ReflectionStructObjectInspector.java

/*
 * Copyright © 2014 Cask Data, Inc.
 *
 * Licensed 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 co.cask.cdap.hive.objectinspector;

import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspectorUtils;
import org.apache.hadoop.hive.serde2.objectinspector.SettableStructObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.StructField;
import org.apache.hadoop.util.ReflectionUtils;

import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

/**
 * ReflectionStructObjectInspector works on struct data that is stored as a
 * native Java object. It will drill down into the Java class to get the fields
 * and construct ObjectInspectors for the fields, if they are not specified.
 *
 * Always use the ObjectInspectorFactory to create new ObjectInspector objects,
 * instead of directly creating an instance of this class.
 *
 */
public class ReflectionStructObjectInspector extends
    SettableStructObjectInspector {

  /**
   * MyField.
   *
   */
  public static class MyField implements StructField {

    protected int fieldId;
    protected Field field;
    protected ObjectInspector fieldObjectInspector;

    public MyField(int fieldId, Field field, ObjectInspector fieldObjectInspector) {
      this.fieldId = fieldId;
      this.field = field;
      this.fieldObjectInspector = fieldObjectInspector;
    }

    public String getFieldName() {
      return field.getName().toLowerCase();
    }

    public ObjectInspector getFieldObjectInspector() {
      return fieldObjectInspector;
    }

    public int getFieldID() {
      return fieldId;
    }

    public String getFieldComment() {
      return null;
    }

    @Override
    public String toString() {
      return field.toString();
    }
  }

  Class<?> objectClass;
  List<MyField> fields;

  public Category getCategory() {
    return Category.STRUCT;
  }

  public String getTypeName() {
    StringBuilder sb = new StringBuilder("struct<");
    boolean first = true;
    for (StructField structField : getAllStructFieldRefs()) {
      if (first) {
        first = false;
      } else {
        sb.append(",");
      }
      ObjectInspector oi = structField.getFieldObjectInspector();
      String typeName;
      // This prevents infinite loop, and prints "this" in case
      // the object contains a reference to itself
      if (oi == this) {
        typeName = "this";
      } else {
        typeName = oi.getTypeName();
      }
      sb.append(structField.getFieldName()).append(":")
        .append(typeName);
    }
    sb.append(">");
    return sb.toString();
  }

  /**
   * This method is only intended to be used by the Utilities class in this
   * package. This creates an uninitialized ObjectInspector so the Utilities
   * class can put it into a cache before it initializes when it might look up
   * the cache for member fields that might be of the same type (e.g. recursive
   * type like linked list and trees).
   */
  ReflectionStructObjectInspector() {
  }

  /**
   * This method is only intended to be used by Utilities class in this package.
   * The reason that this method is not recursive by itself is because we want
   * to allow recursive types.
   */
  void init(Class<?> objectClass, List<ObjectInspector> structFieldObjectInspectors) {
    assert (!List.class.isAssignableFrom(objectClass));
    assert (!Map.class.isAssignableFrom(objectClass));

    this.objectClass = objectClass;
    Field[] reflectionFields = ObjectInspectorUtils.getDeclaredNonStaticFields(objectClass);
    fields = new ArrayList<>(structFieldObjectInspectors.size());
    int used = 0;
    for (int i = 0; i < reflectionFields.length; i++) {
      // Exclude transient fields and synthetic fields. The latter has the effect of excluding the implicit
      // "this" pointer present in nested classes and that references the parent.
      if (Modifier.isTransient(reflectionFields[i].getModifiers()) || reflectionFields[i].isSynthetic()) {
        continue;
      }
      if (!shouldIgnoreField(reflectionFields[i].getName())) {
        reflectionFields[i].setAccessible(true);
        fields.add(new MyField(i, reflectionFields[i], structFieldObjectInspectors.get(used++)));
      }
    }
    assert (fields.size() == structFieldObjectInspectors.size());
  }

  // ThriftStructObjectInspector will override and ignore __isset fields.
  public boolean shouldIgnoreField(String name) {
    return false;
  }

  // Without Data
  @Override
  public StructField getStructFieldRef(String fieldName) {
    return ObjectInspectorUtils.getStandardStructFieldRef(fieldName, fields);
  }

  @Override
  public List<? extends StructField> getAllStructFieldRefs() {
    return fields;
  }

  // With Data
  @Override
  public Object getStructFieldData(Object data, StructField fieldRef) {
    if (data == null) {
      return null;
    }
    if (!(fieldRef instanceof MyField)) {
      throw new RuntimeException("fieldRef has to be of MyField");
    }
    MyField f = (MyField) fieldRef;
    try {
      Object r = f.field.get(data);
      return r;
    } catch (Exception e) {
      throw new RuntimeException("cannot get field " + f.field + " from " + data.getClass() + " " + data, e);
    }
  }

  @Override
  public List<Object> getStructFieldsDataAsList(Object data) {
    if (data == null) {
      return null;
    }
    try {
      ArrayList<Object> result = new ArrayList<>(fields.size());
      for (int i = 0; i < fields.size(); i++) {
        result.add(fields.get(i).field.get(data));
      }
      return result;
    } catch (Exception e) {
      throw new RuntimeException(e);
    }
  }

  @Override
  public Object create() {
    return ReflectionUtils.newInstance(objectClass, null);
  }

  @Override
  public Object setStructFieldData(Object struct, StructField field, Object fieldValue) {
    MyField myField = (MyField) field;
    try {
      myField.field.set(struct, fieldValue);
    } catch (Exception e) {
      throw new RuntimeException("cannot set field " + myField.field + " of " + struct.getClass() + " " + struct, e);
    }
    return struct;
  }

}