2002-01-26 10:01:32 -05:00
|
|
|
<?xml version="1.0"?>
|
|
|
|
|
<document>
|
|
|
|
|
<properties>
|
|
|
|
|
<author email="acoliver@apache.org">Andrew C. Oliver</author>
|
2006-08-03 18:24:42 -04:00
|
|
|
<title>Apache Lucene - Basic Demo Sources Walk-through</title>
|
2002-01-26 10:01:32 -05:00
|
|
|
</properties>
|
|
|
|
|
<body>
|
|
|
|
|
|
|
|
|
|
<section name="About the Code">
|
|
|
|
|
<p>
|
2006-08-03 18:24:42 -04:00
|
|
|
In this section we walk through the sources behind the command-line Lucene demo: where to find them,
|
|
|
|
|
their parts and their function. This section is intended for Java developers wishing to understand
|
|
|
|
|
how to use Lucene in their applications.
|
2002-01-26 10:01:32 -05:00
|
|
|
</p>
|
|
|
|
|
</section>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<section name="Location of the source">
|
2006-08-03 18:24:42 -04:00
|
|
|
|
2002-01-26 10:01:32 -05:00
|
|
|
<p>
|
2006-08-03 18:24:42 -04:00
|
|
|
Relative to the directory created when you extracted Lucene or retrieved it from Subversion, you
|
|
|
|
|
should see a directory called <code>src</code> which in turn contains a directory called
|
|
|
|
|
<code>demo</code>. This is the root for all of the Lucene demos. Under this directory is
|
|
|
|
|
<code>org/apache/lucene/demo</code>. This is where all the Java sources for the demos live.
|
2002-01-26 10:01:32 -05:00
|
|
|
</p>
|
2006-08-03 18:24:42 -04:00
|
|
|
|
2002-01-26 10:01:32 -05:00
|
|
|
<p>
|
2006-08-03 18:24:42 -04:00
|
|
|
Within this directory you should see the <code>IndexFiles.java</code> class we executed earlier.
|
|
|
|
|
Bring it up in <code>vi</code> or your editor of choice and let's take a look at it.
|
2002-01-26 10:01:32 -05:00
|
|
|
</p>
|
2006-08-03 18:24:42 -04:00
|
|
|
|
2002-01-26 10:01:32 -05:00
|
|
|
</section>
|
|
|
|
|
|
|
|
|
|
<section name="IndexFiles">
|
2006-08-03 18:24:42 -04:00
|
|
|
|
2002-01-26 10:01:32 -05:00
|
|
|
<p>
|
2006-08-03 18:24:42 -04:00
|
|
|
As we discussed in the previous walk-through, the <code><a
|
|
|
|
|
href="api/org/apache/lucene/demo/IndexFiles.html">IndexFiles</a></code> class creates a Lucene
|
|
|
|
|
Index. Let's take a look at how it does this.
|
2002-01-26 10:01:32 -05:00
|
|
|
</p>
|
2006-08-03 18:24:42 -04:00
|
|
|
|
2002-01-26 10:01:32 -05:00
|
|
|
<p>
|
2006-08-03 18:24:42 -04:00
|
|
|
The first substantial thing the <code>main</code> function does is instantiate <code><a
|
|
|
|
|
href="api/org/apache/lucene/index/IndexWriter.html">IndexWriter</a></code>. It passes the string
|
|
|
|
|
"<code>index</code>" and a new instance of a class called <code><a
|
|
|
|
|
href="api/org/apache/lucene/analysis/standard/StandardAnalyzer.html">StandardAnalyzer</a></code>.
|
|
|
|
|
The "<code>index</code>" string is the name of the filesystem directory where all index information
|
|
|
|
|
should be stored. Because we're not passing a full path, this will be created as a subdirectory of
|
|
|
|
|
the current working directory (if it does not already exist). On some platforms, it may be created
|
|
|
|
|
in other directories (such as the user's home directory).
|
2002-01-26 10:01:32 -05:00
|
|
|
</p>
|
2006-08-03 18:24:42 -04:00
|
|
|
|
2002-01-26 10:01:32 -05:00
|
|
|
<p>
|
2006-08-03 18:24:42 -04:00
|
|
|
The <code><a href="api/org/apache/lucene/index/IndexWriter.html">IndexWriter</a></code> is the main
|
|
|
|
|
class responsible for creating indices. To use it you must instantiate it with a path that it can
|
|
|
|
|
write the index into. If this path does not exist it will first create it. Otherwise it will
|
|
|
|
|
refresh the index at that path. You can also create an index using one of the subclasses of <code><a
|
|
|
|
|
href="api/org/apache/lucene/store/Directory.html">Directory</a></code>. In any case, you must also pass an
|
|
|
|
|
instance of <code><a
|
|
|
|
|
href="api/org/apache/lucene/analysis/Analyzer.html">org.apache.lucene.analysis.Analyzer</a></code>.
|
2002-01-26 10:01:32 -05:00
|
|
|
</p>
|
2006-08-03 18:24:42 -04:00
|
|
|
|
2002-01-26 10:01:32 -05:00
|
|
|
<p>
|
2006-08-03 18:24:42 -04:00
|
|
|
The particular <code><a href="api/org/apache/lucene/analysis/Analyzer.html">Analyzer</a></code> we
|
|
|
|
|
are using, <code><a
|
|
|
|
|
href="api/org/apache/lucene/analysis/standard/StandardAnalyzer.html">StandardAnalyzer</a></code>, is
|
|
|
|
|
little more than a standard Java Tokenizer, converting all strings to lowercase and filtering out
|
|
|
|
|
useless words and characters from the index. By useless words and characters I mean common language
|
|
|
|
|
words such as articles (a, an, the, etc.) and other strings that would be useless for searching
|
|
|
|
|
(e.g. <b>'s</b>) . It should be noted that there are different rules for every language, and you
|
|
|
|
|
should use the proper analyzer for each. Lucene currently provides Analyzers for a number of
|
|
|
|
|
different languages (see the <code>*Analyzer.java</code> sources under <a
|
|
|
|
|
href="http://svn.apache.org/repos/asf/lucene/java/trunk/contrib/analyzers/src/java/org/apache/lucene/analysis/">contrib/analyzers/src/java/org/apache/lucene/analysis</a>).
|
2002-01-26 10:01:32 -05:00
|
|
|
</p>
|
2006-08-03 18:24:42 -04:00
|
|
|
|
2002-01-26 10:01:32 -05:00
|
|
|
<p>
|
2006-08-03 18:24:42 -04:00
|
|
|
Looking further down in the file, you should see the <code>indexDocs()</code> code. This recursive
|
|
|
|
|
function simply crawls the directories and uses <code><a
|
|
|
|
|
href="api/org/apache/lucene/demo/FileDocument.html">FileDocument</a></code> to create <code><a
|
|
|
|
|
href="api/org/apache/lucene/document/Document.html">Document</a></code> objects. The <code><a
|
|
|
|
|
href="api/org/apache/lucene/document/Document.html">Document</a></code> is simply a data object to
|
|
|
|
|
represent the content in the file as well as its creation time and location. These instances are
|
|
|
|
|
added to the <code>indexWriter</code>. Take a look inside <code><a
|
|
|
|
|
href="api/org/apache/lucene/demo/FileDocument.html">FileDocument</a></code>. It's not particularly
|
|
|
|
|
complicated. It just adds fields to the <code><a
|
|
|
|
|
href="api/org/apache/lucene/document/Document.html">Document</a></code>.
|
2002-01-26 10:01:32 -05:00
|
|
|
</p>
|
2006-08-03 18:24:42 -04:00
|
|
|
|
2002-01-26 10:01:32 -05:00
|
|
|
<p>
|
|
|
|
|
As you can see there isn't much to creating an index. The devil is in the details. You may also
|
2006-08-03 18:24:42 -04:00
|
|
|
wish to examine the other samples in this directory, particularly the <code><a
|
|
|
|
|
href="api/org/apache/lucene/demo/IndexHTML.html">IndexHTML</a></code> class. It is a bit more
|
|
|
|
|
complex but builds upon this example.
|
2002-01-26 10:01:32 -05:00
|
|
|
</p>
|
2006-08-03 18:24:42 -04:00
|
|
|
|
2002-01-26 10:01:32 -05:00
|
|
|
</section>
|
|
|
|
|
|
|
|
|
|
<section name="Searching Files">
|
2006-08-03 18:24:42 -04:00
|
|
|
|
2002-01-26 10:01:32 -05:00
|
|
|
<p>
|
2006-08-03 18:24:42 -04:00
|
|
|
The <code><a href="api/org/apache/lucene/demo/SearchFiles.html">SearchFiles</a></code> class is
|
|
|
|
|
quite simple. It primarily collaborates with an <code><a
|
|
|
|
|
href="api/org/apache/lucene/search/IndexSearcher.html">IndexSearcher</a></code>, <code><a
|
|
|
|
|
href="api/org/apache/lucene/analysis/standard/StandardAnalyzer.html">StandardAnalyzer</a></code>
|
|
|
|
|
(which is used in the <code><a
|
|
|
|
|
href="api/org/apache/lucene/demo/IndexFiles.html">IndexFiles</a></code> class as well) and a
|
|
|
|
|
<code><a href="api/org/apache/lucene/queryParser/QueryParser.html">QueryParser</a></code>. The
|
|
|
|
|
query parser is constructed with an analyzer used to interpret your query text in the same way the
|
|
|
|
|
documents are interpreted: finding the end of words and removing useless words like 'a', 'an' and
|
|
|
|
|
'the'. The <code><a href="api/org/apache/lucene/search/Query.html">Query</a></code> object contains
|
|
|
|
|
the results from the <code><a
|
|
|
|
|
href="api/org/apache/lucene/queryParser/QueryParser.html">QueryParser</a></code> which is passed to
|
|
|
|
|
the searcher. Note that it's also possible to programmatically construct a rich <code><a
|
|
|
|
|
href="api/org/apache/lucene/search/Query.html">Query</a></code> object without using the query
|
|
|
|
|
parser. The query parser just enables decoding the <a href="queryparsersyntax.html">Lucene query
|
|
|
|
|
syntax</a> into the corresponding <code><a
|
|
|
|
|
href="api/org/apache/lucene/search/Query.html">Query</a></code> object. The searcher results are
|
|
|
|
|
returned in a collection of Documents called <code><a
|
|
|
|
|
href="api/org/apache/lucene/search/Hits.html">Hits</a></code> which is then iterated through and
|
|
|
|
|
displayed to the user.
|
2002-01-26 10:01:32 -05:00
|
|
|
</p>
|
2006-08-03 18:24:42 -04:00
|
|
|
|
2002-01-26 10:01:32 -05:00
|
|
|
</section>
|
|
|
|
|
|
|
|
|
|
<section name="The Web example...">
|
2006-08-03 18:24:42 -04:00
|
|
|
|
2002-01-26 10:01:32 -05:00
|
|
|
<p>
|
|
|
|
|
<a href="demo3.html">read on>>></a>
|
|
|
|
|
</p>
|
2006-08-03 18:24:42 -04:00
|
|
|
|
2002-01-26 10:01:32 -05:00
|
|
|
</section>
|
|
|
|
|
|
|
|
|
|
</body>
|
|
|
|
|
</document>
|
|
|
|
|
|
