Java Enterprise Edition Architecture is a specification for software architecture for enterprise context. Therefore the following functionality is in-focus:
- Web applications
- Transaction security
- Administration of users and data
- High availability
- Load safety
- Corruption security
- Scalability
- Cearly defined interfaces
- Modular components
These functionality enhances required functional and non-functional requirements of must enterprises (see iSAQB). Improvements to JEE are covered within a Java Community Process (JCP) and lead to Java Specification Requests (JSR), which are published using a reference implementation. Java EE applications require a compliant application server which requires to provides all container and services of the JEE specification. Required containers might be Web-Container, which contains the runtime for Servlets and JSP, and EJB Container, containing the runtime for Enterprise Java Beans. Thoses application servers provide the following functionality:
- Security
- Transaction management
- Persistence services
- Name and Directory Services (JNDI)
- Communication between the component
- Instantiation of Objects (CDI)
- Deployment support
As application tend to follow architectural patterns, Java EE applications are designed to follow a 3-tier-application-layer:
- Client-Tier
Contains front-end elements using Java build-in (JSP, JSF) or external langauges such as AngularJS.Connects to Business-Tier using JSP (Java Server Pages), JSF (Java Server Faces) technology, Webservices and Servlets. - Business-Tier
Contains business logic which are implemented within EJBs (Enterprise Java Beans). Connects to Data-Tier using JPA (Java Persistence API), JMS (Java Message Service) and JTA (Java Transaction API) or Java frameworks like Hibernate. - Data-Tier
Stores data. Data stores can be in-memory, SQL, NoSQL and many other formates (XML, JSON, persisted POJOs, etc.).
Interdepartmental components include JTA (Java Transaction API) for transaction management, JNDI (Java Naming and Directory Interface) and CDI (Contexts and Dependency Injection).
Spring Architecture
Spring is an open source Java Framework. Spring itself reflects the core framework or the whole set of components of the framework based on context. In most cases the whole eco-system is referenced:
Spring has been introduced with version 1.0 in 2003 to address unnecessary complexity within Java EE architectures. As an alternative for J2EE Spring 2.0 won tje JAX Innovation Award as leightweight system which innovates the Java eco-system. Spring is a POJO (Plain Old Java Object) based model which highly utilizes interfaces and dependency injection. As part of this, Spring controlled resources are called Spring Beans. Spring modules utilize modularity to reduce dependencies between modules. Most known modules are:
- Spring DAO
is utilized for JDBC databases and transaction management. - Spring ORM
integrates popular frameworks for objectrelational mappings, e.g. Hibernate. - Spring Web
implements basic functionality of web-apps. - Spring Web MVC
extends Spring Web by Model-View-Controller architectur capabilities and supports ReST-Webservices.
Brief Introduction into Spring MVC and Spring Boot
An approx. 50 minutes introduction into Spring MVC (Model-View-Controller) and Spring Boot is given by Aisha SheryL on YouTube:
