Support maps which are not present in the YAML, which Jackson appears…

… to be treating differently from explicit nulls. opensearch-project#568

Signed-off-by: David Venable <[email protected]>

data-prepper-logstash-configuration/src/main/java/org/opensearch/dataprepper/logstash/mapping/LogstashMappingModel.java

@@ -9,6 +9,7 @@
 import com.fasterxml.jackson.annotation.JsonSetter;
 import com.fasterxml.jackson.annotation.Nulls;
 
+import java.util.HashMap;
 import java.util.Map;
 
 /**
@@ -26,11 +27,11 @@ class LogstashMappingModel implements LogstashAttributesMappings {
 
     @JsonProperty
     @JsonSetter(nulls = Nulls.AS_EMPTY)
-    private Map<String, String> mappedAttributeNames;
+    private Map<String, String> mappedAttributeNames = new HashMap<>();
 
     @JsonProperty
     @JsonSetter(nulls = Nulls.AS_EMPTY)
-    private Map<String, Object> additionalAttributes;
+    private Map<String, Object> additionalAttributes = new HashMap<>();
 
     public String getPluginName() {
         return pluginName;

data-prepper-logstash-configuration/src/test/java/org/opensearch/dataprepper/logstash/mapping/LogstashMappingModelTest.java

@@ -9,6 +9,8 @@
 import com.fasterxml.jackson.dataformat.yaml.YAMLFactory;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
 
 import java.io.IOException;
 
@@ -42,10 +44,15 @@ void deserialize_from_JSON_should_have_expected_value() throws IOException {
         assertThat(logstashMappingModel.getAdditionalAttributes().get("addB"), equalTo("staticValueB"));
     }
 
-    @Test
-    void deserialize_from_JSON_with_null_values_has_empty_lists() throws IOException {
+    @ParameterizedTest
+    @ValueSource(strings = {
+            "sample-with-nulls.mapping.yaml",
+            "sample-with-empty-maps.mapping.yaml"
+    })
+    void deserialize_from_JSON_with_null_values_has_empty_maps(final String mappingResource) throws IOException {
 
-        final LogstashMappingModel logstashMappingModel = objectMapper.readValue(this.getClass().getResourceAsStream("sample-with-nulls.mapping.yaml"), LogstashMappingModel.class);
+        final LogstashMappingModel logstashMappingModel =
+                objectMapper.readValue(this.getClass().getResourceAsStream(mappingResource), LogstashMappingModel.class);
 
         assertThat(logstashMappingModel.getPluginName(), equalTo("samplePlugin"));
         assertThat(logstashMappingModel.getAttributesMapperClass(), equalTo("org.opensearch.dataprepper.Placeholder"));

data-prepper-logstash-configuration/src/test/resources/org/opensearch/dataprepper/logstash/mapping/sample-with-empty-maps.mapping.yaml

@@ -0,0 +1,2 @@
+pluginName: samplePlugin
+attributesMapperClass: org.opensearch.dataprepper.Placeholder