Java Tech - Chapter 1 : Supplements

We provide here a very brief tutorial on creating and posting web pages. For a full introduction to web page programming, look for one of the many books or on line courses on the topic.

A web page contains a special text based language called hypertext markup language or HTML. The browser interprets the special hypertext code to determine how to display the text, graphics, tables, etc.

The essential element in hypertext is the tag, which provide instructions on form and function. Tags are enclosed in angle brackets: <> and each tag has a corresponding matching tag with a a backslash, </>, to indicate the end of the tag operation. For example,

webpage.html

<HTML> <HEAD> <TITLE> A Simple Program </TITLE> </HEAD> <BODY> <b> Learning Java </b> <br>Java is a trademark of <a href="http://java.sun.com">Sun Microsystems</a> </BODY> </HTML>

We see first that the entire code is enclosed in the <HTML> - </HTML> matching tags. A header section is enclosed in <HEAD> - </HEAD> and so forth.

White space, such as line returns, are ignored by the browser. Instead, you must include tags to create a line return. Here we see the <Br> tag, which causes a line return. It is one of the few tags that does not require a matching right tag.

A web link is created with the

set of tags, where "web address" indicates the Universal Resource Link (URL) address of the web page to link. Here we see a common property of many types of tags in which an attribute is included inside of the left tag.

If you open the file webpage.html in your browser, the above hypertext code will produce a web page that looks something like this:

Learning Java
Java is a trademark of Sun Microsystems.

You can choose different background colors, a color for links, etc. with attributes of the <body> tag. See a hypertext reference for information on this tag and others.

Note that the hypertext is typically stored in a file whose name is appended with the .html or .htm suffix.

You can edit the hypertext code directly as shown above. However, most people use a hypertext graphical editor of some kind in which you edit the text, images, tables, etc in a what-you-see-is-what-you-get (WYSIWYG) approach. That is, the page that you edit looks very similar to the way it will appear in the browser; you don't see the underlying hypertext tags.

If you intend to do extensive web development, you need to know the details of hypertext tags to fix bugs and tune the code to your desired look. For routine web page creation, however, you will want to use a hypertext editor.

Many commercial and free web editors are available. The Netscape browser, for example, provides a free web editor (called Composer).

Once you have your hypertext file, you must place it on a computer that is accessible from the web and that runs a program called a web server. The web server receives requests for files from browsers on the Internet and then sends the files to the requesters. (We will actually show how to create a simple web (or HTTP) server in Chapter 14.

The server obviously needs to know where to find a requested file. If you are developing your programs on a school or work computer that's on the net and runs its own web server, then your system manager will typically provide a directory where you should place your hypertext files.

On a Unix system, for example, you will typically create a sub-directory called public_html where you put your hypertext and Java class files. The system manager will set up the server so that it will look in that directory when it obtains a request for your file webpage.html:

If instead of a local server machine, you are planning to post your pages on a remote web site, you will need to up load your web pages to that site. For example, perhaps you obtained a web site via your dial up account or on one of the free web hosting sites.

In this case, you typically use an ftp (File Transport Protocol) program (or use the ftp capability in your browser) to copy the hypertext and applet class files from your machine to the host's site. The host service should provide directions (what username/password to use, for example) on how to do this for their system.