Java EE reading notes

Architecture layering for Java EE:

1.Domain object (domain) layer: consists of a series of Pojo (plain Java objects) that contain their own business logic

2.DAO (data access) Layer: consists of a series of DAO builds that implement database (CRUD) operations

3. Business Logic Layer: consists of a series of business logic objects, which realizes the business logic method required by the system. These methods may be used only to expose the business logic implemented by the domain object object, or it may be a business logic method that relies on DAO component implementations

4. Control layer: Consists of a series of controllers that are used to intercept user requests and invoke methods of business logic components, process requests, and forward results to presentation layer components

5. Presentation layer: Consists of a series of JSP pages, velocity pages or PDF documents that are intended to collect user requests and display results

Components for Java EE applications:

1. Presentation layer components: Commonly used presentation layer is JSP, can also be done by velocity, freemarker and tapestry technology, can also be ordinary applications, small smart devices

2. Controller components: For Java EE's MVC Framework, the framework provides a core controller that intercepts user requests and forwards the world to user-implemented controller components. The user-implemented component invokes the business logic method to process the request.

3. Business Logic Layer: is the core component of the system, realizes the business logic of the system. The business logic approach is only responsible for implementing the business logic and should not be accessed by the database. Therefore, the original hibernate and JDBC APIs should not appear in the business logic components

4.. DAO components: Each DAO component provides a crud operation of the database that corresponds to the basic operation of the domain object object.

5. Domain Object components: domain object (domain objects) abstracts the system's object model. Each domain object typically corresponds to one or more data tables, often requiring access to data records

Java EE common servers:

Java EE related technologies:

1.jsp,servlet and JavaBean Technology

JSP is mainly used to act as the performance layer of Java EE, and its underlying principle is exactly the same as the servlet. The JSP must be compiled by the server into a servlet, and the server is really running a servlet, so a generalized servlet includes Servlets and JSPs. JSP has nine large built-in objects, seven basic operations, is a very useful technology.

A servlet is a server-side program written in Java. Its main function is to interactively browse and modify data to generate dynamic Web content.

JavaBean is used to transfer data, and the middle-tier component encapsulates the application's underlying state information into a JavaBean set, which is transferred to the JS page.

2.STRUTS2 Technology and alternative technology

The first MVC pattern was the framework of struts, later struts and webwork were combined as STRUTS2, which is now the framework of the mainstream MVC model, with other frameworks being JSF (recommended by Sun), Tapestry (an excellent framework under the Apache organization)

3.hibernate3.6 and Alternative Technologies

Traditional Java applications are using JDBC to access the database, Java EE hopes to operate the database by an object-oriented approach, so there is an ORM (object relation mapping), the earliest ORM is EJB (the core of classic Java EE applications, very cumbersome , Hibernate is a lightweight ORM framework that allows ordinary Java objects (POJO) to be mapped into persistent classes, allowing the object-oriented approach to manipulate POJO, and hibernate is responsible for translating these operations into SQL operations.

　　Its alternative technologies include Sun's JPA, Apache job, and Oracle's TopLink

4.spring3.0 and Alternative Technologies

Java EE reading notes