Overview (Lucene 2.4.1 API)
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# Lucene 2.4.1 API

Apache Lucene is a high-performance, full-featured text search engine library.

See:
Description

Core
org.apache.lucene | Top-level package.
org.apache.lucene.analysis | API and code to convert text into indexable/searchable tokens.
org.apache.lucene.analysis.standard | A fast grammar-based tokenizer constructed with JFlex.
org.apache.lucene.document | The logical representation of a `Document` for indexing and searching.
org.apache.lucene.index | Code to maintain and access indices.
org.apache.lucene.queryParser | A simple query parser implemented with JavaCC.
org.apache.lucene.search | Code to search indices.
org.apache.lucene.search.function | Programmatic control over documents scores.
org.apache.lucene.search.payloads | The payloads package provides Query mechanisms for finding and using payloads.
org.apache.lucene.search.spans | The calculus of spans.
org.apache.lucene.store | Binary i/o API, used for all index data.
org.apache.lucene.util | Some utility classes.
org.apache.lucene.util.cache |

Demo
org.apache.lucene.demo |
org.apache.lucene.demo.html |

contrib: Analysis
org.apache.lucene.analysis.br | Analyzer for Brazilian.
org.apache.lucene.analysis.cjk | Analyzer for Chinese, Japanese and Korean.
org.apache.lucene.analysis.cn | Analyzer for Chinese.
org.apache.lucene.analysis.compound | A filter that decomposes compound words you find in many Germanic languages to the word parts.
org.apache.lucene.analysis.compound.hyphenation | The code for the compound word hyphenation is taken from the Apache FOP project.
org.apache.lucene.analysis.cz | Analyzer for Czech.
org.apache.lucene.analysis.de | Analyzer for German.
org.apache.lucene.analysis.el | Analyzer for Greek.
org.apache.lucene.analysis.fr | Analyzer for French.
org.apache.lucene.analysis.miscellaneous |
org.apache.lucene.analysis.ngram |
org.apache.lucene.analysis.nl | Analyzer for Dutch.
org.apache.lucene.analysis.payloads | Provides various convenience classes for creating payloads on Tokens.
org.apache.lucene.analysis.query |
org.apache.lucene.analysis.ru | Analyzer for Russian.
org.apache.lucene.analysis.shingle |
org.apache.lucene.analysis.sinks | Implementations of the SinkTokenizer that might be useful.
org.apache.lucene.analysis.th |

contrib: Ant
org.apache.lucene.ant | Ant task to create Lucene indexes.

contrib: Benchmark
org.apache.lucene.benchmark |
org.apache.lucene.benchmark.byTask | Benchmarking Lucene By Tasks.
org.apache.lucene.benchmark.byTask.feeds | Sources for benchmark inputs: documents and queries.
org.apache.lucene.benchmark.byTask.programmatic | Sample performance test written programatically - no algorithm file is needed here.
org.apache.lucene.benchmark.byTask.stats | Statistics maintained when running benchmark tasks.
org.apache.lucene.benchmark.byTask.tasks | Extendable benchmark tasks.
org.apache.lucene.benchmark.byTask.utils | Utilities used for the benchmark, and for the reports.
org.apache.lucene.benchmark.quality | Search Quality Benchmarking.
org.apache.lucene.benchmark.quality.trec | Utilities for Trec related quality benchmarking, feeding from Trec Topics and QRels inputs.
org.apache.lucene.benchmark.quality.utils | Miscellaneous utilities for search quality benchmarking: query parsing, submission reports.
org.apache.lucene.benchmark.standard |
org.apache.lucene.benchmark.stats |
org.apache.lucene.benchmark.utils |

contrib: DB
com.sleepycat.db |
org.apache.lucene.store.db |
org.apache.lucene.store.je |

contrib: Highlighter
org.apache.lucene.search.highlight | The highlight package contains classes to provide "keyword in context" features typically used to highlight search terms in the text of results pages.

contrib: Instantiated
org.apache.lucene.store.instantiated | InstantiatedIndex, alternative RAM store for small corpora.

contrib: Lucli
lucli | Lucene Command Line Interface

contrib: Memory
org.apache.lucene.index.memory | High-performance single-document main memory Apache Lucene fulltext search index.

contrib: Miscellaneous
org.apache.lucene.misc |
org.apache.lucene.queryParser.analyzing |
org.apache.lucene.queryParser.precedence |

contrib: Queries
org.apache.lucene.search.similar | Document similarity query generators.

contrib: RegEx
org.apache.lucene.search.regex | Regular expression Query.
org.apache.regexp | This package exists to allow access to useful package protected data within Jakarta Regexp.

contrib: Snowball
org.apache.lucene.analysis.snowball | `TokenFilter` and `Analyzer` implementations that use Snowball stemmers.

contrib: SpellChecker
org.apache.lucene.search.spell | Suggest alternate spellings for words.

contrib: Surround Parser
org.apache.lucene.queryParser.surround.parser | This package contains the QueryParser.jj source file for the Surround parser.
org.apache.lucene.queryParser.surround.query | This package contains SrndQuery and its subclasses.

contrib: Swing
org.apache.lucene.swing.models | Decorators for JTable TableModel and JList ListModel encapsulating Lucene indexing and searching functionality.

contrib: Wikipedia
org.apache.lucene.wikipedia.analysis |

contrib: WordNet
org.apache.lucene.wordnet | This package uses synonyms defined by WordNet to build a Lucene index storing them, which in turn can be used for query expansion.

contrib: XML Query Parser
org.apache.lucene.xmlparser |
org.apache.lucene.xmlparser.builders |

Other Packages
org.tartarus.snowball |
org.tartarus.snowball.ext |

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):

`Analyzer analyzer = new StandardAnalyzer(); // Store the index in memory: Directory directory = new RAMDirectory(); // To store an index on disk, use this instead: //Directory directory = FSDirectory.getDirectory("/tmp/testindex"); IndexWriter iwriter = new IndexWriter(directory, analyzer, true); iwriter.setMaxFieldLength(25000); Document doc = new Document(); String text = "This is the text to be indexed."; doc.add(new Field("fieldname", text, Field.Store.YES, Field.Index.TOKENIZED)); iwriter.addDocument(doc); iwriter.optimize(); iwriter.close(); // Now search the index: IndexSearcher isearcher = new IndexSearcher(directory); // Parse a simple query that searches for "text": QueryParser parser = new QueryParser("fieldname", analyzer); Query query = parser.parse("text"); Hits hits = isearcher.search(query); assertEquals(1, hits.length()); // Iterate through the results: for (int i = 0; i < hits.length(); i++) { Document hitDoc = hits.doc(i); assertEquals("This is the text to be indexed.", hitDoc.get("fieldname")); } isearcher.close(); directory.close();`

The Lucene API is divided into several packages:

- org.apache.lucene.analysis defines an abstract Analyzer API for converting text from a java.io.Reader into a TokenStream, an enumeration of Tokens. A TokenStream is composed by applying TokenFilters to the output of a Tokenizer. A few simple implemenations are provided, including StopAnalyzer and the grammar-based StandardAnalyzer.
- org.apache.lucene.document provides a simple Document class. A document is simply a set of named Fields, whose values may be strings or instances of java.io.Reader.
- org.apache.lucene.index provides two primary classes: IndexWriter, which creates and adds documents to indices; and IndexReader, which accesses the data in the index.
- org.apache.lucene.search provides data structures to represent queries (TermQuery for individual words, PhraseQuery for phrases, and BooleanQuery for boolean combinations of queries) and the abstract Searcher which turns queries into Hits. IndexSearcher implements search over a single IndexReader.
- org.apache.lucene.queryParser uses JavaCC to implement a QueryParser.
- org.apache.lucene.store defines an abstract class for storing persistent data, the Directory, a collection of named files written by an IndexOutput and read by an IndexInput. Two implementations are provided, FSDirectory, which uses a file system directory to store files, and RAMDirectory which implements files as memory-resident data structures.
- org.apache.lucene.util contains a few handy data structures, e.g., BitVector and PriorityQueue.

To use Lucene, an application should:

1. Create Documents by adding Fields;
2. Create an IndexWriter and add documents to it with addDocument();
3. Call QueryParser.parse() to build a query from a string; and
4. Create an IndexSearcher and pass the query to its search() method.

Some simple examples of code which does this are:

- FileDocument.java contains code to create a Document for a file.
- IndexFiles.java creates an index for all the files contained in a directory.
- DeleteFiles.java deletes some of these files from the index.
- SearchFiles.java prompts for queries and searches an index.

To demonstrate these, try something like:

> `> java -cp lucene.jar:lucene-demo.jar org.apache.lucene.demo.IndexFiles rec.food.recipes/soups`
> `adding rec.food.recipes/soups/abalone-chowder`
> `` [ ... ]

> `> java -cp lucene.jar:lucene-demo.jar org.apache.lucene.demo.SearchFiles`
> `Query: chowder`
> `Searching for: chowder`
> `34 total matching documents`
> `1. rec.food.recipes/soups/spam-chowder`
> `` [ ... thirty-four documents contain the word "chowder" ... ]

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

The IndexHTML demo is more sophisticated. It incrementally maintains an index of HTML files, adding new files as they appear, deleting old files as they disappear and re-indexing files as they change.

> `> java -cp lucene.jar:lucene-demo.jar org.apache.lucene.demo.IndexHTML -create java/jdk1.1.6/docs/relnotes`
> `adding java/jdk1.1.6/docs/relnotes/SMICopyright.html`
> `` [ ... create an index containing all the relnotes ]

> `> rm java/jdk1.1.6/docs/relnotes/smicopyright.html`

> `> java -cp lucene.jar:lucene-demo.jar org.apache.lucene.demo.IndexHTML java/jdk1.1.6/docs/relnotes`
> `deleting java/jdk1.1.6/docs/relnotes/SMICopyright.html`

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