KafkaTopology.kt 2.8 KB
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/*
 * Table Data Import Service
 * Copyright (C) 2020 Memoriav
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

package org.memobase

import com.beust.klaxon.JsonArray
import com.beust.klaxon.JsonObject
import com.beust.klaxon.Klaxon
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import com.fasterxml.jackson.databind.ObjectMapper
import com.fasterxml.jackson.module.kotlin.registerKotlinModule
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import java.io.StringReader
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import java.io.StringWriter
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import org.apache.kafka.streams.KeyValue
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import org.apache.kafka.streams.StreamsBuilder
import org.apache.kafka.streams.Topology
import org.apache.logging.log4j.LogManager
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import org.memobase.model.SearchDoc
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import org.memobase.rdf.NS
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import org.memobase.settings.SettingsLoader

class KafkaTopology(private val settings: SettingsLoader) {
    private val log = LogManager.getLogger("StreamsProcessing")

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    private val searchDocTransform = SearchDocTransform(settings.appSettings.getProperty(KEYS.mediaUrlPropName))
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    fun build(): Topology {
        val builder = StreamsBuilder()
        val stream = builder.stream<String, String>(settings.inputTopic)
        stream
            .flatMapValues { value -> parseJson(value) }
            .mapValues { value -> unpackJson(value) }
            .mapValues { value -> transformJson(value) }
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            .map { _, value -> KeyValue(value.id, value) }
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            .mapValues { value ->
                val writer = StringWriter()
                ObjectMapper().registerKotlinModule().writeValue(writer, value)
                writer.toString()
            }
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            .to(settings.outputTopic)

        return builder.build()
    }

    private fun parseJson(data: String): List<JsonObject> {
        val result = Klaxon().parseJsonObject(StringReader(data))
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        return listOf(result)
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    }

    private fun unpackJson(input: JsonObject): Map<String, JsonObject> {
        val graph = input["@graph"] as JsonArray<JsonObject>
        return graph.map {
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            if (it["@type"] == NS.rico + "Record") {
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                Pair("record", it)
            } else {
                Pair(it["@id"] as String, it)
            }
        }.toMap()
    }

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    private fun transformJson(input: Map<String, JsonObject>): SearchDoc {
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        return searchDocTransform.transform(input)
    }
}