# PropertyConsts Description

by Peter B. West

- Introduction

### Introduction

This class, and the singleton object which is generated by the static initializer, is essentially a repository of <property> class instances and the static data from those classes of org.apache.fop.fo.property. The heart of this class is the method setupProperty. Whenever access to the data or methods of a property class is required, this method in the singleton must be called to ensure that an instance of the property exists and that the static data from that instance has been extracted.

Note
An alternative to this requirement would be to pre-load all of the individual property classes during the system initialization phase. This is not done currently because of the start-up expense of the required class loading for over three hundred classes, and the relatively low added expense of checking for the existence of a property instance before every access. Given that FOP is increasingly used in a server environment, it may prove acceptable in the long run to change to pre-loading.

The class name is generated and stored in the classNames array; a class instance is generated from the name and stored in the classes array; and an instance of the class is generated from the class object and stored in the properties array.

The other data gathering facilities and access methods of this class will be examined in conjunction with the various types of property classes.

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