Crawler Plugins hook into the crawling process in order to add advanced functionality.

Some examples:

• Modify the result of preparators
  • by specifying default-values if the chosen preparator does not fill in a certain field (onBeforePrepare)
  • by overriding or modyfing the results of whatever preparator was chosen (onAfterPrepare)
• Modify their storage in the lucene index
• Do sth at every start or end of the crawling process (e.g. inform the administrator via email)

1. Create a class that implements CrawlerPlugin.
2. Packaged it (and all its dependencies) as a .jar
   • In the manifest file, the attribute Plugin-Class must be set to the complete class name of the implementing class.
3. Drop it into the plugins-Directory.

void onStartCrawling(Crawler crawler)

Called before the crawling process starts (Crawler::run()).

This may be called multiple times during the lifetime of a plugin instance, but onFinishCrawling() is always called in between.

Parameters: crawler The crawler instance that is about to begin crawling

• Create Thumbnails of indexed documents: https://github.com/benjamin4ruby/java-thumbnailer