Creating queries with the Lucene QueryParser

Now, we understand that we need to create Query objects to perform a search. We will look at QueryParser and show you how it's done. Lucene supports a powerful query engine that allows for a wide range of query types. You can use search modifier or operator to tell Lucene how matches are done. You can also use fuzzy search and wild card matching.

Internally, Lucene processes Query objects to execute a search. QueryParser is an interpreter that parses a query string into Query objects. It provides the utility to convert textual input into objects. The key method in QueryParser is parse (String). If you want more control over how a search is performed, you can create Query objects directly without using QueryParser, but this would be a much more complicated process. The query string syntax Lucene uses has a few rules. Here is an excerpt from Lucene's Javadoc: https://lucene.apache.org/core/4_10_0/queryparser/org/apache/lucene/queryparser/classic/QueryParser.html.

The syntax for query strings is as follows: a Query is a series of clauses. A clause can be prefixed by:

A clause can be:

Thus, in BNF, the query grammar is:

Query  ::= ( Clause )*    
Clause ::= ["+", "-"] [<TERM> ":"] ( <TERM> | "(" Query ")" ) 

The Backus Normal Form (BNF) is a notation technique to specify syntax for a language, and is often used in computer science.

QueryParser parser = new QueryParser("Content", analyzer);
Query query = parser.parse("Lucene");