Application of Java EE, J2SE and J2ME

With the rapid development of Internet network, enterprise application based on Internet requires that the software platform has the features of openness, distribution and platform independence. So there are rpc/com/corba and other technologies, However, there are many deficiencies and limitations in the application of these technologies. Their specific protocols are difficult to pass through firewalls and are therefore not suitable for application development on the Web. To further develop web-based applications, sun One (Open NET Environment Development network environment) appears. and Microsoft's. NET Web Services technology system. The Sun one architecture is centered around the Java language, including J2se/j2ee/j2me and a range of standards, technologies, and protocols. It includes the Sun's unique iplanet software series, which has popular LDAP directory server software in the marketplace, and Forte for java― -Easy to write software tools for the Java language in any environment. It is easy to get and use products, including Java integrated development environment, Java Database and middleware (application server) servers, and their source code from the Internet for free. Sun one is closer to or satisfies the Internet's demand for distributed, developmental, and platform-independent aspects of intelligent Web services.
With the development of Java technology, it is further subdivided according to the market: Java 2 Enterprise Edition for enterprise Network application, J2SE for common PC application (Java 2 Standard Edition) and J2ME for embedded devices and consumer appliances (Java 2 Micro Edition) Three versions. This article describes the Java core application ――j2se/j2ee/j2me of Sun one.
Application of Java EE Technology
Java EE is a new concept model introduced by Sun, which is more advantageous than the traditional Internet application model.
The application programming model of Java EE model (Java EE Blueprints) provides a system model for implementing document and instance suites based on Java EE multi-tier applications, simplifying this complex task. It is used by developers as a design and optimization component, This allows the developer to work on a strategic division of development effort. The Java EE application programming model requires developers to divide their work into two categories: business logic and presentation logic, and the rest are automatically processed by system resources and do not have to encode the middle-tier pipeline. This allows developers to spend more time on business logic and presentation logic. For companies that focus on shortening the project cycle, This transformation is well received.
Java EE Platform Java platform is to run the standard environment of Java application, by the Java-EE deployment specification (a set of all Java platform products must support the standard), The IETF standard set and the CORBA standard are composed. The latest Java EE platform also adds a JavaBean component model. Developers can use the JavaBean component model to customize Java class instances and to access them through defined events. Java EE supports EJBS, so developers can perform multi-user trading. When running on the Java EE server, Enterprise JavaBeans the application logic into reusable and extensible code snippets. Enterprise JavaBeans is not a new feature, But it enhances its capabilities and portability by defining standard client and service API,J2EE. The EJB runs within a container in the server, provides all typical middle-tier services, such as transaction management, security, remote client connectivity, lifecycle management, and database connection buffering. In order for the transaction system to run in the presence of an EJB container, developers simply define the beans transaction attributes in the deployment description file . The Java EE realizes its advantage by defining a set of standard structure, for example: 1.J2EE application programming model, is a kind of standard design models for developing multi-level, thin customer user program; 2. Java EE Platform, is a standard platform, used to integrate Java EE application, and specify a series of interfaces and methods; 3. Java compatibility Test Suite, is a set of compatible test components to detect whether the product is compatible with the Java EE platform; 4.J2EE Reference implementation, used to demonstrate the ability of the Java EE.
Java EE server Sun's EE server provides naming and directory services through the ability to name and catalog interfaces (JNDI), authentication, HTTP, and Enterprise JavaBeans compatibility. Jndi is a standard extensible version of the Java platform that provides Java-enabled applications with a unified interface, including LDAP, to the naming and directory services within the enterprise. The Java servlet server also takes advantage of java-based technology. The Java servlet can be seen as a small program running on a server that provides developers with a component-based, platform-independent approach to creating a web-based application. It is not as performance-constrained as using CGI. Java A servlet is a simple technique for extending the functionality of a Web server. Because it is written in Java, it is able to access the entire Java API library, as well as the JDBC APIs used to access the enterprise database. JSP is an extension of the Java servlet. The Java servlet provides the development and display of interactive Web pages from the server. Today's JSP has been further improved, making it easier to create and support HTML and XML pages that combine static templates and dynamic content.

Java application Deployment (i): Basic article Java application Deployment (ii): Practical article Java application Deployment (III): Advanced Security Java Platform defines a standard open access control rule that is defined and explained by the program when it is developed on an enterprise platform. Java EE also needs to provide a standard registration mechanism so that applications do not mix these registration mechanisms and logic so that the same work is performed in a large number of different environments without changing the source code. For example: Java EE application developers can specify several levels of security, when users access data, They can write code to check the level of the current user's permissions. During the development phase, developers give multiple groups of users the appropriate level of security that allows applications to easily determine the level of restriction before they perform restricted operations.
The Java EE platform is the best platform for enterprise-class applications of java-based technology, allowing programmers to quickly and rapidly develop and distribute enterprise-class application applications. The following are its related technologies:
1.Enterprise JavaBeans Architecture, Enterprise-class JavaBeans defines an application interface. It enables programmers to quickly develop, publish, and manage Cross-platform, component-based Enterprise-class applications.
2.JavaServer pages,jsp Technology provides a simple, fast way to create dynamic Web pages. It allows you to quickly develop web-based applications that are platform-independent. Because JSP is very similar to ASP, So it's easy for people who are familiar with ASP to learn it.
3.Java Servlet, which provides an application interface. It allows you to quickly and easily develop and extend server functionality. In terms of trends, it could be a substitute for CGI in the future.
4.J2EE Connector provides a standard structure to connect different enterprise information platforms.
5.Java Naming and Directory Interface (JNDI), Jndi provides a unified, seamless, standardized connection between the Java platform and business information. By using Jndi, programmers can transfer Java between enterprise multiple naming and directory services Application.
6.Java Interface Definition Language (jidl), by using CORBA, can provide the ability to work together. Jidl includes a Idl-to-java compiler and an ORB that supports IIOP (Internet inter-orb Protocol).
7.JDBC provides a unified interface for virtually all databases while creating advanced tools and interfaces.
8.Java Message Service (JMS), which provides a standard interface for virtually all enterprise-class messaging services, such as reliable querying, publishing messages, subscribing to magazines, and various Puss/pull technologies.
The 9.Java Transaction API (JTA) provides a high-level management specification for applications that can be processed in distributed systems.
The 10.javamail,javamail application interface provides a complete set of abstract classes that simulate messaging systems. You can create mail or messaging applications by JavaMail.
11.RMI-IIOP, you can use it to develop a remote interface between the client and the server using only Java technology and the Java RMI interface.
Java EE bundles A module with a fixed file format: Bundle the Java application with the. ear file; For example, an. ear file contains an. xml file as its distribution description and contains one or more. jar and. war files; A. jar file contains a. class file as a enterprise bean, in addition to its distribution description.

The development phase of the Java EE application is divided into four steps: 1.Enterprise bean creation, 2.WEB component creation, 3.J2EE application assembly, 4.J2EE application distribution. The following is a list of the EE compatible product sections: BEA WebLogic Server 6.0, Borland App server, HP bluestone total-e-server, IBM WebSphere application Server, Iona Iportal, Application Serve R, iPlanet application Server, Macromedia JRun Server, Oracle 9i application Server, Silverstrean application server, Sybase EAServer, TogetherSoft ControlCenter, Java 2 SDK Enterprise Edition.
Application of J2ME Technology
　　J2ME (Java 2 Platform Micro Edition) is designed for the wireless electronics market, including JVM specifications and API specifications. Its API specification is based on J2SE (Java 2 Standard editon). J2ME defines a set of appropriate class libraries and virtual Machine technology. These technologies enable users, service providers, and device manufacturers to use rich applications at any time as needed, either through physical (wired) or wireless connections. J2ME is also known as the Java 2 Miniature edition, it is used in a variety of consumer electronics, such as smart cards, mobile phones, PDAs, TV set-top boxes and so on. Of course, J2ME also provides a consistent feature of the Java language, that is, cross-platform and secure network transport. It uses a series of smaller packages, And Javax.microedition.io is a subset of the J2SE package. J2ME can be upgraded to J2SE and Java EE. Prior to the advent of J2ME, we were more exposed to Java cards (Java card), embedded Java (Embedded Java), and real-time Java (real time Java). Where Java cards are for SIM cards, A minimal Java subset tailored to devices such as smart cards, smaller than J2ME, and not very portable. Embedded Java configures Java class libraries and VMS (virtual Machine, VM) for special users. It has minimal resource requirements and can be run on devices without a graphical user interface and network , you can add a user-specific API, but it cannot be ported. Real-time Java is being implemented by the IBM-led real-time custom Java Expert Group, and is still being refined. But they are not really j2me in the strictest sense.