> Markdown version of [Vaadin Spring Scopes](https://vaadin.com/docs/v14/flow/integrations/spring/tutorial-spring-scopes). Section index: [llms.txt](https://vaadin.com/docs/v14/flow/llms.txt)

# Vaadin Spring Scopes

## <a id="contexts-and-scopes-in-spring"></a>Contexts and Scopes in Spring

- **Contexts** in Spring are services that manage the lifecycle of objects and handle their injection. Generally, a context refers to a situation in which an instance is used with a unique identity. These objects are essentially "singletons" in the context.

- **Scopes** are narrower than contexts. While conventional singletons are application-wide, objects managed by a Spring container are "singletons" in a narrower scope. Examples include a user session, a particular UI instance associated with the session, or even a single request. A scope defines the lifecycle of the object, that is its creation, use, and destruction.

## <a id="using-spring-scopes"></a>Using Spring Scopes

In most programming languages, a variable name refers to a unique object within the scope of the variable. In Spring, an object has a unique identity within a scope, but instead of identifying the object by its variable name, it is identified by its type (object class) and qualifiers, if any.

In addition to standard Spring scopes, the [Vaadin Spring add-on](https://vaadin.com/directory/component/vaadin-spring/overview) introduces two additional scopes: `VaadinSessionScope` and `UIScope`.

- The `@VaadinSessionScope` annotation manages the Spring beans during the Vaadin session lifecycle. It ensures that the same bean instance is used during the whole Vaadin session.

  **Example**: Using the `@VaadinSessionScope` annotation.

  ```java
  @Route("")
  public class MainLayout extends Div {
      public MainLayout(@Autowired SessionService bean) {
          setText(bean.getText());
      }
  }

  @Route("editor")
  public class Editor extends Div {
      public Editor(@Autowired SessionService bean) {
          setText(bean.getText());
      }
  }

  @Component
  @VaadinSessionScope
  public class SessionService {
      private String uid = UUID.randomUUID().toString();

      public String getText(){
          return "session " + uid;
      }
  }
  ```

  - Provided you access the application from the same Vaadin session, the same instance of `SessionService` is used. This is because it is session scoped.

  - If you open the root target in one tab and the `editor` target in another, the text in both is the same. This happens because the session is the same, even though the tabs (and `UI` instances) are different.

- The `@UIScope` annotation manages the Spring beans during the `UI` lifecycle.

  **Example**: Using the `@UIScope` annotation.

  ```java
  @Route("")
  public class MainLayout extends Div {
      public MainLayout(@Autowired UIService bean) {
          setText(bean.getText());
      }
  }

  @Route("editor")
  public class Editor extends Div {
      public Editor(@Autowired UIService bean) {
          setText(bean.getText());
      }
  }

  @Component
  @UIScope
  public class UIService {
      private String uid = UUID.randomUUID().toString();

      public String getText() {
          return "ui " + uid;
      }
  }
  ```

  - The `UIService` is now the same while in the same `UI`, because it is UI scoped. When using `@UIScope`, the same bean instance is used inside the same `UI` instance.

  - If you open the root target in one tab and the `editor` target in another, the text in each is different, because the `UI` instances are different. However, if you navigate to the `Editor` instance via the router (or a `UI` instance which delegates navigation to the router), the text is the same.

  - **Example**: Navigating to the `editor` target.

    ```java
    public void edit() {
        getUI().get().navigate("editor");
    }
    ```

See [Application Lifecycle > Loading a UI](https://vaadin.com/docs/v14/flow/advanced/tutorial-application-lifecycle.md#application.lifecycle.ui) and [User Session](https://vaadin.com/docs/v14/flow/advanced/tutorial-application-lifecycle.md#application.lifecycle.session) for more.

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