(cookie).get(0));
}
}
// ...
StringBuilder cookieHeader = new StringBuilder();
List<HttpCookie> cookies = cookieManager.getCookieStore().getCookies();
for (int i = 0; i < cookies.size(); i++) {
if (i > 0) {
cookieHeader.append(";");
}
HttpCookie cookie = cookies.get(i);
log.info("Cookie " + i + ": " + cookie.toString());
cookieHeader.append(cookie.toString());
}
requestConnection.setRequestProperty("Cookie", cookieHeader.toString());
I tried to replicate the request using XMLHttpRequest in a Content Navigator window and it works as expected:
var xhr = new XMLHttpRequest();
xhr.open("GET", "plugin.do" +
"?plugin=myPlugin" +
"&action=myPluginService" +
"&myRequestProps=foobar");
xhr.setRequestHeader("security_token", ecm.model.Request._security_token);
xhr.send();

I had a similar challenge for a client a few months ago where i had to automate the process of installing plugins and applying configuration for CI purposes.
I discovered it is key to obtain the desktop as the first api call after login for the session to become 'valid'.
So first jaxrs/logon, then jaxrs/getDesktop, then your service invoke.
A little sidenote: If you plan on having container managed authentication later on, the process will be different. The jaxrs/logon won't work, and instead the jaxrs/getDesktop will deliver the security_token.
A little remark though: wouldn't it be a better solution to have a shared library that you'd be able to use both from your Event Action as the ICN service?

Using shared libraries (see Ivo's answer) is definitely the best approach, calling jaxrs/getDesktop didn't work for me. Instead I just used the Maven Assembly Plugin to include a newer version of the org.apache.httpcomponents dependency and call the requests with an HttpClient.
My final code looks something like this:
CloseableHttpClient httpClient = HttpClients.custom()
.setDefaultCookieStore(cookieStore)
.setDefaultRequestConfig(requestConfig)
.build();
HttpUriRequest logonRequest = RequestBuilder.post()
.setUri("http://icn-host:9081/navigator/jarxrs/logon")
.addParameter("desktop", "admin")
.addParameter("contextPath", "/navigator")
.addParameter("userid", "icnadmin")
.addParameter("password", "password")
.build();
CloseableHttpResponse logonResponse = httpClient.execute(logonRequest);
HttpEntity responseEntity = logonResponse.getEntity();
String responseText = EntityUtils.toString(responseEntity)
.replaceFirst("^\\{}&&", "");
JSONObject responseJson = JSONObject.parse(responseText);
String securityToken = (String) responseJson.get("security_token");
HttpUriRequest request = RequestBuilder.get()
.setUri("http://icn-host:9081/navigator/plugin.do")
.addParameter("plugin", "myPlugin")
.addParameter("action", "myPluginService")
.addParameter("myRequestProps", "foobar")
.addHeader("security_token", securityToken)
.build();
HttpClientContext context = HttpClientContext.create();
CookieStore cookieStore = new BasicCookieStore();
context.setCookieStore(cookieStore);
CloseableHttpResponse response = httpClient.execute(request, context);

Programmatically generate and retrieve BIRT Report from Web-Viewer

I've installed BIRT Web-Viewer on my server and am able to build the report with this URL:
http://hostname:port/birt/run?__report=test.rptdesign
Now I need to programmatically call this URL from my Java Code and retrieve the result as stream or file.
Is there any API for the Web-Viewer?
If not, could I just call the URL like this and extract the PDF?:
HttpClient httpClient = HttpClients.createDefault();
HttpGet postRequest = new HttpPost("http://hostname:port/birt/run");
List<NameValuePair> formData = new ArrayList<>();
formData.add(new BasicNameValuePair("__report", "test.rptdesign"));
HttpEntity entity = new UrlEncodedFormEntity(formData);
HttpResponse response = httpClient.execute(postRequest);

I found out, if I use the __format parameter with the value pdf, the response to the request is the PDF content, which is exactly what I wanted.
The standard response is a HTML, which will be returned with a second request. I'm pretty sure that response has to be retrieved with sessions.
Edit:
As requested I will post my request code. I modified it a bit, because I used some custom classes to hold configuration and the report.
public InputStream getReport() throws Exception {
StringBuilder urlBuilder = new StringBuilder()
.append("http://example.com:9080/contextRoot/run")
.append("?__report=ReportDesign.rptdesign&__format=pdf");
if (reportParameters != null) {
for (Map.Entry<String, String> parameter : reportParameters.entrySet()) {
String key = StringEscapeUtils.escapeHtml(parameter.getKey());
String value = StringEscapeUtils.escapeHtml(parameter.getValue());
urlBuilder.append('&')
.append(key);
.append('=');
.append(value);
}
}
URL requestUrl = new URL(burlBuilder.toString());
HttpURLConnection connection = (HttpURLConnection) requestUrl.openConnection();
connection.setRequestMethod("GET");
connection.setDoInput(true);
connection.connect();
return connection.getInputStream();
}
I also had another method write the used data as XML to the file system before I called requestUrl.openConnection(), but I think this is only necessary if you use very dynamic data like I did.