Nutch 1.3 学习笔记 10-2 插件扩展

Nutch 1.3 学习笔记 插件扩展 10-2

---------------------------------

1. 自己扩展一个简单的插件

这里扩展一个Nutch的URLFilter插件，叫MyURLFilter

1.1 生成一个Package

首先生成一个与urlfilter-regex类似的包结构

如org.apache.nutch.urlfilter.my

1.2 在这个包中生成相应的扩展文件

再生成一个MyURLFilter.java文件，内容如下：

package org.apache.nutch.urlfilter.my;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

import org.apache.hadoop.conf.Configuration;
import org.apache.nutch.net.URLFilter;
import org.apache.nutch.urlfilter.prefix.PrefixURLFilter;

public class MyURLFilter implements URLFilter{   // 这里的继承自Nutch的URLFilter扩展
	private Configuration conf;
	
	public MyURLFilter()
	{}
	@Override
	public String filter(String urlString) {  // 对url字符串进行过滤
		// TODO Auto-generated method stub
		return "My Filter:"+ urlString;
	}

	@Override
	public Configuration getConf() {
		// TODO Auto-generated method stub
		return this.conf;
	}

	@Override
	public void setConf(Configuration conf) {
		// TODO Auto-generated method stub
		this.conf = conf;
	}
	
	public static void main(String[] args) throws IOException
	{
		 
		MyURLFilter filter = new MyURLFilter();
	    
	    BufferedReader in=new BufferedReader(new InputStreamReader(System.in));
	    String line;
	    while((line=in.readLine())!=null) {
	      String out=filter.filter(line);
	      if(out!=null) {
	        System.out.println(out);
	      }
	    }
	}

}

1.3 打包成jar包并生成相应的plugin.xml文件

打包可以用ivy或者是eclipse来打，每一个plugin都有一个描述文件plugin.xml，内容如下：

<plugin
   id="urlfilter-my"
   name="My URL Filter"
   version="1.0.0"
   provider-name="nutch.org">

   <runtime>
      <library name="urlfilter-my.jar">
         <export name="*"/>
      </library>
	<!-- 如果这里你的插件有依赖第三方库的话，可以这样写
      <library name="fontbox-1.4.0.jar"/>
      <library name="geronimo-stax-api_1.0_spec-1.jar"/>
	  -->
   </runtime>

   <requires>
      <import plugin="nutch-extensionpoints"/>
   </requires>

   <extension id="org.apache.nutch.net.urlfilter.my"
              name="Nutch My URL Filter"
              point="org.apache.nutch.net.URLFilter">
      <implementation id="MyURLFilter"
                      class="org.apache.nutch.urlfilter.prefix.MyURLFilter"/>
      <!-- by default, attribute "file" is undefined, to keep classic behavior.
      <implementation id="PrefixURLFilter"
                      class="org.apache.nutch.net.PrefixURLFilter">
        <parameter name="file" value="urlfilter-prefix.txt"/>
      </implementation>
      -->
   </extension>

</plugin>

1.4 把需要的包与配置文件放入plugins目录中

最后把打好的jar包与plugin.xml放到一个urlfilter-my文件夹中，再把这个文件夹到到nutch的plugins目录下

2. 使用bin/nutch plugin来进行测试

在运行bin/nutch plugin命令之前你要修改一下nutch-site.xml这个配置文件，在下面加入我们写的插件，如下

<property>
  <name>plugin.includes</name>
  <value>protocol-http|urlfilter-(regex|prefix|my)|parse-(html|tika)|index-(basic|anchor)|scoring-opic|urlnormalizer-(pass|regex|basic)</value>
  <description>Regular expression naming plugin directory names to
  include.  Any plugin not matching this expression is excluded.
  In any case you need at least include the nutch-extensionpoints plugin. By
  default Nutch includes crawling just HTML and plain text via HTTP,
  and basic indexing and search plugins. In order to use HTTPS please enable 
  protocol-httpclient, but be aware of possible intermittent problems with the 
  underlying commons-httpclient library.
  </description>
</property>

在本机测试结果如下：

lemo@debian:~/Workspace/java/Apache/Nutch/nutch-1.3$ bin/nutch plugin urlfilter-my org.apache.nutch.urlfilter.my.MyURLFilter
        urlString1
        My Filter:urlString1
        urlString2
        My Filter:urlString2

3. 总结

这里只是写了一个简单的插件，当然你可以根据你的需求写出更加复杂的插件.

4. 参考

http://wiki.apache.org/nutch/WritingPluginExample#The_Example