Lucene example source code file (TeeSinkTokenFilter.java)

This example Lucene source code file (TeeSinkTokenFilter.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Lucene tags/keywords

accept_all_filter, io, ioexception, ioexception, iterator, override, override, sinkfilter, sinkfilter, sinktokenstream, sinktokenstream, teesinktokenfilter, the, tokenstream, util, weakreference

The Lucene TeeSinkTokenFilter.java source code

package org.apache.lucene.analysis;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.io.IOException;
import java.lang.ref.WeakReference;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;

import org.apache.lucene.util.AttributeImpl;
import org.apache.lucene.util.AttributeSource;

/**
 * This TokenFilter provides the ability to set aside attribute states
 * that have already been analyzed.  This is useful in situations where multiple fields share
 * many common analysis steps and then go their separate ways.
 * <p/>
 * It is also useful for doing things like entity extraction or proper noun analysis as
 * part of the analysis workflow and saving off those tokens for use in another field.
 *
 * <pre>
TeeSinkTokenFilter source1 = new TeeSinkTokenFilter(new WhitespaceTokenizer(reader1));
TeeSinkTokenFilter.SinkTokenStream sink1 = source1.newSinkTokenStream();
TeeSinkTokenFilter.SinkTokenStream sink2 = source1.newSinkTokenStream();

TeeSinkTokenFilter source2 = new TeeSinkTokenFilter(new WhitespaceTokenizer(reader2));
source2.addSinkTokenStream(sink1);
source2.addSinkTokenStream(sink2);

TokenStream final1 = new LowerCaseFilter(source1);
TokenStream final2 = source2;
TokenStream final3 = new EntityDetect(sink1);
TokenStream final4 = new URLDetect(sink2);

d.add(new Field("f1", final1));
d.add(new Field("f2", final2));
d.add(new Field("f3", final3));
d.add(new Field("f4", final4));
 * </pre>
 * In this example, <code>sink1 and sink2 will both get tokens from both
 * <code>reader1 and reader2 after whitespace tokenizer
 * and now we can further wrap any of these in extra analysis, and more "sources" can be inserted if desired.
 * It is important, that tees are consumed before sinks (in the above example, the field names must be
 * less the sink's field names). If you are not sure, which stream is consumed first, you can simply
 * add another sink and then pass all tokens to the sinks at once using {@link #consumeAllTokens}.
 * This TokenFilter is exhausted after this. In the above example, change
 * the example above to:
 * <pre>
...
TokenStream final1 = new LowerCaseFilter(source1.newSinkTokenStream());
TokenStream final2 = source2.newSinkTokenStream();
sink1.consumeAllTokens();
sink2.consumeAllTokens();
...
 * </pre>
 * In this case, the fields can be added in any order, because the sources are not used anymore and all sinks are ready.
 * <p>Note, the EntityDetect and URLDetect TokenStreams are for the example and do not currently exist in Lucene.
 */
public final class TeeSinkTokenFilter extends TokenFilter {
  private final List<WeakReference sinks = new LinkedList>();
  
  /**
   * Instantiates a new TeeSinkTokenFilter.
   */
  public TeeSinkTokenFilter(TokenStream input) {
    super(input);
  }

  /**
   * Returns a new {@link SinkTokenStream} that receives all tokens consumed by this stream.
   */
  public SinkTokenStream newSinkTokenStream() {
    return newSinkTokenStream(ACCEPT_ALL_FILTER);
  }
  
  /**
   * Returns a new {@link SinkTokenStream} that receives all tokens consumed by this stream
   * that pass the supplied filter.
   * @see SinkFilter
   */
  public SinkTokenStream newSinkTokenStream(SinkFilter filter) {
    SinkTokenStream sink = new SinkTokenStream(this.cloneAttributes(), filter);
    this.sinks.add(new WeakReference<SinkTokenStream>(sink));
    return sink;
  }
  
  /**
   * Adds a {@link SinkTokenStream} created by another <code>TeeSinkTokenFilter
   * to this one. The supplied stream will also receive all consumed tokens.
   * This method can be used to pass tokens from two different tees to one sink.
   */
  public void addSinkTokenStream(final SinkTokenStream sink) {
    // check that sink has correct factory
    if (!this.getAttributeFactory().equals(sink.getAttributeFactory())) {
      throw new IllegalArgumentException("The supplied sink is not compatible to this tee");
    }
    // add eventually missing attribute impls to the existing sink
    for (Iterator<AttributeImpl> it = this.cloneAttributes().getAttributeImplsIterator(); it.hasNext(); ) {
      sink.addAttributeImpl(it.next());
    }
    this.sinks.add(new WeakReference<SinkTokenStream>(sink));
  }
  
  /**
   * <code>TeeSinkTokenFilter passes all tokens to the added sinks
   * when itself is consumed. To be sure, that all tokens from the input
   * stream are passed to the sinks, you can call this methods.
   * This instance is exhausted after this, but all sinks are instant available.
   */
  public void consumeAllTokens() throws IOException {
    while (incrementToken()) {}
  }
  
  @Override
  public boolean incrementToken() throws IOException {
    if (input.incrementToken()) {
      // capture state lazily - maybe no SinkFilter accepts this state
      AttributeSource.State state = null;
      for (WeakReference<SinkTokenStream> ref : sinks) {
        final SinkTokenStream sink = ref.get();
        if (sink != null) {
          if (sink.accept(this)) {
            if (state == null) {
              state = this.captureState();
            }
            sink.addState(state);
          }
        }
      }
      return true;
    }
    
    return false;
  }
  
  @Override
  public final void end() throws IOException {
    super.end();
    AttributeSource.State finalState = captureState();
    for (WeakReference<SinkTokenStream> ref : sinks) {
      final SinkTokenStream sink = ref.get();
      if (sink != null) {
        sink.setFinalState(finalState);
      }
    }
  }
  
  /**
   * A filter that decides which {@link AttributeSource} states to store in the sink.
   */
  public static abstract class SinkFilter {
    /**
     * Returns true, iff the current state of the passed-in {@link AttributeSource} shall be stored
     * in the sink. 
     */
    public abstract boolean accept(AttributeSource source);
    
    /**
     * Called by {@link SinkTokenStream#reset()}. This method does nothing by default
     * and can optionally be overridden.
     */
    public void reset() throws IOException {
      // nothing to do; can be overridden
    }
  }
  
  public static final class SinkTokenStream extends TokenStream {
    private final List<AttributeSource.State> cachedStates = new LinkedList();
    private AttributeSource.State finalState;
    private Iterator<AttributeSource.State> it = null;
    private SinkFilter filter;
    
    private SinkTokenStream(AttributeSource source, SinkFilter filter) {
      super(source);
      this.filter = filter;
    }
    
    private boolean accept(AttributeSource source) {
      return filter.accept(source);
    }
    
    private void addState(AttributeSource.State state) {
      if (it != null) {
        throw new IllegalStateException("The tee must be consumed before sinks are consumed.");
      }
      cachedStates.add(state);
    }
    
    private void setFinalState(AttributeSource.State finalState) {
      this.finalState = finalState;
    }
    
    @Override
    public final boolean incrementToken() throws IOException {
      // lazy init the iterator
      if (it == null) {
        it = cachedStates.iterator();
      }
    
      if (!it.hasNext()) {
        return false;
      }
      
      AttributeSource.State state = it.next();
      restoreState(state);
      return true;
    }
  
    @Override
    public final void end() throws IOException {
      if (finalState != null) {
        restoreState(finalState);
      }
    }
    
    @Override
    public final void reset() {
      it = cachedStates.iterator();
    }
  }
    
  private static final SinkFilter ACCEPT_ALL_FILTER = new SinkFilter() {
    @Override
    public boolean accept(AttributeSource source) {
      return true;
    }
  };
  
}