The boss of J Dao Banq once said that the design model is to measure the high and low of the programmer level. Personally agree with this point of view, learn from this angle J2EE first to understand is a huge complex system, how is it assembled by each module and operates together.
To warm up to a few definitions 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 across boundaries that are mediated by interfaces. Whereas tiers represent processing chains across components, layers represent container / component The concept of Relationships in Implementation and Deployment Of Services. The concept of tiers layer is what we are most often listened. Generally, it can be divided into (customer) <- interactive ---> [Client Interface --- Presentation tier --- BizLogic Tie R --- Integration Tier --- Resource Tier] Client Interface typical customer interface is IE, Swing, Applet, WAP, etc., the customer is responsible for accepting customer requests and returning the corresponding processing results. Login, permission check, session management here, from the technical perspective, business logic tier, such as JSP HTML, responsible for handling business logic and data, is the core of J2EE, which also manages transaction Transaction, EJB, etc. Business logic layer and system resource layer, the most common JDBC database connection is an example resource tier responsible for providing resources required for the upper layer, such as database, file system, legacy system, etc. combined with practical applications and design patterns, we can further divide the hierarchy . Multi-level will reduce efficiency, which will also result in a lot of seemingly "unused" code, but these code achieve low coupling to reduce post-maintenance costs. 1) Presentation tier Apply MVC mode, separating the program process controller (VIEW), and data, such as Struts is one of them.
Filtering and User-Role-Priviledge-Resource are often used (specific to new stickers) 2) Business logic tier and presentation Tier's low coupling by Business delegate layer, typical example businessdelegate -> Businessmgr (EJB ) -> ... and FACADE mode often used here to make packages. Main reference: Software architecture mode Application main reference items: Medlog Logistic Pace2 SCS
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