GenericAvroDao.java

/**
 * Copyright 2013 Cloudera 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 com.cloudera.cdk.data.hbase.avro;

import java.io.InputStream;

import org.apache.avro.generic.GenericRecord;
import org.apache.hadoop.hbase.client.HTablePool;

import com.cloudera.cdk.data.hbase.impl.BaseDao;
import com.cloudera.cdk.data.hbase.impl.BaseEntityMapper;
import com.cloudera.cdk.data.hbase.impl.SchemaManager;

/**
 * A Dao for Avro's GenericRecords. In this Dao implementation, both the
 * underlying key record type, and the entity type are GenericRecords. This Dao
 * allows us to persist and fetch these GenericRecords to and from HBase.
 */
public class GenericAvroDao extends BaseDao<GenericRecord> {

  private static final AvroKeyEntitySchemaParser parser = new AvroKeyEntitySchemaParser();

  /**
   * Construct a GenericAvroDao.
   * 
   * @param tablePool
   *          An HTablePool instance to use for connecting to HBase.
   * @param tableName
   *          The name of the table this Dao will read from and write to in
   *          HBase.
   * @param keySchemaStr
   *          The Avro schema that represents the StorageKey structure for row keys in
   *          this table.
   * @param entitySchemaString
   *          The json string representing the special avro record schema, that
   *          contains metadata in annotations of the Avro record fields. See
   *          {@link AvroEntityMapper} for details.
   */
  public GenericAvroDao(HTablePool tablePool, String tableName,
      String entitySchemaString) {
    super(tablePool, tableName, buildEntityMapper(entitySchemaString));
  }

  /**
   * Construct a GenericAvroDao.
   * 
   * @param tablePool
   *          An HTablePool instance to use for connecting to HBase.
   * @param tableName
   *          The name of the table this Dao will read from and write to in
   *          HBase.
   * @param keySchemaStr
   *          The Avro schema that represents the StorageKey structure for row keys in
   *          this table.
   * @param entitySchemaStream
   *          The InputStream that contains a json string representing the
   *          special avro record schema, that contains metadata in annotations
   *          of the Avro record fields. See {@link AvroEntityMapper} for
   *          details.
   */
  public GenericAvroDao(HTablePool tablePool, String tableName,
      InputStream entitySchemaStream) {

    super(tablePool, tableName, buildEntityMapper(AvroUtils
        .inputStreamToString(entitySchemaStream)));
  }

  /**
   * Construct the GenericAvroDao with an EntityManager, which will provide the
   * entity mapper to this Dao that knows how to map the different entity schema
   * versions defined by the managed schema. The entitySchemaString parameter
   * represents the schema to use for writes.
   * 
   * @param tablePool
   *          An HTabePool instance to use for connecting to HBase.
   * @param tableName
   *          The table name of the managed schema.
   * @param entityName
   *          The entity name of the managed schema.
   * @param schemaManager
   *          The EntityManager which will create the entity mapper that will
   *          power this dao.
   * @param entitySchemaString
   *          The schema as a string representing the schema version that this
   *          DAO should use for writes.
   */
  public GenericAvroDao(HTablePool tablePool, String tableName,
      String entityName, SchemaManager schemaManager, String entitySchemaString) {
    super(tablePool, tableName, new VersionedAvroEntityMapper.Builder()
        .setSchemaManager(schemaManager).setTableName(tableName)
        .setEntityName(entityName).setSpecific(false)
        .setGenericSchemaString(entitySchemaString).<GenericRecord> build());
  }

  /**
   * Construct the GenericAvroDao with an EntityManager, which will provide the
   * entity mapper to this Dao that knows how to map the different entity schema
   * versions defined by the managed schema. The newest schema version available
   * at the time of this dao's creation will be used for writes.
   * 
   * @param tablePool
   *          An HTabePool instance to use for connecting to HBase.
   * @param tableName
   *          The table name of the managed schema.
   * @param entityName
   *          The entity name of the managed schema.
   * @param schemaManager
   *          The SchemaManager which will create the entity mapper that will
   *          power this dao.
   */
  public GenericAvroDao(HTablePool tablePool, String tableName,
      String entityName, SchemaManager schemaManager) {

    super(tablePool, tableName, new VersionedAvroEntityMapper.Builder()
        .setSchemaManager(schemaManager).setTableName(tableName)
        .setEntityName(entityName).setSpecific(false).<GenericRecord> build());
  }

  private static BaseEntityMapper<GenericRecord> buildEntityMapper(
      String readerSchemaStr) {
    return buildEntityMapper(readerSchemaStr, readerSchemaStr);
  }

  private static BaseEntityMapper<GenericRecord> buildEntityMapper(
      String readerSchemaStr, String writtenSchemaStr) {

    AvroEntitySchema readerSchema = parser.parseEntitySchema(readerSchemaStr);
    AvroEntitySchema writtenSchema = parser.parseEntitySchema(writtenSchemaStr);
    AvroEntityComposer<GenericRecord> entityComposer = new AvroEntityComposer<GenericRecord>(
        readerSchema, false);
    AvroEntitySerDe<GenericRecord> entitySerDe = new AvroEntitySerDe<GenericRecord>(
        entityComposer, readerSchema, writtenSchema, false);

    AvroKeySchema keySchema = parser.parseKeySchema(readerSchemaStr);
    AvroKeySerDe keySerDe = new AvroKeySerDe(keySchema.getAvroSchema(),
        keySchema.getPartitionStrategy());

    return new BaseEntityMapper<GenericRecord>(keySchema, readerSchema,
        keySerDe, entitySerDe);
  }
}