以下代码用于从索引获取tf-idf值。但是在运行它时遇到错误，在Correct_ME的行上。
使用Lucene 4.8。
DocIndexing.java
public class DocIndexing {
private DocIndexing() {}
/** Index all text files under a directory.
* @param args
* @throws java.io.IOException */
public static void main(String[] args) throws IOException {
String usage = "java org.apache.lucene.demo.IndexFiles"
+ " [-index INDEX_PATH] [-docs DOCS_PATH] [-update]\n\n"
+ "This indexes the documents in DOCS_PATH, creating a Lucene index"
+ "in INDEX_PATH that can be searched with Searching";
String indexPath = "C:/Users/dell/Documents/NetBeansProjects/IndexingSearching/Index";
String docsPath = "C:/Users/dell/Documents/NetBeansProjects/IndexingSearching/ToBeIndexed";
boolean create = true;
for(int i=0;i<args.length;i++) {
if (null != args[i]) switch (args[i]) {
case "-index":
indexPath = args[i+1];
i++;
break;
case "-docs":
docsPath = args[i+1];
i++;
break;
case "-update":
create = false;
break;
}
}
if (docsPath == null) {
System.err.println("Usage: " + usage);
System.exit(1);
}
final File docDir = new File(docsPath);
if (!docDir.canRead() && !docDir.isDirectory() &&
!docDir.isHidden() &&
!docDir.exists()) {
System.out.println("Document directory '" +docDir.getAbsolutePath()+ "' does not exist or is not readable, please check the path");
System.exit(1);
}
Date start = new Date();
try {
System.out.println("Indexing to directory '" + indexPath + "'...");
Directory dir = FSDirectory.open(new File(indexPath));
Analyzer analyzer = new StandardAnalyzer(Version.LUCENE_48);
//Filter filter = new PorterStemFilter();
IndexWriterConfig iwc = new IndexWriterConfig(Version.LUCENE_48, analyzer);
if (create) {
iwc.setOpenMode(OpenMode.CREATE);
} else {
// Add new documents to an existing index:
iwc.setOpenMode(OpenMode.CREATE_OR_APPEND);
}
try (
IndexWriter writer = new IndexWriter(dir, iwc)) {
indexDocs(writer, docDir);
}
Date end = new Date();
System.out.println(end.getTime() - start.getTime() + " total milliseconds");
} catch (IOException e) {
System.out.println(" caught a " + e.getClass() +
"\n with message: " + e.getMessage());
}
Tf_Idf tfidf = new Tf_Idf();
String field = null,term = null;
tfidf.scoreCalculator(field, term);
}
/*
* @param writer Writer to the index where the given file/dir info will be stored
* @param file The file to index, or the directory to recurse into to find files to index
* @throws IOException If there is a low-level I/O error
*/
static void indexDocs(IndexWriter writer, File file)
throws IOException {
// do not try to index files that cannot be read
if (file.canRead()) {
if (file.isDirectory()) {
String[] files = file.list();
// an IO error could occur
if (files != null) {
for (int i = 0; i < files.length; i++) {
indexDocs(writer, new File(file, files[i]));
}
}
} else {
FileInputStream fis;
try {
fis = new FileInputStream(file);
} catch (FileNotFoundException fnfe) {
return;
}
try {
// make a new, empty document
Document doc = new Document();
// Field termV = new LongField("termVector", file.g)
Field pathField = new StringField("path", file.getPath(), Field.Store.YES);
doc.add(pathField);
Field modifiedField = new LongField("modified", file.lastModified(), Field.Store.NO);
doc.add(modifiedField);
Field titleField = new TextField("title", file.getName(), Field.Store.YES);
doc.add(titleField);
Field contentsField = new TextField("contents", new BufferedReader(new InputStreamReader(fis, StandardCharsets.UTF_8)));
doc.add(contentsField);
//contentsField.setBoost((float)0.5);
//titleField.setBoost((float)2.5);
/* doc.add(new LongField("modified", file.lastModified(), Field.Store.NO));
doc.add(new TextField("title", file.getName(), Field.Store.YES));
doc.add(new TextField("contents", new BufferedReader(new InputStreamReader(fis, StandardCharsets.UTF_8))));
*/
// StringField..setBoost(1.2F);
if (writer.getConfig().getOpenMode() == OpenMode.CREATE) {
// New index, so we just add the document (no old document can be there):
System.out.println("adding " + file);
writer.addDocument(doc);
} else {
// Existing index (an old copy of this document may have been indexed) so
// we use updateDocument instead to replace the old one matching the exact
// path, if present:
System.out.println("updating " + file);
writer.updateDocument(new Term("path", file.getPath()), doc);
}
} finally {
fis.close();
}
}
}
}
}
Tf-idf.java
public class Tf_Idf {
static float tf = 1;
static float idf = 0;
private float tfidf_score;
static float [] tfidf = null;
IndexReader indexReader;
public Tf_Idf() throws IOException {
this.indexReader = DirectoryReader.open(FSDirectory.open(new File("C:/Users/dell/Documents/NetBeansProjects/IndexingSearching/Index")));
}
public void scoreCalculator (String field, String term) throws IOException
{
TFIDFSimilarity tfidfSIM = new DefaultSimilarity();
Bits liveDocs = MultiFields.getLiveDocs(indexReader);
TermsEnum termEnum = MultiFields.getTerms(indexReader, field).iterator(null);
BytesRef bytesRef=null;
while ((bytesRef = termEnum.next()) != null) {
if(bytesRef.utf8ToString().trim().equals(term.trim())) {
if(termEnum.seekExact(bytesRef)) {
idf = tfidfSIM.idf(termEnum.docFreq(), indexReader.numDocs());
DocsEnum docsEnum = termEnum.docs(liveDocs, null);
if(docsEnum != null) {
int doc=0;
while((doc = docsEnum.nextDoc()) != DocIdSetIterator.NO_MORE_DOCS) {
tf = tfidfSIM.tf(docsEnum.freq());
tfidf_score = tf * idf ;
System.out.println(" -tfidf_score-" + tfidf_score);
}
}
}
}
}
}
}
答案 0 :(得分：0)
很明显，您传递给 MultiFields 方法 null IndexReader
IndexReader reader = null;
tfidf.scoreCalculator( reader, field,term);
你需要写这样的东西：
IndexReader reader = DirectoryReader.open(FSDirectory.open(new File(PATH_TO_LUCENE_INDEX)));
tfidf.scoreCalculator( reader, field,term);
当然，您需要使用真实路径重新PATH_TO_LUCENE_INDEX。
我看到的另一个问题是 - 您在Tf_Idf中打开IndexReader但未在任何地方使用它，可能是删除它或使用它的好主意，在{{ 1}}方法，例如
scoreCalculator但是在此类的方法使用字段中， - tfidf.scoreCalculator(field,term);
而非this.indexReader您尝试传递方法indexReader
<强> UPD
scoreCalculator在此代码中，您需要将＆＃34; Index＆＃34; 替换为您的Lucene索引的实际路径，例如 - public Tf_Idf() throws IOException {
this.reader = DirectoryReader.open(FSDirectory.open(new File("Index")));
}
或/home/user/index或您拥有它的任何地方。