com.ottogroup.bi.streaming.source.kafka.KafkaConsumerBuilder.java Source code

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Here is the source code for com.ottogroup.bi.streaming.source.kafka.KafkaConsumerBuilder.java

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/**
 * Copyright 2016 Otto (GmbH & Co KG)
 *
 * 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.ottogroup.bi.streaming.source.kafka;

import java.io.Serializable;
import java.util.Properties;

import org.apache.commons.lang3.StringUtils;
import org.apache.flink.streaming.connectors.kafka.FlinkKafkaConsumer09;
import org.apache.flink.streaming.util.serialization.DeserializationSchema;

/**
 * Provides support for creating {@link FlinkKafkaConsumer} instances
 * @author mnxfst
 * @since Feb 3, 2016
 */
public class KafkaConsumerBuilder<T extends Serializable> implements Serializable {

    private static final long serialVersionUID = -3497945088790519194L;

    public static final String KAFKA_PROPS_GROUP_ID = "group.id";
    public static final String KAFKA_PROPS_AUTO_COMMIT_ENABLE = "enable.auto.commit";
    public static final String KAFKA_PROPS_BOOTSTRAP_SERVERS = "bootstrap.servers";

    private Properties properties = new Properties();
    private String topic;
    private DeserializationSchema<T> deserializationSchema;

    private KafkaConsumerBuilder() {
    }

    /**
     * Returns a new {@link KafkaConsumerBuilder} instance
     * @return
     */
    public static <T extends Serializable> KafkaConsumerBuilder<T> getInstance() {
        return new KafkaConsumerBuilder<T>();
    }

    /**
     * Adds a new key/value pair to properties
     * @param key
     * @param value
     * @return
     */
    public KafkaConsumerBuilder<T> addProperty(final String key, final String value) {
        if (StringUtils.isNotBlank(key) && value != null)
            this.properties.put(StringUtils.lowerCase(StringUtils.trim(key)), value);
        return this;
    }

    /**
     * Adds all key/value pairs to properties
     * @param properties
     * @return
     */
    public KafkaConsumerBuilder<T> addProperties(final Properties properties) {
        if (properties != null && !properties.isEmpty())
            this.properties.putAll(properties);
        return this;
    }

    /**
     * Sets the topic to consume data from
     * @param topic
     * @return
     */
    public KafkaConsumerBuilder<T> topic(final String topic) {
        if (StringUtils.isNotBlank(topic))
            this.topic = topic;
        return this;
    }

    /**
     * Sets the {@link DeserializationSchema} required for reading data from kafka topic into 
     * processable format
     * @param deserializationSchema
     * @return
     */
    public KafkaConsumerBuilder<T> deserializationSchema(final DeserializationSchema<T> deserializationSchema) {
        if (deserializationSchema != null)
            this.deserializationSchema = deserializationSchema;
        return this;
    }

    /**
     * Create a {@link FlinkKafkaConsumer} depending on the provided settings
     * @param version
     * @return
     */
    public FlinkKafkaConsumer09<T> create() {

        /////////////////////////////////////////////////////////////////////////
        // validate provided input
        if (StringUtils.isBlank(this.topic))
            throw new IllegalArgumentException("Missing required topic");
        if (this.properties.isEmpty())
            throw new IllegalArgumentException("Missing required properties");
        if (!this.properties.containsKey(KAFKA_PROPS_AUTO_COMMIT_ENABLE))
            throw new IllegalArgumentException(
                    "Missing value for required property '" + KAFKA_PROPS_AUTO_COMMIT_ENABLE + "'");
        if (!this.properties.containsKey(KAFKA_PROPS_BOOTSTRAP_SERVERS))
            throw new IllegalArgumentException(
                    "Missing value for required property '" + KAFKA_PROPS_BOOTSTRAP_SERVERS + "'");
        if (!this.properties.containsKey(KAFKA_PROPS_GROUP_ID))
            throw new IllegalArgumentException(
                    "Missing value for required property '" + KAFKA_PROPS_GROUP_ID + "'");
        /////////////////////////////////////////////////////////////////////////

        return new FlinkKafkaConsumer09<>(this.topic, this.deserializationSchema, this.properties);
    }

    /**
     * Returns the managed properties - implemented for testing purpose only 
     * @return
     */
    protected Properties getProperties() {
        return this.properties;
    }

    /**
     * Returns the managed topic - implemented for testing purpose only 
     * @return
     */
    protected String getTopic() {
        return this.topic;
    }

    /**
     * Returns the managed deserialization schema - implemented for testing purpose only 
     * @return
     */
    protected DeserializationSchema<T> getDeserializationSchema() {
        return this.deserializationSchema;
    }

}