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Java Enterprise Best Practices
book

Java Enterprise Best Practices

by O'Reilly Java Authors
December 2002
Intermediate to advanced content levelIntermediate to advanced
288 pages
9h 46m
English
O'Reilly Media, Inc.
Content preview from Java Enterprise Best Practices

Use Entity References

An entity reference (also called an entity declaration in some circles) is one of those topics in XML that seems a little obscure. However, just think of an entity reference as a variable in XML. That variable has a declared value, and every time the variable occurs, the parser substitutes that value in the XML output. In that regard, an entity reference is like a static final variable in Java in that it cannot alter its value from an initial value defined in a Document Type Definition (DTD).

An entity reference often refers to an online resource (you’ll see examples of this later in the Section 5.2), but it can also have a value defined in a DTD, such as the following:

<!ENTITY phoneNumber "800-775-7731">

Instead of typing the phone number for O’Reilly several times in your XML document, and possibly introducing typographical errors, you can just refer to the value through its reference:

<content>O'Reilly's phone number is &phoneNumber;.</content>

Of course, this seems pretty trivial, so let’s look at a more realistic example. Example 5-1 shows a simple XML document fragment intended for display on a web page.

Example 5-1. Sample document without entity references
<page> <title>O'Reilly Java Enterprise Best Practices</title> <content type="html"> <center><h1>O'Reilly Java Enterprise Best Practices</h1></center> <p> Welcome to the website for <i>O'Reilly Java Enterprise Best Practices</i>. This book was written by O'Reilly's Java authors for Java Enterprise professionals. ...
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Publisher Resources

ISBN: 0596003846Supplemental ContentErrata Page