field.java

Lucene a java open-source SearchEngine Framework

package org.apache.lucene.document;

/**
 * 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 org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.index.IndexWriter;   // for javadoc
import org.apache.lucene.util.Parameter;

import java.io.Reader;
import java.io.Serializable;

/**
  A field is a section of a Document.  Each field has two parts, a name and a
  value.  Values may be free text, provided as a String or as a Reader, or they
  may be atomic keywords, which are not further processed.  Such keywords may
  be used to represent dates, urls, etc.  Fields are optionally stored in the
  index, so that they may be returned with hits on the document.
  */

public final class Field extends AbstractField implements Fieldable, Serializable {
  
  /** Specifies whether and how a field should be stored. */
  public static final class Store extends Parameter implements Serializable {

    private Store(String name) {
      super(name);
    }

    /** Store the original field value in the index in a compressed form. This is
     * useful for long documents and for binary valued fields.
     */
    public static final Store COMPRESS = new Store("COMPRESS");

    /** Store the original field value in the index. This is useful for short texts
     * like a document's title which should be displayed with the results. The
     * value is stored in its original form, i.e. no analyzer is used before it is
     * stored.
     */
    public static final Store YES = new Store("YES");

    /** Do not store the field value in the index. */
    public static final Store NO = new Store("NO");
  }

  /** Specifies whether and how a field should be indexed. */
  public static final class Index extends Parameter implements Serializable {

    private Index(String name) {
      super(name);
    }

    /** Do not index the field value. This field can thus not be searched,
     * but one can still access its contents provided it is
     * {@link Field.Store stored}. */
    public static final Index NO = new Index("NO");

    /** Index the field's value so it can be searched. An Analyzer will be used
     * to tokenize and possibly further normalize the text before its
     * terms will be stored in the index. This is useful for common text.
     */
    public static final Index TOKENIZED = new Index("TOKENIZED");

    /** Index the field's value without using an Analyzer, so it can be searched.
     * As no analyzer is used the value will be stored as a single term. This is
     * useful for unique Ids like product numbers.
     */
    public static final Index UN_TOKENIZED = new Index("UN_TOKENIZED");

    /** Index the field's value without an Analyzer, and disable
     * the storing of norms.  No norms means that index-time boosting
     * and field length normalization will be disabled.  The benefit is
     * less memory usage as norms take up one byte per indexed field
     * for every document in the index.
     * Note that once you index a given field <i>with</i> norms enabled,
     * disabling norms will have no effect.  In other words, for NO_NORMS
     * to have the above described effect on a field, all instances of that
     * field must be indexed with NO_NORMS from the beginning.
     */
    public static final Index NO_NORMS = new Index("NO_NORMS");

  }

  /** Specifies whether and how a field should have term vectors. */
  public static final class TermVector  extends Parameter implements Serializable {
    
    private TermVector(String name) {
      super(name);
    }
    
    /** Do not store term vectors. 
     */
    public static final TermVector NO = new TermVector("NO");
    
    /** Store the term vectors of each document. A term vector is a list
     * of the document's terms and their number of occurences in that document. */
    public static final TermVector YES = new TermVector("YES");
    
    /**
     * Store the term vector + token position information
     * 
     * @see #YES
     */ 
    public static final TermVector WITH_POSITIONS = new TermVector("WITH_POSITIONS");
    
    /**
     * Store the term vector + Token offset information
     * 
     * @see #YES
     */ 
    public static final TermVector WITH_OFFSETS = new TermVector("WITH_OFFSETS");
    
    /**
     * Store the term vector + Token position and offset information
     * 
     * @see #YES
     * @see #WITH_POSITIONS
     * @see #WITH_OFFSETS
     */ 
    public static final TermVector WITH_POSITIONS_OFFSETS = new TermVector("WITH_POSITIONS_OFFSETS");
  }
  
  
  /** The value of the field as a String, or null.  If null, the Reader value,
   * binary value, or TokenStream value is used.  Exactly one of stringValue(), 
   * readerValue(), binaryValue(), and tokenStreamValue() must be set. */
  public String stringValue()   { return fieldsData instanceof String ? (String)fieldsData : null; }
  
  /** The value of the field as a Reader, or null.  If null, the String value,
   * binary value, or TokenStream value is used.  Exactly one of stringValue(), 
   * readerValue(), binaryValue(), and tokenStreamValue() must be set. */
  public Reader readerValue()   { return fieldsData instanceof Reader ? (Reader)fieldsData : null; }
  
  /** The value of the field in Binary, or null.  If null, the Reader value,
   * String value, or TokenStream value is used. Exactly one of stringValue(), 
   * readerValue(), binaryValue(), and tokenStreamValue() must be set. */
  public byte[] binaryValue()   { return fieldsData instanceof byte[] ? (byte[])fieldsData : null; }
  
  /** The value of the field as a TokesStream, or null.  If null, the Reader value,
   * String value, or binary value is used. Exactly one of stringValue(), 
   * readerValue(), binaryValue(), and tokenStreamValue() must be set. */
  public TokenStream tokenStreamValue()   { return fieldsData instanceof TokenStream ? (TokenStream)fieldsData : null; }
  

  /** <p>Expert: change the value of this field.  This can
   *  be used during indexing to re-use a single Field
   *  instance to improve indexing speed by avoiding GC cost
   *  of new'ing and reclaiming Field instances.  Typically
   *  a single {@link Document} instance is re-used as
   *  well.  This helps most on small documents.</p>
   * 
   *  <p>Note that you should only use this method after the
   *  Field has been consumed (ie, the {@link Document}
   *  containing this Field has been added to the index).
   *  Also, each Field instance should only be used once
   *  within a single {@link Document} instance.  See <a
   *  href="http://wiki.apache.org/lucene-java/ImproveIndexingSpeed">ImproveIndexingSpeed</a>
   *  for details.</p> */
  public void setValue(String value) {
    fieldsData = value;
  }

  /** Expert: change the value of this field.  See <a href="#setValue(java.lang.String)">setValue(String)</a>. */
  public void setValue(Reader value) {
    fieldsData = value;
  }

  /** Expert: change the value of this field.  See <a href="#setValue(java.lang.String)">setValue(String)</a>. */
  public void setValue(byte[] value) {
    fieldsData = value;
  }

  /** Expert: change the value of this field.  See <a href="#setValue(java.lang.String)">setValue(String)</a>. */
  public void setValue(TokenStream value) {
    fieldsData = value;
  }

  /**
   * Create a field by specifying its name, value and how it will
   * be saved in the index. Term vectors will not be stored in the index.
   * 
   * @param name The name of the field
   * @param value The string to process
   * @param store Whether <code>value</code> should be stored in the index
   * @param index Whether the field should be indexed, and if so, if it should
   *  be tokenized before indexing 
   * @throws NullPointerException if name or value is <code>null</code>
   * @throws IllegalArgumentException if the field is neither stored nor indexed 
   */
  public Field(String name, String value, Store store, Index index) {
    this(name, value, store, index, TermVector.NO);
  }