org.apache.commons.digester3.plugins
Class RuleFinder

java.lang.Object
  org.apache.commons.digester3.plugins.RuleFinder

Direct Known Subclasses:

FinderFromClass, FinderFromDfltClass, FinderFromDfltMethod, FinderFromDfltResource, FinderFromFile, FinderFromMethod, FinderFromResource, FinderSetProperties

public abstract class RuleFinder
extends Object

Each concrete implementation of RuleFinder is an algorithm for locating a source of digester rules for a plugin. The algorithm may use info explicitly provided by the user as part of the plugin declaration, or not (in which case the concrete RuleFinder subclass typically has Dflt as part of its name).

Instances of this class can also be regarded as a Factory for RuleLoaders, except that an instance of a RuleLoader is only created if the particular finder algorithm can locate a suitable source of rules given the plugin class and associated properties.

This is an abstract class rather than an interface in order to make it possible to enhance this class in future without breaking binary compatibility; it is possible to add methods to an abstract class, but not to an interface.

Since:

1.6

Constructor Summary

RuleFinder()

Method Summary

abstract RuleLoader

findLoader(Digester d, Class<?> pluginClass, Properties p) Apply the finder algorithm to attempt to locate a source of digester rules for the specified plugin class.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

RuleFinder

public RuleFinder()

Method Detail

findLoader

public abstract RuleLoader findLoader(Digester d,
                                      Class<?> pluginClass,
                                      Properties p)
                               throws PluginException

Apply the finder algorithm to attempt to locate a source of digester rules for the specified plugin class.

This method is invoked when a plugin is declared by the user, either via an explicit use of PluginDeclarationRule, or implicitly via an "inline declaration" where the declaration and use are simultaneous.

If dynamic rules for the specified plugin class are located, then the RuleFinder will return a RuleLoader object encapsulating those rules, and this object will be invoked each time the user actually requests an instance of the declared plugin class, to load the custom rules associated with that plugin instance.

If no dynamic rules can be found, null is returned. This is not an error; merely an indication that this particular algorithm found no matches.

The properties object holds any xml attributes the user may have specified on the plugin declaration in order to indicate how to locate the plugin rules.

Parameters:

d - The digester instance where locating plugin classes

pluginClass - The plugin Java class

p - The properties object that holds any xml attributes the user may have specified on the plugin declaration in order to indicate how to locate the plugin rules.

Returns:

a source of digester rules for the specified plugin class.

Throws:

PluginException - if the algorithm finds a source of rules, but there is something invalid about that source.