J2EE study notes (4) software engineering and system framework

Banq, the boss of J-channel, once said that design patterns are the most important criteria to measure the level of a programmer. I personally agree with this point of view. From this perspective, the first thing we need to know about learning J2EE well is how to assemble and collaborate effectively as a large and complex system.
Let's start with some Definitions of warm bodies Definitions of Different Dimensions in J2EE
Tiers: A logical or physical organization of components into an ordered chain of service providers and consumers. components within a tier typically consume the services of those in an "adjacent" provider tier and provide services to one or more "adjacent" consumer tiers. within a tier, services are grouped to like requirements, such as functionality, security, or load distribution.
Layers: The hardware and software stack that hosts services within a given tier. physical, network, and software platforms and standard API sets support the components that provide a service. layers, like tiers, represent a well-ordered relationship between SS boundaries that are mediated by interfaces. whereas tiers represent processing chains extends SS components, layers represent container/component relationships in implementation and deployment of services.
Tiers layer is the most common concept we hear. Generally, it can be divided into (customer) <--- interaction ---> [Client Interface --- Presentation Tier --- BizLogic Tier --- Integration Tier --- Resource Tier]
The typical Client Interface is IE, Swing, Applet, WAP, etc. The customer interacts with the Client directly.
Presentation Tier is responsible for accepting customer requests and returning corresponding processing results. Login, permission check, and session management are conducted here, technically jsp html, etc.
Business Logic Tier is responsible for processing Business Logic and data, and is the core of J2EE. It also manages Transaction and EJB at this layer.
Integration Tier is responsible for connecting the business logic layer to the system Resource Layer. The most common JDBC database connection is an example.
Resource Tier is responsible for providing resources required by the upper layer, such as databases, File System, and Legacy System.
Based on the actual application and design model, we can further divide the layers. Multiple layers can reduce the efficiency and lead to a lot of seemingly "useless" code, but these codes implement low coupling, thus reducing the maintenance cost in the future.
1) Presentation Tier uses the MVC mode to separate the Controller View from the data. For example, Struts is one of them. Filtering and User-Role-Priviledge-Resource are also frequently used (more details will be posted)
2) the low coupling between Business Logic Tier and Presentation Tier is implemented by the Business Delegate layer. A typical example is BusinessDelegate-> BusinessMgr (EJB)->... the Facade mode is often used for encapsulation here.
References: application of software architecture in J2EE
References: Medlog Logistic PACE2 SCS