Creating Static and Dynamic Content

This section explains how to represent static text and dynamic content in a JSP document. You can represent static text in a JSP document using uninterpreted XML tags or the jsp:text element. The jsp:text element passes its content through to the output.

If you use jsp:text, all white space is preserved. For example, consider this example using XML tags:

<books>
    <book>
        Web Servers for Fun and Profit
    </book>
</books>

The output generated from this XML has all white space removed:

<books><book>
        Web Servers for Fun and Profit
</book></books>

If you wrap the example XML with a <jsp:text> tag, all white space is preserved. The white space characters are #x20, #x9, #xD, and #xA.

You can also use jsp:text to output static data that is not well formed. The ${counter} expression in the following example would be illegal in a JSP document if it were not wrapped in a jsp:text tag.

<c:forEach var="counter" begin="1" end="${3}">
    <jsp:text>${counter}</jsp:text>
</c:forEach>

This example will output

123

The jsp:text tag must not contain any other elements. Therefore, if you need to nest a tag inside jsp:text, you must wrap the tag inside CDATA.

You also need to use CDATA if you need to output some elements that are not well-formed. The following example requires CDATA wrappers around the blockquote start and end tags because the blockquote element is not well formed. This is because the blockquote element overlaps with other elements in the example.

<c:forEach var="i" begin="1" end="${x}">
    <![CDATA[<blockquote>]]>
</c:forEach>
...
<c:forEach var="i" begin="1" end="${x}">
    <![CDATA[</blockquote>]]>
</c:forEach>

Just like JSP pages, JSP documents can generate dynamic content using expressions language (EL) expressions, scripting elements, standard actions, and custom tags. The books.jspx document uses EL expressions and custom tags to generate the XML book data.

As shown in this snippet from books.jspx, the c:forEach JSTL tag iterates through the list of books and generates the XML data stream. The EL expressions access the JavaBeans component, which in turn retrieves the data from the database:

<c:forEach var="book" begin="0" items="${bookDB.books}">
    <book id="${book.bookId}" >
        <surname>${book.surname}</surname>
        <firstname>${book.firstName}</firstname>
        <title>${book.title}</title>
        <price>${book.price}</price>
        <year>${book.year}</year>
        <description>${book.description}</description>
        <inventory>${book.inventory}</inventory>
    </book>
</c:forEach>

When using the expression language in your JSP documents, you must substitute alternative notation for some of the operators so that they will not be interpreted as XML markup. Table 6–2 enumerates the more common operators and their alternative syntax in JSP documents.

You can also use EL expressions with jsp:element to generate tags dynamically rather than hard code them. This example could be used to generate an HTML header tag with a lang attribute:

<jsp:element name="${content.headerName}"
         xmlns:jsp="http://java.sun.com/JSP/Page">
    <jsp:attribute name="lang">${content.lang}</jsp:attribute>
    <jsp:body>${content.body}</jsp:body>
</jsp:element>

The name attribute identifies the generated tag’s name. The jsp:attribute tag generates the lang attribute. The body of the jsp:attribute tag identifies the value of the lang attribute. The jsp:body tag generates the body of the tag. The output of this example jsp:element could be

<h1 lang="fr">Heading in French</h1>

As shown in Table 6–1, scripting elements (described in Chapter 9, Scripting in JSP Pages) are represented as XML elements when they appear in a JSP document. The only exception is a scriptlet expression used to specify a request-time attribute value. Instead of using <%=expr %>, a JSP document uses %= expr % to represent a request-time attribute value.

The three scripting elements are declarations, scriptlets, and expressions.

A jsp:declaration element declares a scripting language construct that is available to other scripting elements. A jsp:declaration element has no attributes and its body is the declaration itself. Its syntax is

<jsp:declaration> declaration goes here </jsp:declaration>

A jsp:scriptlet element contains a Java program fragment called a scriptlet. This element has no attributes, and its body is the program fragment that constitutes the scriptlet. Its syntax is

<jsp:scriptlet> code fragment goes here </jsp:scriptlet>

The jsp:expression element inserts the value of a scripting language expression, converted into a string, into the data stream returned to the client. A jsp:expression element has no attributes and its body is the expression. Its syntax is

<jsp:expression> expression goes here </jsp:expression>