added jackson annotations on oneof generated interface for deserialization

Author: HugoMario

src/main/java/io/swagger/codegen/v3/generators/SchemaHandler.java

@@ -175,7 +175,17 @@ protected void addInterfaces(List<Schema> schemas, CodegenModel codegenModel, Ma
                 continue;
             }
             final String schemaName = ref.substring(ref.lastIndexOf("/") + 1);
-            this.addInterfaceModel(allModels.get(codegenConfig.toModelName(schemaName)), codegenModel);
+
+            final CodegenModel model = allModels.get(codegenConfig.toModelName(schemaName));
+            this.addInterfaceModel(model, codegenModel);
+
+            boolean subTypeAdded = false;
+            if (codegenModel.getSubTypes() != null) {
+                subTypeAdded = codegenModel.getSubTypes().stream().anyMatch(existingSubType -> existingSubType.classname.equalsIgnoreCase(model.classname));
+            }
+            if (!subTypeAdded) {
+                codegenModel.addSubType(model);
+            }
         }
     }
 

src/main/resources/handlebars/Java/interface.mustache

@@ -1,6 +1,21 @@
+{{#jackson}}
+import com.fasterxml.jackson.annotation.JsonSubTypes;
+import com.fasterxml.jackson.annotation.JsonTypeInfo;
+{{/jackson}}
 /**
 * {{#description}}{{.}}{{/description}}{{^description}}{{classname}}{{/description}}
 */
+{{#jackson}}
+@JsonTypeInfo(
+  use = JsonTypeInfo.Id.NAME,
+  include = JsonTypeInfo.As.PROPERTY,
+  property = "type")
+@JsonSubTypes({
+  {{#subTypes}}
+  @JsonSubTypes.Type(value = {{classname}}.class, name = "{{classname}}"){{^@last}},{{/@last}}
+  {{/subTypes}}
+})
+{{/jackson}}
 public interface {{{classname}}} {
 
 }