转：Nutch中Analysis包下的NutchAnalysis.jj详细解读

Nutch需要对抓取回来的网页进行分析，但是传统的编写分析太麻烦，这里用了一个很方便的javacc工具来方便编写分析的java(javacc会自动

根据.jj文件生成java文件),如果您对于javacc的语法不甚了解的话不妨先看看javacc的语法，在这里也会对原代码进行比较详细的注释。用户

如果要给nutch添加中文分词，都可以从这个文件着手。
NutchAnalysis.jj:
/**
 * Copyright 2005 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/** JavaCC code for the Nutch lexical analyzer. */
options {//javacc允许用户在编译的时候添加参数,也可以在这里指定
  STATIC = false;//javacc默认的是所有的在这里的函数都是static的，但是这部允许多个实例，尽管增快的速度，但是不符合nutch多线程

的需求，所以设定为false
  USER_CHAR_STREAM = true;//默认的是false,会在输出的时候转换为Java Unicode(/u...),设置为true表明要从CharStream.java中读取编码

（实现在FastCharStream.java）
  OPTIMIZE_TOKEN_MANAGER = true;//用于token管理的最佳化
  UNICODE_INPUT = true;//设定输入流为unicode
//DEBUG_TOKEN_MANAGER = true;//默认为false,打开debug来跟踪错误，编译的时候会生成一个跟踪文件(trace)
}
PARSER_BEGIN(NutchAnalysis)//类名
package org.apache.nutch.analysis;
import java.io.StringReader;
import org.apache.hadoop.conf.Configuration;
import org.apache.nutch.searcher.Query;
import org.apache.nutch.searcher.QueryFilters;
import org.apache.nutch.searcher.Query.Clause;
import org.apache.nutch.util.NutchConfiguration;
import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.StopFilter;
import org.apache.lucene.analysis.TokenStream;
import java.io.*;
import java.util.*;
/** The JavaCC-generated Nutch lexical analyzer and query parser. */
public class NutchAnalysis {
  private static final String[] STOP_WORDS = {
    "a", "and", "are", "as", "at", "be", "but", "by",
    "for", "if", "in", "into", "is", "it",
    "no", "not", "of", "on", "or", "s", "such",
    "t", "that", "the", "their", "then", "there", "these",
    "they", "this", "to", "was", "will", "with"
  };
  private static final Set STOP_SET = StopFilter.makeStopSet(STOP_WORDS);
  private Analyzer analyzer = null;
  private String queryString;
  private QueryFilters queryFilters;
 
  /** Constructs a nutch analysis. */
  public NutchAnalysis(String query, Analyzer analyzer) {
    this(new FastCharStream(new StringReader(query)));
    this.analyzer = analyzer;
  }
  /** True iff word is a stop word.  Stop words are only removed from queries.
   * Every word is indexed.  */
  public static boolean isStopWord(String word) {
    return STOP_SET.contains(word);
  }
  /** Construct a query parser for the text in a reader. */
  public static Query parseQuery(String queryString, Configuration conf) throws IOException {
    return parseQuery(queryString, null, conf);
  }
  /** Construct a query parser for the text in a reader. */
  public static Query parseQuery(String queryString, Analyzer analyzer, Configuration conf)
    throws IOException {
    NutchAnalysis parser = new NutchAnalysis(
          queryString, (analyzer != null) ? analyzer : new NutchDocumentAnalyzer(conf));
    parser.queryString = queryString;
    parser.queryFilters = new QueryFilters(conf);
    return parser.parse(conf);//parse在下面定义，javacc语法
  }
  /** For debugging. */
  public static void main(String[] args) throws Exception {
    BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
    while (true) {
      System.out.print("Query: ");
      String line = in.readLine();
      System.out.println(parseQuery(line, NutchConfiguration.create()));
    }
  }
}
PARSER_END(NutchAnalysis)
TOKEN_MGR_DECLS : {//设置一个所有分析函数都可以用的变量或者函数,将自动生成NutchAnalysisTokenManager.java
  /** Constructs a token manager for the provided Reader. */
  public NutchAnalysisTokenManager(Reader reader) {
    this(new FastCharStream(reader));
  }
}
TOKEN : {       // token regular expressions
  // basic word -- lowercase it
<WORD: ((<LETTER>|<DIGIT>|<WORD_PUNCT>)+ | <IRREGULAR_WORD>)>//WORD可以是LETTER,DIGIT,WORD_PUNCT的一个或多个或者

IRREGULAR_WORD（为避免同其他分词混淆，特意订制了C++ C#）见下方定义：
  { matchedToken.image = matchedToken.image.toLowerCase(); }//符合WORD的调用这个方法
  // special handling for acronyms: U.S.A., I.B.M., etc: dots are removed
| <ACRONYM: <LETTER> "." (<LETTER> ".")+ >
    {                                             // 去掉.
      for (int i = 0; i < image.length(); i++) {
 if (image.charAt(i) == '.')
   image.deleteCharAt(i--);
      }
      matchedToken.image = image.toString().toLowerCase();
    }
  // chinese, japanese and korean characters
| <SIGRAM: <CJK> >
   // irregular words
| <#IRREGULAR_WORD: (<C_PLUS_PLUS>|<C_SHARP>)>
| <#C_PLUS_PLUS: ("C"|"c") "++" >
| <#C_SHARP: ("C"|"c") "#" >
  // query syntax characters
| <PLUS: "+" >
| <MINUS: "-" >
| <QUOTE: "/"" >
| <COLON: ":" >
| <SLASH: "/" >
| <DOT: "." >
| <ATSIGN: "@" >
| <APOSTROPHE: "'" >
| <WHITE: ~[] >                                   // treat unrecognized chars
                                                  // as whitespace
// primitive, non-token patterns
| <#WORD_PUNCT: ("_"|"&")>                        // allowed anywhere in words
| < #LETTER:       // alphabets
    [
        "/u0041"-"/u005a",
        "/u0061"-"/u007a",
        "/u00c0"-"/u00d6",
        "/u00d8"-"/u00f6",
        "/u00f8"-"/u00ff",
        "/u0100"-"/u1fff"
    ]
    >
|  <#CJK:                                        // non-alphabets
      [
       "/u3040"-"/u318f",
       "/u3300"-"/u337f",
       "/u3400"-"/u3d2d",
       "/u4e00"-"/u9fff",
       "/uf900"-"/ufaff"
      ]
    >   
| < #DIGIT:       // unicode digits
      [
       "/u0030"-"/u0039",
       "/u0660"-"/u0669",
       "/u06f0"-"/u06f9",
       "/u0966"-"/u096f",
       "/u09e6"-"/u09ef",
       "/u0a66"-"/u0a6f",
       "/u0ae6"-"/u0aef",
       "/u0b66"-"/u0b6f",
       "/u0be7"-"/u0bef",
       "/u0c66"-"/u0c6f",
       "/u0ce6"-"/u0cef",
       "/u0d66"-"/u0d6f",
       "/u0e50"-"/u0e59",
       "/u0ed0"-"/u0ed9",
       "/u1040"-"/u1049"
      ]
  >
}

/** Parse a query. */
Query parse(Configuration conf) ://变量+方法
{
  Query query = new Query(conf);
  ArrayList terms;
  Token token;
  String field;
  boolean stop;
  boolean prohibited;
}
{
  nonOpOrTerm()                                   // skip noise，这句话的意思是如果遇到 : +that are @ a good way / to do that

之类的语句的时候，就会把that are和a good way和to do that 分开，分别去执行nonOpOrTerm之间的语句。举个例子，如果输入是：+this的

话，那么就会
  (
    { stop=true; prohibited=false; field = Clause.DEFAULT_FIELD; }
                                                  // optional + or - operator
    ( <PLUS> {stop=false;} | (<MINUS> { stop=false;prohibited=true; } ))?
                                                  // optional field spec.
    ( LOOKAHEAD(<WORD><COLON>(phrase(field)|compound(field)))
      token=<WORD> <COLON> { field = token.image; } )?
    ( terms=phrase(field) {stop=false;} |         // quoted terms or
      terms=compound(field))                      // single or compound term
    nonOpOrTerm()                                 // skip noise
    {
      String[] array = (String[])terms.toArray(new String[terms.size()]);
      if (stop
          && field == Clause.DEFAULT_FIELD
          && terms.size()==1
          && isStopWord(array[0])) {
        // ignore stop words only when single, unadorned terms in default field
      } else {
        if (prohibited)
          query.addProhibitedPhrase(array, field);
        else
          query.addRequiredPhrase(array, field);
      }
    }
  )*
 
  { return query; }
}
/** Parse an explcitly quoted phrase query.  Note that this may return a single
 * term, a trivial phrase.*//*输入的格式类似于：" that is a dog ",QueryFilters类来判断是否对于本类需要进行分析，如果是

rawfield的话，就不需要分析，直接使用。看上面对于本类是引用了一个conf文件来进行判断的。parser.queryFilters = new QueryFilters

(conf);*/
ArrayList phrase(String field) :
{
  int start;
  int end;
  ArrayList result = new ArrayList();
  String term;
}
{
  <QUOTE>
  { start = token.endColumn; }
 
  (nonTerm())*                                    // skip noise
  ( term = term() { result.add(term); }           // parse a term
    (nonTerm())*)*                                // skip noise
  { end = token.endColumn; }
  (<QUOTE>|<EOF>)
   
  {
    if (this.queryFilters.isRawField(field)) {
      result.clear();
      result.add(queryString.substring(start, end));
    }
    return result;
  }
}
/** Parse a compound term that is interpreted as an implicit phrase query.
 * Compounds are a sequence of terms separated by infix characters.  Note that
 * htis may return a single term, a trivial compound. */
ArrayList compound(String field) :
{
  int start;
  ArrayList result = new ArrayList();
  String term;
  StringBuffer terms = new StringBuffer();
}
{
  { start = token.endColumn; }
  term = term() {
    terms.append(term).append(" ");
    //result.add(term);
  }
  ( LOOKAHEAD( (infix())+ term() )//LOOKAHEAD是指定在下面要出现的语法，来方便编译
    (infix())+
    term = term() {
      terms.append(term).append(" ");
      //result.add(term);
    })*//以上是吧一个输入字符流去掉不规则的，完全转换成类似于"word1 word2 word3 word4..."的形式
  {
    if (this.queryFilters.isRawField(field)) {
//      result.clear();
      result.add(queryString.substring(start, token.endColumn));
    } else {
      org.apache.lucene.analysis.Token token;//Token是lucene的词基本单位，代表不能继续分割的单词，比如"take"
      TokenStream tokens = analyzer.tokenStream(
                              field, new StringReader(terms.toString()));//TokenStream是lucene的以Token为单位的流比如"take a

cake"包含三个token,这句是把上面分开的词转换为TokenStream的形式
      while (true) {
        try {
          token = tokens.next();
        } catch (IOException e) {
          token = null;
        }
        if (token == null) { break; }
        result.add(token.termText());
      }
      try {
        tokens.close();
      } catch (IOException e) {
        // ignore
      }
    }
    return result;
  }
}
/** Parse a single term. *///以下不再赘述
String term() :
{
  Token token;
}
{
  ( token=<WORD> | token=<ACRONYM> | token=<SIGRAM>)
  { return token.image; }
}

/** Parse anything but a term or a quote. */
void nonTerm() :
{}
{
  <WHITE> | infix()
}
void nonTermOrEOF() :
{}
{
  nonTerm() | <EOF>
}
/** Parse anything but a term or an operator (plur or minus or quote). */
void nonOpOrTerm() :
{}
{
  (LOOKAHEAD(2) (<WHITE> | nonOpInfix() | ((<PLUS>|<MINUS>) nonTermOrEOF())))*
}
/** Characters which can be used to form compound terms. */
void infix() :
{}
{
  <PLUS> | <MINUS> | nonOpInfix()
}
/** Parse infix characters except plus and minus. */
void nonOpInfix() :
{}
{
  <COLON>|<SLASH>|<DOT>|<ATSIGN>|<APOSTROPHE>
}