lucene/core/src/java/overview.html - lucene-solr - Git at Google

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 <html>
 <head>
    <title>Apache Lucene API</title>
 </head>
 <body>

 <p>Apache Lucene is a high-performance, full-featured text search engine library.
 Here's a simple example how to use Lucene for indexing and searching (using JUnit
 to check if the results are what we expect):</p>

 <!-- code comes from org.apache.lucene.TestDemo.
      See LUCENE-8481 for reasons why it's out of sync with the code.
  -->
 <pre class="prettyprint">
     Analyzer analyzer = new StandardAnalyzer();

     Path indexPath = Files.createTempDirectory("tempIndex");
     Directory directory = FSDirectory.open(indexPath)
     IndexWriterConfig config = new IndexWriterConfig(analyzer);
     IndexWriter iwriter = new IndexWriter(directory, config);
     Document doc = new Document();
     String text = "This is the text to be indexed.";
     doc.add(new Field("fieldname", text, TextField.TYPE_STORED));
     iwriter.addDocument(doc);
     iwriter.close();

     // Now search the index:
     DirectoryReader ireader = DirectoryReader.open(directory);
     IndexSearcher isearcher = new IndexSearcher(ireader);
     // Parse a simple query that searches for "text":
     QueryParser parser = new QueryParser("fieldname", analyzer);
     Query query = parser.parse("text");
     ScoreDoc[] hits = isearcher.search(query, 10).scoreDocs;
     assertEquals(1, hits.length);
     // Iterate through the results:
     for (int i = 0; i &lt; hits.length; i++) {
       Document hitDoc = isearcher.doc(hits[i].doc);
       assertEquals("This is the text to be indexed.", hitDoc.get("fieldname"));
     }
     ireader.close();
     directory.close();
     IOUtils.rm(indexPath);</pre>
 <!-- ======================================================== -->


 <p>The Lucene API is divided into several packages:</p>

 <ul>
 <li>
 <b>{@link org.apache.lucene.analysis}</b>
 defines an abstract {@link org.apache.lucene.analysis.Analyzer Analyzer}
 API for converting text from a {@link java.io.Reader}
 into a {@link org.apache.lucene.analysis.TokenStream TokenStream},
 an enumeration of token {@link org.apache.lucene.util.Attribute Attribute}s.&nbsp;
 A TokenStream can be composed by applying {@link org.apache.lucene.analysis.TokenFilter TokenFilter}s
 to the output of a {@link org.apache.lucene.analysis.Tokenizer Tokenizer}.&nbsp;
 Tokenizers and TokenFilters are strung together and applied with an {@link org.apache.lucene.analysis.Analyzer Analyzer}.&nbsp;
 <a href="../analyzers-common/overview-summary.html">analyzers-common</a> provides a number of Analyzer implementations, including
 <a href="../analyzers-common/org/apache/lucene/analysis/core/StopAnalyzer.html">StopAnalyzer</a>
 and the grammar-based <a href="org/apache/lucene/analysis/standard/StandardAnalyzer.html">StandardAnalyzer</a>.</li>

 <li>
 <b>{@link org.apache.lucene.codecs}</b>
 provides an abstraction over the encoding and decoding of the inverted index structure,
 as well as different implementations that can be chosen depending upon application needs.

 <li>
 <b>{@link org.apache.lucene.document}</b>
 provides a simple {@link org.apache.lucene.document.Document Document}
 class.&nbsp; A Document is simply a set of named {@link org.apache.lucene.document.Field Field}s,
 whose values may be strings or instances of {@link java.io.Reader}.</li>

 <li>
 <b>{@link org.apache.lucene.index}</b>
 provides two primary classes: {@link org.apache.lucene.index.IndexWriter IndexWriter},
 which creates and adds documents to indices; and {@link org.apache.lucene.index.IndexReader},
 which accesses the data in the index.</li>

 <li>
 <b>{@link org.apache.lucene.search}</b>
 provides data structures to represent queries (ie {@link org.apache.lucene.search.TermQuery TermQuery}
 for individual words, {@link org.apache.lucene.search.PhraseQuery PhraseQuery}
 for phrases, and {@link org.apache.lucene.search.BooleanQuery BooleanQuery}
 for boolean combinations of queries) and the {@link org.apache.lucene.search.IndexSearcher IndexSearcher}
 which turns queries into {@link org.apache.lucene.search.TopDocs TopDocs}.
 A number of <a href="../queryparser/overview-summary.html">QueryParser</a>s are provided for producing
 query structures from strings or xml.

 <li>
 <b>{@link org.apache.lucene.store}</b>
 defines an abstract class for storing persistent data, the {@link org.apache.lucene.store.Directory Directory},
 which is a collection of named files written by an {@link org.apache.lucene.store.IndexOutput IndexOutput}
 and read by an {@link org.apache.lucene.store.IndexInput IndexInput}.&nbsp;
 Multiple implementations are provided, but {@link org.apache.lucene.store.FSDirectory FSDirectory} is generally
 recommended as it tries to use operating system disk buffer caches efficiently.</li>

 <li>
 <b>{@link org.apache.lucene.util}</b>
 contains a few handy data structures and util classes, ie {@link org.apache.lucene.util.FixedBitSet FixedBitSet}
 and {@link org.apache.lucene.util.PriorityQueue PriorityQueue}.</li>
 </ul>
 To use Lucene, an application should:
 <ol>
 <li>
 Create {@link org.apache.lucene.document.Document Document}s by
 adding
 {@link org.apache.lucene.document.Field Field}s;</li>

 <li>
 Create an {@link org.apache.lucene.index.IndexWriter IndexWriter}
 and add documents to it with {@link org.apache.lucene.index.IndexWriter#addDocument(Iterable) addDocument()};</li>

 <li>
 Call <a href="../queryparser/org/apache/lucene/queryparser/classic/QueryParserBase.html#parse(java.lang.String)">QueryParser.parse()</a>
 to build a query from a string; and</li>

 <li>
 Create an {@link org.apache.lucene.search.IndexSearcher IndexSearcher}
 and pass the query to its {@link org.apache.lucene.search.IndexSearcher#search(org.apache.lucene.search.Query, int) search()}
 method.</li>
 </ol>
 Some simple examples of code which does this are:
 <ul>
 <li>
 &nbsp;<a href="../demo/src-html/org/apache/lucene/demo/IndexFiles.html">IndexFiles.java</a> creates an
 index for all the files contained in a directory.</li>

 <li>
 &nbsp;<a href="../demo/src-html/org/apache/lucene/demo/SearchFiles.html">SearchFiles.java</a> prompts for
 queries and searches an index.</li>
 </ul>
 To demonstrate these, try something like:
 <blockquote><tt>> <b>java -cp lucene-core.jar:lucene-demo.jar:lucene-analyzers-common.jar org.apache.lucene.demo.IndexFiles -index index -docs rec.food.recipes/soups</b></tt>
 <br><tt>adding rec.food.recipes/soups/abalone-chowder</tt>
 <br><tt>&nbsp; </tt>[ ... ]

 <p><tt>> <b>java -cp lucene-core.jar:lucene-demo.jar:lucene-queryparser.jar:lucene-analyzers-common.jar org.apache.lucene.demo.SearchFiles</b></tt>
 <br><tt>Query: <b>chowder</b></tt>
 <br><tt>Searching for: chowder</tt>
 <br><tt>34 total matching documents</tt>
 <br><tt>1. rec.food.recipes/soups/spam-chowder</tt>
 <br><tt>&nbsp; </tt>[ ... thirty-four documents contain the word "chowder" ... ]

 <p><tt>Query: <b>"clam chowder" AND Manhattan</b></tt>
 <br><tt>Searching for: +"clam chowder" +manhattan</tt>
 <br><tt>2 total matching documents</tt>
 <br><tt>1. rec.food.recipes/soups/clam-chowder</tt>
 <br><tt>&nbsp; </tt>[ ... two documents contain the phrase "clam chowder"
 and the word "manhattan" ... ]
 <br>&nbsp;&nbsp;&nbsp; [ Note: "+" and "-" are canonical, but "AND", "OR"
 and "NOT" may be used. ]</blockquote>

 </body>
 </html>
	<!--
	Licensed to the Apache Software Foundation (ASF) under one or more
	contributor license agreements. See the NOTICE file distributed with
	this work for additional information regarding copyright ownership.
	The ASF licenses this file to You under the Apache License, Version 2.0
	(the "License"); you may not use this file except in compliance with
	the License. You may obtain a copy of the License at

	http://www.apache.org/licenses/LICENSE-2.0

	Unless required by applicable law or agreed to in writing, software
	distributed under the License is distributed on an "AS IS" BASIS,
	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	See the License for the specific language governing permissions and
	limitations under the License.
	-->
	<html>
	<head>
	<title>Apache Lucene API</title>
	</head>
	<body>

	<p>Apache Lucene is a high-performance, full-featured text search engine library.
	Here's a simple example how to use Lucene for indexing and searching (using JUnit
	to check if the results are what we expect):</p>

	<!-- code comes from org.apache.lucene.TestDemo.
	See LUCENE-8481 for reasons why it's out of sync with the code.
	-->
	<pre class="prettyprint">
	Analyzer analyzer = new StandardAnalyzer();

	Path indexPath = Files.createTempDirectory("tempIndex");
	Directory directory = FSDirectory.open(indexPath)
	IndexWriterConfig config = new IndexWriterConfig(analyzer);
	IndexWriter iwriter = new IndexWriter(directory, config);
	Document doc = new Document();
	String text = "This is the text to be indexed.";
	doc.add(new Field("fieldname", text, TextField.TYPE_STORED));
	iwriter.addDocument(doc);
	iwriter.close();

	// Now search the index:
	DirectoryReader ireader = DirectoryReader.open(directory);
	IndexSearcher isearcher = new IndexSearcher(ireader);
	// Parse a simple query that searches for "text":
	QueryParser parser = new QueryParser("fieldname", analyzer);
	Query query = parser.parse("text");
	ScoreDoc[] hits = isearcher.search(query, 10).scoreDocs;
	assertEquals(1, hits.length);
	// Iterate through the results:
	for (int i = 0; i < hits.length; i++) {
	Document hitDoc = isearcher.doc(hits[i].doc);
	assertEquals("This is the text to be indexed.", hitDoc.get("fieldname"));
	}
	ireader.close();
	directory.close();
	IOUtils.rm(indexPath);</pre>
	<!-- ======================================================== -->



	<p>The Lucene API is divided into several packages:</p>

	<ul>
	<li>
	<b>{@link org.apache.lucene.analysis}</b>
	defines an abstract {@link org.apache.lucene.analysis.Analyzer Analyzer}
	API for converting text from a {@link java.io.Reader}
	into a {@link org.apache.lucene.analysis.TokenStream TokenStream},
	an enumeration of token {@link org.apache.lucene.util.Attribute Attribute}s.
	A TokenStream can be composed by applying {@link org.apache.lucene.analysis.TokenFilter TokenFilter}s
	to the output of a {@link org.apache.lucene.analysis.Tokenizer Tokenizer}.
	Tokenizers and TokenFilters are strung together and applied with an {@link org.apache.lucene.analysis.Analyzer Analyzer}.
	<a href="../analyzers-common/overview-summary.html">analyzers-common</a> provides a number of Analyzer implementations, including
	<a href="../analyzers-common/org/apache/lucene/analysis/core/StopAnalyzer.html">StopAnalyzer</a>
	and the grammar-based <a href="org/apache/lucene/analysis/standard/StandardAnalyzer.html">StandardAnalyzer</a>.</li>

	<li>
	<b>{@link org.apache.lucene.codecs}</b>
	provides an abstraction over the encoding and decoding of the inverted index structure,
	as well as different implementations that can be chosen depending upon application needs.

	<li>
	<b>{@link org.apache.lucene.document}</b>
	provides a simple {@link org.apache.lucene.document.Document Document}
	class.  A Document is simply a set of named {@link org.apache.lucene.document.Field Field}s,
	whose values may be strings or instances of {@link java.io.Reader}.</li>

	<li>
	<b>{@link org.apache.lucene.index}</b>
	provides two primary classes: {@link org.apache.lucene.index.IndexWriter IndexWriter},
	which creates and adds documents to indices; and {@link org.apache.lucene.index.IndexReader},
	which accesses the data in the index.</li>

	<li>
	<b>{@link org.apache.lucene.search}</b>
	provides data structures to represent queries (ie {@link org.apache.lucene.search.TermQuery TermQuery}
	for individual words, {@link org.apache.lucene.search.PhraseQuery PhraseQuery}
	for phrases, and {@link org.apache.lucene.search.BooleanQuery BooleanQuery}
	for boolean combinations of queries) and the {@link org.apache.lucene.search.IndexSearcher IndexSearcher}
	which turns queries into {@link org.apache.lucene.search.TopDocs TopDocs}.
	A number of <a href="../queryparser/overview-summary.html">QueryParser</a>s are provided for producing
	query structures from strings or xml.

	<li>
	<b>{@link org.apache.lucene.store}</b>
	defines an abstract class for storing persistent data, the {@link org.apache.lucene.store.Directory Directory},
	which is a collection of named files written by an {@link org.apache.lucene.store.IndexOutput IndexOutput}
	and read by an {@link org.apache.lucene.store.IndexInput IndexInput}.
	Multiple implementations are provided, but {@link org.apache.lucene.store.FSDirectory FSDirectory} is generally
	recommended as it tries to use operating system disk buffer caches efficiently.</li>

	<li>
	<b>{@link org.apache.lucene.util}</b>
	contains a few handy data structures and util classes, ie {@link org.apache.lucene.util.FixedBitSet FixedBitSet}
	and {@link org.apache.lucene.util.PriorityQueue PriorityQueue}.</li>
	</ul>
	To use Lucene, an application should:
	<ol>
	<li>
	Create {@link org.apache.lucene.document.Document Document}s by
	adding
	{@link org.apache.lucene.document.Field Field}s;</li>

	<li>
	Create an {@link org.apache.lucene.index.IndexWriter IndexWriter}
	and add documents to it with {@link org.apache.lucene.index.IndexWriter#addDocument(Iterable) addDocument()};</li>

	<li>
	Call <a href="../queryparser/org/apache/lucene/queryparser/classic/QueryParserBase.html#parse(java.lang.String)">QueryParser.parse()</a>
	to build a query from a string; and</li>

	<li>
	Create an {@link org.apache.lucene.search.IndexSearcher IndexSearcher}
	and pass the query to its {@link org.apache.lucene.search.IndexSearcher#search(org.apache.lucene.search.Query, int) search()}
	method.</li>
	</ol>
	Some simple examples of code which does this are:
	<ul>
	<li>
	<a href="../demo/src-html/org/apache/lucene/demo/IndexFiles.html">IndexFiles.java</a> creates an
	index for all the files contained in a directory.</li>

	<li>
	<a href="../demo/src-html/org/apache/lucene/demo/SearchFiles.html">SearchFiles.java</a> prompts for
	queries and searches an index.</li>
	</ul>
	To demonstrate these, try something like:
	<blockquote><tt>> <b>java -cp lucene-core.jar:lucene-demo.jar:lucene-analyzers-common.jar org.apache.lucene.demo.IndexFiles -index index -docs rec.food.recipes/soups</b></tt>
	<br><tt>adding rec.food.recipes/soups/abalone-chowder</tt>
	<br><tt>  </tt>[ ... ]

	<p><tt>> <b>java -cp lucene-core.jar:lucene-demo.jar:lucene-queryparser.jar:lucene-analyzers-common.jar org.apache.lucene.demo.SearchFiles</b></tt>
	<br><tt>Query: <b>chowder</b></tt>
	<br><tt>Searching for: chowder</tt>
	<br><tt>34 total matching documents</tt>
	<br><tt>1. rec.food.recipes/soups/spam-chowder</tt>
	<br><tt>  </tt>[ ... thirty-four documents contain the word "chowder" ... ]

	<p><tt>Query: <b>"clam chowder" AND Manhattan</b></tt>
	<br><tt>Searching for: +"clam chowder" +manhattan</tt>
	<br><tt>2 total matching documents</tt>
	<br><tt>1. rec.food.recipes/soups/clam-chowder</tt>
	<br><tt>  </tt>[ ... two documents contain the phrase "clam chowder"
	and the word "manhattan" ... ]
	<br>    [ Note: "+" and "-" are canonical, but "AND", "OR"
	and "NOT" may be used. ]</blockquote>

	</body>
	</html>