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Module elements

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  • This section provides you with an overview of the elements that are relevant to the Module (eSpace) level of migration, with details on how to approach creating new logic in Reactive App.


    When migrating logic that deals with Entities to the Reactive Web App, pay attention to those which you need to make public or set Expose Read-Only to false.

    Creating a new Entity in your Reactive Web App creates a new physical table. With this in mind, the suggestion is to change the Entity to be public, then add a reference to it in the Reactive Web Module.

    You can also use the accelerators for migrating Entities (copy and paste them).

    Multilingual Locales

    Starting with the Platform Server release 11.10, OutSystems has an integrated translations mechanism for adding and managing translations in Reactive Web and Mobile apps directly in Service Studio. Refer to Multilingual Reactive Web and Mobile Apps for more information about this feature.

    If you used the Multilingual Forge component to translate your app to several languages, you need to migrate your translations to Service Studio. Read the How to reuse translations from Multilingual Forge component in Service Studio document to learn about this process.

    On session start

    Use the On Application Ready Event in Reactive App to set the initial values of Client Variables as the configuration parameters in the app.

    When you use On Session Start in the Traditional Web App to initialize the Session Variables, migrate the logic in the Reactive Web App in a place where you read the variables, and protect it by checking if you defined the variable. For example, if you're using Cookies, add the logic before calling GetCookie, so it runs only if the Cookie wasn't set before.

    If you use On Session Start otherwise in the Traditional Web App, you need to evaluate case-by-case. Take into consideration that this logic runs on the first server request and when a user logs in and on the first request after having logged out.


    Change the Process to be public in the original Module and reference the Process, to avoid losing data.


    To avoid losing data, change the Role to be public in the original Module and reference the Role. Afterward, confirm that all the Screen permissions are the same.

    Server Action

    The way you migrate a Server Action to the Reactive Web App depends on whether the Action is public, its use on the Screens, and whether you can use it on the client side in the new Reactive Web App. Check the accelerators section to learn how you can use copy and paste with these Actions.

    Not used as a function

    You can migrate it directly to a Server Action in the Reactive Web App.

    Used as a function with input parameters

    Migrate this Action so that it's called after the calculation of the input parameters, typically at the end of a data action. Create a Data Action with an output for each Action. The Data Action should call the server Actions in the same order used in the Traditional Web App screen.

    Used as a function with a constant number of times in a Screen

    The screen uses the Server Action for a constant number of times (not in a List). Migrate the Action to Server Action in the Reactive Web Module while creating a local variable for each function call.

    Used as a function with a variable number of times in a Screen

    The screen uses the Server Action for a variable number of times on the Screen (in a List). Migrate the Action to Server Action in the Reactive Web Module. Then, add a calculated attribute in an Aggregate that creates the list that calls the function.

    Session Variable

    Client Variables in Reactive Web Apps are in many ways similar to the Session Variables. Use them with the On Application Ready Event to initialize global configurations for the apps, like instantiating username, locale, filters.

    Keep in mind:

    • The value of Client Variables clears when the user signs out
    • On Application Ready System Event triggers every time you run the app in a new tab/browser

    The migration of a Session Variable depends on whether it ties to a browser session or user preference, its data type, and whether it contains confidential information.

    Traditional Web Apps use Session Variables to store data on the server side in a key-value format. In Reactive Web Apps, Client Variables are in the Data tab. Create them here, and set their default value.

    Use Client Variables to cache user information that you don't want to fetch multiple times from the server or to store interface state information. Following the Reactive Web Best Practices, it isn't possible to use Client Variables of type: List, Record, Structure, and Entity.

    Share Client Variables in a Module by wrapping with public Client Actions. Initialize the interface state information on the server side through cookie settings, and then load it to Client Variables during the screen initialization.

    Be aware of security best practices, such as not exposing table identifiers which can be exploited by malicious server-side calls. Check the user roles on the server-side calls only. For more information about security in Reactive Web Apps, see the Reactive Web security best practices.

    Site Property

    To preserve their current values, copy the values from the original Traditional Web Module to the new Reactive Web Module via Service Center.

    Tied to a browser session

    If the Session Variable ties to the browser session and the data type is simple, migrate it to a browser-session-lived cookie using some name convention (for example, SessionVariable_NAME). Keep in mind that the values aren't cleared on log out.

    Replace reads and writes by the GetCookie and SetCookie methods of HTTPRequestHandler.

    Alternatively, for better client-side read performance, use a JavaScript Node to get the cookie value from document.cookie.

    If there are Widgets bound to the variable, create a Local Variable to bind them to and then sync the value with the cookie.

    Note that the data type distinction is important because cookies have limits, and storing complex types there can be extremely inefficient.

    Used for storing a user preference

    If you use the variable to store a user preference (meaning it ties to the user, not the browser session):

    • If it's only used in the UI/client-side logic store the value in a client variable
    • If the server side uses session variables, migrate the variable so the logic uses a row in a database Entity, associated with a User Id.

    You might need additional work for variables of List and Record data types (for example, you may need to devise an encoding, use a separate table, or other).


    If you don't find the session variable use case described in this section, then you need to evaluate the migration case-by-case.


    Copy the CSS you need from the Traditional Web App into the Theme of the Reactive Web App.

    Be aware that you may need to adapt your CSS to work with OutSystems UI. If you're migrating from Silk UI, check Migrating UI of the Silk Web applications to OutSystems UI Framework for more information.

    UI flow

    The new UI flows of the Reactive Web App should point to the new Theme. You can't migrate the advanced properties HTTP Security, Integrated Authentication, and Internal Access Only.

    For reference information about migrating the Traditional Web Apps Front-end to Reactive Web continue to Front-end.

    Documents in this section:

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