Java tutorial
package com.thinkbiganalytics.nifi.v2.ingest; /*- * #%L * thinkbig-nifi-core-processors * %% * Copyright (C) 2017 ThinkBig Analytics * %% * Licensed 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. * #L% */ import com.thinkbiganalytics.ingest.StripHeaderSupport; import com.thinkbiganalytics.nifi.processor.AbstractNiFiProcessor; import org.apache.commons.lang3.mutable.MutableLong; import org.apache.nifi.annotation.behavior.EventDriven; import org.apache.nifi.annotation.behavior.InputRequirement; import org.apache.nifi.annotation.behavior.InputRequirement.Requirement; import org.apache.nifi.annotation.behavior.SideEffectFree; import org.apache.nifi.annotation.documentation.CapabilityDescription; import org.apache.nifi.annotation.documentation.Tags; import org.apache.nifi.components.PropertyDescriptor; import org.apache.nifi.flowfile.FlowFile; 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.util.StandardValidators; import java.io.IOException; import java.util.ArrayList; import java.util.Collections; import java.util.HashSet; import java.util.List; import java.util.Set; @EventDriven @SideEffectFree @Tags({ "header", "text" }) @InputRequirement(Requirement.INPUT_REQUIRED) @CapabilityDescription("Splits a text file(s) content from its header. The content of the header is passed through a separate relationship for validation") public class StripHeader extends AbstractNiFiProcessor { public static final PropertyDescriptor ENABLED = new PropertyDescriptor.Builder().name("Enable processing") .description("Whether to strip the header").required(true) .addValidator(StandardValidators.BOOLEAN_VALIDATOR).defaultValue("false") .expressionLanguageSupported(true).build(); public static final PropertyDescriptor HEADER_LINE_COUNT = new PropertyDescriptor.Builder() .name("Header Line Count") .description("The number of lines that should be considered part of the header").required(true) .addValidator(StandardValidators.NON_NEGATIVE_INTEGER_VALIDATOR).defaultValue("1") .expressionLanguageSupported(true).build(); public static final Relationship REL_ORIGINAL = new Relationship.Builder().name("original") .description("The original input file will be routed to this destination").build(); public static final Relationship REL_CONTENT = new Relationship.Builder().name("content") .description("The content (stripped of header if enabled) will be routed to this destination").build(); public static final Relationship REL_HEADER = new Relationship.Builder().name("header") .description("The header will be routed to this destination when header is stripped").build(); public static final Relationship REL_FAILURE = new Relationship.Builder().name("failure").description( "If a file cannot be split for some reason, the original file will be routed to this destination and nothing will be routed elsewhere") .build(); private List<PropertyDescriptor> properties; private Set<Relationship> relationships; @Override protected void init(final ProcessorInitializationContext context) { super.init(context); final List<PropertyDescriptor> properties = new ArrayList<>(); properties.add(ENABLED); properties.add(HEADER_LINE_COUNT); this.properties = Collections.unmodifiableList(properties); final Set<Relationship> relationships = new HashSet<>(); relationships.add(REL_ORIGINAL); relationships.add(REL_CONTENT); relationships.add(REL_HEADER); relationships.add(REL_FAILURE); this.relationships = Collections.unmodifiableSet(relationships); } @Override public Set<Relationship> getRelationships() { return relationships; } @Override protected List<PropertyDescriptor> getSupportedPropertyDescriptors() { return properties; } @Override public void onTrigger(final ProcessContext context, final ProcessSession session) { final StripHeaderSupport headerSupport = new StripHeaderSupport(); final FlowFile flowFile = session.get(); if (flowFile == null) { return; } final boolean isEnabled = context.getProperty(ENABLED).evaluateAttributeExpressions(flowFile).asBoolean(); final int headerCount = context.getProperty(HEADER_LINE_COUNT).evaluateAttributeExpressions(flowFile) .asInteger(); // Empty files and no work to do will simply pass along content if (!isEnabled || headerCount == 0 || flowFile.getSize() == 0L) { final FlowFile contentFlowFile = session.clone(flowFile); session.transfer(contentFlowFile, REL_CONTENT); session.transfer(flowFile, REL_ORIGINAL); return; } final MutableLong headerBoundaryInBytes = new MutableLong(-1); session.read(flowFile, false, rawIn -> { try { // Identify the byte boundary of the header long bytes = headerSupport.findHeaderBoundary(headerCount, rawIn); headerBoundaryInBytes.setValue(bytes); if (bytes < 0) { getLog().error("Unable to strip header {} expecting at least {} lines in file", new Object[] { flowFile, headerCount }); } } catch (IOException e) { getLog().error("Unable to strip header {} due to {}; routing to failure", new Object[] { flowFile, e.getLocalizedMessage() }, e); } }); long headerBytes = headerBoundaryInBytes.getValue(); if (headerBytes < 0) { session.transfer(flowFile, REL_FAILURE); } else { // Transfer header final FlowFile headerFlowFile = session.clone(flowFile, 0, headerBytes); session.transfer(headerFlowFile, REL_HEADER); // Transfer content long contentBytes = flowFile.getSize() - headerBytes; final FlowFile contentFlowFile = session.clone(flowFile, headerBytes, contentBytes); session.transfer(contentFlowFile, REL_CONTENT); session.transfer(flowFile, REL_ORIGINAL); } } }