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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<title>Simple <property> Classes</title>
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<h1>Simple <property> Classes</h1>
<p>
<font size="-2">by Peter B. West</font>
</p>
<ul class="minitoc">
<li>
<a href="#N10014">Introduction</a>
</li>
<li>
<a href="#N10026">Common data</a>
</li>
<li>
<a href="#N10075">Accessing <property> Data Constants</a>
</li>
</ul>
<a name="N10014"></a>
<h3>Introduction</h3>
<p>
An <a href="classes-overview.html">overview of the properties
and classes</a> involved in handling properties has already
been given. This discussion will go in detail into the way
data are represented within properties. Iit is important to
keep in mind that the primary avenue of access to the data and
the methods of property classes is the <a href=
"javascript:window.top.displayCode(
'PropertyConsts.html#PropertyConstsClass' )" ><span
class="codefrag">PropertyConsts</span></a> class and its
singleton object.
</p>
<a name="N10026"></a>
<h3>Common data</h3>
<p>
<a href= "javascript:window.top.displayCode( 'Character.html' )" ><span
class="codefrag">org.apache.fop.fo.properties.Character</span></a>
is an example of a basic property class. The data fields
common to all properties are:
</p>
<dl>
<dt>
<span class="codefrag">final int dataTypes</span>
</dt>
<dd>
This field defines the allowable data types which may be
assigned to the property. The value is chosen from the data
type constants defined in <a href=
"javascript:window.top.displayCode( 'Property.html#NOTYPE' )"
><span
class="codefrag">org.apache.fop.fo.properties.Property</span></a>,
and may consist of more than one of those constants,
bit-ORed together.
</dd>
<dt>
<span class="codefrag">final int traitMapping</span>
</dt>
<dd>
This field defines the mapping of properties to traits in
the <span class="codefrag">Area tree</span>. The value is
chosen from the trait mapping constants defined in <a href=
"javascript:window.top.displayCode( 'Property.html#NO_TRAIT' )"
><span
class="codefrag">org.apache.fop.fo.properties.Property</span></a>,
and may consist of more than one of those constants,
bit-ORed together.
</dd>
<dt>
<span class="codefrag">final int initialValueType</span>
</dt>
<dd>
This field defines the data type of the initial value
assigned to the property. The value is chosen from the
initial value type constants defined in <a href=
"javascript:window.top.displayCode( 'Property.html#NOTYPE_IT' )"
><span
class="codefrag">org.apache.fop.fo.properties.Property</span></a>.
In the simplest property classes, such as <span
class="codefrag">Character</span>, there is no defined
initial value type.
</dd>
<dt>
<span class="codefrag">final int inherited</span>
</dt>
<dd>
This field defines the kind of inheritance applicable to the
property. The value is chosen from the inheritance
constants defined in <a href=
"javascript:window.top.displayCode( 'Property.html#NO' )" ><span
class="codefrag">org.apache.fop.fo.properties.Property</span></a>.
</dd>
</dl>
<a name="N10075"></a>
<h3>Accessing <property> Data Constants</h3>
<p>
The constants above are generally accessed through the arrays
maintained in the <a href= "javascript:window.top.displayCode(
'PropertyConsts.html#PropertyConstsClass' )" ><span
class="codefrag">PropertyConsts</span></a> singleton <a href=
"javascript:window.top.displayCode( 'PropertyConsts.html#pconsts'
)" ><span class="codefrag">pconsts</span></a>. The first
invocation of the method <a href=
"javascript:window.top.displayCode(
'PropertyConsts.html#setupProperty' )" ><span
class="codefrag">setupProperty</span></a> on the property
generates a <span class="codefrag">Class</span> instance for
the class, and stores it in the array <a href=
"javascript:window.top.displayCode( 'PropertyConsts.html#classes'
)" ><span class="codefrag">classes</span></a>. This <span
class="codefrag">Class</span> object is used, in turn, to
instantiate the singleton instance of the class, which is
stored in the <a href= "javascript:window.top.displayCode(
'PropertyConsts.html#properties' )" ><span
class="codefrag">Property[] properties</span></a> array of <a
href= "javascript:window.top.displayCode(
'../PropertyConsts.html#pconsts' )" ><span
class="codefrag">pconsts</span></a>.
</p>
<p>
<em>Reflection</em> methods are then used, via the same <span
class="codefrag">Class</span> instance, to extract and store
the static data fields. These arrays and associated access
methods are:
</p>
<dl>
<dt>
<a href= "javascript:window.top.displayCode(
'PropertyConsts.html#datatypes' )" ><span
class="codefrag">int[] datatypes</span></a>
</dt>
<dd>
<a href= "javascript:window.top.displayCode(
'PropertyConsts.html#getDataTypes' )" ><span
class="codefrag">int getDataTypes(int)</span></a>
</dd>
<dt>
<a href= "javascript:window.top.displayCode(
'PropertyConsts.html#traitMappings' )" ><span
class="codefrag">int[] traitMappings</span></a>
</dt>
<dd>
<em>No access method yet defined.</em>
</dd>
<dt>
<a href= "javascript:window.top.displayCode(
'PropertyConsts.html#initialValueTypes' )" ><span
class="codefrag">int[] initialValueTypes</span></a>
</dt>
<dd>
<a href= "javascript:window.top.displayCode(
'PropertyConsts.html#getInitialValueType' )" ><span
class="codefrag">int getInitialValueType(int)</span></a>
</dd>
<dt>
<a href= "javascript:window.top.displayCode(
'PropertyConsts.html#inherited' )" ><span
class="codefrag">int[] inherited</span></a>
</dt>
<dd>
<a href= "javascript:window.top.displayCode(
'PropertyConsts.html#inheritance' )" ><span
class="codefrag">int inheritance(int)</span></a>
</dd>
</dl>
<p>
<strong>Previous:</strong> <a href = "PropertyConsts-class.html"
>PropertyConsts class</a>
</p>
<p>
<strong>Next:</strong> <a href= "getInitialValue.html"
>getInitialValue()</a>
</p>
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