For forward compatibility and prevent deserialization exceptions, allow unknown enums to be deserialized to null

Author: arturo-w

src/main/java/com/taboola/rest/api/internal/config/SerializationConfig.java

@@ -8,6 +8,7 @@ public class SerializationConfig {
     private boolean shouldIgnoreAnySetterAnnotation;
     private boolean shouldDisableReadUnknownEnumValuesAsDefaultValue;
     private boolean shouldUseSnakeCase;
+    private boolean shouldAllowNullAsDefaultValueForReadUnknownEnums;
 
     public SerializationConfig() {
         mixins = new HashMap<>();
@@ -36,6 +37,11 @@ public SerializationConfig setShouldUseSnakeCase() {
         return this;
     }
 
+    public SerializationConfig setShouldAllowNullAsDefaultValueForReadUnknownEnums() {
+        this.shouldAllowNullAsDefaultValueForReadUnknownEnums = true;
+        return this;
+    }
+
     public Map<Class<?>, Class<?>> getMixins() {
         return mixins;
     }
@@ -50,12 +56,19 @@ public boolean shouldUseSnakeCase() {
         return shouldUseSnakeCase;
     }
 
+    public boolean shouldAllowNullAsDefaultValueForReadUnknownEnums() {
+        return shouldAllowNullAsDefaultValueForReadUnknownEnums;
+    }
+
+
     @Override
     public String toString() {
         return "SerializationConfig{" +
                 "mixins=" + mixins +
                 ", shouldIgnoreAnySetterAnnotation=" + shouldIgnoreAnySetterAnnotation +
+                ", shouldDisableReadUnknownEnumValuesAsDefaultValue=" + shouldDisableReadUnknownEnumValuesAsDefaultValue +
                 ", shouldUseSnakeCase=" + shouldUseSnakeCase +
+                ", shouldAllowNullAsDefaultValueForReadUnknownEnums=" + shouldAllowNullAsDefaultValueForReadUnknownEnums +
                 '}';
     }
 }

src/main/java/com/taboola/rest/api/internal/serialization/SerializationMapperCreator.java

@@ -20,6 +20,10 @@ public static ObjectMapper createObjectMapper(SerializationConfig serializationC
         if (!serializationConfig.shouldDisableReadUnknownEnumValuesAsDefaultValue()) {
             objectMapper.configure(DeserializationFeature.READ_UNKNOWN_ENUM_VALUES_USING_DEFAULT_VALUE, true);
         }
+        if (serializationConfig.shouldAllowNullAsDefaultValueForReadUnknownEnums()) {
+            // NOTE: default enum value takes precedence over null
+            objectMapper.configure(DeserializationFeature.READ_UNKNOWN_ENUM_VALUES_AS_NULL, true);
+        }
 
         serializationConfig.getMixins().forEach(objectMapper::addMixIn);
 

src/test/java/com/taboola/rest/api/internal/serialization/SerializationMapperCreatorTest.java

@@ -90,16 +90,36 @@ public void createObjectMapper_defaultSerializationConfigAndApiObjectHasInvalidE
         Assert.assertEquals("Unknown enum is parsed incorrectly", SampleEnum.UNKNOWN, sampleApi.letter);
     }
 
+    @Test
+    public void createObjectMapper_serializationConfigAndAllowNullAsDefaultValueForReadUnknownEnumsAndApiObjectHasInvalidEnum_defaultValueUsedOnSerialization() throws IOException {
+        SerializationConfig serializationConfig = new SerializationConfig().setShouldAllowNullAsDefaultValueForReadUnknownEnums();
+        ObjectMapper objectMapper = SerializationMapperCreator.createObjectMapper(serializationConfig);
+
+        SampleApi sampleApi = objectMapper.readValue("{ \"letter\": \"D\" }", SampleApi.class);
+
+        Assert.assertEquals("Unknown enum is parsed incorrectly. Default takes precedence before null", SampleEnum.UNKNOWN, sampleApi.letter);
+    }
+
     @Test
     public void createObjectMapper_defaultSerializationConfigAndApiObjectHasEmptyEnumValue_defaultValueUsedOnSerialization() throws IOException {
         SerializationConfig serializationConfig = new SerializationConfig();
         ObjectMapper objectMapper = SerializationMapperCreator.createObjectMapper(serializationConfig);
 
-        SampleApi sampleApi = objectMapper.readValue("{ \"letter\": \"D\" }", SampleApi.class);
+        SampleApi sampleApi = objectMapper.readValue("{ \"letter\": \"\" }", SampleApi.class);
 
         Assert.assertEquals("Unknown enum is parsed incorrectly", SampleEnum.UNKNOWN, sampleApi.letter);
     }
 
+    @Test
+    public void createObjectMapper_defaultSerializationConfigAndApiObjectHasNullEnumValue_nullOnSerialization() throws IOException {
+        SerializationConfig serializationConfig = new SerializationConfig();
+        ObjectMapper objectMapper = SerializationMapperCreator.createObjectMapper(serializationConfig);
+
+        SampleApi sampleApi = objectMapper.readValue("{ \"letter\": null }", SampleApi.class);
+
+        Assert.assertNull("Unknown enum is parsed incorrectly", sampleApi.letter);
+    }
+
     @Test
     public void createObjectMapper_serializationConfigWithReadUnknownEnumsDisabledAndApiObjectHasValidEnum_enumParsedCorrectly() throws IOException {
         SerializationConfig serializationConfig = new SerializationConfig().setShouldDisableReadUnknownEnumValuesAsDefaultValue();
@@ -118,6 +138,16 @@ public void createObjectMapper_serializationConfigWithReadUnknownEnumsDisabledAn
         objectMapper.readValue("{ \"letter\": \"D\" }", SampleApi.class);
     }
 
+    @Test
+    public void createObjectMapper_serializationConfigWithReadUnknownEnumsDisabledAndAllowNullAsDefaultValueForReadUnknownEnumsAndApiObjectHasInvalidEnum_nullOnSerialization() throws IOException {
+        SerializationConfig serializationConfig = new SerializationConfig().setShouldDisableReadUnknownEnumValuesAsDefaultValue().setShouldAllowNullAsDefaultValueForReadUnknownEnums();
+        ObjectMapper objectMapper = SerializationMapperCreator.createObjectMapper(serializationConfig);
+
+        SampleApi sampleApi = objectMapper.readValue("{ \"letter\": \"D\" }", SampleApi.class);
+
+        Assert.assertNull("Unknown enum is parsed incorrectly", sampleApi.letter);
+    }
+
     @Test(expected = InvalidFormatException.class)
     public void createObjectMapper_serializationConfigWithReadUnknownEnumsDisabledAndApiObjectHasEmptyEnumValue_InvalidFormatExceptionIsThrown() throws IOException {
         SerializationConfig serializationConfig = new SerializationConfig().setShouldDisableReadUnknownEnumValuesAsDefaultValue();
@@ -126,9 +156,70 @@ public void createObjectMapper_serializationConfigWithReadUnknownEnumsDisabledAn
         objectMapper.readValue("{ \"letter\": \"\" }", SampleApi.class);
     }
 
+    @Test
+    public void createObjectMapper_serializationConfigWithReadUnknownEnumsDisabledAndAllowNullAsDefaultValueForReadUnknownEnumsAndApiObjectHasEmptyEnumValue_nullOnSerialization() throws IOException {
+        SerializationConfig serializationConfig = new SerializationConfig().setShouldDisableReadUnknownEnumValuesAsDefaultValue().setShouldAllowNullAsDefaultValueForReadUnknownEnums();
+        ObjectMapper objectMapper = SerializationMapperCreator.createObjectMapper(serializationConfig);
+
+        SampleApi sampleApi = objectMapper.readValue("{ \"letter\": \"\" }", SampleApi.class);
+
+        Assert.assertNull("Unknown enum is parsed incorrectly", sampleApi.letter);
+    }
+
+    @Test
+    public void createObjectMapper_defaultSerializationConfigAndNoDefaultEnumIsValid_enumParsedCorrectly() throws IOException {
+        SerializationConfig serializationConfig = new SerializationConfig();
+        ObjectMapper objectMapper = SerializationMapperCreator.createObjectMapper(serializationConfig);
+
+        SampleApi sampleApi = objectMapper.readValue("{ \"letterNoDefault\": \"BB\" }", SampleApi.class);
+
+        Assert.assertEquals("shouldAllowNullAsDefaultValueForReadUnknownEnums should not affect deserializing valid enums",
+                SampleEnumNoDefault.BB, sampleApi.letterNoDefault);
+    }
+
+    @Test
+    public void createObjectMapper_defaultSerializationConfigAndNoDefaultEnumIsNull_enumIsNull() throws IOException {
+        SerializationConfig serializationConfig = new SerializationConfig();
+        ObjectMapper objectMapper = SerializationMapperCreator.createObjectMapper(serializationConfig);
+
+        SampleApi sampleApi = objectMapper.readValue("{ \"letterNoDefault\": null }", SampleApi.class);
+
+        Assert.assertNull("shouldAllowNullAsDefaultValueForReadUnknownEnums should not affect deserializing null enums", sampleApi.letterNoDefault);
+    }
+
+    @Test(expected = InvalidFormatException.class)
+    public void createObjectMapper_defaultSerializationConfigAndNoDefaultEnumIsEmpty_InvalidFormatExceptionIsThrown() throws IOException {
+        SerializationConfig serializationConfig = new SerializationConfig();
+        ObjectMapper objectMapper = SerializationMapperCreator.createObjectMapper(serializationConfig);
+
+        objectMapper.readValue("{ \"letterNoDefault\": \"\" }", SampleApi.class);
+    }
+
+    @Test(expected = InvalidFormatException.class)
+    public void createObjectMapper_defaultSerializationConfigAndNoDefaultEnumIsInvalid_InvalidFormatExceptionIsThrown() throws IOException {
+        SerializationConfig serializationConfig = new SerializationConfig();
+        ObjectMapper objectMapper = SerializationMapperCreator.createObjectMapper(serializationConfig);
+
+        objectMapper.readValue("{ \"letterNoDefault\": \"BBB\" }", SampleApi.class);
+    }
+
+    @Test
+    public void createObjectMapper_serializationConfigAndAllowNullAsDefaultValueForReadUnknownEnumsAndNoDefaultEnumIsInvalid_enumIsNull() throws IOException {
+        SerializationConfig serializationConfig = new SerializationConfig().setShouldAllowNullAsDefaultValueForReadUnknownEnums();
+        ObjectMapper objectMapper = SerializationMapperCreator.createObjectMapper(serializationConfig);
+
+        SampleApi sampleApi = objectMapper.readValue("{ \"letterNoDefault\": \"BBB\" }", SampleApi.class);
+
+        Assert.assertNull("Even though enum has no set default value and deserialization not configured to use default value, null should be default",
+                sampleApi.letterNoDefault);
+    }
+
     private enum SampleEnum {
         A, B, @JsonEnumDefaultValue UNKNOWN
     }
+    private enum SampleEnumNoDefault {
+        AA, BB
+    }
 
     private static class SampleApi {
         @JsonProperty("id")
@@ -137,6 +228,9 @@ private static class SampleApi {
         @JsonProperty("letter")
         SampleEnum letter;
 
+        @JsonProperty("letterNoDefault")
+        SampleEnumNoDefault letterNoDefault;
+
         @JsonProperty("name")
         String name;