如何在Java中實現全文檢索

在Java中實現全文檢索，可以使用Apache Lucene庫

1. 首先，確保你已經安裝了Java開發環境（JDK）和構建工具（如Maven或Gradle）。

2. 在項目的pom.xml文件中添加Apache Lucene依賴項（如果使用Maven）：

   <dependency>
       <groupId>org.apache.lucene</groupId>
       <artifactId>lucene-core</artifactId>
       <version>8.10.1</version>
    </dependency>
   <dependency>
       <groupId>org.apache.lucene</groupId>
       <artifactId>lucene-analyzers-common</artifactId>
       <version>8.10.1</version>
    </dependency>
   <dependency>
       <groupId>org.apache.lucene</groupId>
       <artifactId>lucene-queryparser</artifactId>
       <version>8.10.1</version>
    </dependency>
</dependencies>

3. 創建一個索引：

import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.document.StringField;
import org.apache.lucene.document.TextField;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.IndexWriterConfig;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.RAMDirectory;

public class Indexer {
    public static void main(String[] args) throws Exception {
        Directory directory = new RAMDirectory();
        StandardAnalyzer analyzer = new StandardAnalyzer();
        IndexWriterConfig config = new IndexWriterConfig(analyzer);
        IndexWriter indexWriter = new IndexWriter(directory, config);

        Document doc1 = new Document();
        doc1.add(new StringField("id", "1", Field.Store.YES));
        doc1.add(new TextField("content", "This is a sample document.", Field.Store.NO));
        indexWriter.addDocument(doc1);

        Document doc2 = new Document();
        doc2.add(new StringField("id", "2", Field.Store.YES));
        doc2.add(new TextField("content", "Another sample document for testing.", Field.Store.NO));
        indexWriter.addDocument(doc2);

        indexWriter.close();
    }
}

4. 執行查詢：

import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.index.DirectoryReader;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.queryparser.classic.QueryParser;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.ScoreDoc;
import org.apache.lucene.search.TopDocs;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.RAMDirectory;

public class Searcher {
    public static void main(String[] args) throws Exception {
        Directory directory = new RAMDirectory();
        IndexReader indexReader = DirectoryReader.open(directory);
        IndexSearcher indexSearcher = new IndexSearcher(indexReader);
        QueryParser queryParser = new QueryParser("content", new StandardAnalyzer());

        Query query = queryParser.parse("sample");
        TopDocs topDocs = indexSearcher.search(query, 10);

        for (ScoreDoc scoreDoc : topDocs.scoreDocs) {
            Document doc = indexSearcher.doc(scoreDoc.doc);
            System.out.println("ID: " + doc.get("id") + ", Content: " + doc.get("content"));
        }

        indexReader.close();
    }
}

5. 運行這兩個類，首先運行Indexer類創建索引，然后運行Searcher類執行查詢。你應該會看到與查詢相關的文檔作為結果返回。

這只是一個簡單的示例，實際應用中可能需要處理更復雜的文檔結構、查詢和分析器。但這為你提供了一個基本的全文檢索實現的概述。