org.apache.lucene.document.DocumentStoredFieldVisitor.java Source code

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Here is the source code for org.apache.lucene.document.DocumentStoredFieldVisitor.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.document;

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.util.HashSet;
import java.util.Set;

import org.apache.lucene.index.FieldInfo;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.StoredFieldVisitor;

/** A {@link StoredFieldVisitor} that creates a {@link
 *  Document} from stored fields.
 *  <p>
 *  This visitor supports loading all stored fields, or only specific
 *  requested fields provided from a {@link Set}.
 *  <p>
 *  This is used by {@link IndexReader#document(int)} to load a
 *  document.
 *
 * @lucene.experimental */

public class DocumentStoredFieldVisitor extends StoredFieldVisitor {
    private final Document doc = new Document();
    private final Set<String> fieldsToAdd;

    /** 
     * Load only fields named in the provided <code>Set&lt;String&gt;</code>. 
     * @param fieldsToAdd Set of fields to load, or <code>null</code> (all fields).
     */
    public DocumentStoredFieldVisitor(Set<String> fieldsToAdd) {
        this.fieldsToAdd = fieldsToAdd;
    }

    /** Load only fields named in the provided fields. */
    public DocumentStoredFieldVisitor(String... fields) {
        fieldsToAdd = new HashSet<>(fields.length);
        for (String field : fields) {
            fieldsToAdd.add(field);
        }
    }

    /** Load all stored fields. */
    public DocumentStoredFieldVisitor() {
        this.fieldsToAdd = null;
    }

    @Override
    public void binaryField(FieldInfo fieldInfo, byte[] value) throws IOException {
        doc.add(new StoredField(fieldInfo.name, value));
    }

    @Override
    public void stringField(FieldInfo fieldInfo, byte[] value) throws IOException {
        final FieldType ft = new FieldType(TextField.TYPE_STORED);
        ft.setStoreTermVectors(fieldInfo.hasVectors());
        ft.setOmitNorms(fieldInfo.omitsNorms());
        ft.setIndexOptions(fieldInfo.getIndexOptions());
        doc.add(new StoredField(fieldInfo.name, new String(value, StandardCharsets.UTF_8), ft));
    }

    @Override
    public void intField(FieldInfo fieldInfo, int value) {
        doc.add(new StoredField(fieldInfo.name, value));
    }

    @Override
    public void longField(FieldInfo fieldInfo, long value) {
        doc.add(new StoredField(fieldInfo.name, value));
    }

    @Override
    public void floatField(FieldInfo fieldInfo, float value) {
        doc.add(new StoredField(fieldInfo.name, value));
    }

    @Override
    public void doubleField(FieldInfo fieldInfo, double value) {
        doc.add(new StoredField(fieldInfo.name, value));
    }

    @Override
    public Status needsField(FieldInfo fieldInfo) throws IOException {
        return fieldsToAdd == null || fieldsToAdd.contains(fieldInfo.name) ? Status.YES : Status.NO;
    }

    /**
     * Retrieve the visited document.
     * @return {@link Document} populated with stored fields. Note that only
     *         the stored information in the field instances is valid,
     *         data such as indexing options, term vector options,
     *         etc is not set.
     */
    public Document getDocument() {
        return doc;
    }
}