| /* |
| * 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.response.transform; |
| |
| import java.io.IOException; |
| |
| import org.apache.solr.common.SolrDocument; |
| import org.apache.solr.response.QueryResponseWriter; |
| import org.apache.solr.response.ResultContext; |
| import org.apache.solr.search.SolrIndexSearcher; |
| |
| /** |
| * A DocTransformer can add, remove or alter a Document before it is written out to the Response. For instance, there are implementations |
| * that can put explanations inline with a document, add constant values and mark items as being artificially boosted (see {@link org.apache.solr.handler.component.QueryElevationComponent}) |
| * |
| * <p> |
| * New instance for each request |
| * |
| * @see TransformerFactory |
| * |
| */ |
| public abstract class DocTransformer { |
| protected ResultContext context; |
| /** |
| * |
| * @return The name of the transformer |
| */ |
| public abstract String getName(); |
| |
| /** |
| * This is called before {@link #transform} to provide context for any subsequent transformations. |
| * |
| * @param context The {@link ResultContext} stores information about how the documents were produced. |
| * @see #needsSolrIndexSearcher |
| */ |
| public void setContext( ResultContext context ) { |
| this.context = context; |
| |
| } |
| |
| /** |
| * Indicates if this transformer requires access to the underlying index to perform it's functions. |
| * |
| * In some situations (notably RealTimeGet) this method <i>may</i> be called before {@link #setContext} |
| * to determine if the transformer must be given a "full" ResultContext and accurate docIds |
| * that can be looked up using {@link ResultContext#getSearcher}, or if optimizations can be taken |
| * advantage of such that {@link ResultContext#getSearcher} <i>may</i> return null, and docIds passed to |
| * {@link #transform} <i>may</i> be negative. |
| * |
| * The default implementation always returns <code>false</code>. |
| * |
| * @see ResultContext#getSearcher |
| * @see #transform |
| */ |
| public boolean needsSolrIndexSearcher() { return false; } |
| |
| /** |
| * This is where implementations do the actual work. |
| * If implementations require a valid docId and index access, the {@link #needsSolrIndexSearcher} |
| * method must return true |
| * |
| * Default implementation calls {@link #transform(SolrDocument, int)}. |
| * |
| * @param doc The document to alter |
| * @param docid The Lucene internal doc id, or -1 in cases where the <code>doc</code> did not come from the index |
| * @param score the score for this document |
| * @throws IOException If there is a low-level I/O error. |
| * @see #needsSolrIndexSearcher |
| */ |
| public void transform(SolrDocument doc, int docid, float score) throws IOException { |
| transform(doc, docid); |
| } |
| |
| /** |
| * This is where implementations do the actual work. |
| * If implementations require a valid docId and index access, the {@link #needsSolrIndexSearcher} |
| * method must return true |
| * |
| * @param doc The document to alter |
| * @param docid The Lucene internal doc id, or -1 in cases where the <code>doc</code> did not come from the index |
| * @throws IOException If there is a low-level I/O error. |
| * @see #needsSolrIndexSearcher |
| */ |
| public abstract void transform(SolrDocument doc, int docid) throws IOException; |
| |
| /** |
| * When a transformer needs access to fields that are not automatically derived from the |
| * input fields names, this option lets us explicitly say the field names that we hope |
| * will be in the SolrDocument. These fields will be requested from the |
| * {@link SolrIndexSearcher} but may or may not be returned in the final |
| * {@link QueryResponseWriter} |
| * |
| * @return a list of extra lucene fields |
| */ |
| public String[] getExtraRequestFields() { |
| return null; |
| } |
| |
| @Override |
| public String toString() { |
| return getName(); |
| } |
| |
| /** |
| * Trivial Impl that ensure that the specified field is requested as an "extra" field, |
| * but then does nothing during the transformation phase. |
| */ |
| public static final class NoopFieldTransformer extends DocTransformer { |
| final String field; |
| |
| public NoopFieldTransformer() { |
| this.field = null; |
| } |
| |
| public NoopFieldTransformer(String field ) { |
| this.field = field; |
| } |
| public String getName() { return "noop"; } |
| public String[] getExtraRequestFields() { |
| return this.field==null? null: new String[] { field }; |
| } |
| public void transform(SolrDocument doc, int docid) { |
| // No-Op |
| } |
| } |
| } |