core/src/main/java/org/apache/accumulo/core/iterators/conf/ColumnToClassMapping.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.accumulo.core.iterators.conf;

import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;

import org.apache.accumulo.core.data.Key;
import org.apache.accumulo.core.iterators.conf.ColumnUtil.ColFamHashKey;
import org.apache.accumulo.core.iterators.conf.ColumnUtil.ColHashKey;
import org.apache.accumulo.core.util.Pair;
import org.apache.accumulo.start.classloader.vfs.AccumuloVFSClassLoader;
import org.apache.hadoop.io.Text;

public class ColumnToClassMapping<K> {

  private HashMap<ColFamHashKey,K> objectsCF;
  private HashMap<ColHashKey,K> objectsCol;

  private ColHashKey lookupCol = new ColHashKey();
  private ColFamHashKey lookupCF = new ColFamHashKey();

  public ColumnToClassMapping() {
    objectsCF = new HashMap<>();
    objectsCol = new HashMap<>();
  }

  public ColumnToClassMapping(Map<String,String> objectStrings, Class<? extends K> c)
      throws InstantiationException, IllegalAccessException, ClassNotFoundException, IOException {
    this(objectStrings, c, null);
  }

  public ColumnToClassMapping(Map<String,String> objectStrings, Class<? extends K> c,
      String context)
      throws InstantiationException, IllegalAccessException, ClassNotFoundException, IOException {
    this();

    for (Entry<String,String> entry : objectStrings.entrySet()) {
      String column = entry.getKey();
      String className = entry.getValue();

      Pair<Text,Text> pcic = ColumnSet.decodeColumns(column);

      Class<?> clazz;
      if (context != null && !context.equals(""))
        clazz =
            AccumuloVFSClassLoader.getContextManager().getClassLoader(context).loadClass(className);
      else
        clazz = AccumuloVFSClassLoader.loadClass(className, c);

      @SuppressWarnings("unchecked")
      K inst = (K) clazz.newInstance();
      if (pcic.getSecond() == null) {
        addObject(pcic.getFirst(), inst);
      } else {
        addObject(pcic.getFirst(), pcic.getSecond(), inst);
      }
    }
  }

  protected void addObject(Text colf, K obj) {
    objectsCF.put(new ColFamHashKey(new Text(colf)), obj);
  }

  protected void addObject(Text colf, Text colq, K obj) {
    objectsCol.put(new ColHashKey(colf, colq), obj);
  }

  public K getObject(Key key) {
    K obj = null;

    // lookup column family and column qualifier
    if (objectsCol.size() > 0) {
      lookupCol.set(key);
      obj = objectsCol.get(lookupCol);
      if (obj != null) {
        return obj;
      }
    }

    // lookup just column family
    if (objectsCF.size() > 0) {
      lookupCF.set(key);
      obj = objectsCF.get(lookupCF);
    }

    return obj;
  }

  public boolean isEmpty() {
    return objectsCol.size() == 0 && objectsCF.size() == 0;
  }
}