Example converting between Java class, JSON, and Beam Row.

SomeThing.java

/*
 * 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,
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 */
package example;

import com.google.auto.value.AutoValue;
import com.google.common.collect.ImmutableMap;
import org.apache.beam.sdk.schemas.AutoValueSchema;
import org.apache.beam.sdk.schemas.Schema;
import org.apache.beam.sdk.schemas.SchemaProvider;
import org.apache.beam.sdk.schemas.annotations.DefaultSchema;
import org.apache.beam.sdk.schemas.io.payloads.JsonPayloadSerializerProvider;
import org.apache.beam.sdk.schemas.io.payloads.PayloadSerializer;
import org.apache.beam.sdk.transforms.SerializableFunction;
import org.apache.beam.sdk.values.Row;
import org.apache.beam.sdk.values.TypeDescriptor;

import java.nio.charset.StandardCharsets;

import static org.apache.beam.sdk.util.Preconditions.checkStateNotNull;

@DefaultSchema(AutoValueSchema.class)
@AutoValue
abstract class SomeThing {

    private static final SchemaProvider SCHEMA_PROVIDER = new AutoValueSchema();

    private static final TypeDescriptor<SomeThing> TYPE_DESCRIPTOR = TypeDescriptor.of(SomeThing.class);

    private static final SerializableFunction<SomeThing, Row> TO_ROW_FN = checkStateNotNull(SCHEMA_PROVIDER.toRowFunction(TYPE_DESCRIPTOR));

    private static final SerializableFunction<Row, SomeThing> FROM_ROW_FN = checkStateNotNull(SCHEMA_PROVIDER.fromRowFunction(TYPE_DESCRIPTOR));

    static final Schema SCHEMA = checkStateNotNull(SCHEMA_PROVIDER.schemaFor(TYPE_DESCRIPTOR));

    private static final PayloadSerializer JSON_PAYLOAD_SERIALIZER = new JsonPayloadSerializerProvider().getSerializer(SCHEMA, ImmutableMap.of());

    String toJson() {
        byte[] bytes = checkStateNotNull(JSON_PAYLOAD_SERIALIZER.serialize(toRow()));
        return new String(bytes, StandardCharsets.UTF_8);
    }

    static SomeThing fromJson(String json) {
        Row row = checkStateNotNull(JSON_PAYLOAD_SERIALIZER.deserialize(json.getBytes(StandardCharsets.UTF_8)));
        return fromRow(row);
    }

    Row toRow() {
        return TO_ROW_FN.apply(this);
    }

    static SomeThing fromRow(Row row) {
        return FROM_ROW_FN.apply(row);
    }

    abstract Boolean getABoolean();

    abstract String getAString();

    abstract Integer getAnInteger();

    abstract Long getALong();

    abstract Float getAFloat();

    abstract Double getADouble();

    @AutoValue.Builder
    abstract static class Builder {
        abstract Builder setABoolean(Boolean aBoolean);

        abstract Builder setAString(String value);

        abstract Builder setAnInteger(Integer value);

        abstract Builder setALong(Long value);

        abstract Builder setAFloat(Float value);

        abstract Builder setADouble(Double value);

        abstract SomeThing build();
    }
}