org.apache.lucene.analysis.Tokenizer.java Source code

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Here is the source code for org.apache.lucene.analysis.Tokenizer.java

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/*
 * 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.
 */
package org.apache.lucene.analysis;

import java.io.IOException;
import java.io.Reader;

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

/** A Tokenizer is a TokenStream whose input is a Reader.
  <p>
  This is an abstract class; subclasses must override {@link #incrementToken()}
  <p>
  NOTE: Subclasses overriding {@link #incrementToken()} must
  call {@link AttributeSource#clearAttributes()} before
  setting attributes.
 */
public abstract class Tokenizer extends TokenStream {
    /** The text source for this Tokenizer. */
    protected Reader input = ILLEGAL_STATE_READER;

    /** Pending reader: not actually assigned to input until reset() */
    private Reader inputPending = ILLEGAL_STATE_READER;

    /**
     * Construct a tokenizer with no input, awaiting a call to {@link #setReader(java.io.Reader)}
     * to provide input.
     */
    protected Tokenizer() {
        //
    }

    /**
     * Construct a tokenizer with no input, awaiting a call to {@link #setReader(java.io.Reader)} to
     * provide input.
     * @param factory attribute factory.
     */
    protected Tokenizer(AttributeFactory factory) {
        super(factory);
    }

    /**
     * {@inheritDoc}
     * <p>
     * <b>NOTE:</b> 
     * The default implementation closes the input Reader, so
     * be sure to call <code>super.close()</code> when overriding this method.
     */
    @Override
    public void close() throws IOException {
        input.close();
        // LUCENE-2387: don't hold onto Reader after close, so
        // GC can reclaim
        inputPending = input = ILLEGAL_STATE_READER;
    }

    /** Return the corrected offset. If {@link #input} is a {@link CharFilter} subclass
     * this method calls {@link CharFilter#correctOffset}, else returns <code>currentOff</code>.
     * @param currentOff offset as seen in the output
     * @return corrected offset based on the input
     * @see CharFilter#correctOffset
     */
    protected final int correctOffset(int currentOff) {
        return (input instanceof CharFilter) ? ((CharFilter) input).correctOffset(currentOff) : currentOff;
    }

    /** Expert: Set a new reader on the Tokenizer.  Typically, an
     *  analyzer (in its tokenStream method) will use
     *  this to re-use a previously created tokenizer. */
    public final void setReader(Reader input) {
        if (input == null) {
            throw new NullPointerException("input must not be null");
        } else if (this.input != ILLEGAL_STATE_READER) {
            throw new IllegalStateException("TokenStream contract violation: close() call missing");
        }
        this.inputPending = input;
        setReaderTestPoint();
    }

    @Override
    public void reset() throws IOException {
        super.reset();
        input = inputPending;
        inputPending = ILLEGAL_STATE_READER;
    }

    // only used for testing
    void setReaderTestPoint() {
    }

    private static final Reader ILLEGAL_STATE_READER = new Reader() {
        @Override
        public int read(char[] cbuf, int off, int len) {
            throw new IllegalStateException("TokenStream contract violation: reset()/close() call missing, "
                    + "reset() called multiple times, or subclass does not call super.reset(). "
                    + "Please see Javadocs of TokenStream class for more information about the correct consuming workflow.");
        }

        @Override
        public void close() {
        }
    };
}