JavaServer Pages, 3rd Edition

Encoding Non-XML Data and Special Characters

Since a JSP Document is a formal XML document, all template data must be well- formed XML. Example 17-10 is well-formed because it contains XHTML elements, such as the <ul> and <li> elements, represented by opening and closing tags, and an empty <br/> tag.

If you use a JSP Document to generate a response in a format that is not XML-based, you can embed the template data that is not well-formed in XML CDATA sections. For instance, if the response must be accessible to older browsers that only understand HTML 3.2, you can’t use the XHTML <br/> empty tag syntax, but using HTML 3.2 syntax with a single opening <br> tag violates the well-formedness requirement. Embedding the HTML 3.2 single opening <br> tag in a CDATA section solves the problem; it satisfies the container’s well-formed XML requirement and feeds the browser the HTML 3.2 tag it understands:

<ul> 
  <c:forEach items="${paramValues}" var="current"> 
    <li> 
      ${current.key}:
      <c:forEach items="${current.value}" var="parValue">
        <![CDATA[<br>]]>${parValue}
      </c:forEach>
    </li> 
  </c:forEach>

In an XML document, special characters such as greater-than and less-than in an element body (or attribute) must be replaced with character entity codes, for example, the < character must be replaced with < and > must be replaced with >. These characters are common in Java code, so if you need to use scripting elements in a JSP Document, you can use a CDATA section to work around this issue as well: