NIFI-3912: This closes #1809. Fixed NPE that would result in validation failure for FreeFormTextRecordSetWriter

Signed-off-by: joewitt <joewitt@apache.org>

nifi-nar-bundles/nifi-standard-services/nifi-record-serialization-services-bundle/nifi-record-serialization-services/src/main/java/org/apache/nifi/serialization/SchemaRegistryRecordSetWriter.java

@@ -21,6 +21,7 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
+import java.util.EnumSet;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
@@ -124,6 +125,10 @@ public abstract class SchemaRegistryRecordSetWriter extends SchemaRegistryServic
     }
 
     protected SchemaAccessWriter getSchemaWriteStrategy(final String allowableValue) {
+        if (allowableValue == null) {
+            return null;
+        }
+
         if (allowableValue.equalsIgnoreCase(SCHEMA_NAME_ATTRIBUTE.getValue())) {
             return new SchemaNameAsAttribute();
         } else if (allowableValue.equalsIgnoreCase(AVRO_SCHEMA_ATTRIBUTE.getValue())) {
@@ -140,6 +145,10 @@ public abstract class SchemaRegistryRecordSetWriter extends SchemaRegistryServic
     protected Set<SchemaField> getRequiredSchemaFields(final ValidationContext validationContext) {
         final String writeStrategyValue = validationContext.getProperty(getSchemaWriteStrategyDescriptor()).getValue();
         final SchemaAccessWriter writer = getSchemaWriteStrategy(writeStrategyValue);
+        if (writer == null) {
+            return EnumSet.noneOf(SchemaField.class);
+        }
+
         final Set<SchemaField> requiredFields = writer.getRequiredSchemaFields();
         return requiredFields;
     }

nifi-nar-bundles/nifi-standard-services/nifi-record-serialization-services-bundle/nifi-record-serialization-services/src/main/java/org/apache/nifi/serialization/SchemaRegistryService.java

@@ -38,6 +38,7 @@ import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.Collections;
+import java.util.EnumSet;
 import java.util.List;
 import java.util.Set;
 
@@ -103,6 +104,11 @@ public abstract class SchemaRegistryService extends AbstractControllerService {
     }
 
     public RecordSchema getSchema(final FlowFile flowFile, final InputStream contentStream) throws SchemaNotFoundException, IOException {
+        final SchemaAccessStrategy accessStrategy = getSchemaAccessStrategy();
+        if (accessStrategy == null) {
+            throw new SchemaNotFoundException("Could not determine the Schema Access Strategy for this service");
+        }
+
         return getSchemaAccessStrategy().getSchema(flowFile, contentStream);
     }
 
@@ -121,15 +127,25 @@ public abstract class SchemaRegistryService extends AbstractControllerService {
         final SchemaRegistry schemaRegistry = validationContext.getProperty(SCHEMA_REGISTRY).asControllerService(SchemaRegistry.class);
         final SchemaAccessStrategy accessStrategy = getSchemaAccessStrategy(accessStrategyValue, schemaRegistry, validationContext);
 
+        if (accessStrategy == null) {
+            return EnumSet.noneOf(SchemaField.class);
+        }
         final Set<SchemaField> suppliedFields = accessStrategy.getSuppliedSchemaFields();
         return suppliedFields;
     }
 
     protected SchemaAccessStrategy getSchemaAccessStrategy(final String allowableValue, final SchemaRegistry schemaRegistry, final ConfigurationContext context) {
+        if (allowableValue == null) {
+            return null;
+        }
+
         return SchemaAccessUtils.getSchemaAccessStrategy(allowableValue, schemaRegistry, context);
     }
 
     protected SchemaAccessStrategy getSchemaAccessStrategy(final String allowableValue, final SchemaRegistry schemaRegistry, final ValidationContext context) {
+        if (allowableValue == null) {
+            return null;
+        }
         return SchemaAccessUtils.getSchemaAccessStrategy(allowableValue, schemaRegistry, context);
     }
 

nifi-nar-bundles/nifi-standard-services/nifi-record-serialization-services-bundle/nifi-record-serialization-services/src/main/java/org/apache/nifi/text/FreeFormTextRecordSetWriter.java

@@ -17,8 +17,11 @@
 
 package org.apache.nifi.text;
 
+import java.io.IOException;
+import java.io.InputStream;
 import java.nio.charset.Charset;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 
 import org.apache.nifi.annotation.documentation.CapabilityDescription;
@@ -27,11 +30,14 @@ import org.apache.nifi.annotation.lifecycle.OnEnabled;
 import org.apache.nifi.components.PropertyDescriptor;
 import org.apache.nifi.components.PropertyValue;
 import org.apache.nifi.controller.ConfigurationContext;
+import org.apache.nifi.flowfile.FlowFile;
 import org.apache.nifi.logging.ComponentLog;
 import org.apache.nifi.processor.util.StandardValidators;
+import org.apache.nifi.schema.access.SchemaNotFoundException;
 import org.apache.nifi.serialization.RecordSetWriter;
 import org.apache.nifi.serialization.RecordSetWriterFactory;
 import org.apache.nifi.serialization.SchemaRegistryRecordSetWriter;
+import org.apache.nifi.serialization.SimpleRecordSchema;
 import org.apache.nifi.serialization.record.RecordSchema;
 
 @Tags({"text", "freeform", "expression", "language", "el", "record", "recordset", "resultset", "writer", "serialize"})
@@ -39,6 +45,8 @@ import org.apache.nifi.serialization.record.RecordSchema;
     + "text is able to make use of the Expression Language to reference each of the fields that are available "
     + "in a Record. Each record in the RecordSet will be separated by a single newline character.")
 public class FreeFormTextRecordSetWriter extends SchemaRegistryRecordSetWriter implements RecordSetWriterFactory {
+    private static final RecordSchema EMPTY_SCHEMA = new SimpleRecordSchema(Collections.emptyList());
+
     static final PropertyDescriptor TEXT = new PropertyDescriptor.Builder()
         .name("Text")
         .description("The text to use when writing the results. This property will evaluate the Expression Language using any of the fields available in a Record.")
@@ -76,4 +84,9 @@ public class FreeFormTextRecordSetWriter extends SchemaRegistryRecordSetWriter i
     public RecordSetWriter createWriter(final ComponentLog logger, final RecordSchema schema) {
         return new FreeFormTextWriter(textValue, characterSet);
     }
+
+    @Override
+    public RecordSchema getSchema(final FlowFile flowFile, final InputStream contentStream) throws SchemaNotFoundException, IOException {
+        return EMPTY_SCHEMA;
+    }
 }