J2EE (ie Java 2 Platform Enterprise Edition) is a middleware technology that is launched by Sun. From CORBA, IDL to the message-oriented system, middleware technology has already passed a long distance, and now J2EE is a decisive milestone in the history of middleware, and is being received and adopted by the industry.
J2EE, on the one hand, there is a very large standard system and several different versions. On the other hand, due to the variety of application server, the terms used by the developers are not the same, so, around J2EE, often there Many places that are misunderstood. This article will discuss what J2EE is what it is, what can it do.
What is J2EE?
Before trying to give J2EE, we must first learn that J2EE is not just a language, a tool or a service.
· J2EE - JAVA 2 Platform Enterprise Edition
Simply put, J2EE is a standard middleware architecture that is designed to simplify and regulate the development and deployment of multi-layer distributed enterprise application systems. The implementation of the J2EE scheme can significantly improve the portability, safety, scalability, load balance and reusability of the system.
Before J2EE technology, several major middleware developers have their own array, and there is a lack of compatibility, transplantability, difficult to achieve interoperability, and no universally recognized industry standards. J2EE's emergence marks that the middleware technology has experienced the continuous exploration and experience of many years, it is gradually ripening.
J2EE's core is a set of specifications and guides, defining a standard platform for developing multi-layer distributed enterprise application systems using Java languages. Developers develop enterprise applications on the basis of these norms and guides, while ensuring compatibility between different J2EE platforms by J2EE vendors. Since there is good compatibility based on specification-based J2EE platforms, the J2EE application system can be deployed on different application servers, without or only a small amount of code modifications.
· J2EE viewpoint
Below we will examine J2EE from several different sides, with a view of the reader to have a more comprehensive and clear impression on J2EE.
(1) J2EE: Multi-layer, distributed middleware syntax
With multi-layer distributed application model, J2EE divides application development into multiple different layers and defines components at each layer. Each application component is a component-based multi-layer distributed system based on their layer distribution on the same or different servers. A typical J2EE four-layer structure includes a client layer, representing a logic layer (web layer), a business logic layer, and a corporate information system layer.
With J2EE, the development of distributed systems has become simple, and the deployment can be accelerated. The distribution of J2EE components is independent of the server environment, and all resources can be accessed through a distributed directory. This means that developers do no longer need to consume energy for the distribution of components and resources, so that there can be more time to focus on the implementation of business logic and improve development efficiency.
(2) J2EE: Enterprise Application System Development Platform
J2EE itself is a standard, a standard platform provided for the development of a distributed application. The J2EE is implemented, specifically manifested as a specific web server product such as a BEA Web Logic or IBM Web Sphere. Using the J2EE application-programming model development, you can deploy on a J2EE application server produced by different vendors, but compatible with each other.
At present, the market based on J2EE-based web server varieties, performance characteristics have thousands of autumn, and each manufacturer's products have carefully designed unique. But it is independent of product personality, all J2EE application servers provide a common foundation for the development and deployment of an enterprise-level application system.
(3) J2EE: Electronic application development model
J2EE applications are easy to post to WEB, handheld, or mobile phones. In other words, the application components can be easily achieved. J2EE Application - Programming Model guarantees that the assembly remains unchanged during commercial logic and backend systems during different types of client transplantation. In addition, the other main advantages of the J2EE platform also include automatic load balancing, scalable, fault tolerance, and troubleshooting. The components deployed in the J2EE environment will automatically get the above features without having to increase the additional code overhead.
All of J2EE All these features are especially important for companies that need to build a full-weather network portal.
(4) J2EE: Widely used standards on web application servers
It can be said that J2EE is the first middleware standard that is widely recognized and adopted by the industry. At present, almost all first-class web applications, such as the Web Logic, IBM Web Sphere, HP application servers, Sun's iPlanet, and Macromedia's JRUN, are based on J2EE. To date, there is no other standard that can get the unanimous support of such a large number of middleware vendors.
Moreover, with J2EE, the company's application development is smaller for a particular developer or application service provider. Application components can be deployed on different application servers as long as they meet the J2EE specification. To ensure compatibility and consistency of different vendors' J2EE application servers, Sun has released the J2EE compatibility test package.
· What is J2EE?
At this point, we can try to use a sentence to summarize J2EE, which is: J2EE is a middleware infrastructure. With it, developers only need to focus on writing code to express business applications, and represent logic, as for other system problems. Such as memory management, multi-thread, resource distribution, and garbage collection, will be automatically completed by J2EE.
How does J2EE respond to challenges?
In this section, we will explore how J2EE should respond to problems in the process of enterprise development, and how to provide space for future development.
· Independent hardware configuration and operating system
J2EE runs on the Java Virtual Machine (JVM), using Java itself cross-platform features, independent of the hardware configuration and operating system. Java Operation Environment (JRE) - The installed version of JVM plus other important components - almost all hardware / OS combinations. Therefore, by adopting Java, J2EE enables companies from high hardware devices and operating systems to protect existing IT resources. In many cases, J2EE can also be run directly in the EIS server environment, saving network bandwidth and improving performance.
· Adhere to object-oriented design principles
As a language that is fully object-to-object, Java almost supports all object-oriented programming features. Object-oriented and component-based design principles constitute the basis of the J2EE application programming model.
Each layer of the J2EE multilayer structure has a variety of component models. Therefore, developers have to do to select the appropriate component model combination, flexibly develop and assemble components for the application project, but not only help to improve the scalability of the application system, but also effectively improve the development speed and shorten the development cycle. In addition, J2EE-based applications also have advantages of good structural, modular, flexible, and highly reusable.
· Flexibility, portability and interoperability
With Java cross-platform features, J2EE components can be easily ported to different application server environments. This means that companies don't have to stick to a single development platform.
J2EE's application system can be deployed on a different application server, and J2EE components can work together with each other in different application servers. This feature enables assembly applications to get unprecedented interoperability for the first time. For example, installing EJB in the IBM WebSphere environment, on the one hand, you can directly interact directly with CICS in the WebSphere environment, and on the other hand, you can also access the EJB installed on an elsewhere. · Easy business information system integration
Shortly after J2EE technology, JDBC, JMS, and JCA will soon return a number of standards such as JDBC, JMS and JCA, which greatly simplifies the workload of corporate information system integration, so that companies will be such as Legacy System, Multiple different information systems such as ERP and databases perform seamless integration.
Since almost all relational database systems support JDBC, just use the necessary JDBC drivers, J2EE applications can communicate with all mainstream database systems. Similarly, the current industry is an EI adapter based on Java connector system standards, also used to provide seamless integration of various Legacy System and ERP / CRM.
· Introducing service-oriented architecture
With the appearance of Web services and Open standards such as SOAP, interoperability between enterprise heterogeneous systems is possible. J2EE, as an expandable platform, naturally need to join the Web service characteristics. To this end, Sun has released a set of APIs called "JAX Packages", supports all various Web service requirements from XML syntax analysis, XML binding, SOAP messaging, registry, XML RPC to XML messaging.
Although the J2EE platform appears earlier than Web service technology, its scalable ability enables it to adapt to the latest developments in technology. We have reason to believe that in the future, J2EE will introduce more technological advances without shaking its core framework and application - programming model.
Conclude
As an intermediate piece standard widely used in the industry, J2EE is an ideal platform for developing scalable, multi-layer distributed cross-platform enterprise applications with load balancing capabilities. J2EE's primary task is to provide a standard middleware infrastructure, which is responsible for handling all system-level issues involved in corporate development, making developers to focus on the design and application of business logic, and improve development work. s efficiency.
J2EE effectively meets industry needs and provides an development environment independent of the operating system. Based on the J2EE application system flexible and easy to transplant and reuse, you can run on a web server of different manufacturers. More importantly, J2EE is an open system that fully adapts to the advancement and development of future technology.
