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j2eePDF格式的电子书

ELEMENT: <slideshow
  ATTR: ...
>
<code class="cCodeBold">IGNORABLE
IGNORABLE
</code>PROCESS: ...
<code class="cCodeBold">IGNORABLE
IGNORABLE
</code>&nbsp;&nbsp;ELEMENT: &lt;slide
&nbsp;&nbsp;&nbsp;&nbsp;ATTR: ...
&nbsp;&nbsp;&gt;
&nbsp;&nbsp;<code class="cCodeBold">IGNORABLE
</code>&nbsp;&nbsp;&nbsp;&nbsp;ELEMENT: &lt;title&gt;
&nbsp;&nbsp;&nbsp;&nbsp;CHARS:   Wake up to ...
&nbsp;&nbsp;&nbsp;&nbsp;END_ELM: &lt;/title&gt;
&nbsp;&nbsp;<code class="cCodeBold">IGNORABLE
</code>&nbsp;&nbsp;END_ELM: &lt;/slide&gt;
<code class="cCodeBold">IGNORABLE
IGNORABLE
</code>&nbsp;&nbsp;ELEMENT: &lt;slide
&nbsp;&nbsp;&nbsp;&nbsp;ATTR: ...
&nbsp;&nbsp;&gt;
&nbsp;&nbsp;...<a name="wp64996"> </a>
</pre></div>
<a name="wp64997"> </a><p class="pBody">
Here, it is apparent that the ignorableWhitespace is being invoked before and after comments and slide elements, where characters was being invoked before there was a DTD. 
</p>
<a name="wp64999"> </a><h3 class="pHeading2">
Cleanup
</h3>
<a name="wp65000"> </a><p class="pBody">
Now that you have seen ignorable whitespace echoed, remove that code from your version of the Echo program--you won't be needing it any more in the exercises ahead. 
</p>
<hr>
<a name="wp65001"> </a><p class="pNote">
Note: That change has been made in <code class="cCode"><a  href="../examples/jaxp/sax/samples/Echo09.java" target="_blank">Echo09.java</a></code>. 
</p>
<hr><a name="wp65008"> </a><h3 class="pHeading2">
Empty Elements, Revisited
</h3>
<a name="wp65009"> </a><p class="pBody">
Now that you understand how certain instances of whitespace can be ignorable, it is time revise the definition of an &quot;empty&quot; element. That definition can now be expanded to include 
</p>
<div class="pPreformattedRelative"><pre class="pPreformattedRelative">
  &lt;foo&gt;   &lt;/foo&gt;<a name="wp65010"> </a>
</pre></div>
<a name="wp65011"> </a><p class="pBody">
where there is whitespace between the tags and the DTD says that whitespace as ignorable.
</p>
<a name="wp65166"> </a><h3 class="pHeading2">
Echoing Entity References
</h3>
<a name="wp95106"> </a><p class="pBody">
When you wrote <code class="cCode">slideSample06.xml</code>, you defined entities for the product name. Now it's time to see how they're echoed when you process them with the SAX parser.
</p>
<hr>
<a name="wp95131"> </a><p class="pNote">
Note: The XML used here is contained in <code class="cCode"><a  href="../examples/xml/samples/slideSample06.xml" target="_blank">slideSample06.xml</a></code>, which references <code class="cCode"><a  href="../examples/xml/samples/slideshow1b.dtd" target="_blank">slideshow1b.dtd</a></code>, as described in <a  href="IntroXML4.html#wp68104">Defining Attributes and Entities in the DTD</a>. The output is shown in <code class="cCode"><a  href="../examples/jaxp/sax/samples/Echo09-06.txt" target="_blank">Echo09-06.txt</a></code>. (The browsable versions are <code class="cCode"><a  href="../examples/xml/samples/slideSample06-xml.html" target="_blank">slideSample06-xml.html</a></code>, <code class="cCode"><a  href="../examples/xml/samples/slideshow1b-dtd.html" target="_blank">slideshow1b-dtd.html</a></code> and <code class="cCode"><a  href="../examples/jaxp/sax/samples/Echo09-06.html" target="_blank">Echo09-06.html</a></code>.)
</p>
<hr><a name="wp95140"> </a><p class="pBody">
When you run the Echo program on <code class="cCode">slideSample06.xml</code>, here is the kind of thing you see:
</p>
<div class="pPreformattedRelative"><pre class="pPreformattedRelative">
ELEMENT:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&lt;title&gt;
CHARS:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Wake up to <code class="cCodeBold">WonderWidgets</code>!
END_ELM:&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&lt;/title&gt;<a name="wp65168"> </a>
</pre></div>
<a name="wp65169"> </a><p class="pBody">
Note that the product name has been substituted for the entity reference.
</p>
<a name="wp65191"> </a><h3 class="pHeading2">
Echoing the External Entity
</h3>
<a name="wp95190"> </a><p class="pBody">
In <code class="cCode">slideSample07.xml</code>, you defined an external entity to reference a copyright file.
</p>
<hr>
<a name="wp95193"> </a><p class="pNote">
Note: The XML used here is contained in <code class="cCode"><a  href="../examples/xml/samples/slideSample07.xml" target="_blank">slideSample07.xml</a></code> and in <code class="cCode"><a  href="../examples/jaxp/sax/samples/copyright.xml" target="_blank">copyright.xml</a></code>. The output is shown in <code class="cCode"><a  href="../examples/jaxp/sax/samples/Echo09-07.txt" target="_blank">Echo09-07.txt</a></code>. (The browsable versions are <code class="cCode"><a  href="../examples/xml/samples/slideSample07-xml.html" target="_blank">slideSample07-xml.html</a></code>, <code class="cCode"><a  href="../examples/jaxp/sax/samples/copyright-xml.html" target="_blank">copyright-xml.html</a></code> and<code class="cCode"><a  href="../examples/jaxp/sax/samples/Echo09-07.html" target="_blank"> Echo09-07.html</a></code>.)
</p>
<hr><a name="wp65192"> </a><p class="pBody">
When you run the Echo program on that version of the slide presentation, here is what you see:
</p>
<div class="pPreformattedRelative"><pre class="pPreformattedRelative">
...
END_ELM: &lt;/slide&gt;
ELEMENT: &lt;slide
&nbsp;&nbsp;ATTR: type&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&quot;all&quot;
&gt;
&nbsp;&nbsp;ELEMENT: &lt;item&gt;
&nbsp;&nbsp;CHARS: 
This is the standard copyright message that our lawyers
make us put everywhere so we don&#39;t have to shell out a
million bucks every time someone spills hot coffee in their
lap...
&nbsp;&nbsp;END_ELM: &lt;/item&gt;
END_ELM: &lt;/slide&gt;
...<a name="wp65193"> </a>
</pre></div>
<a name="wp65194"> </a><p class="pBody">
Note that the newline which follows the comment in the file is echoed as a character, but that the comment itself is ignored. That is the reason that the copyright message appears to start on the next line after the <code class="cCode">CHARS:</code> label, instead of immediately after the label--the first character echoed is actually the newline that follows the comment.
</p>
<a name="wp65196"> </a><h3 class="pHeading2">
Summarizing Entities
</h3>
<a name="wp65197"> </a><p class="pBody">
An entity that is referenced in the document content, whether internal or external, is termed a general entity. An entity that contains DTD specifications that are referenced from within the DTD is termed a parameter entity. (More on that later.) 
</p>
<a name="wp65198"> </a><p class="pBody">
An entity which contains XML (text and markup), and which is therefore parsed, is known as a <em class="cEmphasis">parsed entity</em>. An entity which contains binary data (like images) is known as an <em class="cEmphasis">unparsed entity</em>. (By its very nature, it must be external.) We'll be discussing references to unparsed entities in the next section of this tutorial.
</p>
    </blockquote>

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