Lucene中的自定義排序功能和Java集合中的自定義排序的實現方法差不多,都要實現一下比較接口. 在Java中只要實現Comparable接口就可以了.但是在Lucene中要實現SortComparatorSource接口和ScoreDocComparator接口.在了解具體實現方法之前先來看看這兩個接口的定義吧.
SortComparatorSource接口的功能是返回一個用來排序ScoreDocs的comparator(Expert: returns a comparator for sorting ScoreDocs).該接口只定義了一個方法.如下:
Java代碼
/**
* Creates a comparator for the field in the given index.
* @param reader - Index to create comparator for.
* @param fieldname - Field to create comparator for.
* @return Comparator of ScoreDoc objects.
* @throws IOException - If an error occurs reading the index.
*/
public ScoreDocComparator newComparator(IndexReader reader,String fieldname) throws IOException
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/**
* Creates a comparator for the field in the given index.
* @param reader - Index to create comparator for.
* @param fieldname - Field to create comparator for.
* @return Comparator of ScoreDoc objects.
* @throws IOException - If an error occurs reading the index.
*/
public ScoreDocComparator newComparator(IndexReader reader,String fieldname) throws IOException
/**
* Creates a comparator for the field in the given index.
* @param reader - Index to create comparator for.
* @param fieldname - Field to create comparator for.
* @return Comparator of ScoreDoc objects.
* @throws IOException - If an error occurs reading the index.
*/
public ScoreDocComparator newComparator(IndexReader reader,String fieldname) throws IOException
該方法只是創造一個ScoreDocComparator 實例用來實現排序.所以我們還要實現ScoreDocComparator 接口.來看看ScoreDocComparator 接口.功能是比較來兩個ScoreDoc 對象來排序(Compares two ScoreDoc objects for sorting) 里面定義了兩個Lucene實現的靜態實例.如下:
Java代碼
//Special comparator for sorting hits according to computed relevance (document score).
public static final ScoreDocComparator RELEVANCE;
//Special comparator for sorting hits according to index order (document number).
public static final ScoreDocComparator INDEXORDER;
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//Special comparator for sorting hits according to computed relevance (document score).
public static final ScoreDocComparator RELEVANCE;
//Special comparator for sorting hits according to index order (document number).
public static final ScoreDocComparator INDEXORDER;
//Special comparator for sorting hits according to computed relevance (document score).
public static final ScoreDocComparator RELEVANCE;

//Special comparator for sorting hits according to index order (document number).
public static final ScoreDocComparator INDEXORDER;
有3個方法與排序相關,需要我們實現 分別如下:
Java代碼
/**
* Compares two ScoreDoc objects and returns a result indicating their sort order.
* @param i First ScoreDoc
* @param j Second ScoreDoc
* @return -1 if i should come before j;
* 1 if i should come after j;
* 0 if they are equal
*/
public int compare(ScoreDoc i,ScoreDoc j);
/**
* Returns the value used to sort the given document. The object returned must implement the java.io.Serializable interface. This is used by multisearchers to determine how to collate results from their searchers.
* @param i Document
* @return Serializable object
*/
public Comparable sortValue(ScoreDoc i);
/**
* Returns the type of sort. Should return SortField.SCORE, SortField.DOC, SortField.STRING, SortField.INTEGER, SortField.FLOAT or SortField.CUSTOM. It is not valid to return SortField.AUTO. This is used by multisearchers to determine how to collate results from their searchers.
* @return One of the constants in SortField.
*/
public int sortType();
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/**
* Compares two ScoreDoc objects and returns a result indicating their sort order.
* @param i First ScoreDoc
* @param j Second ScoreDoc
* @return -1 if i should come before j;
* 1 if i should come after j;
* 0 if they are equal
*/
public int compare(ScoreDoc i,ScoreDoc j);
/**
* Returns the value used to sort the given document. The object returned must implement the java.io.Serializable interface. This is used by multisearchers to determine how to collate results from their searchers.
* @param i Document
* @return Serializable object
*/
public Comparable sortValue(ScoreDoc i);
/**
* Returns the type of sort. Should return SortField.SCORE, SortField.DOC, SortField.STRING, SortField.INTEGER, SortField.FLOAT or SortField.CUSTOM. It is not valid to return SortField.AUTO. This is used by multisearchers to determine how to collate results from their searchers.
* @return One of the constants in SortField.
*/
public int sortType();
/**
* Compares two ScoreDoc objects and returns a result indicating their sort order.
* @param i First ScoreDoc
* @param j Second ScoreDoc
* @return -1 if i should come before j;
* 1 if i should come after j;
* 0 if they are equal
*/
public int compare(ScoreDoc i,ScoreDoc j);
/**
* Returns the value used to sort the given document. The object returned must implement the java.io.Serializable interface. This is used by multisearchers to determine how to collate results from their searchers.
* @param i Document
* @return Serializable object
*/
public Comparable sortValue(ScoreDoc i);
/**
* Returns the type of sort. Should return SortField.SCORE, SortField.DOC, SortField.STRING, SortField.INTEGER, SortField.FLOAT or SortField.CUSTOM. It is not valid to return SortField.AUTO. This is used by multisearchers to determine how to collate results from their searchers.
* @return One of the constants in SortField.
*/
public int sortType();
看個例子吧!
該例子為Lucene in Action中的一個實現,用來搜索距你最近的餐館的名字. 餐館坐標用字符串"x,y"來存儲.
Java代碼
package com.nikee.lucene;
import java.io.IOException;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.TermDocs;
import org.apache.lucene.index.TermEnum;
import org.apache.lucene.search.ScoreDoc;
import org.apache.lucene.search.ScoreDocComparator;
import org.apache.lucene.search.SortComparatorSource;
import org.apache.lucene.search.SortField;
//實現了搜索距你最近的餐館的名字. 餐館坐標用字符串"x,y"來存儲
//DistanceComparatorSource 實現了SortComparatorSource接口
public class DistanceComparatorSource implements SortComparatorSource {
private static final long serialVersionUID = 1L;
// x y 用來保存 坐標位置
private int x;
private int y;
public DistanceComparatorSource(int x, int y) {
this.x = x;
this.y = y;
}
// 返回ScoreDocComparator 用來實現排序功能
public ScoreDocComparator newComparator(IndexReader reader, String fieldname) throws IOException {
return new DistanceScoreDocLookupComparator(reader, fieldname, x, y);
}
//DistanceScoreDocLookupComparator 實現了ScoreDocComparator 用來排序
private static class DistanceScoreDocLookupComparator implements ScoreDocComparator {
private float[] distances; // 保存每個餐館到指定點的距離
// 構造函數 , 構造函數在這里幾乎完成所有的準備工作.
public DistanceScoreDocLookupComparator(IndexReader reader, String fieldname, int x, int y) throws IOException {
System.out.println("fieldName2="+fieldname);
final TermEnum enumerator = reader.terms(new Term(fieldname, ""));
System.out.println("maxDoc="+reader.maxDoc());
distances = new float[reader.maxDoc()]; // 初始化distances
if (distances.length > 0) {
TermDocs termDocs = reader.termDocs();
try {
if (enumerator.term() == null) {
throw new RuntimeException("no terms in field " + fieldname);
}
int i = 0,j = 0;
do {
System.out.println("in do-while :" + i ++);
Term term = enumerator.term(); // 取出每一個Term
if (term.field() != fieldname) // 與給定的域不符合則比較下一個
break;
//Sets this to the data for the current term in a TermEnum.
//This may be optimized in some implementations.
termDocs.seek(enumerator); //參考TermDocs Doc
while (termDocs.next()) {
System.out.println(" in while :" + j ++);
System.out.println(" in while ,Term :" + term.toString());
String[] xy = term.text().split(","); // 去處x y
int deltax = Integer.parseInt(xy[0]) - x;
int deltay = Integer.parseInt(xy[1]) - y;
// 計算距離
distances[termDocs.doc()] = (float) Math.sqrt(deltax * deltax + deltay * deltay);
}
}
while (enumerator.next());
} finally {
termDocs.close();
}
}
}
//有上面的構造函數的準備 這里就比較簡單了
public int compare(ScoreDoc i, ScoreDoc j) {
if (distances[i.doc] < distances[j.doc])
return -1;
if (distances[i.doc] > distances[j.doc])
return 1;
return 0;
}
// 返回距離
public Comparable sortValue(ScoreDoc i) {
return new Float(distances[i.doc]);
}
//指定SortType
public int sortType() {
return SortField.FLOAT;
}
}
public String toString() {
return "Distance from (" + x + "," + y + ")";
}
}
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package com.nikee.lucene;
import java.io.IOException;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.TermDocs;
import org.apache.lucene.index.TermEnum;
import org.apache.lucene.search.ScoreDoc;
import org.apache.lucene.search.ScoreDocComparator;
import org.apache.lucene.search.SortComparatorSource;
import org.apache.lucene.search.SortField;
//實現了搜索距你最近的餐館的名字. 餐館坐標用字符串"x,y"來存儲
//DistanceComparatorSource 實現了SortComparatorSource接口
public class DistanceComparatorSource implements SortComparatorSource {
private static final long serialVersionUID = 1L;
// x y 用來保存 坐標位置
private int x;
private int y;
public DistanceComparatorSource(int x, int y) {
this.x = x;
this.y = y;
}
// 返回ScoreDocComparator 用來實現排序功能
public ScoreDocComparator newComparator(IndexReader reader, String fieldname) throws IOException {
return new DistanceScoreDocLookupComparator(reader, fieldname, x, y);
}
//DistanceScoreDocLookupComparator 實現了ScoreDocComparator 用來排序
private static class DistanceScoreDocLookupComparator implements ScoreDocComparator {
private float[] distances; // 保存每個餐館到指定點的距離
// 構造函數 , 構造函數在這里幾乎完成所有的準備工作.
public DistanceScoreDocLookupComparator(IndexReader reader, String fieldname, int x, int y) throws IOException {
System.out.println("fieldName2="+fieldname);
final TermEnum enumerator = reader.terms(new Term(fieldname, ""));
System.out.println("maxDoc="+reader.maxDoc());
distances = new float[reader.maxDoc()]; // 初始化distances
if (distances.length > 0) {
TermDocs termDocs = reader.termDocs();
try {
if (enumerator.term() == null) {
throw new RuntimeException("no terms in field " + fieldname);
}
int i = 0,j = 0;
do {
System.out.println("in do-while :" + i ++);
Term term = enumerator.term(); // 取出每一個Term
if (term.field() != fieldname) // 與給定的域不符合則比較下一個
break;
//Sets this to the data for the current term in a TermEnum.
//This may be optimized in some implementations.
termDocs.seek(enumerator); //參考TermDocs Doc
while (termDocs.next()) {
System.out.println(" in while :" + j ++);
System.out.println(" in while ,Term :" + term.toString());
String[] xy = term.text().split(","); // 去處x y
int deltax = Integer.parseInt(xy[0]) - x;
int deltay = Integer.parseInt(xy[1]) - y;
// 計算距離
distances[termDocs.doc()] = (float) Math.sqrt(deltax * deltax + deltay * deltay);
}
}
while (enumerator.next());
} finally {
termDocs.close();
}
}
}
//有上面的構造函數的準備 這里就比較簡單了
public int compare(ScoreDoc i, ScoreDoc j) {
if (distances[i.doc] < distances[j.doc])
return -1;
if (distances[i.doc] > distances[j.doc])
return 1;
return 0;
}
// 返回距離
public Comparable sortValue(ScoreDoc i) {
return new Float(distances[i.doc]);
}
//指定SortType
public int sortType() {
return SortField.FLOAT;
}
}
public String toString() {
return "Distance from (" + x + "," + y + ")";
}
}
package com.nikee.lucene;
import java.io.IOException;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.TermDocs;
import org.apache.lucene.index.TermEnum;
import org.apache.lucene.search.ScoreDoc;
import org.apache.lucene.search.ScoreDocComparator;
import org.apache.lucene.search.SortComparatorSource;
import org.apache.lucene.search.SortField;
//實現了搜索距你最近的餐館的名字. 餐館坐標用字符串"x,y"來存儲
//DistanceComparatorSource 實現了SortComparatorSource接口
public class DistanceComparatorSource implements SortComparatorSource {
private static final long serialVersionUID = 1L;

// x y 用來保存 坐標位置
private int x;
private int y;

public DistanceComparatorSource(int x, int y) {
this.x = x;
this.y = y;
}

// 返回ScoreDocComparator 用來實現排序功能
public ScoreDocComparator newComparator(IndexReader reader, String fieldname) throws IOException {
return new DistanceScoreDocLookupComparator(reader, fieldname, x, y);
}

//DistanceScoreDocLookupComparator 實現了ScoreDocComparator 用來排序
private static class DistanceScoreDocLookupComparator implements ScoreDocComparator {
private float[] distances; // 保存每個餐館到指定點的距離

// 構造函數 , 構造函數在這里幾乎完成所有的準備工作.
public DistanceScoreDocLookupComparator(IndexReader reader, String fieldname, int x, int y) throws IOException {
System.out.println("fieldName2="+fieldname);
final TermEnum enumerator = reader.terms(new Term(fieldname, ""));

System.out.println("maxDoc="+reader.maxDoc());
distances = new float[reader.maxDoc()]; // 初始化distances
if (distances.length > 0) {
TermDocs termDocs = reader.termDocs();
try {
if (enumerator.term() == null) {
throw new RuntimeException("no terms in field " + fieldname);
}
int i = 0,j = 0;
do {
System.out.println("in do-while :" + i ++);
Term term = enumerator.term(); // 取出每一個Term
if (term.field() != fieldname) // 與給定的域不符合則比較下一個
break;

//Sets this to the data for the current term in a TermEnum.
//This may be optimized in some implementations.
termDocs.seek(enumerator); //參考TermDocs Doc
while (termDocs.next()) {
System.out.println(" in while :" + j ++);
System.out.println(" in while ,Term :" + term.toString());

String[] xy = term.text().split(","); // 去處x y
int deltax = Integer.parseInt(xy[0]) - x;
int deltay = Integer.parseInt(xy[1]) - y;
// 計算距離
distances[termDocs.doc()] = (float) Math.sqrt(deltax * deltax + deltay * deltay);
}
}
while (enumerator.next());
} finally {
termDocs.close();
}
}
}
//有上面的構造函數的準備 這里就比較簡單了
public int compare(ScoreDoc i, ScoreDoc j) {
if (distances[i.doc] < distances[j.doc])
return -1;
if (distances[i.doc] > distances[j.doc])
return 1;
return 0;
}

// 返回距離
public Comparable sortValue(ScoreDoc i) {
return new Float(distances[i.doc]);
}

//指定SortType
public int sortType() {
return SortField.FLOAT;
}
}

public String toString() {
return "Distance from (" + x + "," + y + ")";
}
}
這是一個實現了上面兩個接口的兩個類, 里面帶有詳細注釋, 可以看出 自定義排序并不是很難的. 該實現能否正確實現,我們來看看測試代碼能否通過吧.
Java代碼
package com.nikee.lucene.test;
import java.io.IOException;
import junit.framework.TestCase;
import org.apache.lucene.analysis.WhitespaceAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.Term;
import org.apache.lucene.search.FieldDoc;
import org.apache.lucene.search.Hits;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.ScoreDoc;
import org.apache.lucene.search.Sort;
import org.apache.lucene.search.SortField;
import org.apache.lucene.search.TermQuery;
import org.apache.lucene.search.TopFieldDocs;
import org.apache.lucene.store.RAMDirectory;
import com.nikee.lucene.DistanceComparatorSource;
public class DistanceComparatorSourceTest extends TestCase {
private RAMDirectory directory;
private IndexSearcher searcher;
private Query query;
//建立測試環境
protected void setUp() throws Exception {
directory = new RAMDirectory();
IndexWriter writer = new IndexWriter(directory, new WhitespaceAnalyzer(), true);
addPoint(writer, "El Charro", "restaurant", 1, 2);
addPoint(writer, "Cafe Poca Cosa", "restaurant", 5, 9);
addPoint(writer, "Los Betos", "restaurant", 9, 6);
addPoint(writer, "Nico's Taco Shop", "restaurant", 3, 8);
writer.close();
searcher = new IndexSearcher(directory);
query = new TermQuery(new Term("type", "restaurant"));
}
private void addPoint(IndexWriter writer, String name, String type, int x, int y) throws IOException {
Document doc = new Document();
doc.add(new Field("name", name, Field.Store.YES, Field.Index.TOKENIZED));
doc.add(new Field("type", type, Field.Store.YES, Field.Index.TOKENIZED));
doc.add(new Field("location", x + "," + y, Field.Store.YES, Field.Index.UN_TOKENIZED));
writer.addDocument(doc);
}
public void testNearestRestaurantToHome() throws Exception {
//使用DistanceComparatorSource來構造一個SortField
Sort sort = new Sort(new SortField("location", new DistanceComparatorSource(0, 0)));
Hits hits = searcher.search(query, sort); // 搜索
//測試
assertEquals("closest", "El Charro", hits.doc(0).get("name"));
assertEquals("furthest", "Los Betos", hits.doc(3).get("name"));
}
public void testNeareastRestaurantToWork() throws Exception {
Sort sort = new Sort(new SortField("location", new DistanceComparatorSource(10, 10))); // 工作的坐標 10,10
//上面的測試實現了自定義排序,但是并不能訪問自定義排序的更詳細信息,利用
//TopFieldDocs 可以進一步訪問相關信息
TopFieldDocs docs = searcher.search(query, null, 3, sort);
assertEquals(4, docs.totalHits);
assertEquals(3, docs.scoreDocs.length);
//取得FieldDoc 利用FieldDoc可以取得關于排序的更詳細信息 請查看FieldDoc Doc
FieldDoc fieldDoc = (FieldDoc) docs.scoreDocs[0];
assertEquals("(10,10) -> (9,6) = sqrt(17)", new Float(Math.sqrt(17)), fieldDoc.fields[0]);
Document document = searcher.doc(fieldDoc.doc);
assertEquals("Los Betos", document.get("name"));
dumpDocs(sort, docs); // 顯示相關信息
}
// 顯示有關排序的信息
private void dumpDocs(Sort sort, TopFieldDocs docs) throws IOException {
System.out.println("Sorted by: " + sort);
ScoreDoc[] scoreDocs = docs.scoreDocs;
for (int i = 0; i < scoreDocs.length; i++) {
FieldDoc fieldDoc = (FieldDoc) scoreDocs[i];
Float distance = (Float) fieldDoc.fields[0];
Document doc = searcher.doc(fieldDoc.doc);
System.out.println(" " + doc.get("name") + " @ (" + doc.get("location") + ") -> " + distance);
}
}
}