UML Weekend Crash Course™ - To Parent Directory

Session 27—Introduction to Web Development with Java 279
fixed text, images, and hyperlinks to other pages. In this case, you would write an HTML
page with this content and place it on your Web server. A shell of the HTML page is shown
in Listing 27-1. (HTML is a markup language that is composed of plain text accompanied by
markup tags to specify how to format the text. HTML can be stored in a plain text file and
does not need to be compiled or processed in any way before it is placed on the Web server.)
Listing 27-1
HTML sample
Next Step Education
Next Step Education
(...more content...)
HTML is the most common form of Web content and is the form I focus on in
this session. However, this session’s discussion of generating and sending
Note HTML can also be applied to other forms of Web content, such as XML for
data interchange.
Usually, HTML files are stored on a Web server and loaded over a network such as the
Internet. This architecture is shown in the UML Deployment diagram in Figure 27-1. When
the user types a URL into a Web browser, the browser needs to communicate with a Web
server to get that document, in this case “index.html.” The HyperText Transfer Protocol
(HTTP) defines the communication protocol for that communication between the Web
browser and the Web server.
Client
Web
Browser
Web Server
Web
Server
index.html
Figure 27-1 UML Deployment diagram, HTML on a Web server
The full sequence of events for retrieving a Web document is shown in the UML Sequence
diagram in Figure 27-2. When the user enters a URL, the Web browser creates an HTTP request,
which is a packet of information including the name of the Web server, the name of the document,
and other information about the request being made. The Web browser then sends that
HTTP request over the network to the Web server that was specified in the URL. The Web
Server then looks up the Web page “index.html” and returns it as part of the response.