> Markdown version of [Step 3 - Running a Spring Boot application with MPR and Flow](https://vaadin.com/docs/v14/tools/mpr/introduction/step-3-spring-boot). Section index: [llms.txt](https://vaadin.com/docs/v14/tools/llms.txt)

# Step 3 - Running a Spring Boot application with MPR and Flow

> **Note:** This step is needed in case your Vaadin 7 or 8 application uses Spring Boot. If it is not the case, go back to the [framework selection](https://vaadin.com/docs/v14/tools/mpr/introduction/step-3-legacy-uis.md).

## <a id="updating-to-the-correct-spring-version"></a>Updating to the correct Spring version

Update parent `org.springframework.boot:spring-boot-starter-parent` to `2.1.7.RELEASE` or newer.

The dependency `com.vaadin:vaadin-spring-boot-starter` should not have a version defined as it comes from `vaadin-bom`.

```xml
<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.1.6.RELEASE</version>
</parent>

<dependency>
    <groupId>com.vaadin</groupId>
    <artifactId>vaadin-spring-boot-starter</artifactId>
</dependency>
```

> **Note:** Also take a look at the [Use Vaadin with Spring](https://vaadin.com/docs/v14/flow/integrations/spring) documentation on how Flow integrates with Spring.

## <a id="handling-of-springui"></a>Handling of SpringUI

The `@SpringUI` can be replaced with a `@Route`. For example this UI:

```java
@SpringUI
@Theme("valo")
public class TodoUI extends UI {
    @Override
    protected void init(VaadinRequest vaadinRequest) {
        setContent(new HorizontalLayout());
    }
}
```

Can be replaced with:

```java
@Route("")
public class TodoUI extends Div implements HasLegacyComponents {
    @PostConstruct
    private void buildLayouts() {
        setSizeFull();
        add(new HorizontalLayout());
    }
}
```

> **Note:** Annotations in the UI, such as `@Theme` and `@Title` and so on, will be dealt with later on in the tutorial. Most of them have similar counterpart in either Flow or MPR.

## <a id="update-imports"></a>Update imports

Then any `com.vaadin.spring.annotation` imports needs to be changed to `com.vaadin.flow.spring.annotation`.

> **Note:** The V14 Spring add-on doesn’t have a feature comparable with `ViewScope`

## <a id="what-to-do-with-springview"></a>What to do with SpringView

Any `@SpringView` should be updated to a Flow Route by wrapping them as a `MprRouteAdapter<? extends View>` or re-writing it to be a Flow Component. See [Migrating Views to Flow Routes](https://vaadin.com/docs/v14/tools/mpr/introduction/step-3-navigator.md#no-navigator) for details.

## <a id="things-to-keep-in-mind"></a>Things to keep in mind

- When porting the UI to a flow component, you lose the ability to use UI methods, such as `setErrorHandler`. You can still access those by using `UI.getCurrent()`. The method `setContent` is not supported though - you should use the `add` method from your Flow layout instead.

- When running MPR with Spring, the Spring integration is done with Flow (and not anymore with Vaadin 7 or 8), so in some cases you will need to import classes from the old `vaadin-spring` project in order to make your MPR project to compile, since those classes are not present anymore in the new versions of `vaadin-spring`. The source code of `vaadin-spring` can be found on [GitHub](https://github.com/vaadin/spring). Examples of such classes:

  - com.vaadin.spring.access.SecuredViewAccessControl;

  - com.vaadin.spring.access.ViewAccessControl;

  - com.vaadin.spring.internal.SpringBeanUtil;

  - com.vaadin.spring.internal.VaadinSpringComponentFactory;

  - com.vaadin.spring.server.SpringVaadinServletService;

- If your routes are defined in a different package than the Spring application itself, you need to annotate your application with `@EnableVaadin`, in order to Spring to scan the appropriate folders for beans. For example:

```java
// Assuming that Application is in a different package than the classes
// annotated with @Route
@SpringBootApplication
@EnableVaadin("com.mycompany.views")
public class Application extends SpringBootServletInitializer {
```

## <a id="next-step"></a>Next step

- [Step 4 - Configuring UI parameters →](https://vaadin.com/docs/v14/tools/mpr/introduction/step-4-ui-parameters.md)

Or:

- [← Go back to step 2](https://vaadin.com/docs/v14/tools/mpr/introduction/step-2-legacy-servlets.md)

- [← Go back to the overview](https://vaadin.com/docs/v14/tools/mpr/overview.md)

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