Search Framework

Apache Lucene

Apache Lucene is a high-performance, full-featured text search engine library written entirely in Java. It is a technology suitable for nearly any application that requires full-text search, especially cross-platform.

Carrot2

Carrot2 is an Open Source Search Results Clustering Engine. It can automatically organize (cluster) search results into thematic categories.

Carrot2 provides an architecture for acquiring search results from various sources (YahooAPI, GoogleAPI, MSN Search API, OpenSearch, Lucene index), clustering the results and visualising the clusters. Currently, 5 clustering algorithms are available that are suitable for different kinds of document clustering tasks.

MG4J

MG4J (Managing Gigabytes for Java) is a free full-text search engine for large document collections written in Java. MG4J is a highly customisable, high-performance, full-fledged search engine providing state-of-the-art features (such as BM25/BM25F scoring) and new research algorithms.

Sphinx

Sphinx is a full-text search engine, distributed under GPL version 2. Commercial license is also available for embedded use.

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Enhydra Snapper

Enhydra Snapper is a fulltext search library / framework in Java based on Apache Lucene to build search engine applications or integrate fulltext search into applications.