co.cask.cdap.api.dataset.lib.PartitionKey.java Source code

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Here is the source code for co.cask.cdap.api.dataset.lib.PartitionKey.java

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/*
 * Copyright  2015 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.api.dataset.lib;

import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Maps;

import java.util.LinkedHashMap;
import java.util.Map;
import javax.annotation.Nonnull;

/**
 * Types and methods to specify partitioning keys for datasets.
 */
public class PartitionKey {

    private final Map<String, Comparable> fields;

    /**
     * Private constructor to force use of the builder.
     */
    private PartitionKey(@Nonnull Map<String, Comparable> fields) {
        this.fields = ImmutableMap.copyOf(fields);
    }

    /**
     * @return all field names and their values in a map.
     */
    public Map<String, Comparable> getFields() {
        return fields;
    }

    /**
     * @return the value of a field
     */
    public Comparable getField(String fieldName) {
        return fields.get(fieldName);
    }

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

    @Override
    public boolean equals(Object other) {
        return this == other || (other != null && getClass() == other.getClass()
                && getFields().equals(((PartitionKey) other).getFields())); // fields is never null
    }

    @Override
    public int hashCode() {
        return fields.hashCode(); // fields is never null
    }

    /**
     * @return a builder for a partitioning
     */
    public static Builder builder() {
        return new Builder();
    }

    /**
     * A builder for partitioning objects.
     */
    public static class Builder {

        private final LinkedHashMap<String, Comparable> fields = Maps.newLinkedHashMap();

        private Builder() {
        }

        /**
         * Add a field with a given name and value.
         *
         * @param name the field name
         * @param value the value of the field
         *
         * @throws java.lang.IllegalArgumentException if the field name is null, empty, or already exists,
         *         or if the value is null.
         */
        public Builder addField(String name, Comparable value) {
            Preconditions.checkArgument(name != null && !name.isEmpty(), "field name cannot be null or empty.");
            Preconditions.checkArgument(value != null, "field name cannot be null.");
            if (fields.containsKey(name)) {
                throw new IllegalArgumentException(
                        String.format("Field '%s' already exists in partition key.", name));
            }
            fields.put(name, value);
            return this;
        }

        /**
         * Add field of type STRING.
         *
         * @param name the field name
         * @param value the value of the field
         *
         * @throws java.lang.IllegalArgumentException if the field name is null, empty, or already exists,
         *         or if the value is null.
         */
        public Builder addStringField(String name, String value) {
            return addField(name, value);
        }

        /**
         * Add field of type INT.
         *
         * @param name the field name
         * @param value the value of the field
         *
         * @throws java.lang.IllegalArgumentException if the field name is null, empty, or already exists,
         *         or if the value is null.
         */
        public Builder addIntField(String name, int value) {
            return addField(name, value);
        }

        /**
         * Add field of type LONG.
         *
         * @param name the field name
         * @param value the value of the field
         *
         * @throws java.lang.IllegalArgumentException if the field name is null, empty, or already exists,
         *         or if the value is null.
         */
        public Builder addLongField(String name, long value) {
            return addField(name, value);
        }

        /**
         * Create the partition key.
         *
         * @throws java.lang.IllegalStateException if no fields have been added
         */
        public PartitionKey build() {
            Preconditions.checkState(!fields.isEmpty(), "Partition key cannot be empty.");
            return new PartitionKey(fields);
        }
    }

}