5.1.1. Application Tiers and Blocks
The platform enables building applications according to the classic three-tier pattern: client tier, middleware, database. The tier indicates the degree of "remoteness" from the stored data.
Further on, mainly middleware and client tiers will be described, therefore the words "all tiers" will refer to these tiers only.
Each tier enables creating one or more application blocks. A block is a separate executable program interacting with other blocks in the application. CUBA platform tools enable the creation of blocks in the form of web or desktop applications.
- Middleware
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The middle tier contains core business logic of the application and provides access to the database. It is represented by a separate web application running on Java EE Web Profile standard container. See Middleware Components.
- Web Client
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A main block of the client tier. It contains the interface designed primarily for internal users. It is represented by a separate web application running on Java EE Web Profile standard container. The user interface is implemented on the base of Vaadin framework. See Generic User Interface.
- Desktop Client
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An additional block of the client tier. It contains the interface designed primarily for internal users. It is represented by a desktop Java application; the user interface is implemented on the base of Java Swing framework. See Generic User Interface.
- Web Portal
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An additional block of the client tier. It can contain an interface for external users and entry points for integration with mobile devices and third-party applications. It is represented by a separate web application running on Java EE Web Profile standard container. The user interface is implemented on the base of Spring MVC framework. See Portal Components.
- Polymer Client
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An optional client designed for external users and written in pure JavaScript. It is based on Google Polymer framework and communicates with the middleware via REST API running either in Web Client or in Web Portal blocks. See Polymer User Interface.
Middleware is the mandatory block for any application. User interface can be implemented by one or several blocks, such as Web Client and Polymer Client.
All of the Java-based client blocks interact with the middle tier uniformly via HTTP protocol enabling to deploy the middle tier arbitrarily, behind a firewall as well. In the simplest case when the middle tier and the web client are deployed on the same server local interaction between them can bypass the network stack for better performance.