nifi-system-tests/nifi-system-test-extensions-bundle/nifi-system-test-extensions/src/main/java/org/apache/nifi/processors/tests/system/ConcatenateFlowFiles.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,
 * 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.tests.system;

import org.apache.nifi.components.PropertyDescriptor;
import org.apache.nifi.components.PropertyDescriptor.Builder;
import org.apache.nifi.flowfile.FlowFile;
import org.apache.nifi.processor.AbstractProcessor;
import org.apache.nifi.processor.ProcessContext;
import org.apache.nifi.processor.ProcessSession;
import org.apache.nifi.processor.Relationship;
import org.apache.nifi.processor.exception.ProcessException;
import org.apache.nifi.processor.util.StandardValidators;
import org.apache.nifi.stream.io.StreamUtils;

import java.io.InputStream;
import java.io.OutputStream;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class ConcatenateFlowFiles extends AbstractProcessor {
    static final PropertyDescriptor FLOWFILE_COUNT = new Builder()
        .name("FlowFile Count")
        .displayName("FlowFile Count")
        .description("Number of FlowFiles to concatenate together")
        .required(true)
        .addValidator(StandardValidators.POSITIVE_INTEGER_VALIDATOR)
        .build();

    static final Relationship ORIGINAL = new Relationship.Builder()
        .name("original")
        .build();
    static final Relationship MERGED = new Relationship.Builder()
        .name("merged")
        .build();

    @Override
    protected List<PropertyDescriptor> getSupportedPropertyDescriptors() {
        return Collections.singletonList(FLOWFILE_COUNT);
    }

    @Override
    public Set<Relationship> getRelationships() {
        return new HashSet<>(Arrays.asList(ORIGINAL, MERGED));
    }

    @Override
    public void onTrigger(final ProcessContext context, final ProcessSession session) throws ProcessException {
        final int flowFileCount = context.getProperty(FLOWFILE_COUNT).asInteger();
        final List<FlowFile> flowFiles = session.get(flowFileCount);
        if (flowFiles.size() != flowFileCount) {
            session.rollback();
            context.yield();
            getLogger().debug("Need {} FlowFiles but currently on {} are available. Will not merge.", flowFileCount, flowFiles.size());
            return;
        }

        FlowFile merged = session.create(flowFiles);
        try (final OutputStream out = session.write(merged)) {
            for (final FlowFile input : flowFiles) {
                try (final InputStream in = session.read(input)) {
                    StreamUtils.copy(in, out);
                }
            }
        } catch (final Exception e) {
            throw new ProcessException("Failed to merge", e);
        }

        session.transfer(merged, MERGED);
        session.transfer(flowFiles, ORIGINAL);
    }

}