Optimized the business logic to show the preview of files by Get Info

(as reported at https://support.d4science.org/issues/19600#note-7)

src/main/java/org/gcube/portlets/user/workspace/client/view/windows/DialogGetInfoBootstrap.java

@@ -62,6 +62,9 @@ import com.google.gwt.user.client.ui.Widget;
 public class DialogGetInfoBootstrap extends Composite {
 
 	private static final int PREVIEW_WAITING_TIME = 9000; //9 sec
+	private static final int PREVIEW_MAX_RETRIES = 3;
+	private int showPreviewAttempt = 0;
+	private long loaderPreviewStartTime = 0;
 
 	private static DialogGetInfoBootstrapUiBinder uiBinder = GWT.create(DialogGetInfoBootstrapUiBinder.class);
 
@@ -396,12 +399,14 @@ public class DialogGetInfoBootstrap extends Composite {
 										return;
 									}
 			
-									String googleDocViewerURL = "https://docs.google.com/viewer?url="
+									final String googleDocViewerURL = "https://docs.google.com/viewer?url="
 											+ URL.encode(result.getCompleteURL()) + "&embedded=true";
 			
 									iFrameGDV = instanceFrame(googleDocViewerURL, loadingPreviewHTML);
 			
-									final long startTime = new Date().getTime();
+									loaderPreviewStartTime = new Date().getTime();
+									showPreviewAttempt = 1;
+									
 									timerGDV = new Timer() {
 			
 										@Override
@@ -414,22 +419,42 @@ public class DialogGetInfoBootstrap extends Composite {
 												return;
 											}
 											long checkTime = new Date().getTime();
-											long diff = checkTime - startTime;
-											if (diff > PREVIEW_WAITING_TIME) {// is greater than 10 sec
-												try {
-													GWT.log("iFrameGoogleDocViewer not loaded within "+PREVIEW_WAITING_TIME+" sec, cancelling timer, removing iframe");
-													cancel();
-													removePlaceHolder(loadingPreviewHTML);
-													htmlPanelFilePreview.add(noPreviewAvailable);
-													iFrameGDV.setVisible(false);
-													htmlPanelFilePreview.remove(iFrameGDV);
-												} catch (Exception e) {
-													// Silent
+											long diff = checkTime - loaderPreviewStartTime;
+											if (diff > PREVIEW_WAITING_TIME) { // is greater than PREVIEW_WAITING_TIME, performs a new attempt or terminate
+												if(showPreviewAttempt >= PREVIEW_MAX_RETRIES) {
+													try {
+														GWT.log("iFrameGoogleDocViewer not loaded within "+PREVIEW_WAITING_TIME+" sec and max retries "+PREVIEW_MAX_RETRIES+", cancelling timer, removing iframe");
+														cancel();
+														removePlaceHolder(loadingPreviewHTML);
+														htmlPanelFilePreview.add(noPreviewAvailable);
+														iFrameGDV.setVisible(false);
+														htmlPanelFilePreview.remove(iFrameGDV);
+													} catch (Exception e) {
+														// Silent
+													}
+												}else {
+													GWT.log("iFrameGoogleDocViewer not loaded on attempt "+showPreviewAttempt+", instancing new iFrame");
+													//new retry by instancing the iFrame again...
+													iFrameGDV = instanceFrame(googleDocViewerURL, loadingPreviewHTML);
+													try {
+														//removing old iFrame
+														htmlPanelFilePreview.remove(iFrameGDV);
+													}catch (Exception e) {
+														//silent
+													}
+													//adding the new one
+													htmlPanelFilePreview.add(iFrameGDV);
+													//new attempt so incrementing it
+													showPreviewAttempt++;
+													GWT.log("Retry, go to attempt "+showPreviewAttempt);
+													//resetting start time for new attempt
+													loaderPreviewStartTime = new Date().getTime();
 												}
 											}
 										}
 									};
-									timerGDV.scheduleRepeating(PREVIEW_WAITING_TIME/3);
+									int attemptRepeater = PREVIEW_WAITING_TIME / 3;
+									timerGDV.scheduleRepeating(attemptRepeater);
 									htmlPanelFilePreview.add(iFrameGDV);
 
 								}