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. */ html' target='_blank'>public ScoreDocComparator newComparator(IndexReader reader,String fieldname) throws IOException view plaincopy to clipboardprint? /** * 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; view plaincopy to clipboardprint? //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(); view plaincopy to clipboardprint? /** * 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. */
