WriteResourceToStream.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;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;

import org.apache.commons.io.IOUtils;
import org.apache.nifi.annotation.documentation.CapabilityDescription;
import org.apache.nifi.annotation.documentation.Tags;
import org.apache.nifi.annotation.lifecycle.OnScheduled;
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.ProcessorInitializationContext;
import org.apache.nifi.processor.Relationship;
import org.apache.nifi.processor.exception.ProcessException;
import org.apache.nifi.processor.io.OutputStreamCallback;

@Tags({ "example", "resources" })
@CapabilityDescription("This example processor loads a resource from the nar and writes it to the FlowFile content")
public class WriteResourceToStream extends AbstractProcessor {

    public static final Relationship REL_SUCCESS = new Relationship.Builder()
            .name("success")
            .description("files that were successfully processed").build();
    public static final Relationship REL_FAILURE = new Relationship.Builder()
            .name("failure")
            .description("files that were not successfully processed").build();

    private Set<Relationship> relationships;

    private String resourceData;

    @Override
    protected void init(final ProcessorInitializationContext context) {

        final Set<Relationship> relationships = new HashSet<Relationship>();
        relationships.add(REL_SUCCESS);
        relationships.add(REL_FAILURE);
        this.relationships = Collections.unmodifiableSet(relationships);
        final InputStream resourceStream = Thread.currentThread()
                .getContextClassLoader().getResourceAsStream("file.txt");
        try {
            this.resourceData = IOUtils.toString(resourceStream);
        } catch (IOException e) {
            throw new RuntimeException("Unable to load resources", e);
        } finally {
            IOUtils.closeQuietly(resourceStream);
        }

    }

    @Override
    public Set<Relationship> getRelationships() {
        return this.relationships;
    }

    @OnScheduled
    public void onScheduled(final ProcessContext context) {

    }

    @Override
    public void onTrigger(final ProcessContext context,
            final ProcessSession session) throws ProcessException {
        FlowFile flowFile = session.get();
        if (flowFile == null) {
            return;
        }

        try {
            flowFile = session.write(flowFile, new OutputStreamCallback() {

                @Override
                public void process(OutputStream out) throws IOException {
                    IOUtils.write(resourceData, out);

                }
            });
            session.transfer(flowFile, REL_SUCCESS);
        } catch (ProcessException ex) {
            getLogger().error("Unable to process", ex);
            session.transfer(flowFile, REL_FAILURE);
        }
    }
}