Add Cache Control Headers for Angular Generator Rest Services.

common/src/main/java/com/genexus/ClientInformation.java

@@ -73,4 +73,12 @@ static public String getPlatformName()
 			platformName =  SpecificImplementation.Application.getModelContext().getHttpContext().getHeader("DevicePlatform");
 		return platformName;
 	}
+
+	public final class DeviceTypeEnum {
+		public static final int iOS = 0;
+		public static final int Android = 1;
+		public static final int Blackberry = 2;
+		public static final int Windows = 3;
+		public static final int Web = 4;
+	}
 }

common/src/main/java/com/genexus/GXSmartCacheProvider.java

@@ -63,7 +63,7 @@ public void discardUpdates()
 	// <param name="dateLastModified"></param>
 	// <param name="dateUpdated"></param>
 	// <returns>Unknown/Invalid/UpToDate</returns>
-	static public DataUpdateStatus CheckDataStatus(String queryId, Date dateLastModified, Date[] dateUpdated_arr)
+	static public DataUpdateStatus checkDataStatus(String queryId, Date dateLastModified, Date[] dateUpdated_arr)
 	{
 		return (DataUpdateStatus) provider.CheckDataStatus(queryId, dateLastModified, dateUpdated_arr);
 	}

java/src/main/java/com/genexus/GxRestService.java

@@ -258,41 +258,68 @@ public boolean processHeaders(String queryId, IHttpServletRequest myServletReque
 		{
 			setTheme(theme);
 		}
-		String etag = myServletRequest.getMethod().equalsIgnoreCase(POST) ? null : myServletRequest.getHeader("If-Modified-Since");
+		String eTag = isPostRequest(myServletRequest) ? null : myServletRequest.getHeader("If-Modified-Since");
 		Date dt = Application.getStartDateTime();
 		Date newDt = new Date();
 		GXSmartCacheProvider.DataUpdateStatus status;
 		Date[] newDt_arr = new Date[] { newDt };
-		if (etag == null)
+		if (eTag == null)
 		{
 			status = GXSmartCacheProvider.DataUpdateStatus.Invalid;
-			GXSmartCacheProvider.CheckDataStatus(queryId, dt, newDt_arr);
+			GXSmartCacheProvider.checkDataStatus(queryId, dt, newDt_arr);
 		}
 		else
 		{
-			dt = HTMLDateToDatetime(etag);
-			status = GXSmartCacheProvider.CheckDataStatus(queryId, dt, newDt_arr);
+			dt = HTMLDateToDatetime(eTag);
+			status = GXSmartCacheProvider.checkDataStatus(queryId, dt, newDt_arr);
 		}
 		newDt = newDt_arr[0];
-		if (myServletResponse != null) // Temporary: Jersey Service called through AWS Lambda where HttpResponse is null.
-			myServletResponse.addHeader("Last-Modified", DateTimeToHTMLDate(newDt)); 
+		addHeader(myServletResponse, "Last-Modified", DateTimeToHTMLDate(newDt));
+		addCacheHeaders(myServletResponse);
 		if (status == GXSmartCacheProvider.DataUpdateStatus.UpToDate)
 		{
 			return false;
 		}
 		return true;
 	}
-
+
+	private void addCacheHeaders(HttpServletResponse myServletResponse) {
+		/*
+		 * https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cache-Control
+		 * Specifying no-cache or max-age=0 indicates that
+		 * clients can cache a resource and must revalidate each time before using it.
+		 * This means HTTP request occurs each time, but it can skip downloading HTTP body if the content is valid.
+		 */
+		if (ClientInformation.getDeviceType() == ClientInformation.DeviceTypeEnum.Web) {
+			addHeader(myServletResponse, "Cache-Control", "no-cache, max-age=0");
+		}
+	}
+
+	boolean isPostRequest(HttpServletRequest request)
+	{
+		return request.getMethod().equalsIgnoreCase(POST);
+	}
+
+	void addHeader(HttpServletResponse response, String headerName, String headerValue)
+	{
+		if (response != null) {
+			// Temporary: Jersey Service called through AWS Lambda where HttpResponse is null.
+			response.addHeader(headerName, headerValue);
+		}
+		else {
+			logger.warn("Could add HttpHeader to Response");
+		}
+	}
+
 	Date HTMLDateToDatetime(String s)
 	{
-		// Formato fecha: RFC 1123
+		// Date Format: RFC 1123
 		try
 		{
 			SimpleDateFormat sdf = new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss z", java.util.Locale.US);
 			java.util.TimeZone tz = java.util.TimeZone.getTimeZone("GMT");
 			sdf.setTimeZone(tz);
 			return sdf.parse(s);
-
 		}
 		catch(ParseException p)
 		{
@@ -308,4 +335,6 @@ String DateTimeToHTMLDate(Date dt)
 		sdf.setTimeZone(tz);		
 		return sdf.format(dt);
 	}
+
+
 }