| package org.apache.lucene.index; |
| |
| /** |
| * 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 org.apache.lucene.util.AttributeSource; |
| |
| /** Enumerates indexed fields. You must first call {@link |
| * #next} before calling {@link #terms}. |
| * |
| * @lucene.experimental */ |
| |
| public abstract class FieldsEnum { |
| |
| // TODO: maybe allow retrieving FieldInfo for current |
| // field, as optional method? |
| |
| private AttributeSource atts = null; |
| |
| /** |
| * Returns the related attributes. |
| */ |
| public AttributeSource attributes() { |
| if (atts == null) { |
| atts = new AttributeSource(); |
| } |
| return atts; |
| } |
| |
| /** Increments the enumeration to the next field. The |
| * returned field is always interned, so simple == |
| * comparison is allowed. Returns null when there are no |
| * more fields.*/ |
| public abstract String next() throws IOException; |
| |
| /** Get {@link TermsEnum} for the current field. You |
| * should not call {@link #next} until you're done using |
| * this {@link TermsEnum}. After {@link #next} returns |
| * null this method should not be called. This method |
| * will not return null. */ |
| public abstract TermsEnum terms() throws IOException; |
| |
| public final static FieldsEnum[] EMPTY_ARRAY = new FieldsEnum[0]; |
| |
| /** Provides zero fields */ |
| public final static FieldsEnum EMPTY = new FieldsEnum() { |
| |
| @Override |
| public String next() { |
| return null; |
| } |
| |
| @Override |
| public TermsEnum terms() { |
| throw new IllegalStateException("this method should never be called"); |
| } |
| }; |
| } |