Hi,Andrzej Thank you for your detail answers.I have understood it uses.[?]
2012/4/10 Andrzej Bialecki <[email protected]> > On 10/04/2012 05:00, Xiaolong Yang wrote: > >> Hiļ¼all >> >> I'm reading source code of nutch and I have some puzzled about the >> ObjectCache.java in package org.apache.nutch.util.I just find it may be >> little benefit to use it in urlnormalizers and urlfiters.I also have >> read some discuss about cache in Nutch-169 and Nutch-501.But I can't >> understand it. >> >> Can anyone tell me where ObjectCache be used and get a good benefit in >> nutch ? >> > > ObjectCache is designed to cache ready-to-use instances of Nutch plugins. > The process of finding, instantiating and initializing plugins is > inefficient, because it involves parsing plugin descriptors, initializing > plugins, collecting the ones that implement correct extension points, etc. > > It would kill performance if this process were invoked each time you want > to run all plugins of a given type (e.g. URLNormalizer-s). The facade > URLNormalizers/URLFilters and others make sure that plugin instances of a > given type are initialized once per lifetime of a JVM, and then they are > cached in ObjectCache, so that next time you want to use them they can be > retrieved from a cache, instead of going again through the process of > parsing/instantiating/**initializing. > > -- > Best regards, > Andrzej Bialecki <>< > ___. ___ ___ ___ _ _ ______________________________**____ > [__ || __|__/|__||\/| Information Retrieval, Semantic Web > ___|||__|| \| || | Embedded Unix, System Integration > http://www.sigram.com Contact: info at sigram dot com > >
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