<apex:page id="MyVisualforcePage" standardController="Document_102__c" extensions="checkingAccessToken" action="{!accessToken}" showHeader="false">  <apex:iframe src="{!imageUrl}" width="100%" height="1000px"/> <script> setTimeout(function(){alert("your response time is exited, If you want to see the Page, Please the Click the again"); window.close();},60000); </script>

public class checkingAccessToken {
public Id pageId;
public String objName;
public String claimId;
public String documentId;
public String access_token;
public blob image {get;set;}

public checkingAccessToken(ApexPages.StandardController controller){
    pageId = ApexPages.currentPage().getParameters().get('id');
    objName =   pageId.getSObjectType().getDescribe().getName();
    List<sObject> objs= Database.query('Select Id,ICA_Claim_Number__c,DocumentId__c from '+objName+' where id =:pageId Limit 1');
    Sobject obj = objs.get(0);
    claimId = String.valueOf(obj.get('ICA_Claim_Number__c'));
    documentId = String.valueOf(obj.get('DocumentId__c'));
}

public void accessToken()
{
    HttpRequest req = new HttpRequest();
    req.setEndpoint('https://{ThridPartyWebsite}/external/access_token_short?grant_type=client_credentials');
    req.setMethod('GET');

    List<Access_Token__mdt> accessTokenList = [Select Username__c, Password__c from Access_Token__mdt where  MasterLabel= 'CloudHub'];
    if(accessTokenList.size() != 0) {
        Access_Token__mdt accessToken = accessTokenList.get(0);
        String username = accessToken.Username__c;
        String password = accessToken.Password__c;

        Blob headerValue = Blob.valueOf(username + ':' + password);
        String authorizationHeader = 'Basic ' +
            EncodingUtil.base64Encode(headerValue);
        req.setHeader('Authorization', authorizationHeader);

        Http http = new Http();
        HTTPResponse res = http.send(req);
        System.debug(res.getBody());

        if (res.getStatusCode() == 200) {
            Map<String, Object> results = (Map<String, Object>)JSON.deserializeUntyped(res.getBody());
            access_token = (String)results.get('access_token');

            imageUrl = 'https://{ThridPartyWebsite}/api/document'+'?claimId='+claimId+'&documentId='+documentId+'&access_token='+access_token;
        }
    }
}