Java EE application components

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1, Presentation layer components: mainly responsible for collecting user input data, or to display the system status to the customer. The most common presentation layer technology is JSP, but JSP is not the only presentation layer technology.

2. Controller components: For the MVC framework of Java EE, the framework provides a front-end core controller, which is responsible for intercepting user requests and forwarding user requests to the controller components implemented by the user. The controllers implemented by these users are responsible for processing calls to the business logic method and processing user requests.

3, Business logic component: is the core component of the system, realizes the business logic of the system. Typically, a business logic method corresponds to a user action. A business logic approach should be a whole, and therefore requires an increased transactional approach to business logic methods. The business logic approach is only responsible for implementing business logic and should not be accessed by the database, so the original hibernate, JDBC, and other APIs should not appear in the business logic components.

4. DAO Component: Data Access object, also known as a DataSource. This type of object is less varied, and each DAO component provides basic creation, query, update, and delete operations for the domain object object, which correspond to atomic operations such as CRUD in a data table. Of course, the implementation of DAO components will be completely different if different persistent layer access techniques are used. To separate the implementation of the business logic component from the implementation of the DAO component, the program should provide an interface for each DAO component, and the business logic component is programmed for the DAO interface to provide better decoupling.

5. Domain Object component: Abstract the system's object model. In general, the state of these domain objects must be stored in the database. So each domain object typically corresponds to one or more data tables, and domain objects often need to provide access to the data records

Java EE application components