* In order to define what analysis is done, subclasses must define their
* {@link TokenStreamComponents TokenStreamComponents} in {@link #createComponents(String)}.
* The components are then reused in each call to {@link #tokenStream(String, Reader)}.
*
* For some concrete implementations bundled with Lucene, look in the analysis modules:
*
storedValue = new CloseableThreadLocal<>();
/**
* Create a new Analyzer, reusing the same set of components per-thread
* across calls to {@link #tokenStream(String, Reader)}.
*/
public Analyzer() {
this(GLOBAL_REUSE_STRATEGY);
}
/**
* Expert: create a new Analyzer with a custom {@link ReuseStrategy}.
*
* NOTE: if you just want to reuse on a per-field basis, it's easier to
* use a subclass of {@link AnalyzerWrapper} such as
*
* PerFieldAnalyerWrapper instead.
*/
public Analyzer(ReuseStrategy reuseStrategy) {
this.reuseStrategy = reuseStrategy;
}
/**
* 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
* @return the {@link TokenStreamComponents} for this analyzer.
*/
protected abstract TokenStreamComponents createComponents(String fieldName);
/**
* Returns a TokenStream suitable for fieldName, tokenizing
* the contents of reader.
*
* This method uses {@link #createComponents(String)} 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 after resetting them
* through {@link TokenStreamComponents#setReader(Reader)}.
*
* NOTE: After calling this method, the consumer must follow the
* workflow described in {@link TokenStream} to properly consume its contents.
* See the {@link org.apache.lucene.analysis Analysis package documentation} for
* some examples demonstrating this.
*
* NOTE: If your data is available as a {@code String}, use
* {@link #tokenStream(String, String)} which reuses a {@code StringReader}-like
* instance internally.
*
* @param fieldName the name of the field the created TokenStream is used for
* @param reader the reader the streams source reads from
* @return TokenStream for iterating the analyzed content of reader
* @throws AlreadyClosedException if the Analyzer is closed.
* @see #tokenStream(String, String)
*/
public final TokenStream tokenStream(final String fieldName,
final Reader reader) {
TokenStreamComponents components = reuseStrategy.getReusableComponents(this, fieldName);
final Reader r = initReader(fieldName, reader);
if (components == null) {
components = createComponents(fieldName);
reuseStrategy.setReusableComponents(this, fieldName, components);
}
components.setReader(r);
return components.getTokenStream();
}
/**
* Returns a TokenStream suitable for fieldName, tokenizing
* the contents of text.
*
* This method uses {@link #createComponents(String)} 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 after resetting them
* through {@link TokenStreamComponents#setReader(Reader)}.
*
* NOTE: After calling this method, the consumer must follow the
* workflow described in {@link TokenStream} to properly consume its contents.
* See the {@link org.apache.lucene.analysis Analysis package documentation} for
* some examples demonstrating this.
*
* @param fieldName the name of the field the created TokenStream is used for
* @param text the String the streams source reads from
* @return TokenStream for iterating the analyzed content of reader
* @throws AlreadyClosedException if the Analyzer is closed.
* @see #tokenStream(String, Reader)
*/
public final TokenStream tokenStream(final String fieldName, final String text) {
TokenStreamComponents components = reuseStrategy.getReusableComponents(this, fieldName);
@SuppressWarnings("resource") final ReusableStringReader strReader =
(components == null || components.reusableStringReader == null) ?
new ReusableStringReader() : components.reusableStringReader;
strReader.setValue(text);
final Reader r = initReader(fieldName, strReader);
if (components == null) {
components = createComponents(fieldName);
reuseStrategy.setReusableComponents(this, fieldName, components);
}
components.setReader(r);
components.reusableStringReader = strReader;
return components.getTokenStream();
}
/**
* Override this if you want to add a CharFilter chain.
*
* The default implementation returns reader
* unchanged.
*
* @param fieldName IndexableField name being indexed
* @param reader original Reader
* @return reader, optionally decorated with CharFilter(s)
*/
protected Reader initReader(String fieldName, Reader reader) {
return reader;
}
/**
* Invoked before indexing a IndexableField instance if
* terms have already been added to that field. This allows custom
* analyzers to place an automatic position increment gap between
* IndexbleField instances using the same field name. The default value
* position increment gap is 0. With a 0 position increment gap and
* the typical default token position increment of 1, all terms in a field,
* including across IndexableField instances, are in successive positions, allowing
* exact PhraseQuery matches, for instance, across IndexableField instance boundaries.
*
* @param fieldName IndexableField name being indexed.
* @return position increment gap, added to the next token emitted from {@link #tokenStream(String,Reader)}.
* This value must be {@code >= 0}.
*/
public int getPositionIncrementGap(String fieldName) {
return 0;
}
/**
* Just like {@link #getPositionIncrementGap}, except for
* Token offsets instead. By default this returns 1.
* This method is only called if the field
* produced at least one token for indexing.
*
* @param fieldName the field just indexed
* @return offset gap, added to the next token emitted from {@link #tokenStream(String,Reader)}.
* This value must be {@code >= 0}.
*/
public int getOffsetGap(String fieldName) {
return 1;
}
/**
* Returns the used {@link ReuseStrategy}.
*/
public final ReuseStrategy getReuseStrategy() {
return reuseStrategy;
}
/**
* Set the version of Lucene this analyzer should mimic the behavior for for analysis.
*/
public void setVersion(Version v) {
version = v; // TODO: make write once?
}
/**
* Return the version of Lucene this analyzer will mimic the behavior of for analysis.
*/
public Version getVersion() {
return version;
}
/** Frees persistent resources used by this Analyzer */
@Override
public void close() {
if (storedValue != null) {
storedValue.close();
storedValue = null;
}
}
/**
* 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)}.
*/
public static class TokenStreamComponents {
/**
* Original source of the tokens.
*/
protected final Tokenizer source;
/**
* Sink tokenstream, such as the outer tokenfilter decorating
* the chain. This can be the source if there are no filters.
*/
protected final TokenStream sink;
/** Internal cache only used by {@link Analyzer#tokenStream(String, String)}. */
transient ReusableStringReader reusableStringReader;
/**
* 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. If the components
* cannot be reset, an Exception should be thrown.
*
* @param reader
* a reader to reset the source component
*/
protected void setReader(final Reader reader) {
source.setReader(reader);
}
/**
* Returns the sink {@link TokenStream}
*
* @return the sink {@link TokenStream}
*/
public TokenStream getTokenStream() {
return sink;
}
/**
* Returns the component's {@link Tokenizer}
*
* @return Component's {@link Tokenizer}
*/
public Tokenizer getTokenizer() {
return source;
}
}
/**
* Strategy defining how TokenStreamComponents are reused per call to
* {@link Analyzer#tokenStream(String, java.io.Reader)}.
*/
public static abstract class ReuseStrategy {
/** Sole constructor. (For invocation by subclass constructors, typically implicit.) */
public ReuseStrategy() {}
/**
* Gets the reusable TokenStreamComponents for the field with the given name.
*
* @param analyzer Analyzer from which to get the reused components. Use
* {@link #getStoredValue(Analyzer)} and {@link #setStoredValue(Analyzer, Object)}
* to access the data on the Analyzer.
* @param fieldName Name of the field whose reusable TokenStreamComponents
* are to be retrieved
* @return Reusable TokenStreamComponents for the field, or {@code null}
* if there was no previous components for the field
*/
public abstract TokenStreamComponents getReusableComponents(Analyzer analyzer, String fieldName);
/**
* Stores the given TokenStreamComponents as the reusable components for the
* field with the give name.
*
* @param fieldName Name of the field whose TokenStreamComponents are being set
* @param components TokenStreamComponents which are to be reused for the field
*/
public abstract void setReusableComponents(Analyzer analyzer, String fieldName, TokenStreamComponents components);
/**
* Returns the currently stored value.
*
* @return Currently stored value or {@code null} if no value is stored
* @throws AlreadyClosedException if the Analyzer is closed.
*/
protected final Object getStoredValue(Analyzer analyzer) {
if (analyzer.storedValue == null) {
throw new AlreadyClosedException("this Analyzer is closed");
}
return analyzer.storedValue.get();
}
/**
* Sets the stored value.
*
* @param storedValue Value to store
* @throws AlreadyClosedException if the Analyzer is closed.
*/
protected final void setStoredValue(Analyzer analyzer, Object storedValue) {
if (analyzer.storedValue == null) {
throw new AlreadyClosedException("this Analyzer is closed");
}
analyzer.storedValue.set(storedValue);
}
}
/**
* A predefined {@link ReuseStrategy} that reuses the same components for
* every field.
*/
public static final ReuseStrategy GLOBAL_REUSE_STRATEGY = new ReuseStrategy() {
@Override
public TokenStreamComponents getReusableComponents(Analyzer analyzer, String fieldName) {
return (TokenStreamComponents) getStoredValue(analyzer);
}
@Override
public void setReusableComponents(Analyzer analyzer, String fieldName, TokenStreamComponents components) {
setStoredValue(analyzer, components);
}
};
/**
* A predefined {@link ReuseStrategy} that reuses components per-field by
* maintaining a Map of TokenStreamComponent per field name.
*/
public static final ReuseStrategy PER_FIELD_REUSE_STRATEGY = new ReuseStrategy() {
@SuppressWarnings("unchecked")
@Override
public TokenStreamComponents getReusableComponents(Analyzer analyzer, String fieldName) {
Map componentsPerField = (Map) getStoredValue(analyzer);
return componentsPerField != null ? componentsPerField.get(fieldName) : null;
}
@SuppressWarnings("unchecked")
@Override
public void setReusableComponents(Analyzer analyzer, String fieldName, TokenStreamComponents components) {
Map componentsPerField = (Map) getStoredValue(analyzer);
if (componentsPerField == null) {
componentsPerField = new HashMap<>();
setStoredValue(analyzer, componentsPerField);
}
componentsPerField.put(fieldName, components);
}
};
}
