What are the common middleware?

Common local development often uses Tomcat.

Linux systems often use jetty or Apache HPPTD

Large projects with JBoss or WEBLOIGC

Small projects, or individuals developing tomcat major projects or commercial projects are generally used: Weblgoic/webshere
Other, as well as JBoss, Glasshfish and other
examples of projects or small projects often used jetty

Tomcat, JBoss, WebLogic, WebSphere General project Tomcat on it.

Tomcat is the operating environment (Servlet container) of the servlet in Sun's JSWDK (JavaServer Web Development Kit). Tomcat is a subproject of the Apache Jakarta Software organization, Tomcat is a jsp/servlet container, it is in the Sun company JSWDK (Java Server Web Development Kit) builds on the standard implementation of a JSP and servlet specification, using Tomcat to experience the latest specifications for JSPs and servlet. After years of development, Tomcat is not only a standard implementation of JSP and servlet specifications, but also features many commercial Java servlet containers and is used by some businesses for commercial purposes.

JBoss is a Java application server that runs EJBS. It is an open source project that follows the latest Java EE specification. Since the JBoss project began, it has evolved from an EJB container to a web-based operating system based on Java EE (operating system for Web), which embodies the latest technology in the Java EE specification

The WebLogic server is an enterprise-class application server that supports the connectivity of EJBS, clusters, and ERP (Enterprise resource Planning), the development company: BEA.

The WebSphere product family is a typical IBM Business application development tool and operating environment

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Tomcat Introduction Today, web-based applications are growing, and traditional HTML has not met today's needs.
We needed an interactive web, so we created a variety of web languages. such as asp,jsp,php and so on. Of course, these languages are closely related to traditional languages, such as PHP based on the C and C + + languages, and JSP is based on the Java language.
Tomcat is a running platform for both JSP and servlet. Tomcat is a free open source Serlvet container, a core project in the Apache Foundation's Jakarta Project, developed by Apache,sun and other companies and individuals. Thanks to Sun's involvement and support, the latest servlet and JSP specifications are always reflected in Tomcat.
Tomcat was selected by Javaworld magazine's editor as the most innovative Java product of the 2001, which shows its position in the industry. The latest version of Tomcat is different from the architecture of the 3.x, but is redesigned 4.0x.4.0x. A new servlet container is used in tomcat4.0x: Catalina, complete with Servlet2.3 and Jsp1.2 specifications. Tomcat provides a variety of platform versions for downloading, from http://jakarta.apache.org to download its source code version or binary sedan.
Java-based Tomcat is cross-platform because of the cross-platform nature of Java. Unlike a traditional desktop application, the application in Tomcat is a war (webarchive) file. The war is a Web application format presented by Sun, similar to a jar, and a compressed package for many files. The files in this package are organized in a certain directory structure: usually the root directory contains HTML and JSP files or directories containing both files, plus a web-inf directory, which is important.
Usually in the Web-inf directory there is a Web.xml file and a classes directory, Web.xml is the application of the configuration file, and The classes directory contains the compiled servlet class and other classes (such as JavaBean) that the JSP or servlet relies on.
Usually these dependent classes can also be packaged into a jar under the Web-inf Lib directory, of course, can also be placed in the classpath of the system, but it is not convenient to transplant and management. In Tomcat, the deployment of the application is simple, you just put your war in Tomcat's WebApp directory, Tomcat will automatically detect the file and unzip it. When you access this application's JSP in a browser, it is usually very slow for the first time because TOmcat to convert the JSP to a servlet file and compile it. After compiling, the access will be very quick. In addition Tomcat also provides an application: Manager, access to this application requires a username and password, and the username and password are stored in an XML file. With this application, you can deploy and revoke applications remotely via the Web, aided by FTP.
Of course, local also can. Tomcat is not just a servlet container, it also has the functionality of a traditional Web server: processing HTML pages.
But compared to Apache, its ability to process static HTML is less than
Apache. We can integrate Tomcat and Apache together, let Apache handle static HTML, while Tomcat handles JSP and servlet. This integration requires only a few changes to Apache and Tomcat configuration files. Additionally, Tomcat provides realm support. Realm is similar to a group within UNIX. In Unix, a group corresponds to a certain resource of the system, and a group cannot access resources that are not part of it. Tomcat uses realm to assign different applications (similar to system resources) to different users (similar to group). Users who do not have permissions will not be able to access this application. Tomcat provides three kinds of realm,1:jdbcrealm, this Realm the user information in the database, through JDBC to obtain user information to authenticate. 2:jndirealm, user information exists in an LDAP based server, and user information is obtained through JNDI.
3:memoryrealm, the user information exists in an XML file, which is used by the manager in the application to authenticate users. By realm we can easily authenticate customers who access an application. In Tomcat4, you can also use the event listener function provided by Servlet2.3 to monitor your application or session. Tomcat also provides some other features, such as integration with SSL to secure transmission. Tomcat also provides JNDI support, which is consistent with those provided by the Java application Server. Speaking of which, we would like to introduce how the usual application server, such as WebLogic, differs from Tomcat. The application server provides more Java EE features, such as Ejb,jms,jaas, and also supports JSP and servlet. While Tomcat is less powerful, it does not provide support such as EJBS. However, if you integrate with JBoss (an open source application server), you can achieve the full functionality of Java EE. Now that the application server has Tomcat capabilities, is there a need for Tomcat?it. In fact, many of our small and medium applications do not need to use the EJB technology, JSP and servlet is enough, then if the application server is a bit wasteful.
And Tomcat is short, easy to configure, to meet our needs, in this case we will naturally choose Tomcat. Tomcat based development is essentially the development of JSP and servlet, the development of JSP and servlet is very simple, you can use a normal text editor or IDE, and then pack it into a war. We're going to mention another tool here. Ant,ant is also a subproject in Jakarta that functions like make in UNIX. You need to write a build.xml file, and then run ant to complete the work defined in the XML file.
This tool is great for a large application, and we can compile and package it with just a few things written in XML
Into war. In fact, Ant is included in the release of many application servers. In addition, in the Jsp1.2, you can use the tag library to achieve the separation of Java code and HTML files, so that JSP maintenance more convenient. Tomcat can also integrate with some other software to achieve more functionality.
If you integrate with the above JBoss to develop EJBS, integrate with Cocoon (another Apache project) to develop xml-based applications, integrate with OPENJMS to develop JMS applications, there are a lot of software that can be integrated with Tomcat in addition to the few we mentioned. Tomcat is really a good tool, not only because it's free, powerful, but also because it's open.

Today, more and more people pay attention to open source software, Linux is a typical success. A variety of middleware (, Apache, Nginx, MQ, etc.) performance parameters settings, monitoring and optimization;

What is the "middleware" in Java? What is the meaning of distinction.

Middleware: Non-underlying operating system software, non-business application software, not directly to the end user, can not directly bring value to customers software, collectively referred to as middleware. There are several common types: service middleware, integration middleware, data middleware, message middleware, security middleware.

Middleware implemented in Java, collectively known as Java Middleware. Middleware, can be understood as class library, between class library and product.

To put it simply, your program A and program B communicate with each other in the protocol, program A,b can be built by different platforms in different languages. But the agreement will guarantee that they will know each other's things.

Simply put, the middleware has a very big feature, is separated from the specific design objectives, but with the provision of universal independent functional requirements of the module. This makes the middleware must be replaceable. If in a system design, the middleware is irreplaceable, not the architecture, the framework design has the problem, then is this middleware, elsewhere may be a middleware, in this system is the engine.