1、什么是middleware,有什么功能？
Middleware is computer software that connects software components or applications. It is used most often to support complex, distributed applications. It includes web servers, application servers, content management systems, and similar tools that support application development and delivery. Middleware is especially integral to modern information based on XML, SOAP, Web services, and service-oriented architecture.
中間件是連接應(yīng)用軟件或組件的一種軟件，通常用來(lái)支持整合或分布式應(yīng)用，包括WEB服務(wù)，應(yīng)用服務(wù)器，CMS以及其他類(lèi)似的東東。中間件在XML，SOAP，SOA的應(yīng)用中特別需要。
2、objectweb的定義
Middleware is the enabling technology of Enterprise application integration. It describes a piece of software that allows two or more software applications to connect together so that they can exchange data.
ObjectWeb defines middleware as "the software layer that lies between the operating system and the applications on each side" of a distributed computing system.
中間件是一種能夠整合企業(yè)應(yīng)用的技術(shù)，它是一種可以讓兩個(gè)或更多應(yīng)用軟件連接在一起交換數(shù)據(jù)的軟件。
objectweb定義中間件是分布式系統(tǒng)中一個(gè)介于操作系統(tǒng)和應(yīng)用軟件之間的層次。
3、起源
Middleware is a relatively new addition to the computing landscape. It gained popularity in the 1980's as a solution to the problem of how to link new applications to older legacy systems, although the term had been in use since 1968. It also facilitated distributed processing – the connection of multiple applications together to create a larger application, usually over a network.
中間為計(jì)算機(jī)發(fā)展的前景提供了新的選擇，作為一種連接新老系統(tǒng)的解決方案，老系統(tǒng)中甚至有1968年起用的，所以它在上實(shí)際80年代贏得很好的聲譽(yù)。它還推動(dòng)了基于網(wǎng)絡(luò)的分布式計(jì)算的發(fā)展，分布式計(jì)算是一種靠連接多個(gè)應(yīng)用形成一個(gè)大的新應(yīng)用的方式。
4、組織
In addition to the existing vendors updating their wares to address the newly expanded vision, vendors such as Mercator, Vitria, and webMethods were specifically founded to provide Web-oriented middleware tools. Groups such as the Apache Software Foundation and the ObjectWeb Consortium encourage the development of open source middleware.
除了已經(jīng)存在的供應(yīng)商升級(jí)了他們的產(chǎn)品以便應(yīng)對(duì)延伸的應(yīng)用之外，象mercator,vitria,webmethods都特別提供了面向WEB的中間件產(chǎn)品。象apache和objectweb這樣的組織鼓勵(lì)開(kāi)源的中間件。
5、中間件的類(lèi)型
Hurwitz's classification system that organizes the many types of middleware that are currently available. These classifications are based on scalability and recoverability:
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Remote Procedure Call (RPCs) - Client makes calls to procedures running on remote systems. Can be asynchronous or synchronous.
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Publish/subscribe - This type of middleware monitors activity and pushes relevant information to subscribers.
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Message Oriented Middleware (MOM) - Messages sent to the client are collected and stored until they are acted upon, while the client continues with other processing.
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Object Request Broker (ORB) - This type of middleware makes it possible for applications to send objects and request services in an object-oriented system.
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SQL-oriented Data Access - middleware between applications and database servers.
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Other sources include these additional classifications:
- Transaction processing (TP) monitors - Provides tools and an environment for developing and deploying distributed applications.
- Application servers - software installed on a computer to facilitate the serving (running) of other applications.
- Enterprise Service Bus - An abstraction layer on top of an Enterprise Messaging System.
1、RPCs 遠(yuǎn)程調(diào)用：客戶端調(diào)用遠(yuǎn)程系統(tǒng)上的應(yīng)用，呼叫和可以是同步或異步的。
2、MOM 面向消息的中間件：發(fā)送到客戶端的消息被收集和存儲(chǔ)起來(lái)直到他們被遵照?qǐng)?zhí)行，同時(shí)客戶端還繼續(xù)進(jìn)行其他操作。
3、publish/subscribe 發(fā)布/訂閱：這種類(lèi)型的中間件監(jiān)視和發(fā)布相關(guān)信息給訂閱者。
4、ORB 對(duì)象請(qǐng)求代理：它可以在一個(gè)面向?qū)ο蟮南到y(tǒng)中（OO system)建立對(duì)象之間的client/server關(guān)系。通過(guò)ORB，一個(gè)client可以透明的引用同一臺(tái)機(jī)器上或網(wǎng)絡(luò)上的一個(gè)server對(duì)象的方法。
5、SQL-oriented Data Access 應(yīng)用程序和數(shù)據(jù)庫(kù)服務(wù)之間的中間件
6其他的如下：
TP monitors 事物處理監(jiān)視器：用于分布式系統(tǒng)
application servers 應(yīng)用服務(wù)：安裝在一臺(tái)計(jì)算機(jī)上用來(lái)實(shí)現(xiàn)幫助其他應(yīng)用服務(wù)
ESB 企業(yè)服務(wù)總線：抽取出來(lái)的東東，SOA中。。