solr/core/src/java/org/apache/solr/handler/component/SearchComponent.java

/*
 * 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.handler.component;

import java.io.IOException;
import java.util.Map;
import org.apache.solr.core.SolrInfoBean;
import org.apache.solr.metrics.SolrMetricsContext;
import org.apache.solr.search.facet.FacetModule;
import org.apache.solr.util.plugin.NamedListInitializedPlugin;

/**
 * TODO!
 *
 * @since solr 1.3
 */
public abstract class SearchComponent implements SolrInfoBean, NamedListInitializedPlugin {
  /** The name given to this component in solrconfig.xml file */
  private String name = this.getClass().getName();

  protected SolrMetricsContext solrMetricsContext;

  /**
   * Prepare the response. Guaranteed to be called before any SearchComponent {@link
   * #process(org.apache.solr.handler.component.ResponseBuilder)} method. Called for every incoming
   * request.
   *
   * <p>The place to do initialization that is request dependent.
   *
   * @param rb The {@link org.apache.solr.handler.component.ResponseBuilder}
   * @throws IOException If there is a low-level I/O error.
   */
  public abstract void prepare(ResponseBuilder rb) throws IOException;

  /**
   * Process the request for this component
   *
   * @param rb The {@link ResponseBuilder}
   * @throws IOException If there is a low-level I/O error.
   */
  public abstract void process(ResponseBuilder rb) throws IOException;

  /**
   * Process for a distributed search.
   *
   * @return the next stage for this component
   */
  public int distributedProcess(ResponseBuilder rb) throws IOException {
    return ResponseBuilder.STAGE_DONE;
  }

  /** Called after another component adds a request */
  public void modifyRequest(ResponseBuilder rb, SearchComponent who, ShardRequest sreq) {}

  /** Called after all responses for a single request were received */
  public void handleResponses(ResponseBuilder rb, ShardRequest sreq) {}

  /**
   * Called after all responses have been received for this stage. Useful when different requests
   * are sent to each shard.
   */
  public void finishStage(ResponseBuilder rb) {}

  /**
   * Sets the name of the SearchComponent. The name of the component is usually the name defined for
   * it in the configuration.
   */
  public void setName(String name) {
    this.name = name;
  }

  //////////////////////// SolrInfoBean methods //////////////////////

  @Override
  public String getName() {
    return name;
  }

  @Override
  public abstract String getDescription();

  @Override
  public Category getCategory() {
    return Category.OTHER;
  }

  @Override
  public SolrMetricsContext getSolrMetricsContext() {
    return solrMetricsContext;
  }

  @Override
  public void initializeMetrics(SolrMetricsContext parentContext, String scope) {
    // By default don't register any metrics - but prepare a child context
    this.solrMetricsContext = parentContext.getChildContext(this);
  }

  public static final Map<String, Class<? extends SearchComponent>> standard_components =
      Map.of(
          HighlightComponent.COMPONENT_NAME, HighlightComponent.class,
          QueryComponent.COMPONENT_NAME, QueryComponent.class,
          FacetComponent.COMPONENT_NAME, FacetComponent.class,
          FacetModule.COMPONENT_NAME, FacetModule.class,
          MoreLikeThisComponent.COMPONENT_NAME, MoreLikeThisComponent.class,
          StatsComponent.COMPONENT_NAME, StatsComponent.class,
          DebugComponent.COMPONENT_NAME, DebugComponent.class,
          RealTimeGetComponent.COMPONENT_NAME, RealTimeGetComponent.class,
          ExpandComponent.COMPONENT_NAME, ExpandComponent.class,
          TermsComponent.COMPONENT_NAME, TermsComponent.class);
}