Property Data Handling

- Property Data Handling - - - -

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- Introduction -

- An overview of the - properties and classes involved in handling properties - has already been given. This discussion will go in detail - into the way data are represented within properties. -

- Common data - -

- org.apache.fop.fo.properties.Character is an example - of a basic <property> class. The data fields common to - all properties are: -

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- final int dataTypes -: - 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 org.apache.fop.fo.properties.Property, and may consist of more than one of those - constants, bit-ORed together. -
- final int traitMapping -: - This field defines the mapping of properties to traits in - the Area tree. The value is chosen from the - trait mapping constants defined in org.apache.fop.fo.properties.Property, and - may consist of more than one of those constants, bit-ORed - together. -
- final int initialValueType -: - 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 org.apache.fop.fo.properties.Property. In - the simplest <property> classes, such as - Character, - there is no defined initial value type. -
- final int inherited -: - This field defines the kind of inheritance applicable to the - property. The value is chosen from the inheritance - constants defined in org.apache.fop.fo.properties.Property. -

- Accessing <property> Data Constants - -

- The constants above are generally accessed through the arrays - maintained in the PropertyConsts singleton pconsts. The first invocation of the method setupProperty on the property generates a - Class instance for the class, and stores it in - the array classes. This Class object is - used, in turn, to instantiate the singleton instance of the - class, which is stored in the Property[] - properties array of pconsts. -

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- Reflection methods are then used, via the same - Class instance, to extract and store the static - data fields. These arrays and associated access methods are: -

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- int[] datatypes -: - int getDataTypes(int) -
- int[] traitMappings -: - No access method yet defined. -
- int[] initialValueTypes -: - int getInitialValueTypes(int) -
- int[] inherited -: - int inheritance(int) -

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