.net 平台下的lucene.net 开源项目维护进度一直不是很理想，因为需要移植的包太多，因此维护者的进度比较慢，虽然网上有一些文章是针对.net core平台移植之前3.0.3版本的改造版，但文章数目极少，能有个参考已经很不错了，因此我就把今天的趟坑之旅写出来，以供大家实施中参考。
1、Lucene介绍
按照惯例，先抄袭一段描述，这里省略8000字，自己脑补吧。
简言之，Lucene就是apache基金会下的开源全文搜索类库，其强劲的搜索能力不是其他类库可以比拟的。而Lucene.net是 其.net平台的适配移植类库，目前支持.net framework和.net core系列平台。
最新版本： 4.8.0 ，4.其他版本是没有的，因为是移植的原因，因此目前从4.8迁移，对于全文搜索，基本够用了。
这么牛逼，感觉掌握了Lucene，就掌握了搜索引擎!
摘抄下开源组织的工作，已经非常辛苦了，我就不给他们添麻烦了，然而，今天的大坑和其必不可分，后面小节再说。
ICU4J是Lucene最大的依赖项。已经进行了多种尝试来利用各种替代方法： ICU4NET icu-dotnet 但是我们遇到了几个问题： 缺乏对32/64位的支持 缺乏对.NET标准平台的支持 缺少功能，以及在尝试实现它们时遇到的问题 缺乏线程安全性 我们最终完成了直接移植ICU4J功能40％的功能，以支持Lucene.NET。该项目名为ICU4N，并在外部GitHub存储库中进行。有几个亟待解决的问题，我们可以使用一些帮助将Lucene.NET投入生产。
2、SmartChineseAnalyzer
很早前接触Lucene时，都是采用盘古分词，没想到几年过去了，Lucene已经内置了个不错的分词器，SmartChineseAnalyzer，可以自定义分词词典，内置的比较香。 其他几个推荐的分词器：
3、一个建立索引的例子
4.8以后已经更换为 MMapDirectory目录管理索引目录了，这里使用其建立索引。
var dir = MMapDirectory.Open(@"E:\lucene", new NativeFSLockFactory());
//var dir = new RAMDirectory(,);
var t = "cn";
Analyzer analyzer;
switch (t)
{
case "std":
analyzer = new StandardAnalyzer(LuceneVersion.LUCENE_48);
break;
case "cn":
analyzer = new SmartChineseAnalyzer(LuceneVersion.LUCENE_48,true);
break;
case "ws":
analyzer = new WhitespaceAnalyzer(LuceneVersion.LUCENE_48);
break;
default:
throw new NotImplementedException();
}
//准备数据
IndexWriterConfig iwc = new IndexWriterConfig(LuceneVersion.LUCENE_48, analyzer);
//当IndexWriter添加的文档的大小超过RAMBufferSizeMB ，IndexWriter就会把在内存中的操作，写入到硬盘中。
iwc.RAMBufferSizeMB = 32;
//当IndexWriter添加的文档数量超过MaxBufferedDocs的时候，IndexWriter就会把内存中写入的文档
iwc.MaxBufferedDocs = 32;
iwc.MergePolicy = new TieredMergePolicy();
iwc.OpenMode = OpenMode.CREATE_OR_APPEND;
IndexWriter writer = new IndexWriter(dir, iwc);
if (IndexWriter.IsLocked(dir))
{
IndexWriter.Unlock(dir); //unlock:强制解锁
}
//writer.Commit();
Document doc = new Document();
//只索引不分词
Field pathField = new StringField("id", Guid.NewGuid().ToString("N"), Field.Store.YES);
doc.Add(pathField);
//既索引又分词
Field contentField = new TextField("bb", GetContent(), Field.Store.YES);
doc.Add(contentField);
Field dblField = new DoubleField("cc", 1000.12d, Field.Store.YES);
doc.Add(dblField);
string s = "adfadfasfwerewre";
Field binaryField = new StoredField("bin", new BytesRef(Encoding.UTF8.GetBytes(s)));
doc.Add(binaryField);
writer.UpdateDocument(new Term("id", "1"), doc);
writer.AddDocument(doc);
writer.Flush(triggerMerge: false, applyAllDeletes: false);
//写入比较慢，注意时机
writer.Commit();
writer.Dispose();
4、坑来了
在执行 writer.Commit();时，发生了Stack Overflow，查看异常：
at ICU4N.Globalization.CultureInfoExtensions.ToUCultureInfo(System.Globalization.CultureInfo)
at ICU4N.Globalization.UCultureInfo.GetCurrentCulture()
at ICU4N.Globalization.UCultureInfo.get_CurrentCulture()
at ICU4N.Impl.ICUResourceBundle.GetBundleInstance(System.String, System.String, System.Reflection.Assembly, ICU4N.Impl.OpenType)
at ICU4N.Impl.ICUResourceBundle.GetBundleInstance(System.String, System.String, System.Reflection.Assembly, Boolean)
at ICU4N.Util.UResourceBundle+<>c__DisplayClass25_0.<GetRootType>b__0(System.String)
at System.Collections.Concurrent.ConcurrentDictionary`2[[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[ICU4N.Util.UResourceBundle+RootType, ICU4N, Version=60.0.0.0, Culture=neutral, PublicKeyToken=efb17c8e4f0e291b]].GetOrAdd(System.__Canon, System.Func`2<System.__Canon,RootType>)
at ICU4N.Util.UResourceBundle.GetRootType(System.String, System.Reflection.Assembly)
at ICU4N.Util.UResourceBundle.InstantiateBundle(System.String, System.String, System.Reflection.Assembly, Boolean)
at ICU4N.Util.UResourceBundle.GetBundleInstance(System.String, System.String, System.Reflection.Assembly, Boolean)
at ICU4N.Util.UResourceBundle.GetBundleInstance(System.String, System.String)
at ICU4N.Impl.ICUResourceBundle.GetBundle(ICU4N.Impl.ICUResourceBundleReader, System.String, System.String, System.Reflection.Assembly)
at ICU4N.Impl.ICUResourceBundle.CreateBundle(System.String, System.String, System.Reflection.Assembly)
at ICU4N.Impl.ICUResourceBundle+<>c__DisplayClass59_0.<InstantiateBundle>b__0(System.String)
at ICU4N.Impl.SoftCache`2+<>c__DisplayClass1_0[[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].<GetOrCreate>b__0(System.__Canon)
at System.Collections.Concurrent.ConcurrentDictionary`2[[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].GetOrAdd(System.__Canon, System.Func`2<System.__Canon,System.__Canon>)
at ICU4N.Impl.SoftCache`2[[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].GetOrCreate(System.__Canon, System.Func`2<System.__Canon,System.__Canon>)
at ICU4N.Impl.ICUResourceBundle.InstantiateBundle(System.String, System.String, System.String, System.Reflection.Assembly, ICU4N.Impl.OpenType)
at ICU4N.Impl.ICUResourceBundle.GetBundleInstance(System.String, System.String, System.String, System.Reflection.Assembly, ICU4N.Impl.OpenType)
at ICU4N.Globalization.UCultureInfo+DotNetLocaleHelper.GetDefaultCalendar(System.String)
at ICU4N.Globalization.UCultureInfo+DotNetLocaleHelper.ToUCultureInfo(System.Globalization.CultureInfo)
at ICU4N.Globalization.CultureInfoExtensions+<>c.<ToUCultureInfo>b__1_0(System.Globalization.CultureInfo)
at J2N.Collections.Concurrent.Add2Info`2[[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].CreateValue(System.__Canon, System.__Canon ByRef)
at J2N.Collections.Concurrent.LurchTable`2[[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].InternalInsert[[J2N.Collections.Concurrent.Add2Info`2[[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]], J2N, Version=2.0.0.0, Culture=neutral, PublicKeyToken=f39447d697a969af]](Int32, System.__Canon, Int32 ByRef, J2N.Collections.Concurrent.Add2Info`2<System.__Canon,System.__Canon> ByRef)
at J2N.Collections.Concurrent.LurchTable`2[[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].Insert[[J2N.Collections.Concurrent.Add2Info`2[[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]], J2N, Version=2.0.0.0, Culture=neutral, PublicKeyToken=f39447d697a969af]](System.__Canon, J2N.Collections.Concurrent.Add2Info`2<System.__Canon,System.__Canon> ByRef)
at J2N.Collections.Concurrent.LurchTable`2[[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].GetOrAdd(System.__Canon, System.Func`2<System.__Canon,System.__Canon>)
at ICU4N.Globalization.CultureInfoExtensions.ToUCultureInfo(System.Globalization.CultureInfo)
at ICU4N.Globalization.UCultureInfo.GetCurrentCulture()
at ICU4N.Globalization.UCultureInfo.get_CurrentCulture()
at ICU4N.Impl.ICUResourceBundle.GetBundleInstance(System.String, System.String, System.Reflection.Assembly, ICU4N.Impl.OpenType)
at ICU4N.Impl.ICUResourceBundle.GetBundleInstance(System.String, System.String, System.Reflection.Assembly, Boolean)
at ICU4N.Util.UResourceBundle+<>c__DisplayClass25_0.<GetRootType>b__0(System.String)
at System.Collections.Concurrent.ConcurrentDictionary`2[[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[ICU4N.Util.UResourceBundle+RootType, ICU4N, Version=60.0.0.0, Culture=neutral, PublicKeyToken=efb17c8e4f0e291b]].GetOrAdd(System.__Canon, System.Func`2<System.__Canon,RootType>)
at ICU4N.Util.UResourceBundle.GetRootType(System.String, System.Reflection.Assembly)
at ICU4N.Util.UResourceBundle.InstantiateBundle(System.String, System.String, System.Reflection.Assembly, Boolean)
at ICU4N.Util.UResourceBundle.GetBundleInstance(System.String, System.String, System.Reflection.Assembly, Boolean)
at ICU4N.Util.UResourceBundle.GetBundleInstance(System.String, System.String)
at ICU4N.Impl.ICUResourceBundle.GetBundle(ICU4N.Impl.ICUResourceBundleReader, System.String, System.String, System.Reflection.Assembly)
at ICU4N.Impl.ICUResourceBundle.CreateBundle(System.String, System.String, System.Reflection.Assembly)
at ICU4N.Impl.ICUResourceBundle+<>c__DisplayClass59_0.<InstantiateBundle>b__0(System.String)
at ICU4N.Impl.SoftCache`2+<>c__DisplayClass1_0[[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].<GetOrCreate>b__0(System.__Canon)
at System.Collections.Concurrent.ConcurrentDictionary`2[[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].GetOrAdd(System.__Canon, System.Func`2<System.__Canon,System.__Canon>)
at ICU4N.Impl.SoftCache`2[[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].GetOrCreate(System.__Canon, System.Func`2<System.__Canon,System.__Canon>)
at ICU4N.Impl.ICUResourceBundle.InstantiateBundle(System.String, System.String, System.String, System.Reflection.Assembly, ICU4N.Impl.OpenType)
at ICU4N.Impl.ICUResourceBundle.GetBundleInstance(System.String, System.String, System.String, System.Reflection.Assembly, ICU4N.Impl.OpenType)
at ICU4N.Globalization.UCultureInfo+DotNetLocaleHelper.GetDefaultCalendar(System.String)
at ICU4N.Globalization.UCultureInfo+DotNetLocaleHelper.ToUCultureInfo(System.Globalization.CultureInfo)
at ICU4N.Globalization.CultureInfoExtensions+<>c.<ToUCultureInfo>b__1_0(System.Globalization.CultureInfo)
at J2N.Collections.Concurrent.Add2Info`2[[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].CreateValue(System.__Canon, System.__Canon ByRef)
at J2N.Collections.Concurrent.LurchTable`2[[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].InternalInsert[[J2N.Collections.Concurrent.Add2Info`2[[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]], J2N, Version=2.0.0.0, Culture=neutral, PublicKeyToken=f39447d697a969af]](Int32, System.__Canon, Int32 ByRef, J2N.Collections.Concurrent.Add2Info`2<System.__Canon,System.__Canon> ByRef)
at J2N.Collections.Concurrent.LurchTable`2[[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].Insert[[J2N.Collections.Concurrent.Add2Info`2[[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]], J2N, Version=2.0.0.0, Culture=neutral, PublicKeyToken=f39447d697a969af]](System.__Canon, J2N.Collections.Concurrent.Add2Info`2<System.__Canon,System.__Canon> ByRef)
at J2N.Collections.Concurrent.LurchTable`2[[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.__Canon, System.Private.CoreLib, Version=5.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].GetOrAdd(System.__Canon, System.Func`2<System.__Canon,System.__Canon>)
at ICU4N.Globalization.CultureInfoExtensions.ToUCultureInfo(System.Globalization.CultureInfo)
at ICU4N.Globalization.UCultureInfo.GetCurrentCulture()
at ICU4N.Globalization.UCultureInfo.get_CurrentCulture()
at ICU4N.Impl.ICUResourceBundle.GetBundleInstance(System.String, System.String, System.Reflection.Assembly, ICU4N.Impl.OpenType)
at ICU4N.Impl.ICUResourceBundle.GetBundleInstance(System.String, ICU4N.Globalization.UCultureInfo, System.Reflection.Assembly, ICU4N.Impl.OpenType)
at ICU4N.Impl.ICUResourceBundle.GetBundleInstance(System.String, ICU4N.Globalization.UCultureInfo, ICU4N.Impl.OpenType)
at ICU4N.Text.BreakIteratorFactory.CreateBreakInstance(ICU4N.Globalization.UCultureInfo, Int32)
at ICU4N.Text.BreakIteratorFactory.CreateBreakIterator(ICU4N.Globalization.UCultureInfo, Int32)
at ICU4N.Text.BreakIterator.GetBreakInstance(ICU4N.Globalization.UCultureInfo, Int32)
at ICU4N.Text.BreakIterator.GetSentenceInstance(System.Globalization.CultureInfo)
at Lucene.Net.Analysis.Cn.Smart.HMMChineseTokenizer..cctor()
at Lucene.Net.Analysis.Cn.Smart.HMMChineseTokenizer..ctor(AttributeFactory, System.IO.TextReader)
at Lucene.Net.Analysis.Cn.Smart.HMMChineseTokenizer..ctor(System.IO.TextReader)
at Lucene.Net.Analysis.Cn.Smart.SmartChineseAnalyzer.CreateComponents(System.String, System.IO.TextReader)
at Lucene.Net.Analysis.Analyzer.GetTokenStream(System.String, System.IO.TextReader)
at Lucene.Net.Documents.Field.GetTokenStream(Lucene.Net.Analysis.Analyzer)
at Lucene.Net.Index.DocInverterPerField.ProcessFields(Lucene.Net.Index.IIndexableField[], Int32)
at Lucene.Net.Index.DocFieldProcessor.ProcessDocument(Builder)
at Lucene.Net.Index.DocumentsWriterPerThread.UpdateDocument(System.Collections.Generic.IEnumerable`1<Lucene.Net.Index.IIndexableField>, Lucene.Net.Analysis.Analyzer, Lucene.Net.Index.Term)
at Lucene.Net.Index.DocumentsWriter.UpdateDocument(System.Collections.Generic.IEnumerable`1<Lucene.Net.Index.IIndexableField>, Lucene.Net.Analysis.Analyzer, Lucene.Net.Index.Term)
at Lucene.Net.Index.IndexWriter.UpdateDocument(Lucene.Net.Index.Term, System.Collections.Generic.IEnumerable`1<Lucene.Net.Index.IIndexableField>, Lucene.Net.Analysis.Analyzer)
at Lucene.Net.Index.IndexWriter.UpdateDocument(Lucene.Net.Index.Term, System.Collections.Generic.IEnumerable`1<Lucene.Net.Index.IIndexableField>)
一开始，我以为是.net core环境没有设置中文的原因，因为异常里有一堆的国际化语言的相关函数，设置为中文，代码如下：
Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);
CultureInfo culture1 = CultureInfo.CurrentCulture;
CultureInfo culture2 = Thread.CurrentThread.CurrentCulture;
Console.WriteLine("The current culture is {0}", culture1.Name);
Console.WriteLine("The two CultureInfo objects are equal: {0}",
culture1 == culture2);
打印已经是完美的zh-CN了，但是异常如旧，这是why？难道是ICU4N类库出现麻大了？
在github上找到 ICU4N类库，终于发现了issue：Getting UCultureInfo.CurrentCulture will throw a StackOverflowException if the current culture is any of the following: zh-CN, zh-HK, zh-MO, zh-SG, zh-TW.
好了，有空拉下需求，可以帮着改改bug哦。知道问题了，先解决问题吧。
代码前加上如下代码，F5，一切OK。
//https://github.com/NightOwl888/ICU4N/issues/29
Thread.CurrentThread.CurrentCulture = CultureInfo.GetCultureInfo("en-us");
一个坑，就这么趟过去了！
5、搜索结果
搜索相对比较顺利，代码如下：
//下面来查询 bb字段
var a = "bb";
IndexReader reader = DirectoryReader.Open(dir);
IndexSearcher searcher = new IndexSearcher(reader);
QueryParser parser = new QueryParser(LuceneVersion.LUCENE_48, a, analyzer);
BooleanQuery mp = new BooleanQuery();
mp.Add(new TermQuery(new Term(a, "服装")), Occur.MUST);
//查询前10条结果
var r = searcher.Search(mp, null, Convert.ToInt32(10));
//获取第一条结果值，危险警示，这里并没有检查结果索引，仅供测试用
var b = r.ScoreDocs[0];
var docRst = reader.Document(b.Doc);
var f = docRst.GetBinaryValue("bin");
var fdoc = Encoding.UTF8.GetString(f.Bytes);
Console.WriteLine(fdoc);
Console.WriteLine("Hello World!");
6、小结
简单的例子已经搞定了，如果要用到全文搜索，利用这个再进一步深化，相信不是问题了。
