What can jini bring to you?
Jini is a key technique for achieving large-scale distributed calculations. It can not only solve the problem of network compatibility, but more all the sound is that this technology can be effectively interactive and cooperated between network computer devices and applications. JINI gives a wide variety of devices, such as PC, handheld computers, cellular phones, and 48KB small memory devices to reduce conflicts on the network. However, the implementation of the Jini network also requires difficult efforts to develop people. Prior to this, programmers still face the challenge of writing distributed applications.
Jini is a code written in Java language that automatically detects computer devices on the network, and registers the services they provide. It is a core part of the open architecture adopted by providing distributed operating system services on the network.
Sun is a blueprint for the next century 's network, and the technology that changes this blueprint to reality is JINI. Jini is a Java-based architecture that provides operating system services and extends their feature to the entire network. More general, JINI is a Java software running at the top of Java Virtual Machine (JVM) to provide a plug-and-play network function for the device. Sun depicts such a scene in its blueprint: In the future, any one equipped with a microprocessor and the small capacity RAM can cooperate with each other, thereby achieving a new realm. Although this is a kind of advance consciousness, it uses Jini to make us in the future blueprint. It allows us to prevent us from being difficult to compatibility with the device driver, and no longer allow users to log in to the network. have trouble with.
For example, in the blueprint out of Sun, the user can insert the palm into the network slot and can be immediately identified to automatically become part of the network. With such a handheld device, the user can easily access the data on a computer, and use the services provided by another computer to handle these data; then you can print data on the nearest printer No need to pre-install the printer driver on your handheld computer. This incredible thing is to automatically download a Java-based printer driver through this palm-based computer. This automatic and convenient integration between networks and applications can be applied to almost any electronic device from the PC to the cellular phone.
This distributed computing architecture is not new. Sun's JINI is not the only technology for operating the operating system in the next century. Lucent Technologies launched Inferno technology designed for embedded systems in 1997, the technology is logically very similar to Java, also contains virtual machine concepts, programming languages, and communication protocols; Oak Ridge National Labs also introduced The technology of parallel virtual machine (PVM) is designed to cooperate between completely different machines on the network to provide a low-priced supercomputer; IBM force push T spaces is also similar to Sun in concept and implementation And the Microsoft on the two boats is also studying the distributed operating system, and their big hand projects on the distributed operating system are called Millennium. Microsoft hopes to get two great achievements through Millennium: First, the desktop operating system is completely seamlessly distributed into the world's network, and the second is to bring the programmer to a higher abstract level that no longer considers the details of the underlying machine. These two goals are quite critical for distributed systems. However, since Sun has a Java programming language and the corresponding virtual platform, it is in an extremely special position in the next century.
How does Jini work?
JINI is not a detailed problem such as a particular application to work on the network, but provides an extremely critical capability for these services, making them aware of each other's presence, and then establishing Mutual connection. The core of Jini is Java Remote Method Invocation (RMI) in Sun JDK1.2, which is a network service that enables Java objects to interact online. In this way, Jini can be seen as an extension of JavaBeans in Java Software Component Model. The JINI network is like a market, in which businessmen are selling their own goods. In a JINI network, merchants are end users, devices, or applications. The process of trafficking is this: a new businessman came to this market, he declared his own arrival, and quickly established a store; then he wrote the goods sold and the service provided, like many other businessmen. Written on a card, and the information of these cards is published in a bulletin board; Jini provides this mechanism of sales, according to its provisions, the merchants are granted where the advertisements are posted on the bulletin board, and There is a message there; the customers are in front of the bulletin column, find the card information they are interested, then copy the way to contact the merchant from the card; next customer is such as "when delivery" or "how Bargaining on such a detail question; the transaction rules followed when the businessmen traded were specified by another standard javaspaces of Sun; for customers, the free transaction between the merchants was invisible.
JINI's meaning is of course much better than this metaphor: For example, the message will not be stolen on the bulletin board, and the actual space occupied by the advertisement does not need to be considered. However, this virtual market has an inherent problem: such as the guidelines for their customers lack judgments, and how the merchants suddenly disappear when the network has disappeared.
In JINI, this market consisting of businessmen and customers is called a "alliance." JINI is allocated for the alliance allocation through a "discovery and join service; its other" lookup "service is used to publish information in the check bar, and accept the transaction requirements; Jini is A "Leasing" model to explain when the card can be removed from the bullion bar, as well as the rules needed to follow the contract; and by a "Access Control List) who can use Specific services; the service provides and performs together by JavaSpaces and actual applications; the general language used by the businessman is determined by Java's RMI regulations.
JINI and Javaspaces have a change in current centralized system services. One operating system is actually a collection of some sub-functions, but it is performed some composite operations. JINI and Javaspaces break this single mode, and distributes many services to different parts of the network to divide the OS into several subsystems and dispersed these subsystems to network, clients, and servers. For distributed collaboration, JINI is a key step in starting in this Java infrastructure. Because Java has an object-oriented characteristic and the ability to transmit the transmitted code, JINI can distribute a large number of software objects on the network. These independent applications or objects can be transmitted over the network according to the needs of users, thereby interacting with other objects.
How does Jini work?
Jini will have the impact of the company
JINI and distributed systems will enable companies to benefit from the complexity of network interaction. Many companies within the company have a wide variety of computer equipment, such as PCs, printers, handheld devices, cellular phones, and servers, etc., simply a headache. For example, if a printer has failed, then all network users immediately need to modify the print settings on their workstation. JINI can automatically identify changes on the network and transparently transmitting code like printing drivers on the network, thus solving such problems. Jini's dreams also created a new business operation mode. Sun hopes that in the near future, new business models will be generated in JINI-based, flexible mobile phones, such as the disk space for rent large hard disk groups, and more. Since companies are working to excavate new business opportunities, Jini is likely to provide the basis required for the computer hardware working model that anyone thinks. JINI out the first step
Distributed system technology like Jini will undoubtedly become the main force developed in the next decade, but JINI's application is still immature. Currently, it is just a basic tool for developers to better use the network and its resources. At the more basic level, the manufacturers need to write Java-based drivers for all devices that may run on the JINI network, or write a Java interface for the driver.
The problem is that when JINI can come out of research and development, when can it become a real product to benefit?
The essence of Jini is Java. It is the goal of Java on the network or multiple computers. Since the JINI infrastructure uses Java RMI and object-oriented programming, JINI will look more directly for Java and object-oriented programmers, but write distributed applications is more complex than a separate application. . For example, developing a application "Hello World" that is often used as an introduction at the beginning, in the centralized operating system and application model, you may only need to write a few lines of code, you can display the "HelloWorld" message on the screen, even Novice can write this program within a few minutes. But if it is in a distributed environment, the complexity of writing the same application will greatly increase. Programmers must take into account problems such as network failures, delays, and security. Although JINI and Javaspaces provide distributed security models and object processing mechanisms, it is necessary to have a considerable time for today's programmers. Just like other computers, this is a training and popular issue, because programmers need to learn how to write high quality distributed applications.
On the other hand, Jini has been encouraging support. Sun has established partnerships with companies such as Quantum and Ericsson. They all express this technology; Novell also means providing services to JINI to create a directory. Although important partners have not made any promise, at least one is not well-known company --- Malaysian has applied JINI.
JINI is in many ways that most traditional operating systems cannot match. Although companies like Microsoft are studying their distributed computing systems, JINI is still leading. On the one hand, the programmers can have created Jini applications. For Java programmers, they are already familiar with many JINI features; on the other hand, JINI must cooperate with a wide variety of environments due to the popularity of JVM. And integrate. Due to the foreground of the distributed system, we can bet: Sun or Microsoft will develop standards for future distributed operating environments. JINI is built on the streptite of Java, and Java deeply enters into the heart, which represents a boom in which the extensive and far-reaching transformation in computing mode will be made earlier; and Microsoft controls the current OS standard.
Create powerful systems and applications to better utilize network resources, using scattered resources to solve large problems, which is our goal. It takes a long effort to reality, but at least, JINI has brought us hope on the contradiction between interoperability on the network, and it has made the problem of the device driver has become. JINI's role in distributed system provides a plug-and-play network function with Jini competition technology Lucent's Inferno Oak Ridge National Laboratory Parallel Virtual Machine (PVM) IBM's T Spacesjini's shortcomings for programmers require high, Programming is complex, you need to learn for a while to master
Excerpt from China Computer Newspaper Date: 1998-11-05 Total number: 774 This year: 84
