Fix server error issue when calling get logged-in user in APPM

The following changes are with this commit,
- Check authData object is null in UserHandler class
- Add check logged-in user functionality to APPM UI

components/application-mgt/org.wso2.carbon.device.application.mgt.publisher.ui/react-app/src/App.js

@@ -102,8 +102,9 @@ class App extends React.Component {
             window.location.origin + "/publisher-ui-request-handler/user",
             "platform=publisher"
         ).then(res => {
+            const pageURL = window.location.pathname;
             const lastURLSegment = pageURL.substr(pageURL.lastIndexOf('/') + 1);
-            if (lastURLSegment !== "login") {
+            if (lastURLSegment === "login") {
                 window.location.href = window.location.origin + `/publisher/`;
             } else {
                 this.getAndroidEnterpriseToken(config);

components/application-mgt/org.wso2.carbon.device.application.mgt.store.ui/react-app/src/App.js

@@ -78,14 +78,20 @@ class App extends React.Component {
     }
 
     checkUserLoggedIn = (config) => {
-        axios.get(
-            window.location.origin + config.serverConfig.invoker.uri +
-            config.serverConfig.invoker.publisher + "/applications/categories"
+        axios.post(
+            window.location.origin + "/store-ui-request-handler/user",
+            "platform=publisher"
         ).then(res => {
+            const pageURL = window.location.pathname;
+            const lastURLSegment = pageURL.substr(pageURL.lastIndexOf('/') + 1);
+            if (lastURLSegment === "login") {
+                window.location.href = window.location.origin + `/store/`;
+            } else {
                 this.setState({
                     loading: false,
                     config: config
-            })
+                });
+            }
         }).catch((error) => {
             if (error.hasOwnProperty("response") && error.response.status === 401) {
                 const redirectUrl = encodeURI(window.location.href);
@@ -106,7 +112,7 @@ class App extends React.Component {
                 })
             }
         });
-    }
+    };
 
     render() {
         const {loading, error} = this.state;

components/ui-request-interceptor/io.entgra.ui.request.interceptor/src/main/java/io/entgra/ui/request/interceptor/UserHandler.java

@@ -43,32 +43,36 @@ import javax.servlet.http.HttpServletResponse;
 import javax.servlet.http.HttpSession;
 import java.io.IOException;
 
-@MultipartConfig @WebServlet("/user") public class UserHandler extends HttpServlet {
+@MultipartConfig
+@WebServlet("/user")
+public class UserHandler extends HttpServlet {
     private static final Log log = LogFactory.getLog(UserHandler.class);
     private static final long serialVersionUID = 9050048549140517002L;
 
-    @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) {
+    @Override
+    protected void doPost(HttpServletRequest req, HttpServletResponse resp) {
         try {
             String platform = req.getParameter(HandlerConstants.PLATFORM);
             String serverUrl =
                     req.getScheme() + HandlerConstants.SCHEME_SEPARATOR + req.getServerName() + HandlerConstants.COLON
                             + System.getProperty("iot.gateway.https.port");
             if (StringUtils.isBlank(platform)) {
-                ProxyResponse proxyResponse = new ProxyResponse();
-                proxyResponse.setCode(HttpStatus.SC_BAD_REQUEST);
-                HandlerUtil.handleError(req, resp, serverUrl, platform, proxyResponse);
+                sendUnAuthorizeResponse(req, resp, serverUrl, platform);
                 return;
             }
 
             HttpSession httpSession = req.getSession(false);
             if (httpSession == null) {
-                ProxyResponse proxyResponse = new ProxyResponse();
-                proxyResponse.setCode(HttpStatus.SC_UNAUTHORIZED);
-                HandlerUtil.handleError(req, resp, serverUrl, platform, proxyResponse);
+                sendUnAuthorizeResponse(req, resp, serverUrl, platform);
                 return;
             }
 
             AuthData authData = (AuthData) httpSession.getAttribute(HandlerConstants.SESSION_AUTH_DATA_KEY);
+            if (authData == null) {
+                sendUnAuthorizeResponse(req, resp, serverUrl, platform);
+                return;
+            }
+
             String accessToken = authData.getAccessToken();
 
             HttpPost tokenEndpoint = new HttpPost(serverUrl + HandlerConstants.INTROSPECT_ENDPOINT);
@@ -94,9 +98,7 @@ import java.io.IOException;
             if (jTokenResult.isJsonObject()) {
                 JsonObject jTokenResultAsJsonObject = jTokenResult.getAsJsonObject();
                 if (!jTokenResultAsJsonObject.get("active").getAsBoolean()) {
-                    ProxyResponse proxyResponse = new ProxyResponse();
-                    proxyResponse.setCode(HttpStatus.SC_UNAUTHORIZED);
-                    HandlerUtil.handleError(req, resp, serverUrl, platform, proxyResponse);
+                    sendUnAuthorizeResponse(req, resp, serverUrl, platform);
                     return;
                 }
                 ProxyResponse proxyResponse = new ProxyResponse();
@@ -110,4 +112,11 @@ import java.io.IOException;
             log.error("Error occurred while parsing the response. ", e);
         }
     }
+
+    private void sendUnAuthorizeResponse(HttpServletRequest req, HttpServletResponse resp, String serverUrl, String platform)
+            throws IOException {
+        ProxyResponse proxyResponse = new ProxyResponse();
+        proxyResponse.setCode(HttpStatus.SC_UNAUTHORIZED);
+        HandlerUtil.handleError(req, resp, serverUrl, platform, proxyResponse);
+    }
 }