- * ReusableAnalyzerBase is a simplification of Analyzer that supports easy reuse - * for the most common use-cases. Analyzers such as - * {@link PerFieldAnalyzerWrapper} that behave differently depending upon the - * field name need to subclass Analyzer directly instead. - *
- *- * To prevent consistency problems, this class does not allow subclasses to - * extend {@link #reusableTokenStream(String, Reader)} or - * {@link #tokenStream(String, Reader)} directly. Instead, subclasses must - * implement {@link #createComponents(String, Reader)}. - *
- */ -public abstract class ReusableAnalyzerBase extends Analyzer { - - /** - * Creates a new {@link TokenStreamComponents} instance for this analyzer. - * - * @param fieldName - * the name of the fields content passed to the - * {@link TokenStreamComponents} sink as a reader - * @param aReader - * the reader passed to the {@link Tokenizer} constructor - * @return the {@link TokenStreamComponents} for this analyzer. - */ - protected abstract TokenStreamComponents createComponents(String fieldName, - Reader aReader); - - /** - * This method uses {@link #createComponents(String, Reader)} to obtain an - * instance of {@link TokenStreamComponents}. It returns the sink of the - * components and stores the components internally. Subsequent calls to this - * method will reuse the previously stored components if and only if the - * {@link TokenStreamComponents#reset(Reader)} method returned - *true. Otherwise a new instance of
- * {@link TokenStreamComponents} is created.
- *
- * @param fieldName the name of the field the created TokenStream is used for
- * @param reader the reader the streams source reads from
- */
- @Override
- public final TokenStream reusableTokenStream(final String fieldName,
- final Reader reader) throws IOException {
- TokenStreamComponents streamChain = (TokenStreamComponents)
- getPreviousTokenStream();
- final Reader r = initReader(reader);
- if (streamChain == null || !streamChain.reset(r)) {
- streamChain = createComponents(fieldName, r);
- setPreviousTokenStream(streamChain);
- }
- return streamChain.getTokenStream();
- }
-
- /**
- * This method uses {@link #createComponents(String, Reader)} to obtain an
- * instance of {@link TokenStreamComponents} and returns the sink of the
- * components. Each calls to this method will create a new instance of
- * {@link TokenStreamComponents}. Created {@link TokenStream} instances are
- * never reused.
- *
- * @param fieldName the name of the field the created TokenStream is used for
- * @param reader the reader the streams source reads from
- */
- @Override
- public final TokenStream tokenStream(final String fieldName,
- final Reader reader) {
- return createComponents(fieldName, initReader(reader)).getTokenStream();
- }
-
- /**
- * Override this if you want to add a CharFilter chain.
- */
- protected Reader initReader(Reader reader) {
- return reader;
- }
-
- /**
- * This class encapsulates the outer components of a token stream. It provides
- * access to the source ({@link Tokenizer}) and the outer end (sink), an
- * instance of {@link TokenFilter} which also serves as the
- * {@link TokenStream} returned by
- * {@link Analyzer#tokenStream(String, Reader)} and
- * {@link Analyzer#reusableTokenStream(String, Reader)}.
- */
- public static class TokenStreamComponents {
- protected final Tokenizer source;
- protected final TokenStream sink;
-
- /**
- * Creates a new {@link TokenStreamComponents} instance.
- *
- * @param source
- * the analyzer's tokenizer
- * @param result
- * the analyzer's resulting token stream
- */
- public TokenStreamComponents(final Tokenizer source,
- final TokenStream result) {
- this.source = source;
- this.sink = result;
- }
-
- /**
- * Creates a new {@link TokenStreamComponents} instance.
- *
- * @param source
- * the analyzer's tokenizer
- */
- public TokenStreamComponents(final Tokenizer source) {
- this.source = source;
- this.sink = source;
- }
-
- /**
- * Resets the encapsulated components with the given reader. This method by
- * default returns true indicating that the components have
- * been reset successfully. Subclasses of {@link ReusableAnalyzerBase} might use
- * their own {@link TokenStreamComponents} returning false if
- * the components cannot be reset.
- *
- * @param reader
- * a reader to reset the source component
- * @return true if the components were reset, otherwise
- * false
- * @throws IOException
- * if the component's reset method throws an {@link IOException}
- */
- protected boolean reset(final Reader reader) throws IOException {
- source.reset(reader);
- return true;
- }
-
- /**
- * Returns the sink {@link TokenStream}
- *
- * @return the sink {@link TokenStream}
- */
- protected TokenStream getTokenStream() {
- return sink;
- }
-
- }
-
-}