What is Application Server

Application Server (Application Server) - a program that is a server that deals with system support for applications and ensures their life cycle in accordance with the rules defined in the specifications. It can operate as a full-fledged stand-alone web server or be a page provider for another web server. Provides data exchange between applications and clients, assumes the implementation of such functions as creating a software environment for a functioning application, identifying and authorizing clients, organizing a session for each of them.

The most famous Java application servers are:

  • Apache Tomcat
  • Jetty
  • JBoss
  • GlassFish
  • IBM WebSphere
  • Oracle Weblogic

What is the difference between Web server and Application server

The concept of a web server refers rather to a method of transferring data (specifically, over the HTTP protocol), while the concept of Application server refers to a way of executing these very applications (specifically, remote processing of client requests using some programs hosted on the server). These concepts cannot be put in one row. They represent different features of the program. Some programs satisfy only one criterion, some - several at once.

Apache Tomcat can run applications? Yes, it means it is an application server. Apache Tomcat can send data over HTTP? - Yes. Hence it is a web server.

Take some database in which complex logic is described on stored procedures and you can even send sms in response to SQL queries. Such a database can be called an application server, but the web server is no longer, because all this does not work with the client over the HTTP protocol.

Take pure Apache, which doesn't include any modules to support programming languages. He knows how to serve only static files and pictures via the HTTP protocol. It is a web server, but not an application server. Include the PHP support module and put a PHP program there that makes database queries and dynamically renders pages. Now Apache is also an application server.

Read also:


Comments

Post a Comment

Popular posts from this blog

Methods for reading XML in Java

Image
DOM (Document Object Model) - object - reads XML, recreating it in memory in the form of an object structure, while the XML document is represented as a set of tags - nodes. Each node can have an unlimited number of child nodes. Each child can also contain several levels of descendants or none at all. Thus, the result is a kind of tree. Pluses: Easy to program. If there are many objects in XML with cross-references to each other, it is enough to go through the document twice: first time create objects without references and fill in the name-object dictionary, the second time - restore links. If an error occurs in XML, a half-created XML structure remains in memory, which will be automatically destroyed. Suitable for both reading and writing. Minuses: Low speed. Wastes a lot of memory. SAX (Simple API for XML) - event-driven - reads an XML document, responding to emerging events (opening or closing tag, string, attribute) by calling the event handlers provided by the appl...
Read more

XML, well-formed XML and valid XML

Image
XML, the eXtensible Markup Language, is a language with a simple formal syntax, well suited for creating and manipulating documents with programs, and at the same time easy to read and create documents by humans. XML is extensible, it does not fix the markup used in documents, and the developer is free to create markup in accordance with the needs of a particular area, being limited only by the syntax rules of the language. DTD A DTD, Document Type Definition, is a predefined set of rules that defines the relationships between elements and attributes. For example, the DTD for HTML says that the DIV tag must be inside the BODY tag and can appear multiple times, TITLE - in HEAD and only once, and SCRIPT - both there and there as many times as you want. A DTD is usually described directly in the document as a formulation line starting with <!DOCTYPE ... > or in a separate file. Difference between well-formed XML and valid XML Depending on the level of compliance, the document...
Read more

ArrayList and LinkedList in Java, memory usage and speed

Image
How much extra memory is needed when calling ArrayList.add()? If there is enough space in the array to accommodate a new element, then no additional memory is required. Otherwise, a new array is created, 1.5 times larger than the existing one (this is true for JDK above 1.7, in earlier versions the size of the increase is different). How much extra memory is allocated when you call LinkedList.add()? One new instance of the nested Node class is created. How much memory to store one byte primitive in LinkedList? Each LinkedList element stores a link to the previous element, the next element, and a data link. private static class Node<E> { E item; Node<E> next; Node<E> prev; //... } For 32-bit systems, each link is 32 bits (4 bytes). The object (header) of the nested Node class itself takes 8 bytes. 4 + 4 + 4 + 8 = 20 bytes, and since the size of each object in Java is a multiple of 8, so we get 24 bytes. A byte primitive occupies 1 by...
Read more