| /** |
| * 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 com.datatorrent.lib.appdata.schemas; |
| |
| import java.io.Serializable; |
| import java.util.Map; |
| |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| import com.google.common.base.Preconditions; |
| |
| /** |
| * This schema registry holds a single schema. It is intended to be used in operators |
| * which serve a single schema. |
| * @since 3.0.0 |
| */ |
| public class SchemaRegistrySingle implements SchemaRegistry, Serializable |
| { |
| private static final long serialVersionUID = 20150513928L; |
| private static final Logger logger = LoggerFactory.getLogger(SchemaRegistrySingle.class); |
| |
| /** |
| * The schema held by this schema registry. |
| */ |
| private Schema schema; |
| |
| /** |
| * Creates a schema registry whose schema will be registered later. |
| */ |
| public SchemaRegistrySingle() |
| { |
| } |
| |
| /** |
| * Creates a schema registry with the given schema. |
| * @param schema |
| */ |
| public SchemaRegistrySingle(Schema schema) |
| { |
| setSchema(schema); |
| } |
| |
| private void setSchema(Schema schema) |
| { |
| Preconditions.checkNotNull(schema); |
| Preconditions.checkArgument(schema.getSchemaKeys() == null, "The provided schema should not have schema keys " |
| + schema.getSchemaKeys() + " since they will never be used."); |
| |
| this.schema = schema; |
| } |
| |
| @Override |
| public SchemaResult getSchemaResult(SchemaQuery schemaQuery) |
| { |
| Preconditions.checkNotNull(schemaQuery, "This should never happen."); |
| |
| if (schemaQuery.getSchemaKeys() != null) { |
| logger.error("Schema keys in the given query don't apply for single schema registry: schemaKeys={}", |
| schemaQuery.getSchemaKeys()); |
| return null; |
| } |
| |
| return new SchemaResult(schemaQuery, schema); |
| } |
| |
| @Override |
| public void registerSchema(Schema schema) |
| { |
| Preconditions.checkState(this.schema == null, "A schema is already set."); |
| this.schema = schema; |
| } |
| |
| @Override |
| public Schema getSchema(Map<String, String> schemaKeys) |
| { |
| return schema; |
| } |
| |
| @Override |
| public void registerSchema(Schema schema, Map<String, String> schemaKeys) |
| { |
| throw new UnsupportedOperationException("Schema keys are not supported in SchemaRegistrySingle."); |
| } |
| |
| @Override |
| public int size() |
| { |
| return schema == null ? 0 : 1; |
| } |
| } |