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第四章      分词

时间:2014-09-09 13:48:09      阅读:250      评论:0      收藏:0      [点我收藏+]

标签:lucene

4.1 分词器的核心类

1. Analyzer

       Lucene内置分词器SimpleAnalyzerStopAnalyzerWhitespaceAnalyzerStandardAnalyzer

主要作用:

KeywordAnalyzer分词,没有任何变化;

SimpleAnalyzer对中文效果太差;

StandardAnalyzer对中文单字拆分;

StopAnalyzerSimpleAnalyzer差不多;

WhitespaceAnalyzer只按空格划分。

 

2. TokenStream

分词器做好处理之后得到的一个流,这个流中存储了分词的各种信息,可以通过TokenStream有效的获取到分词单元信息

生成的流程

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在这个流中所需要存储的数据

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3. Tokenizer

主要负责接收字符流Reader,Reader进行分词操作。有如下一些实现类

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4. TokenFilter

将分词的语汇单元,进行各种各样过滤

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5.扩展:TokenFilter各类介绍:

(1),TokenFilter

输入参数为另一个TokerStreamTokerStream,其子类必须覆盖incrementToken()函数。

 

(2),LowerCaseFilter

Token分词转换为小写。

 

(3),FilteringTokenFilter

 

TokenFilters的一个抽象类,可能会删除分词。如果当前分词要保存,则需要实现accept()方法

并返回一个boolean值。incrementToken()方法将调用accept()方法来决定是否将当前的分词返回

给调用者。

 

(4),StopFilter

token stream中移除停止词(stop words.

protected boolean accept() {
     return!stopWords.contains(termAtt.buffer(), 0, termAtt.length());//返回不是stop word的分词
 }

(5),TypeTokenFilter

token stream中移除指定类型的分词。

protected boolean accept() {
     returnuseWhiteList == stopTypes.contains(typeAttribute.type());
}

(6),LetterTokenizer

是一个编译器,将文本在非字母。说,它定义了令牌的最大字符串相邻的字母

 

 

(7),TokenFilter的顺序问题

此时停止词 the 就未被去除了。先全部转换为小写字母,再过滤停止词(The 转换成 the 才可以与停止词词组里的 the 匹配),如果不限制大小写,停止词的组合就太多了。

import java.io.Reader;
import java.util.Set;
import org.apache.lucene.analysis.Analyzer;
importorg.apache.lucene.analysis.LetterTokenizer;
importorg.apache.lucene.analysis.LowerCaseFilter;
import org.apache.lucene.analysis.StopAnalyzer;
import org.apache.lucene.analysis.StopFilter;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.util.Version;
public class MyStopAnalyzer extends Analyzer {
  privateSet<Object> words;
  publicMyStopAnalyzer(){}
  publicMyStopAnalyzer(String[] words ){
     this.words=StopFilter.makeStopSet(Version.LUCENE_35,words, true);
     this.words.addAll(StopAnalyzer.ENGLISH_STOP_WORDS_SET)
  }
 
  @Override
  publicTokenStream tokenStream(String fieldName, Reader reader) {
     // TODO Auto-generatedmethod stub
     return newStopFilter(Version.LUCENE_35,new LowerCaseFilter(Version.LUCENE_35, newLetterTokenizer(Version.LUCENE_35,reader)),this.words);
  }
}

4.2Attribute

public static void displayAllTokenInfo(Stringstr,Analyzer a) {
           try{
                 TokenStreamstream = a.tokenStream("content",new StringReader(str));
                 //位置增量的属性,存储语汇单元之间的距离
                 PositionIncrementAttributepia = 
                                  stream.addAttribute(PositionIncrementAttribute.class);
                 //每个语汇单元的位置偏移量
                 OffsetAttributeoa = 
                                  stream.addAttribute(OffsetAttribute.class);
                 //存储每一个语汇单元的信息(分词单元信息)
                 CharTermAttributecta = 
                                  stream.addAttribute(CharTermAttribute.class);
                 //使用的分词器的类型信息
                 TypeAttributeta = 
                                  stream.addAttribute(TypeAttribute.class);
                 for(;stream.incrementToken();){
                      System.out.print(pia.getPositionIncrement()+":");
                      System.out.print(cta+"["+oa.startOffset()+"-"+oa.endOffset()+"]-->"+ta.type()+"\n");
                 }
           }catch (Exception e) {
                 e.printStackTrace();
           }
      }

4.3 自定义分词器

1.自定义Stop分词器

package com.mzsx.analyzer;
 
import java.io.Reader;
import java.util.Set;
 
import org.apache.lucene.analysis.Analyzer;
importorg.apache.lucene.analysis.LetterTokenizer;
importorg.apache.lucene.analysis.LowerCaseFilter;
import org.apache.lucene.analysis.StopAnalyzer;
import org.apache.lucene.analysis.StopFilter;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.util.Version;
 
public class MyStopAnalyzer extends Analyzer {
      privateSet<Object> words;
      publicMyStopAnalyzer(){}
      publicMyStopAnalyzer(String[] words ){
           this.words=StopFilter.makeStopSet(Version.LUCENE_35,words, true);
           this.words.addAll(StopAnalyzer.ENGLISH_STOP_WORDS_SET);
           
      }
 
      @Override
      publicTokenStream tokenStream(String fieldName, Reader reader) {
           returnnew StopFilter(Version.LUCENE_35,new LowerCaseFilter(Version.LUCENE_35, newLetterTokenizer(Version.LUCENE_35,reader)),this.words);
      }
}
//测试代码
@Test
      publicvoid myStopAnalyzer() {
           Analyzera1 = new MyStopAnalyzer(new String[]{"I","you","hate"});
           Analyzera2 = new MyStopAnalyzer();
           Stringtxt = "how are you thank you I hate you";
           AnalyzerUtils.displayAllTokenInfo(txt,a1);
           //AnalyzerUtils.displayToken(txt,a2);
      }


 

2.简单实现同义词索引

package com.mzsx.analyzer;
 
public interface SamewordContext {
      publicString[] getSamewords(String name);
}
package com.mzsx.analyzer;
 
import java.util.HashMap;
import java.util.Map;
 
public class SimpleSamewordContext implementsSamewordContext {
      
      Map<String,String[]>maps = new HashMap<String,String[]>();
      publicSimpleSamewordContext() {
           maps.put("中国",new String[]{"天朝","大陆"});
           maps.put("我",new String[]{"咱","俺"});
           maps.put("china",new String[]{"chinese"});
      }
 
      @Override
      publicString[] getSamewords(String name) {
           returnmaps.get(name);
      }
}
package com.mzsx.analyzer;
 
import java.io.IOException;
import java.util.Stack;
 
import org.apache.lucene.analysis.TokenFilter;
import org.apache.lucene.analysis.TokenStream;
importorg.apache.lucene.analysis.tokenattributes.CharTermAttribute;
importorg.apache.lucene.analysis.tokenattributes.PositionIncrementAttribute;
import org.apache.lucene.util.AttributeSource;
 
public class MySameTokenFilter extendsTokenFilter {
      privateCharTermAttribute cta = null;
      privatePositionIncrementAttribute pia = null;
      privateAttributeSource.State current;
      privateStack<String> sames = null;
      privateSamewordContext samewordContext;
 
      protectedMySameTokenFilter(TokenStream input,SamewordContext samewordContext) {
           super(input);
           cta= this.addAttribute(CharTermAttribute.class);
           pia= this.addAttribute(PositionIncrementAttribute.class);
           sames= new Stack<String>();
           this.samewordContext= samewordContext;
      }
 
      @Override
      publicboolean incrementToken() throws IOException {
           if(sames.size()>0){
                 //将元素出栈,并且获取这个同义词
                 Stringstr = sames.pop();
                 //还原状态
                 restoreState(current);
                 cta.setEmpty();
                 cta.append(str);
                 //设置位置0
                 pia.setPositionIncrement(0);
                 returntrue;
           }
           
           if(!this.input.incrementToken())return false;
           
           if(addSames(cta.toString())){
                 //如果有同义词将当前状态先保存
                 current= captureState();
           }
           returntrue;
      }
      
      privateboolean addSames(String name) {
           String[]sws = samewordContext.getSamewords(name);
           if(sws!=null){
                 for(Stringstr:sws) {
                      sames.push(str);
                 }
                 returntrue;
           }
           returnfalse;
      }
}
package com.mzsx.analyzer;
 
import java.io.Reader;
 
import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.TokenStream;
 
import com.chenlb.mmseg4j.Dictionary;
import com.chenlb.mmseg4j.MaxWordSeg;
importcom.chenlb.mmseg4j.analysis.MMSegTokenizer;
 
public class MySameAnalyzer extends Analyzer {
      privateSamewordContext samewordContext;
      
      publicMySameAnalyzer(SamewordContext swc) {
           samewordContext= swc;
      }
 
      @Override
      publicTokenStream tokenStream(String fieldName, Reader reader) {
           Dictionarydic = Dictionary.getInstance("D:/luceneIndex/dic");
           returnnew MySameTokenFilter(
                      newMMSegTokenizer(new MaxWordSeg(dic), reader),samewordContext);
      }
 
}
//测试代码
@Test
      publicvoid testSameAnalyzer() {
           try{
                 Analyzera2 = new MySameAnalyzer(new SimpleSamewordContext());
                 Stringtxt = "我来自中国海南儋州第一中学,welcome to china !";
                 Directorydir = new RAMDirectory();
                 IndexWriterwriter = new IndexWriter(dir,new IndexWriterConfig(Version.LUCENE_35, a2));
                 Documentdoc = new Document();
                 doc.add(newField("content",txt,Field.Store.YES,Field.Index.ANALYZED));
                 writer.addDocument(doc);
                 writer.close();
                 IndexSearchersearcher = new IndexSearcher(IndexReader.open(dir));
                 TopDocstds = searcher.search(new TermQuery(new Term("content","咱")),10);
                 Documentd = searcher.doc(tds.scoreDocs[0].doc);
                 System.out.println("原文:"+d.get("content"));
                 AnalyzerUtils.displayAllTokenInfo(txt,a2);
           }catch (CorruptIndexException e) {
                 e.printStackTrace();
           }catch (LockObtainFailedException e) {
                 e.printStackTrace();
           }catch (IOException e) {
                 e.printStackTrace();
           }
      }









本文出自 “梦朝思夕” 博客,请务必保留此出处http://qiangmzsx.blog.51cto.com/2052549/1549902

第四章      分词

标签:lucene

原文地址:http://qiangmzsx.blog.51cto.com/2052549/1549902

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