Java tutorial
/* * 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.solr.search.function; import java.io.IOException; import java.util.Map; import org.apache.lucene.index.LeafReaderContext; import org.apache.lucene.queries.function.FunctionValues; import org.apache.lucene.queries.function.ValueSource; /** Placeholder value source. * @lucene.internal */ public class FieldNameValueSource extends ValueSource { private String fieldName; public FieldNameValueSource(String fieldName) { this.fieldName = fieldName; } public String getFieldName() { return fieldName; } @Override public FunctionValues getValues(Map context, LeafReaderContext readerContext) throws IOException { throw new UnsupportedOperationException("FieldNameValueSource should not be directly used: " + this); } @Override public boolean equals(Object o) { return o instanceof FieldNameValueSource && fieldName.equals(((FieldNameValueSource) o).getFieldName()); } @Override public int hashCode() { return fieldName.hashCode(); } @Override public String description() { return "FIELDNAME(" + fieldName + ")"; } }