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Author's profile photo John Patterson

Restoring Fiori Application State

When doing cross application navigation in Fiori, that is navigating between applications. On return, rather than picking up from where you left off, a new instance of the application is created. Meaning the app is in an initial state and not in the state when you left it. To solve this we need to persist the state between calls. Store any filters, search options, interactions the user has applied, then reapply them on return.

There has not been a documented standard approach for solving this. As a result we see and hear many different ways UI5 developers are solving this by themselves. If you study some of the standard SAP applications, there is an approach for managing state using existing Fiori services. In this blog I will highlight how it works, providing an easy way to do it yourself using generic reusable SAP code.

In the video above we see a variety of different filters being applied to a work list. We then see navigation to a second application. On return all those filters and interactions are reapplied.

Behind the scenes

Prior to navigation the application state is persisted on the server.

We can see below that the API /UI2/INTEROP/GlobalContainers is called and values are posted to the Layered Repository (LRep) table /uif/lrepdcontcd on the Gateway server.

The key for retrieving this data is added as a parameter to the URL.
On return the key is read from the URL, the data is retrieved and the app state is restored.
Because the data is persisted on the server, you can bookmark the URL, reopen in a browser and restore the state of the application. You can share bookmarks between different makes of browsers and different users. However the state key is recreated each time the data is loaded.

How does it work?

1. Prior to navigation save the app state
// create a new Application state (oAppState) for this Application instance
oAppState = sap.ushell.Container
            .getService("CrossApplicationNavigation")
            .createEmptyAppState(this);
oAppState.setData(oStateToSave); // object of values needed to be restored
oAppState.save();

2. Update the URL hash with the key

var oHashChanger = sap.ui.core.routing.HashChanger.getInstance();
var sOldHash = oHashChanger.getHash();
var sNewHash = sOldHash + "?" + "sap-iapp-state=" + this.oAppState.getKey();
oHashChanger.replaceHash(sNewHash);

3. Navigate to another Fiori application

sap.ushell.Container
	.getService("CrossApplicationNavigation")
	.toExternal({
		target: {
	   		semanticObject: sSemanticObject,
           		action: sAction
 		}, 
		params: oParams,
		appStateKey : oAppState.getKey()
});

4. On return read the key from the URL, retrieve the data and restore the app

var sHash = oHashChanger.getHash()
var sAppStateKey = /(?:sap-iapp-state=)([^&=]+)/.exec(sHash)[1]; 

sap.ushell.Container
 .getService("CrossApplicationNavigation")
 .getAppState(sAppStateKey)
 .done(function (oSavedAppState) {
       << code for restoring app state >>
});

Things you need to consider doing it this way, AppState instances are immutable, means the key will change, the URL may include routing and parameters in the hash.

Alternative Approach

The last couple of months I have been helping customers investigate and adopt the ABAP Programming Model for SAP Fiori, in preparation for thier S/4 HANA transformation. Part of this has been Developing Apps with SAP Fiori Elements. Fiori Elements uses the sap.ui.generic.app library, which has a very easy to reuse standalone NavigationHandler which abstracts away a lot of the complexity.

NOTE: This option is only available on SDK version 1.36.X and higher. There are other alternatives which work like sap/suite/ui/generic/template/ListReport/nav/NavigationHandler on 1.34 and below.

To implement

1. Import the Navigation handler into your controller

sap.ui.define([
..
    "sap/ui/generic/app/navigation/service/NavigationHandler",
    "sap/ui/generic/app/navigation/service/NavType"
], function(.. NavigationHandler, NavType) {

 

2. Instantiate the navigation handler and provide a callback for after navigation

onInit: function() {
..
// create an instance of the navigation handler
this.oNavigationHandler = new NavigationHandler(this);

// on back navigation, the previous app state is returned in a Promise
this.oNavigationHandler
   .parseNavigation()
   .done(this.onNavigationDone.bind(this));

// the app state which needs persisting
this._oAppState = {
    selectedTabFilter: "all",
    searchText: "",
    selectedContextPaths: [],
    selectedCategories: [],
    selectedSuppliers: []
};

3. Do the cross app navigation

onPress: function(oEvent) {
    .
//(sSemanticObject, sActionName, vParameters?, oAppData?, fnError?)
this.oNavigationHandler
   .navigate("Navigation", "sample",{},{ customData: this._oAppState });

4. Restore the application state

/**
 * if navigated back with appstate enabled then rehydrate the page using the
 * stored data
 * @param {Object} oAppData data persisted via iAppState
 * @param {Object} oURLParameters paramters passed in
 * @param {String} sNavType type of navigation
 */
onNavigationDone: function(oAppData, oURLParameters, sNavType) {
switch (sNavType) {
case NavType.initial:
    break;
case NavType.iAppState:
    this._oAppState = oAppData.customData;
    // set the previously selected icon filter tab
    this.byId("iconTabBar").setSelectedKey(oAppState.selectedTabFilter);

    // apply previous filters to table
    this._applyFilters();

    // set the previous search state
    this.byId("searchField").setValue(oAppState.searchText);

    // set the previously selected multi combo tokens
    this.byId("categories").setSelectedKeys(oAppState.selectedCategories);
    this.byId("suppliers").setSelectedKeys(oAppState.selectedSuppliers);

    // select previously selected rows
    this.byId("table")
        .setSelectedContextPaths(oAppState.selectedContextPaths);
    break;
}

Want More?

Demo Application in video

Source Code for Demo Application

Not on S/4 Hana yet or want to know more about the “ABAP Programming Model for SAP Fiori” a best practice for rapidly building meta-driven SAP Fiori apps on top of ABAP OData Services?

Come to my session at SAP TECHED Las Vegas

Ten tips from Using the ABAP Programming Model for SAP Fiori on AnyDB

 

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      22 Comments
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      Author's profile photo Simon Kemp
      Simon Kemp

      Great stuff. Thanks for sharing your knowledge on this topic John.

      Author's profile photo Mike Doyle
      Mike Doyle

      Great blog as always, John.  I hadn't come across NavigationHandler before, and it looks very interesting.

      Regarding the first method, am I right in thinking that the replaceHash method will trigger events in the router, such as onRouteMatched?  That's not really want we want in this case, is it?

       

       

      Author's profile photo John Patterson
      John Patterson
      Blog Post Author

      Hi Mike

      Thanks,

      AFAICS a Fiori hash is made up of multiple parts,

      shellhash /  intent / appSpecficRoute / params etc.

      i have a feeling param changes are ignored and (route) events are fired for app-specific parts only

      you would have to debug  sap.ushell.services.ShellNavigationHashChanger to see what really happens

      JSP

      Author's profile photo John Patterson
      John Patterson
      Blog Post Author

      I just debugged

      sap.ui.core.routing.HashChanger.getInstance() returns

      sap.ushell.services.ShellNavigationHashChanger when u run in FLP

      sap.ushell.services.ShellNavigationHashChanger.prototype.replaceHash - doesnt replace the browser history, therefore no route change, I debugged to confirm

      JSP

      Author's profile photo Jiawei Cao
      Jiawei Cao

      Hi John,

      both ShellNavigationHashChanger and sap.ui.core.routing.HashChanger modify the browser hash but don't create the new history entry in the browser once the replaceHash method is called. The same route is matched again after only appending the sap-iapp-state id is appended to the hash. Therefore there's no UI change made since the matched route isn't changed. However, the pattern of the route needs to be able to handle this optional query parameter and define ":?sapiappstate:" in the route's pattern where an inner-app state can be appended.

      Could you please verify whether the routes in your app have the optional query parameter?

      Best regards,

      Jiawei

      Author's profile photo Phil Cooley
      Phil Cooley

      Nice John. Definitely an interesting topic and a nice easy explanation on how this can be achieved.  Thanks!

      Author's profile photo Nabi Zamani
      Nabi Zamani

      Pretty cool blog, John! After the Navigation & Routing tutorial I thought about publishing something like "Fiori Cross App Navigation" which should include app states as well. With this great blog it might be obsolete now... Thanks for sharing!

      Author's profile photo John Patterson
      John Patterson
      Blog Post Author

      Hi Nabi

      Mate please do publish, in my case by writing the blog I have significantly increased my understanding, if others do likewise we can fill more gaps.

      Cheers

      JSP

       

      Author's profile photo Former Member
      Former Member

      This is nice, works similar to the Saved searches option in FPM etc..

      If you want to store data across applications, you can simply store it on the Window, so in this case you can store the Search Filters as an object and also the search results on the Window as a JS object (JSON)

      Simply write "window.myName = 'Sai' " and it should persist in the same browser session. SAP stores all its framework objects this way.. See pic.

       

       

      Author's profile photo Former Member
      Former Member

      Author's profile photo Former Member
      Former Member

      hi John,

       

      Good article. I’d like to hear your thoughts about storing client state in the server.. isn’t this exactly the problem we tried to solve using stateless apps? – As far I can see (in fact, as far the payload is concerned) a “session” is sort of created and you chunk the session reference in the URL, not too different from a jsessionid.

       

      I understand limitations that a URL may have, but why not qs the same payload into the URL and relieve the server from a request while also removing all the issues the same approach used by SAP will cause?

       

      Because now you’ve bound the access URL to a session, the session must remain “infinite” in the server… that table which saves each JSON can never be deleted anymore neither cleared, and if it is, then you broke your resource locator and you made a valid resource become an invalid resource.

       

      I’d also suggest you add a version identifier so when you modify applications and later on a bookmarked resource comes back in, you can fail gracefully – not always necessary but often good to keep track.

       

      Would like to understand how many times have you faced the limit of 2048 when dropping state into parameters?

       

       

      Cheers,
      Dan.

      Author's profile photo John Patterson
      John Patterson
      Blog Post Author

      Hi Dan

      Thanks

      This is a standard SAP approach, as much as I like writing code, I would rather reuse other peoples.

      The appstate is persisted to the back end, however it is not retrieved from the back end if found in the FLP session memory.

      I am in two minds about the backend state persistence, but can see some wins for users.

      There are standard jobs for purging LRep data. One of many jobs for Fiori cache and data management.

      If you debug the sample application provided you will see it uses Local Storage, it delegates to Fiori Personalization service, which supports Session, Local Storage, Server side caching and DB options.

      I have faced the URL limitation a few times, not with this technique though.

      Cheers
      JSP

       

       

       

      Author's profile photo Tom Van Doorslaer
      Tom Van Doorslaer

      But wait, there’s more!

      You can also pass an appstate to your navigation target:

      var oNav = sap.ushell.Container.getService("CrossApplicationNavigation");
      oNav.toExternal({ target: { shellHash: sIntent + "?sap-xapp-state=" + encodeURIComponent(JSON.stringify(oJson)) + sAction } });
      
      (example: 
      sIntent: "#Notificaton",
      sAction: "Create",
      oJson: {type:"D1", text:"a really long text here", image="data:image/png,base64...." }
      )

      This allows you to pass large JSON objects to your target, rather than just an ID.

      Example: you want to create a follow on document, which contains the entire text from the original document. A large text cannot be passed via the URL… so you add the text into a json object

      { text: sText}

      and you pass it as an x-app-state. This saves the object and generates a key.

      In the target app, you load your app state (ui5 will automatically use the key from the url) and hey, presto! you now have access to the json object.

       

      Edit: Completely missed the ball here. We have a redefinition of the navigation handler which automatically transforms any URL parameters into an appState in the local storage....

      Author's profile photo Vladislav Volodin
      Vladislav Volodin

       

      You know about the maximum URI length limitation, don't you? I wouldn't use the poor URI to store as a storage for strange objects.

      Author's profile photo Tom Van Doorslaer
      Tom Van Doorslaer

      Didn't I say that we store the "big" object in the local state and only pass the identifier of the local state through URL?

      I thought I did...

      Author's profile photo Krishna Kishor Kammaje
      Krishna Kishor Kammaje

      I have expanded a little on sap-xapp-state here. If anyone is interested.  OVP-Navigation

      Author's profile photo Anmol Goel
      Anmol Goel

      Hi John,

      Do you know for how long does it persist the app state in the table?

      Regards,

      Anmol

      Author's profile photo Tobias Schnur
      Tobias Schnur

      Hello,

      thanks for the great blog. I actually think there is a big disadvantage of the generic Navigation Handler. It can only navigate based on the intent (object + action). It is not possible to provide any additional hash to trigger an inner app navigation in the target app in case you do not want to navigate to the start page of the target app.

      However I think it's possible to use method "storeInnerAppState" of the navigation handler instead:

      _storeState: function () {
      		this._oAppState.selectionVariant = this._oSmartFilterBar.getDataSuiteFormat(true);
      		this._oAppState.tableVariantId = this._oSmartTable.getCurrentVariantId();
      		this._oNavigationHandler.storeInnerAppState(this._oAppState);
      	 }

       

      and trigger the navigation "manually:

      			if (this._oIsNavSupported) {
      				this._oIsNavSupported.done(jQuery.proxy(function (aIntentSupported) {
      					if (aIntentSupported[0].supported) {
      						this._storeState();
      
      						oCrossApp.toExternal({
      							target: {
      								semanticObject: "ServiceOrder",
      								action: "manage"
      							},
      							appSpecificRoute: "&/HeaderSet/" + sSrvOrderGuid
      						});
      					}
      				}, this));
      			}

       

      The "sap-iapp-state" is added to the URL:

      "/sap/bc/ui5_ui5/ui2/ushell/shells/abap/FioriLaunchpad.html?sap-client=100&sap-language=EN#Shipment-display&/?sap-iapp-state=ASJKBG22X5TO0I1Q6ANGB6C5HCL95RFQCMP6DMQG"

      However when I navigate back from the target it does not work. It seems that there is no matching route to this hash. I haven't found the exact issue yet. The Component.js is loaded but no view is loaded.Someone has an idea? Is the syntax used in the URL above not correct?

      Regards

      Tobias

       

       

      Author's profile photo Jiawei Cao
      Jiawei Cao

      Hi Tobias,

      I am from the SAPUI5 Core Framework team where the modules under sap.ui.core.routing are maintained. I came across this blogpost through a bug report and the issue which is reported there is the same one as what you wrote.

      Once the inner-app state is used in one application, all of the routes where an inner-app state id can be appended need to define an optional query parameter in their pattern to make the hash that has an inner-app state id in it can still match the route and not lead to the "bypassed" event in UI5 routing. Suppose you have a route with an empty string pattern "", the pattern needs to be changed to ":?sapiappstate:" (the query parameter can have any arbitrary name) in order to let the route be matched after the inner-app state is appended to the hash.

      Best regards,

      Jiawei

      Author's profile photo Ekansh Saxena
      Ekansh Saxena

      Hi Jiawei Cao ,

      I am on version 1.60.6 and found that 'getDataSuiteFormat' function is deprecated and I should use getUiState function instead. Now I use this getUiState() and save the UiState in app state. When I navigate back to my source app and retrieve the UiState from the app state data, I try to use function setUiState to set the filter data in smart filter bar. It gives error that it couldn't find method getSelectionVariant from the UiState data that I passed since it is a shallow copy of data returned from getUiState() thus doesn't have any methods.

      Am I doing something wrong here or is it a bug?

      BR, Ekansh

      Author's profile photo Melvin Poinoosawmy
      Melvin Poinoosawmy

      Hello,

      Do you have any idea how to preserve the state of the column of Smart table ?

      Lets assume we reverse the Supplier and the Price Column, how can we store the order and the visibility of columns ?

       

      Best regards

       

      Melvin

      Author's profile photo Jan Mattfeld
      Jan Mattfeld

      You could read the UIState of your SmartTable [1] and store/apply that.

      However, I was under the impression this would happen automatically when using Fiori Elements. Apparently it doesn’t. The captured app state does not include any changes to the underlying SmartTable in a List Report. Is that correct John Patterson ?

      [1] https://sapui5.hana.ondemand.com/#/api/sap.ui.comp.state.UIState