org.apache.lucene.queryparser.flexible.core (Lucene 10.5.0 queryparser API)
Description: declaration: package: org.apache.lucene.queryparser.flexible.core

# Package org.apache.lucene.queryparser.flexible.core

package org.apache.lucene.queryparser.flexible.core
Core classes of the flexible query parser framework.

## Flexible Query Parser

This package contains the necessary classes to implement a query parser.

A query parser is divided in at least 2 phases, text parsing and query building, and one optional phase called query processing.

### First Phase: Text Parsing

The text parsing phase is performed by a text parser, which implements `SyntaxParser` interface. A text parser is responsible to get a query string and convert it to a `QueryNode` tree, which is an object structure that represents the elements defined in the query string.

### Second (optional) Phase: Query Processing

The query processing phase is performed by a query processor, which implements `QueryNodeProcessor`. A query processor is responsible to perform any processing on a `QueryNode` tree. This phase is optional and is used only if an extra processing, validation, query expansion, etc needs to be performed in a `QueryNode` tree. The `QueryNode` tree can be either be generated by a text parser or programmatically created.

### Third Phase: Query Building

The query building phase is performed by a query builder, which implements `QueryBuilder`. A query builder is responsible to convert a `QueryNode` tree into an arbitrary object, which is usually used to be executed against a search index.

- Related Packages
  Package
  Description
  org.apache.lucene.queryparser.flexible.core.builders
  Necessary classes to implement query builders.
  org.apache.lucene.queryparser.flexible.core.config
  Base classes used to configure the query processing.
  org.apache.lucene.queryparser.flexible.core.messages
  Messages usually used by query parser implementations.
  org.apache.lucene.queryparser.flexible.core.nodes
  Query nodes commonly used by query parser implementations.
  org.apache.lucene.queryparser.flexible.core.parser
  Necessary interfaces to implement text parsers.
  org.apache.lucene.queryparser.flexible.core.processors
  Interfaces and implementations used by query node processors
  org.apache.lucene.queryparser.flexible.core.util
  Utility classes to used with the Query Parser.
- Class
  Description
  QueryNodeError
  Error class with NLS support
  QueryNodeException
  This exception should be thrown if something wrong happens when dealing with `QueryNode`s.
  QueryNodeParseException
  This should be thrown when an exception happens during the query parsing from string to the query node tree.
  QueryParserHelper
  This class is a helper for the query parser framework, it does all the three query parser phrases at once: text parsing, query processing and query building.