Solr is a standalone enterprise search server with a REST-like API. You put documents in it (called "indexing") via JSON, XML, CSV or binary over HTTP. You query it via HTTP GET and receive JSON, XML, CSV or binary results.
Features
Advanced Full-Text Search Capabilities
Optimized for High Volume Traffic
Standards Based Open Interfaces - XML, JSON and HTTP
Comprehensive Administration Interfaces
Easy Monitoring
Highly Scalable and Fault Tolerant
Flexible and Adaptable with easy configuration
Near Real-Time Indexing
Extensible Plugin Architecture
Schema when you want, schemaless when you don't
Powerful Extensions
Faceted Search and Filtering
Geospatial Search
Advanced Configurable Text Analysis
Highly Configurable and User Extensible Caching
Performance Optimizations
Secure Solr with SSL, Authentication and Role based Authorization
Advanced Storage Options (codecs, directories and more)
Monitorable Logging
Query Suggestions, Spelling and More
JSON, CSV, XML and more are supported out of the box.