Lucene is an open source Full-text search library that provides efficient text indexing and search functions. It is not a database, but a tool library for building full-text indexes.
Installing Lucene requires the following steps:
1. Download Lucene:
On Lucene's official website（ https://lucene.apache.org/ ）Download the latest Lucene version from. After downloading, extract the file to the specified directory.
2. Import Lucene library:
In your Java project, add Lucene's jar file to the project's classpath.
3. Create index:
Firstly, you need to create an index directory to store Lucene's indexes. Create a new Java class named IndexDemo, and then write the following code in that class:
```java
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.IndexWriterConfig;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.FSDirectory;
import java.io.IOException;
import java.nio.file.Paths;
public class IndexDemo {
public static void main(String[] args) {
//Create an index directory
String indexPath = "path/to/index";
Directory indexDirectory;
try {
indexDirectory = FSDirectory.open(Paths.get(indexPath));
} catch (IOException e) {
e.printStackTrace();
return;
}
//Create an IndexWriter object and configure its parser
StandardAnalyzer analyzer = new StandardAnalyzer();
IndexWriterConfig config = new IndexWriterConfig(analyzer);
IndexWriter indexWriter;
try {
indexWriter = new IndexWriter(indexDirectory, config);
//Create a Document object and add a Field to it
Document document = new Document();
document.add(new Field("id", "1", Field.Store.YES, Field.Index.NO));
document.add(new Field("title", "Lucene Introduction", Field.Store.YES, Field.Index.ANALYZED));
document.add(new Field("content", "This is a Lucene tutorial.", Field.Store.YES, Field.Index.ANALYZED));
//Using IndexWriter to Write Document Objects to an Index
indexWriter.addDocument(document);
//Submit index and close IndexWriter
indexWriter.commit();
indexWriter.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
```
In the above code, we first created an index directory, indexDirectory, and then created an IndexWriterConfig to configure the analyzer and other parameters. Next, we created a Document object and added Fields to it to represent the different properties of the document. Finally, we use IndexWriter to write the Document object to the index, submit the index, and close IndexWriter.
4. Search index:
The following is an example code for using Lucene search index:
```java
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
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.FSDirectory;
import org.apache.lucene.util.Version;
import java.io.IOException;
import java.nio.file.Paths;
public class SearchDemo {
public static void main(String[] args) {
//Open index directory
String indexPath = "path/to/index";
Directory indexDirectory;
try {
indexDirectory = FSDirectory.open(Paths.get(indexPath));
} catch (IOException e) {
e.printStackTrace();
return;
}
//Create a search object
IndexReader indexReader;
try {
indexReader = DirectoryReader.open(indexDirectory);
} catch (IOException e) {
e.printStackTrace();
return;
}
IndexSearcher searcher = new IndexSearcher(indexReader);
//Create a query object
StandardAnalyzer analyzer = new StandardAnalyzer();
QueryParser parser = new QueryParser("content", analyzer);
Query query;
try {
query = parser.parse("Lucene tutorial");
} catch (Exception e) {
e.printStackTrace();
return;
}
//Execute Query
TopDocs topDocs;
try {
topDocs = searcher.search(query, 10);
} catch (IOException e) {
e.printStackTrace();
return;
}
//Process search results
for (ScoreDoc scoreDoc : topDocs.scoreDocs) {
try {
Document document = searcher.doc(scoreDoc.doc);
System.out.println("Score: " + scoreDoc.score);
System.out.println("Title: " + document.get("title"));
System.out.println("Content: " + document.get("content"));
System.out.println();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
```
In the above code, we first open the index directory indexDirectory and create an IndexSearcher object to perform the search operation. Then we use StandardAnalyzer and QueryParser to create a query object that represents the content to be searched for. Next, we perform a search operation and process the search results.
5. Delete index:
To delete an index, you need to first create an IndexWriter object and then use IndexWriter's deleteDocuments method to delete the specified document. The example code is as follows:
```java
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.document.IntPoint;
import org.apache.lucene.document.StringField;
import org.apache.lucene.document.TextField;
import org.apache.lucene.index.DirectoryReader;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.IndexWriterConfig;
import org.apache.lucene.index.Term;
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.FSDirectory;
import java.io.IOException;
import java.nio.file.Paths;
public class DeleteDemo {
public static void main(String[] args) {
//Create an index directory
String indexPath = "path/to/index";
Directory indexDirectory;
try {
indexDirectory = FSDirectory.open(Paths.get(indexPath));
} catch (IOException e) {
e.printStackTrace();
return;
}
//Create an IndexWriter object and configure its parser
StandardAnalyzer analyzer = new StandardAnalyzer();
IndexWriterConfig config = new IndexWriterConfig(analyzer);
IndexWriter indexWriter;
try {
indexWriter = new IndexWriter(indexDirectory, config);
//Create a Document object and add a Field to it
Document document1 = new Document();
document1.add(new StringField("id", "1", Field.Store.YES));
document1.add(new TextField("content", "This is document 1.", Field.Store.YES));
Document document2 = new Document();
document2.add(new StringField("id", "2", Field.Store.YES));
document2.add(new TextField("content", "This is document 2.", Field.Store.YES));
//Using IndexWriter to Write Document Objects to an Index
indexWriter.addDocument(document1);
indexWriter.addDocument(document2);
//Delete document with id 1
indexWriter.deleteDocuments(new Term("id", "1"));
//Submit index and close IndexWriter
indexWriter.commit();
indexWriter.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
```
In the above code, we first created an index directory, indexDirectory, and then created an IndexWriter object and configured its parser. Next, we created two Document objects and added Fields to them. Then, we use IndexWriter to write the Document object to the index, and use the deleteDocuments method to delete the document with id 1. Finally, we submit the index and close IndexWriter.
Through the above steps, you can achieve Lucene's installation, index creation, search, deletion, and other functions. In most cases, Lucene should be integrated into your Java application for use, rather than being used as a standalone database.
