利用 Lucene.Net 建完索引後，如果想檢視程式到底如何建立索引，可以利用現成 API 來檢查索引裡的 Term。所謂的 Term，用一個例子來說明就是，假設有一個句子”This is a book.”，用 Lucene.Net 建完索引後，正常情況下會將這個句子拆成”This”、”is”、”a”、”book”然後再存進檔案裡。當然，如果有過濾 stop word，那就只有”book”會被記錄。
接下來示範如何列出索引裡的 Term。
public void StartIndex(List<Product> ProductList)
{
DirectoryInfo dirInfo = new DirectoryInfo(this.IndexPath);
FSDirectory dir = FSDirectory.Open(dirInfo);
IndexWriter indexWriter = new IndexWriter(dir, new StandardAnalyzer(Lucene.Net.Util.Version.LUCENE_29), true, IndexWriter.MaxFieldLength.UNLIMITED);
foreach (Product product in ProductList)
{
Document doc = new Document();
Field field = new Field("SaleName", product.SaleName, Field.Store.YES, Field.Index.ANALYZED, Field.TermVector.YES);
Field field2 = new Field("Desc", product.Desc, Field.Store.YES, Field.Index.ANALYZED, Field.TermVector.YES);
NumericField field3 = new NumericField("Price", Field.Store.YES, true);
field3.SetIntValue(product.Price);
doc.Add(field);
doc.Add(field2);
doc.Add(field3);
indexWriter.AddDocument(doc);
}
indexWriter.Close();
}
上面的程式碼示範如何建立索引，這裡只需注意，宣告 Field 物件時，要設定 Field.TermVector.Yes 這個屬性。
接下來列出索引裡的 Term。
public List<string> ListTerms()
{
DirectoryInfo dirInfo = new DirectoryInfo(this.IndexPath);
FSDirectory dir = FSDirectory.Open(dirInfo);
IndexReader reader = IndexReader.Open(dir, true);
List<string> list = new List<string>();
Term t = new Term("SaleName");
TermEnum termEnum = reader.Terms(t);
while (termEnum.Next())
{
Term term = termEnum.Term();
if (term != null)
list.Add(term.Field() + ":" + term.Text());
}
return list;
}
程式碼並沒有特別難，只要注意 term 這個物件是否為 null 就可以了。
然後是 main function。
static void Main(string[] args)
{
LuceneClass lucene = new LuceneClass(@"INDEX_DIR");
List<Product> list = new List<Product>();
list.Add(new Product { SaleName = "iphone", Desc = "Apple's iphone", Price = 100 });
list.Add(new Product { SaleName = "iphone4s", Desc = "Apple's iphone", Price = 120 });
list.Add(new Product { SaleName = "iphone 4s", Desc = "Apple's iphone", Price = 130 });
list.Add(new Product { SaleName = "iphone 3gs", Desc = "Apple's iphone", Price = 90 });
list.Add(new Product { SaleName = "愛瘋機", Desc = "中國出品", Price = 100 });
list.Add(new Product { SaleName = "蘋果機", Desc = "中國出品", Price = 100 });
list.Add(new Product { SaleName = "HTC Hero", Desc = "Android Phone", Price = 50 });
lucene.StartIndex(list);
List<string> result = lucene.ListTerms();
foreach (string item in result)
{
Console.WriteLine(item);
}
}
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