org.apache.nifi.processors.kite.JSONFileReader.java Source code

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Here is the source code for org.apache.nifi.processors.kite.JSONFileReader.java

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/*
 * 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 org.apache.nifi.processors.kite;

import com.fasterxml.jackson.databind.JsonNode;
import com.google.common.base.Function;
import com.google.common.base.Preconditions;
import com.google.common.collect.Iterators;
import java.io.IOException;
import java.io.InputStream;
import java.util.Iterator;
import javax.annotation.Nullable;
import org.apache.avro.Schema;
import org.apache.avro.generic.GenericData;
import org.kitesdk.data.DatasetIOException;
import org.kitesdk.data.spi.AbstractDatasetReader;
import org.kitesdk.data.spi.DataModelUtil;
import org.kitesdk.data.spi.JsonUtil;
import org.kitesdk.data.spi.ReaderWriterState;

/**
 * This is a temporary addition. The version in 0.18.0 throws a NPE when the
 * InputStream constructor is used.
 */
class JSONFileReader<E> extends AbstractDatasetReader<E> {

    private final GenericData model;
    private final Schema schema;

    private InputStream incoming = null;

    // state
    private ReaderWriterState state = ReaderWriterState.NEW;
    private Iterator<E> iterator;

    public JSONFileReader(InputStream incoming, Schema schema, Class<E> type) {
        this.incoming = incoming;
        this.schema = schema;
        this.model = DataModelUtil.getDataModelForType(type);
        this.state = ReaderWriterState.NEW;
    }

    @Override
    public void initialize() {
        Preconditions.checkState(state.equals(ReaderWriterState.NEW),
                "A reader may not be opened more than once - current state:%s", state);
        Preconditions.checkArgument(Schema.Type.RECORD.equals(schema.getType()),
                "Schemas for JSON files should be record");

        this.iterator = Iterators.transform(JsonUtil.parser(incoming), new Function<JsonNode, E>() {
            @Override
            @SuppressWarnings("unchecked")
            public E apply(@Nullable JsonNode node) {
                return (E) JsonUtil.convertToAvro(model, node, schema);
            }
        });

        this.state = ReaderWriterState.OPEN;
    }

    @Override
    public boolean hasNext() {
        Preconditions.checkState(state.equals(ReaderWriterState.OPEN), "Attempt to read from a file in state:%s",
                state);
        return iterator.hasNext();
    }

    @Override
    public E next() {
        Preconditions.checkState(state.equals(ReaderWriterState.OPEN), "Attempt to read from a file in state:%s",
                state);
        return iterator.next();
    }

    @Override
    public void close() {
        if (!state.equals(ReaderWriterState.OPEN)) {
            return;
        }

        iterator = null;
        try {
            incoming.close();
        } catch (IOException e) {
            throw new DatasetIOException("Unable to close reader path", e);
        }

        state = ReaderWriterState.CLOSED;
    }

    @Override
    public boolean isOpen() {
        return (this.state == ReaderWriterState.OPEN);
    }

}