Dissecting The Nutch Crawler - Command "inject": net.nutch.db.WebDBInjector-优快云博客

本文详细介绍了Nutch爬虫中的注入模块(WebDBInjector)的使用方法及工作原理。该模块负责将新的URLs插入数据库中，支持从简单的URL列表文件或DMOZ RDF文件中读取数据。

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英文原文出处： DissectingTheNutchCrawler
转载本文请注明出处：http://blog.youkuaiyun.com/pwlazy

Command "inject": net.nutch.db.WebDBInjector

> "inject: inject new urls into the database"
> Usage: WebDBInjector<db_dir>(-urlfile<url_file>|-dmozfile<dmoz_file>)[-subset<subsetDenominator>][-includeAdultMaterial][-skewskew][-noDmozDesc][-topicFile<topiclistfile>][-topic<topic>[-topic<topic>[...]]]

WebDBInjector.main() accepts two input-type options. "-urlfile" parses a simple list ofURLs with oneURL per line. "-dmozfile" is for parsingDMOZRDF files, which is useful for bootstrapping a whole-web database.

Let's see how it works. Create a file with oneURL, then run "bin/nutch inject":

$ vi spam_url.txt 
$ bin/nutch inject spam -urlfile spam_url.txt
$ find spam -type file | xargs ls -l
-rw-r--r--  1 kangas  users    0 Oct 25 18:57 spam/dbreadlock
-rw-r--r--  1 kangas  users    0 Oct 25 18:57 spam/dbwritelock
-rw-r--r--  1 kangas  users   16 Oct 25 18:57 spam/webdb/linksByMD5/data
-rw-r--r--  1 kangas  users   16 Oct 25 18:57 spam/webdb/linksByMD5/index
-rw-r--r--  1 kangas  users   16 Oct 25 18:57 spam/webdb/linksByURL/data
-rw-r--r--  1 kangas  users   16 Oct 25 18:57 spam/webdb/linksByURL/index
-rw-r--r--  1 kangas  users   89 Oct 25 18:57 spam/webdb/pagesByMD5/data
-rw-r--r--  1 kangas  users   97 Oct 25 18:57 spam/webdb/pagesByMD5/index
-rw-r--r--  1 kangas  users  115 Oct 25 18:57 spam/webdb/pagesByURL/data
-rw-r--r--  1 kangas  users   58 Oct 25 18:57 spam/webdb/pagesByURL/index
-rw-r--r--  1 kangas  users   17 Oct 25 18:57 spam/webdb/stats

We can see that a new "stats" file was created, and the data/index files in the "pagesBy..." directories were modified.

命令：inject 对应net.nutch.db.WebDBInjector类
inject 将新的urls插入到数据库
调用方式： WebDBInjector<db_dir>(-urlfile<url_file>|-dmozfile<dmoz_file>)[-subset<subsetDenominator>][-includeAdultMaterial][-skewskew][-noDmozDesc][-topicFile<topiclistfile>][-topic<topic>[-topic<topic>[...]]]

WebDBInjector.main()方法接受两个输入选项。"-urlfile"以每行一个url的方式解析一个简单url列表。 "-dmozfile"用于解析DMOZRDF文件，后者用于启动基于整个web的数据库

然我看看命令是如何工作的，产生一个文件，填入url,然后运行bin/nutch inject