Contains the base classes used to configure the query processing

## Query Configuration Interfaces

The package `org.apache.lucene.queryParser.core.config` contains query configuration handler abstract class that all config handlers should extend.

See {@link org.apache.lucene.queryParser.standard.config.StandardQueryConfigHandler} for a reference implementation.

The {@link org.apache.lucene.queryParser.core.config.QueryConfigHandler} and {@link org.apache.lucene.queryParser.core.config.FieldConfig} are used in the processors to access config information in a flexible and independent way. See {@link org.apache.lucene.queryParser.standard.processors.ParametricRangeQueryNodeProcessor} for a reference implementation.

Since version 3.4, the configuration API has changed. It no longer uses {@link org.apache.lucene.util.Attribute} objects to configure a query parser. Instead, it uses {@link org.apache.lucene.queryParser.core.config.ConfigurationKey} objects to set any configuration to a {@link org.apache.lucene.queryParser.core.config.QueryConfigHandler}. For now, both configuration APIs are working, however, they cannot be used at the same time. So if you start moving your code to the new API, move it completely or keep using the old API.

Here is an example about how the new configuration API works:

>     ...
>     // this constant will be the key to get and set your configuration. This should be unique in your application.
>     final public static {@link org.apache.lucene.queryParser.core.config.ConfigurationKey}<{@link java.text.NumberFormat}> MY_CONFIG = {@link org.apache.lucene.queryParser.core.config.ConfigurationKey}.newInstance();
>     ...
>     // make sure to use your unique key instance to set and get your configuration
>     queryConfigHandler.set(MY_CONFIG, {@link java.text.NumberFormat}.getInstance());
>     {@link java.text.NumberFormat} numberFormat = queryConfigHandler.get(MY_CONFIG);
>     ...