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Editor to share with you how to use Spring Web Flow and Terracotta to build Web applications, I hope you will learn something after reading this article, let's discuss it together!

What is Spring Web Flow?

Spring Web Flow is a web application component in Spring Framework, which provides a simple way to write stateful and session-based web applications. Spring Web Flow makes logical processes a first-class citizen in web applications, allowing you to define them as self-contained modules that can be configured and reused independently of the rest of the application. It does not depend on the framework so that it can be easily used with optional web application frameworks, such as Spring MVC, Struts, or JSF.

Page flows are configured using a domain definition language (DSL) that is specifically developed to define and combine page flows. The current implementation methods are XML and Java.

Spring Web Flow introduces several stateful data fields that can meet a variety of user cases and needs: request, flash, flow and conversation, which provides you with great flexibility and ability to develop stateful web applications.

Here is a quick summary of the most interesting features in 1.0 release:

Define all the control logic of an application task, such as a search process, in one place rather than spreading the logic in many places.

Combine simple flows to create a rich control module.

Use natural and object-oriented linear programming models instead of lengthy if/else blocks to define strict user navigation rules.

However, when the flow ends or expires, it automatically clears the memory you allocate during the flow execution.

Deploy an executable flow in a Servlet environment that uses the underlying web framework of your choice.

Change the web framework (such as Struts, Spring MVC, JSF, and others) without changing the flow definition.

Change with the environment without changing your flow definition, such as from JUnit testing to Portlet.

Develop to constantly improve your application navigation rules without restarting the container.

Automatically and correctly respond to browser buttons (back, forward, refresh) without custom programming.

Task data is stored in four managed domains: request, flash, flow, and, conversation, each with its own unique semantics.

Test the flow separately from the container. Be able to ensure the proper operation of the application control logic before deployment.

Use Spring IDE 2.0 to visually edit your flow navigation logic diagram

What is Terracotta for Spring?

Terracotta for Spring is a runtime based on Spring applications. It provides transparent and high-performance cluster support for Spring applications with little impact on application code and deployment and configuration processes. It is clustered at the heap level below the application rather than directly clustered applications.

This allows developers to develop single-node stateful Spring applications that are different from stateless methods. This allows clustering not to be considered at the beginning of the design of applications that need to be extended. When applications need to be extended or to ensure availability and failure recovery, they only need to define in the Terracotta configuration file which beans in the Spring application context needs to be clustered. Terracotta for Spring enables applications to be clustered automatically and transparently, and ensures that the semantics between clusters are the same as those of single nodes.

For Spring Web Flow, this is actually simpler. In order to obtain the status of web applications and the clustering capabilities of continuous repositories, users only need to declare a specific web application as "session-support" enabled in the Terracotta configuration file. (for details, see the following section, "declarative configuration")

From a macro point of view, Terracotta for Spring provides:

Cluster with HTTP session status. Ensure high availability and fault recovery of user states in Spring Web Flow and extended warehouses or other states put into HTTP session.

The cluster of Spring bean. The lifecycle semantics and domains of Springbean are saved between clusters, and they are in the same "logically" ApplicationContext. At present, the bean types that can be clustered are singleton and session scoped. Users can declaratively configure which application contexts and which bean needs to be clustered.

Transparent cluster POJO. There is no need to modify existing code, or even source code. The application is based on a few declarative XML configuration files and takes effect transparently at load time. Terracotta for Spring does not require classes that implement Serializable, Externalizable, or other interfaces. The reason for this is that instead of using serialization, it just transfers the actual difference and changed data to the currently needed node (lazily).

Virtual memory management. It also provides distributed garbage collection and virtual heap capabilities. For example, because physical memory is swapped in and out when needed, it can run Web applications that require a 200G heap on a 4G RAM machine. This also means that you don't need to worry about whether the size of the Spring Web Flow session data exceeds the physical heap size.

After reading this article, I believe you have a certain understanding of "how to use Spring Web Flow and Terracotta to build Web applications". If you want to know more about it, welcome to follow the industry information channel, thank you for reading!

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