What is Spring Web Flow?

Spring Web Flow is a framework for building and managing complex workflows in web applications. It provides a flexible and scalable way to manage the flow of pages, actions, and events in a web application.

In this blog post, we will cover the major features and components of Spring Web Flow with code examples and detailed explanations.

Let’s take a look at a simple example to see how Spring Web Flow works. Suppose we are building an online store where users can browse products and place orders. We want to create a flow that allows users to browse products, add items to their cart, and check out.

We will define our flow using an XML file called order-flow.xml. Here's what it looks like:

In the order-flow.xml file, we have defined a flow called order-flow. We have also defined a variable called cart of type com.example.Cart, which will store the items in the user's cart.

The flow starts with a view-state called browseProducts, which displays a list of products for the user to browse. When the user selects a product and clicks the "Add to Cart" button, the flow transitions to a sub-flow called addToCart.

The addToCart sub-flow is defined in a separate file called add-to-cart-flow.xml. Here's what it looks like:

In the add-to-cart-flow.xml file, we have defined a sub-flow called addToCart. We have also defined two variables: product of type com.example.Product, which represents the product being added to the cart, and quantity of type java.lang.Integer, which represents the quantity of the product being added.

The addToCart sub-flow starts with a view-state that displays the product being added and prompts the user to enter the quantity. When the user clicks the "Add to Cart" button, the flow transitions back to the same view-state and adds the product and quantity to the cart. When the user clicks the "Checkout" button, the flow transitions to an end-state called checkout.

To execute the flow, we need to create a flow controller that maps requests to the order-flow flow. Here's what the controller looks like:

The OrderController extends AbstractFlowController<Order>, which provides the basic infrastructure for handling flow requests. We have also defined two methods: getFlowDefinitionResource(), which returns the location of the flow definition file, and createFlowExecutionInput(), which creates the initial flow input object.

To start the flow, we can simply map a request to the controller:

This maps a GET request to /order/browse to the browseProducts view-state in the order-flow flow.

Spring Web Flow provides a powerful way to manage complex workflows in web applications. It allows you to define flows in a declarative manner, execute them using a flexible and scalable execution engine, and manage the flow state between requests.

Thank You for your attention! Happy Learning!

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