Web Development with Java

content type
. There are content types for text, graphics, spreadsheets, 
word processors and more.
These content types are expressed as 
Multipurpose Internet Mail Extensions
[MIME] types. MIME types are used by web servers and web browsers. Each will 
contain a fi le that has a table of MIME types with the associated fi le extension for 
that type.
MIME types are defi ned by a general type followed by a specifi c type. For 
example, there is a general type for text that has several specifi c types for plain 
text, HTML text and style sheet text. These types are represented as text/plain, 
text/html and text/css, respectively. When the server sends a fi le to the browser, it 
will also include the MIME type for the fi le in the header that is sent to the 
browser.
MIME types are universal. All systems have agreed to use MIME types to iden-
tify the content of a fi le transmitted over the web. File extensions are too limiting 
for this purpose. Many different word processor programs might use the extension 
.doc
to identify a fi le. For instance, 
.doc
might refer to an MS WORD document or 
to an MS WORDPAD document. It is impossible to tell from the extension which 
program actually created the program. In addition, other programs could use 
the 
.doc
extension to identify a program: for instance, WordPerfect could also use 
the 
.doc
extension. Using the extension to identify the content of the fi le would be 
too confusing.
The most common content type on the web is HTML text, represented as the 
MIME type text/html.
1.2 Markup 
Language
I am confi dent that most students have seen a markup language. I remember my 
days in English composition classes: my returned papers would always have cryptic 
squiggles written all over them (Figure 1.2).
Some of these would mean that a word was omitted (^), that two letters were 
transposed (a sideways “S”, enclosing the transposed letters), or that a new para-
graph was needed (a backwards, double-stemmed “P”). These marks were invalu-
able to the teacher who had to correct the paper because they conveyed a lot of 
Figure 1.2
Editors use markup to annotate text.

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Web Development with Java
meaning in just a few pen strokes. Imagine if there were a program that would 
accept such a paper that is covered with markup, read the markup and generate a 
new version with all the corrections made.
There are other forms of markup languages. The script of a play has a markup 
language that describes the action that is proceeding while the dialog takes place. 
For instance, the following is a hypothetical script for The Three Stooges:
Moe
: Oh, a wise guy, huh?
Larry
: It wasn’t me.
Moe
: What are you doing?
Curly
: Nyuk, nyuk, nyuk.
Moe
: Ignoramus.
Word processors have an internal markup language that is used to indicate the 
format of the text: bold, italic, font, colour, etc. These codes are hidden from the 
user. 
WordPerfect
has an additional view of the document that displays all of these 
hidden codes (Figure 1.3).
There are two parts to any markup language
1. The plain text
2. The markup, which contains additional information about the plain text
1.2.1 Hypertext 
Markup 
Language
HTML is the markup language for the web. It is what allows the browser to display 
colours, fonts, links and graphics. All markup is enclosed within the angle brackets 
<
and 
>
. Directly adjacent to the opening bracket is the name of the tag. There can 
be additional attributes after the name of the tag and the closing bracket.
HTML tags are intermixed with plain text. The plain text is what the viewer of 
a web page will see. The HTML tags are commands to the browser for displaying 
the text. In this example, the plain text “This text is underlined” is enclosed within 
the HTML tags for underlining:
This text is underlined
The viewer of the web page would see: This text is underlined.
There are two types of HTML tags: singletons and paired tags.
Figure 1.3
Word processors use markup to format text.

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Browser – Server Communication 
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