基于lucene.net 和ICTCLAS2014的站内搜索的实现1

Lucene.net是一个搜索引擎的框架，它自身并不能实现搜索，需要我们自己在其中实现索引的建立，索引的查找。所有这些都是根据它自身提供的API来实现。Lucene.net本身是基于java的，但是经过翻译成.ne版本的，可以在ASP.net中使用这个来实现站内搜索。

         要实现基于汉语的搜索引擎，首先的要实现汉语的分词。目前网上大部分都是利用已经有的盘古分词来实现的分词系统，但是盘古分词效果不太好。在这里我把最新的ICTCLAS2014嵌入到Lucene.net中。Lucene.net中所有的分词系统都是基于Analyzer类来继承实现的。所以如果要使用ICTCLAS2014嵌入到Lucene.net中，就必要要继承Analyzer类实现自己的分词类。

1 ICTCLAS的引入

         首先我们要把ICTCLAS的dll引入到C#文件中 ，因为这个dll不是在C#中建立的类库，所以无法直接将其加入到C#的引用中。我们考虑使用下面的方法来实现，为了方便，我们把引入的函数以及结构体放入一个类中。如下所示：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;
using Lucene.Net.Analysis;

namespace Lucene.Net.Analysis.DChinese
{
[StructLayout(LayoutKind.Explicit)]
public struct result_t
{
[FieldOffset(0)]
public int start;
[FieldOffset(4)]
public int length;
[FieldOffset(8)]
public int sPos1;
[FieldOffset(12)]
public int sPos2;
[FieldOffset(16)]
public int sPos3;
[FieldOffset(20)]
public int sPos4;
[FieldOffset(24)]
public int sPos5;
[FieldOffset(28)]
public int sPos6;
[FieldOffset(32)]
public int sPos7;
[FieldOffset(36)]
public int sPos8;
[FieldOffset(40)]
public int sPos9;
[FieldOffset(44)]
public int sPos10;
//[FieldOffset(12)] public int sPosLow;
[FieldOffset(48)]
public int POS_id;
[FieldOffset(52)]
public int word_ID;
[FieldOffset(56)]
public int word_type;
[FieldOffset(60)]
public double weight;
}
public class SplitWord
{
const string path = @"NLPIR.dll";//设定dll的路径

//对函数进行申明
[DllImport(path, CharSet = CharSet.Ansi, EntryPoint = "NLPIR_Init", CallingConvention = CallingConvention.Cdecl)]
public static extern bool NLPIR_Init(String sInitDirPath, int encoding = 0, String sLicenceCode = null);

//特别注意，C语言的函数NLPIR_API const char * NLPIR_ParagraphProcess(const char *sParagraph,int bPOStagged=1);必须对应下面的申明
[DllImport(path, CharSet = CharSet.Ansi, CallingConvention = CallingConvention.Cdecl, EntryPoint = "NLPIR_ParagraphProcess")]
public static extern IntPtr NLPIR_ParagraphProcess(String sParagraph, int bPOStagged = 1);

[DllImport(path, CharSet = CharSet.Ansi, EntryPoint = "NLPIR_Exit", CallingConvention = CallingConvention.Cdecl)]
public static extern bool NLPIR_Exit();

[DllImport(path, CharSet = CharSet.Ansi, EntryPoint = "NLPIR_ImportUserDict", CallingConvention = CallingConvention.Cdecl)]
public static extern int NLPIR_ImportUserDict(String sFilename);

[DllImport(path, CharSet = CharSet.Ansi, EntryPoint = "NLPIR_FileProcess", CallingConvention = CallingConvention.Cdecl)]
public static extern bool NLPIR_FileProcess(String sSrcFilename, String sDestFilename, int bPOStagged = 1);

[DllImport(path, CharSet = CharSet.Ansi, EntryPoint = "NLPIR_FileProcessEx", CallingConvention = CallingConvention.Cdecl)]
public static extern bool NLPIR_FileProcessEx(String sSrcFilename, String sDestFilename);

[DllImport(path, CharSet = CharSet.Ansi, EntryPoint = "NLPIR_GetParagraphProcessAWordCount", CallingConvention = CallingConvention.Cdecl)]
public static extern int NLPIR_GetParagraphProcessAWordCount(String sParagraph);

//NLPIR_GetParagraphProcessAWordCount
[DllImport(path, CharSet = CharSet.Ansi, EntryPoint = "NLPIR_ParagraphProcessAW", CallingConvention = CallingConvention.Cdecl)]
public static extern void NLPIR_ParagraphProcessAW(int nCount, [Out, MarshalAs(UnmanagedType.LPArray)] result_t[] result);

[DllImport(path, CharSet = CharSet.Ansi, EntryPoint = "NLPIR_AddUserWord", CallingConvention = CallingConvention.Cdecl)]
public static extern int NLPIR_AddUserWord(String sWord);

[DllImport(path, CharSet = CharSet.Ansi, EntryPoint = "NLPIR_SaveTheUsrDic", CallingConvention = CallingConvention.Cdecl)]
public static extern int NLPIR_SaveTheUsrDic();

[DllImport(path, CharSet = CharSet.Ansi, EntryPoint = "NLPIR_DelUsrWord", CallingConvention = CallingConvention.Cdecl)]
public static extern int NLPIR_DelUsrWord(String sWord);

[DllImport(path, CharSet = CharSet.Ansi, EntryPoint = "NLPIR_NWI_Start", CallingConvention = CallingConvention.Cdecl)]
public static extern bool NLPIR_NWI_Start();

[DllImport(path, CharSet = CharSet.Ansi, EntryPoint = "NLPIR_NWI_Complete", CallingConvention = CallingConvention.Cdecl)]
public static extern bool NLPIR_NWI_Complete();

[DllImport(path, CharSet = CharSet.Ansi, EntryPoint = "NLPIR_NWI_AddFile", CallingConvention = CallingConvention.Cdecl)]
public static extern bool NLPIR_NWI_AddFile(String sText);

[DllImport(path, CharSet = CharSet.Ansi, EntryPoint = "NLPIR_NWI_AddMem", CallingConvention = CallingConvention.Cdecl)]
public static extern bool NLPIR_NWI_AddMem(String sText);

[DllImport(path, CharSet = CharSet.Ansi, CallingConvention = CallingConvention.Cdecl, EntryPoint = "NLPIR_NWI_GetResult")]
public static extern IntPtr NLPIR_NWI_GetResult(bool bWeightOut = false);

[DllImport(path, CharSet = CharSet.Ansi, EntryPoint = "NLPIR_NWI_Result2UserDict", CallingConvention = CallingConvention.Cdecl)]
public static extern uint NLPIR_NWI_Result2UserDict();

[DllImport(path, CharSet = CharSet.Ansi, EntryPoint = "NLPIR_GetKeyWords", CallingConvention = CallingConvention.Cdecl)]
public static extern IntPtr NLPIR_GetKeyWords(String sText, int nMaxKeyLimit = 50, bool bWeightOut = false);

[DllImport(path, CharSet = CharSet.Ansi, CallingConvention = CallingConvention.Cdecl, EntryPoint = "NLPIR_GetFileKeyWords")]
public static extern IntPtr NLPIR_GetFileKeyWords(String sFilename, int nMaxKeyLimit = 50, bool bWeightOut = false);
}
}

这个类里面包含了所有的ICTCLAS的API函数，包含初始化，添加词语，添加词典，词典保存，分词等各种API。并且都是STATIC函数。

2 分词类DChineseAnalyzer的建立

分词类的建立我们参考StandarAnalyzer分词的实现，再次基础上实现了DChineseAnalyzer类。在分词类中实现必要的构造函数，以及

public overrideTokenStream TokenStream(System.String fieldName, System.IO.TextReader
reader)
public overrideTokenStream ReusableTokenStream(System.String fieldName, System.IO.TextReader
reader)
这两个函数。他们的作用是在函数中调用用分词器Tokenizer的派生类来实现分词。在现有的版本中一般是在使用分词类的时候，直接调用ReusableTokenStream函数，而不是调用TokenStream函数，这样可以做到一个分词类对象的建立可供多个分词文本的使用。从而减少内存的浪费，提高效率。

以及一些字段，利用这些字段，我们可以加入一些停用词，用户自己的词典。

3 分词器DChineseTokenizer的建立
这个类是分词的核心关键所在。我们要在其中调用ICTCLAS中的分词。在这里面要注意的一个函数是publicoverride
bool IncrementToken()
它是我们获取下一个分词结果要用到的函数，如果想要遍历分词结果，就要建立一个循环，不断的调用IncrementToken函数。
整个分词系统代码如下所示：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;
using System.Runtime.InteropServices;
using Lucene.Net.Analysis;
using Lucene.Net.Analysis.Standard;
using Lucene.Net.Util;
using Lucene.Net.Documents;
using Lucene.Net.Analysis.Tokenattributes;
using Version = Lucene.Net.Util.Version;

namespace Lucene.Net.Analysis.DChinese
{
public class DChineseAnalyzer : Analyzer
{
private ISet<string> stopSet;
public static readonly ISet<string> STOP_WORDS_SET;
private Version matchVersion;
private bool replaceInvalidAcronym;
private bool enableStopPositionIncrements;

public DChineseAnalyzer(Version version, ISet<string> stopWords)
{
stopSet = stopWords;
replaceInvalidAcronym = false;
enableStopPositionIncrements = StopFilter.GetEnablePositionIncrementsVersionDefault(version);
replaceInvalidAcronym = matchVersion.OnOrAfter(Version.LUCENE_24);
this.matchVersion = version;
}

public DChineseAnalyzer(Version version)
: this(version, STOP_WORDS_SET)
{
}

public DChineseAnalyzer(Version version, System.IO.FileInfo stopWords)
: this(version, WordlistLoader.GetWordSet(stopWords))
{
}

static DChineseAnalyzer()
{
STOP_WORDS_SET = StopAnalyzer.ENGLISH_STOP_WORDS_SET;
}
public override TokenStream TokenStream(System.String fieldName, System.IO.TextReader reader)
{
TokenStream result = new DChineseTokenizer(matchVersion, reader);
result = new LowerCaseFilter(result);
result = new StopFilter(enableStopPositionIncrements, result, stopSet);
result = new PorterStemFilter(result);
return result;
}

private class SavedStreams
{
protected internal DChineseTokenizer source;
protected internal TokenStream result;
};
public override TokenStream ReusableTokenStream(System.String fieldName, System.IO.TextReader reader)
{
SavedStreams streams = (SavedStreams)PreviousTokenStream;
if (streams == null)
{
streams = new SavedStreams();
streams.source = new DChineseTokenizer(matchVersion, reader);
streams.result = new LowerCaseFilter(streams.source);
streams.result = new StopFilter(enableStopPositionIncrements, streams.result, stopSet);
streams.result = new PorterStemFilter(streams.result);
PreviousTokenStream = streams;
}
else
{
streams.source.Reset(reader);
}

streams.source.SetReplaceInvalidAcronym(replaceInvalidAcronym);
return streams.result;
}

}

public sealed class DChineseTokenizer : Tokenizer
{

private bool m_replaceInvalidAcronym;
private int offset = 0;
private int bufferIndex = 0;
private int dataLen = 0;
private const int MAX_WORD_LEN = 255;
private const int IO_BUFFER_SIZE = 4096;
private readonly char[] ioBuffer = new char[IO_BUFFER_SIZE];

private ITermAttribute termAtt;
private IOffsetAttribute offsetAtt;
private IPositionIncrementAttribute posIncrAtt;

private void Init(System.IO.TextReader input, Version matchVersion)
{
if (matchVersion.OnOrAfter(Version.LUCENE_24))
{
m_replaceInvalidAcronym = true;
}
else
{
m_replaceInvalidAcronym = false;
}
//this.input = input;
this.input = ChangeInput(input);
termAtt = AddAttribute<ITermAttribute>();
offsetAtt = AddAttribute<IOffsetAttribute>();
posIncrAtt = AddAttribute<IPositionIncrementAttribute>();
}

public DChineseTokenizer(Version matchVersion, System.IO.TextReader input)
: base()
{
Init(input, matchVersion);
}

public DChineseTokenizer(Version matchVersion, System.IO.TextReader input, AttributeSource source)
: base(source)
{
Init(input, matchVersion);
}

public DChineseTokenizer(Version matchVersion, System.IO.TextReader input, AttributeFactory factory)
: base(factory)
{
Init(input, matchVersion);
}

public override bool IncrementToken()
{
ClearAttributes();
int length = 0;
int start = bufferIndex;
char[] buffer = termAtt.TermBuffer();
while (true)
{

if (bufferIndex >= dataLen)
{
offset += dataLen;
dataLen = input.Read(ioBuffer, 0, ioBuffer.Length);
if (dataLen <= 0)
{
dataLen = 0;
if (length > 0)
break;
return false;
}
bufferIndex = 0;
}

char c = ioBuffer[bufferIndex++];

if (!System.Char.IsWhiteSpace(c))
{
if (length == 0)
{
start = offset + bufferIndex - 1;
}
else if (length == buffer.Length)
{
buffer = termAtt.ResizeTermBuffer(1 + length);
}

buffer[length++] = c;
if (length == MAX_WORD_LEN)
break;
}
else if (length > 0)
break;
}

termAtt.SetTermLength(length);
offsetAtt.SetOffset(CorrectOffset(start), CorrectOffset(start + length));
posIncrAtt.PositionIncrement = 1;
return true;
}

public override void Reset()
{
base.Reset(input);
bufferIndex = 0;
offset = 0;
dataLen = 0;
}

public override void Reset(TextReader input)
{
String inputString = input.ReadToEnd();
IntPtr intPtr = SplitWord.NLPIR_ParagraphProcess(inputString, 0);
string strResult = Marshal.PtrToStringAnsi(intPtr);
this.input = new StringReader(strResult);
bufferIndex = 0;
offset = 0;
dataLen = 0;
}

public override void End()
{
int finalOffset = CorrectOffset(offset);
offsetAtt.SetOffset(finalOffset, finalOffset);
}

public void SetReplaceInvalidAcronym(bool replaceInvalidAcronym)
{
this.m_replaceInvalidAcronym = replaceInvalidAcronym;
}

private TextReader ChangeInput(TextReader input)
{
//string indexPath = System.Environment.CurrentDirectory;
//string indexPath = GetType().Assembly.Location;
//string indexPath = System.IO.Path.GetDirectoryName(Page.Request.PhysicalPath);
//string dirParent = Directory.GetParent(indexPath).Parent.FullName;
string dirParent = System.AppDomain.CurrentDomain.BaseDirectory;

bool bInit = SplitWord.NLPIR_Init(dirParent, 0, null);
if (!bInit)
{
return null;
}
String inputString = input.ReadToEnd();
IntPtr intPtr = SplitWord.NLPIR_ParagraphProcess(inputString, 0);
string strResult = Marshal.PtrToStringAnsi(intPtr);
return new StringReader(strResult);
}
}
}