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New property (wrap as array) in avro2json converter #85

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4 changes: 4 additions & 0 deletions nifi-nar-bundles/nifi-avro-bundle/nifi-avro-processors/pom.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -54,6 +54,10 @@
<artifactId>junit</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
</dependency>
</dependencies>

<build>
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36 changes: 33 additions & 3 deletions ...nifi-avro-processors/src/main/java/org/apache/nifi/processors/avro/ConvertAvroToJSON.java
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Original file line number Diff line number Diff line change
Expand Up @@ -23,8 +23,11 @@
import java.io.OutputStream;
import java.nio.charset.StandardCharsets;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.collect.ImmutableList;
import org.apache.avro.file.DataFileStream;
import org.apache.avro.generic.GenericData;
import org.apache.avro.generic.GenericDatumReader;
Expand All @@ -34,6 +37,7 @@
import org.apache.nifi.annotation.behavior.WritesAttribute;
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.flowfile.attributes.CoreAttributes;
import org.apache.nifi.processor.AbstractProcessor;
Expand All @@ -42,6 +46,7 @@
import org.apache.nifi.processor.Relationship;
import org.apache.nifi.processor.exception.ProcessException;
import org.apache.nifi.processor.io.StreamCallback;
import org.apache.nifi.processor.util.StandardValidators;

@SideEffectFree
@SupportsBatching
Expand All @@ -53,6 +58,16 @@
@WritesAttribute(attribute = "mime.type", description = "Sets the mime type to application/json")
public class ConvertAvroToJSON extends AbstractProcessor {

@VisibleForTesting
static final PropertyDescriptor WRAP_AS_ARRAY
= new PropertyDescriptor.Builder()
.name("Expose stream of records as array of JSON Objects")
.description("Determines how stream of records is exposed: either as a sequence of single Objects (false), writing every Object to a new line, or as an array of Objects (true). Default value is true, meaning that the Avro content is exposed as a sequence of root-level Object entries.")
.addValidator(StandardValidators.BOOLEAN_VALIDATOR)
.allowableValues("true", "false")
.defaultValue(String.valueOf("true"))
.build();

static final Relationship REL_SUCCESS = new Relationship.Builder()
.name("success")
.description("A FlowFile is routed to this relationship after it has been converted to JSON")
Expand All @@ -62,6 +77,15 @@ public class ConvertAvroToJSON extends AbstractProcessor {
.description("A FlowFile is routed to this relationship if it cannot be parsed as Avro or cannot be converted to JSON for any reason")
.build();

private static final List<PropertyDescriptor> PROPERTIES
= ImmutableList.<PropertyDescriptor>builder()
.add(WRAP_AS_ARRAY)
.build();

@Override
protected List<PropertyDescriptor> getSupportedPropertyDescriptors() {
return PROPERTIES;
}
@Override
public Set<Relationship> getRelationships() {
final Set<Relationship> rels = new HashSet<>();
Expand All @@ -77,11 +101,14 @@ public void onTrigger(ProcessContext context, ProcessSession session) throws Pro
return;
}

final boolean wrapAsArray = context.getProperty(WRAP_AS_ARRAY).asBoolean();

try {
flowFile = session.write(flowFile, new StreamCallback() {
@Override
public void process(final InputStream rawIn, final OutputStream rawOut) throws IOException {
try (final InputStream in = new BufferedInputStream(rawIn);

final OutputStream out = new BufferedOutputStream(rawOut);
final DataFileStream<GenericRecord> reader = new DataFileStream<>(in, new GenericDatumReader<GenericRecord>())) {

Expand All @@ -90,21 +117,24 @@ public void process(final InputStream rawIn, final OutputStream rawOut) throws I
final String json = genericData.toString(record);

int recordCount = 0;
if (reader.hasNext()) {
if (reader.hasNext() && wrapAsArray) {
out.write('[');
}

out.write(json.getBytes(StandardCharsets.UTF_8));
recordCount++;

while (reader.hasNext()) {
out.write(',');
if (wrapAsArray) {
out.write(',');
}

final GenericRecord nextRecord = reader.next(record);
out.write(genericData.toString(nextRecord).getBytes(StandardCharsets.UTF_8));
recordCount++;
}

if (recordCount > 1) {
if (recordCount > 1 && wrapAsArray) {
out.write(']');
}
}
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