Lucene源码分析 - queryparser > flexible

Flexible

This project contains the new Lucene query parser implementation, which matches the syntax of the core QueryParser but offers a more modular architecture to enable customization.

This project contains the new Lucene query parser implementation,
which matches the syntax
of the core QueryParser
but offers a more modular architecture
to enable customization.

包含新Lucene查询解析实现，匹配core QueryParser语法，在自定义方面，结构更加模块化。

It's currently divided in 2 main packages:
分布在2个包中：
org.apache.lucene.queryparser.flexible.core
包含query parser api类，可以被query parser 实现扩展。

org.apache.lucene.queryparser.flexible.standard
包new query parser api实现的Lucene query parser 实现。

{@link org.apache.lucene.queryparser.flexible.core}: it contains the query parser API classes, which should be extended by query parser implementations.

{@link org.apache.lucene.queryparser.flexible.standard}: it contains the current Lucene query parser implementation using the new query parser API.

Features

1. Full support for boolean logic (not enabled)
   完全支持boolean 逻辑

2. ueryNode Trees - support for several syntaxes, that can be converted into similar syntax QueryNode trees.
   支持几种语法，可以转换成相似的语法 QueryNode 树。

3. QueryNode Processors - Optimize, validate, rewrite the QueryNode trees
   QueryNode Processors - 优化，验证，rewrite QueryNode 树。

4. Processors Pipelines - Select your favorite Processor and build a processor pipeline, to implement the features you need
   Pipelines处理器，选择你最喜欢的处理器，构建一个pipeline处理器，来实现你需要的特性。

5. Config Interfaces - Allow the consumer of the Query Parser to implement a diff Config Handler Objects to suite their needs.
   配置接口，允许Query Parser的consumer来实现一个diff 配置处理对象来

6. Standard Builders - convert QueryNode's into several lucene representations. Supported conversion is using a 2.4 compatible logic
   独立的builders -

7. QueryNode tree's can be converted to a lucene 2.4 syntax string, using toQueryString

Design

This new query parser was designed to have very generic architecture, so that it can be easily used for different products with varying query syntaxes. This code is much more flexible and extensible than the Lucene query parser in 2.4.X.

1、新的query parser 被设计有一种通用的结构
2、很容易被用在不同的产品上
3、比起2.4.x中的Lucene query parser 扩展性和灵活性更好

The new query parser goal is to separate syntax and semantics of a query. E.g. 'a AND b', '+a +b', 'AND(a,b)' could be different syntaxes for the same query. It distinguishes the semantics of the different query components, e.g. whether and how to tokenize/lemmatize/normalize the different terms or which Query objects to create for the terms. It allows to write a parser with a new syntax, while reusing the underlying semantics, as quickly as possible.

The query parser has three layers and its core is what we call the QueryNode tree. It is a tree that initially represents the syntax of the original query, e.g. for 'a AND b':

  AND
 /   \
A     B

The three layers are:

QueryParser

• This layer is the text parsing layer which simply transforms the query text string into a {@link org.apache.lucene.queryparser.flexible.core.nodes.QueryNode} tree. Every text parser must implement the interface {@link org.apache.lucene.queryparser.flexible.core.parser.SyntaxParser}. Lucene default implementations implements it using JavaCC.

QueryNodeProcessor

• The query node processors do most of the work. It is in fact a configurable chain of processors. Each processors can walk the tree and modify nodes or even the tree's structure. That makes it possible to e.g. do query optimization before the query is executed or to tokenize terms.

QueryBuilder:

• The third layer is a configurable map of builders, which map {@link org.apache.lucene.queryparser.flexible.core.nodes.QueryNode} types to its specific builder that will transform the QueryNode into Lucene Query object.

Furthermore, the query parser uses flexible configuration objects. It also uses message classes that allow to attach resource bundles. This makes it possible to translate messages, which is an important feature of a query parser.

This design allows to develop different query syntaxes very quickly.

StandardQueryParser and QueryParserWrapper

The classic Lucene query parser is located under {@link org.apache.lucene.queryparser.classic}.

To make it simpler to use the new query parser the class {@link org.apache.lucene.queryparser.flexible.standard.StandardQueryParser} may be helpful, specially for people that do not want to extend the Query Parser. It uses the default Lucene query processors, text parser and builders, so you don't need to worry about dealing with those. {@link org.apache.lucene.queryparser.flexible.standard.StandardQueryParser} usage:

  StandardQueryParser qpHelper = new StandardQueryParser();
  StandardQueryConfigHandler config =  qpHelper.getQueryConfigHandler();
  config.setAllowLeadingWildcard(true);
  config.setAnalyzer(new WhitespaceAnalyzer());
  Query query = qpHelper.parse("apache AND lucene", "defaultField");