Lucene 2.9 core API

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

See:
          Description

Packages
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.analysis.tokenattributes  
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.messages For Native Language Support (NLS), system of software internationalization.
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  

 

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(Version.LUCENE_CURRENT);

    // Store the index in memory:
    Directory directory = new RAMDirectory();
    // To store an index on disk, use this instead:
    //Directory directory = FSDirectory.open("/tmp/testindex");
    IndexWriter iwriter = new IndexWriter(directory, analyzer, true,
                                          new IndexWriter.MaxFieldLength(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.ANALYZED));
    iwriter.addDocument(doc);
    iwriter.close();
    
    // Now search the index:
    IndexSearcher isearcher = new IndexSearcher(directory, true)// read-only=true
    // Parse a simple query that searches for "text":
    QueryParser parser = new QueryParser("fieldname", analyzer);
    Query query = parser.parse("text");
    ScoreDoc[] hits = isearcher.search(query, null, 1000).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"));
    }
    isearcher.close();
    directory.close();

The Lucene API is divided into several packages:

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: 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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