Lucene – Analysis
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In one of our previous chapters, we have seen that Lucene uses IndexWriter to analyze the Document(s) using the Analyzer and then creates/open/edit indexes as required. In this chapter, we are going to discuss the various types of Analyzer objects and other relevant objects which are used during the analysis process. Understanding the Analysis process and how analyzers work will give you great insight over how Lucene indexes the documents.
Following is the list of objects that we”ll discuss in due course.
| S.No. | Class & Description |
|---|---|
| 1 | Token
Token represents text or word in a document with relevant details like its metadata (position, start offset, end offset, token type and its position increment). |
| 2 | TokenStream
TokenStream is an output of the analysis process and it comprises of a series of tokens. It is an abstract class. |
| 3 | Analyzer
This is an abstract base class for each and every type of Analyzer. |
| 4 | WhitespaceAnalyzer
This analyzer splits the text in a document based on whitespace. |
| 5 | SimpleAnalyzer
This analyzer splits the text in a document based on non-letter characters and puts the text in lowercase. |
| 6 | StopAnalyzer
This analyzer works just as the SimpleAnalyzer and removes the common words like ”a”, ”an”, ”the”, etc. |
| 7 | StandardAnalyzer
This is the most sophisticated analyzer and is capable of handling names, email addresses, etc. It lowercases each token and removes common words and punctuations, if any. |
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