问题
I'am new to Apache Lucene, I'm using Apache Lucene 8.4.1, I can do Lucene Indexing and Searching but don't know how to read and list index / print index using java. How to get indexed fields and term list ? .
I was able to get Fileds list by using following function grabbed from Other Stackoverflow article.
public static String[] getFieldNames(IndexReader reader) {
List<String> fieldNames = new ArrayList<String>();
//For a simple reader over only one index, reader.leaves() should only return one LeafReaderContext
for (LeafReaderContext readerCtx : reader.leaves()) {
FieldInfos fields = readerCtx.reader().getFieldInfos();
for (FieldInfo field : fields) {
//Check whether the field is indexed and searchable, perhaps?
fieldNames.add(field.name);
}
}
return fieldNames.toArray(new String[fieldNames.size()]);
}
Thanks
回答1:
package com.lucene.ram;
import java.io.IOException;
import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field.Store;
import org.apache.lucene.document.TextField;
import org.apache.lucene.index.DirectoryReader;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.IndexWriterConfig;
import org.apache.lucene.index.IndexWriterConfig.OpenMode;
import org.apache.lucene.queryparser.classic.ParseException;
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.RAMDirectory;
/**
*
* @author W.P.Roshan
* @email sunone5 at gmail.com
*
* The RAMDirector is deprecated instead you can use
*
* import org.apache.lucene.index.memory.MemoryIndex;
*
*/
public class RAMDirectoryExample {
public RAMDirectoryExample() {
// TODO Auto-generated constructor stub
}
static void writeIndex(RAMDirectory ramDir, Analyzer analyzer) {
try {
// IndexWriter Configuration
IndexWriterConfig iwc = new IndexWriterConfig(analyzer);
iwc.setOpenMode(OpenMode.CREATE);
// IndexWriter writes new index files to the directory
IndexWriter writer = new IndexWriter(ramDir, iwc);
// Create some docs with name and content
indexDoc(writer, "document-1", "hello world");
indexDoc(writer, "document-2", "hello happy world");
indexDoc(writer, "document-3", "hello happy world");
indexDoc(writer, "document-4", "hello hello world");
// don't forget to close the writer
writer.close();
} catch (IOException e) {
// Any error goes here
e.printStackTrace();
}
}
static void indexDoc(IndexWriter writer, String name, String content) throws IOException {
Document doc = new Document();
doc.add(new TextField("name", name, Store.YES));
doc.add(new TextField("content", content, Store.YES));
writer.addDocument(doc);
}
static void searchIndex(RAMDirectory ramDir, Analyzer analyzer) {
IndexReader reader = null;
try {
// Create Reader
reader = DirectoryReader.open(ramDir);
// Create index searcher
IndexSearcher searcher = new IndexSearcher(reader);
// Build query
QueryParser qp = new QueryParser("content", analyzer);
Query query = qp.parse("happy");
// Search the index
TopDocs foundDocs = searcher.search(query, 10);
// Total found documents
System.out.println("Total Results :: " + foundDocs.totalHits);
// Let's print found doc names and their content along with score
for (ScoreDoc sd : foundDocs.scoreDocs) {
Document d = searcher.doc(sd.doc);
System.out.println("Document Number : " + sd.doc + " :: Document Name : " + d.get("name")
+ " :: Content : " + d.get("content") + " :: Score : " + sd.score);
}
System.out.println("");
// don't forget to close the reader
reader.close();
} catch (IOException e) {
// Any error goes here
e.printStackTrace();
} catch (ParseException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
static void readIndex_Get_Documents(RAMDirectory ramDir) {
IndexReader reader = null;
try {
// Create Reader
reader = DirectoryReader.open(ramDir);
// Create index searcher
IndexSearcher searcher = new IndexSearcher(reader);
System.out.println("-----------------------Document List-----------------------");
int maxDoc = reader.maxDoc();
for (int i = 0; i < maxDoc; i++) {
Document d = reader.document(i);
/**
* There are three types of method to retrieve indexed document name list
*/
/**
* Method 1 for get document name list
*/
// System.out.println(""+d.getFields().iterator().next().stringValue());
/**
* Method 2 for get document name list
*/
// System.out.println(""+d.iterator().next().stringValue());
/**
* Method 3 for get document name list
*/
String[] vls = d.getValues("name");
for (int j = 0; j < vls.length; j++) {
System.out.println("" + vls[j].toString());
}
}
// don't forget to close the reader
reader.close();
} catch (IOException e) {
// Any error goes here
e.printStackTrace();
}
}
static void readIndex_Get_Terms(RAMDirectory ramDir) {
IndexReader reader = null;
try {
// Create Reader
reader = DirectoryReader.open(ramDir);
// Create index searcher
IndexSearcher searcher = new IndexSearcher(reader);
System.out.println("");
System.out.println("--------------------------Term List------------------------");
int maxDoc = reader.maxDoc();
for (int i = 0; i < maxDoc; i++) {
Document d = reader.document(i);
/**
* There are three types of methods to retrieve indexed term list
*/
/**
* Method 1 for retrieve terms list
*/
// System.out.println(""+d.get("content").toString());
/**
* Method 2 for retrieve terms list
*/
// System.out.println(""+d.getField("content").stringValue());
/**
* Method 3 for retrieve terms list
*/
String[] vl = searcher.doc(i).getValues("content");
for (int k = 0; k < vl.length; k++) {
System.out.println("" + vl[k].toString());
}
}
// don't forget to close the reader
reader.close();
} catch (IOException e) {
// Any error goes here
e.printStackTrace();
}
}
public static void main(String[] args) {
// Create RAMDirectory instance
RAMDirectory ramDir = new RAMDirectory();
// Builds an analyzer with the default stop words
Analyzer analyzer = new StandardAnalyzer();
// Write some docs to RAMDirectory
writeIndex(ramDir, analyzer);
// Search indexed docs in RAMDirectory
searchIndex(ramDir, analyzer);
// read Index get indexed document list
readIndex_Get_Documents(ramDir);
// read Index get indexed terms list
readIndex_Get_Terms(ramDir);
}
}
I found the way to list documents & terms list . complete example will be available on git-hub for anyone reference. https://github.com/sunone5/lucene-ramdirectory-index
来源：https://stackoverflow.com/questions/60371411/apache-lucene-8-4-1-how-to-get-indexed-fields-and-term-list