Recall the brief introduction to Web and application servers from session one of this module. Explain in detail what a Web server and an application server are and differentiate between them. Explain how Web servers work. Explain some important HTTP headers referring to the Focus Areas section. Also, enumerate some of the popular application servers given in the Focus Areas section.Explain the deployment process of a Web application on the Tomcat server in detail.
Some of the commonly used important headers include:
n Connection: It is used to specify connection type such as secure channel. It is also used to specify content, which must not be propagated through proxies.
n Pragma: It is used for specifying implementation specific values.
n Upgrade: It is used by browser to inform the server about the additional protocols it can support. The server uses it to tell the browser of any switches.
n Referer: It enables the browser to send the URL of the page from which the current resource was accessed.
n Retry-After: When a particular server is unavailable, it is used to inform the client the time period after which it should send the request again.
n Content Encoding: Used to specify by which scheme, transmitted content is compressed.
For information on other headers, refer to http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html and http://www.cs.tut.fi/~jkorpela/http.html.
Java Web servers are considered the most powerful and popular by various industry experts. Following is a list for some of the famous J2EE servers with their support technologies and URLs:
| Server Name | Supported Technologies | Website |
| JRun | J2EE, JMS, Servlets, JSP | http://www.macromedia.com/software/jrun/ |
| WebLogic | J2EE, WAP, JMS | http://www.bea.com/framework.jsp?CNT=index.htm&FP=/content/products/Weblogic/server/ |
| JBoss | EJB, SOAP, JMX | http://www.jboss.com/products/jbossas |
| IBM WebSphere | J2EE, WAP, SOAP, UDDI, WSDL | http://www?306.ibm.com/software/Webservers/appserv/express/ |
| Sun ONE Web Server | Sun ONE server is a specialized server which can work as a single deployment platform for number of technologies like ASP, CGI, PHP apart from servlets and JSP | http://www.sun.com/software/products/Web_srvr/home_Web_srvr.xml |
MIME
MIME stands for Multipurpose Internet Mail Extensions. MIME is a standard, which defines the type of files shared/transmitted over the Internet, and the program that will be used to view or process that file. MIME type is an integral part of any Web application programming as it is specified in the headers of a Web page as the Content-Type HTTP header.
MIME type is specified as type/sub type. Examples of MIME types for different categories of content are listed below:
n Text:
- text/plain
- text/html
- text/richtext
n Image:
- image/gif
- image/jpeg
- image/tiff
n Multipart:
- multipart/mixed
- multipart/encrypted
- multipart/x-zip
n Application:
- application/excel
- application/pdf
- application/word
n Message:
- message/news
- message/http
- message/external-body
n Audio:
- audio/x-wav
- audio/x-aiff
- audio/x-midi
n Video:
- video/mpeg
- video/quicktime
- video/x-msvideo