[Java][Spring] enumUnknownDefaultCase true now returns correctly in fromValue (#18914)

* enumUnknownDefaultCase true added for Spring

* Resource added for test

* Updated tests

---------

Co-authored-by: Dean <dean.kane@opencastsoftware.com>

modules/openapi-generator/src/main/resources/JavaSpring/enumClass.mustache

@@ -55,6 +55,6 @@
           return b;
         }
       }
-      {{#isNullable}}return null;{{/isNullable}}{{^isNullable}}throw new IllegalArgumentException("Unexpected value '" + value + "'");{{/isNullable}}
+      {{#isNullable}}return null;{{/isNullable}}{{^isNullable}}{{#enumUnknownDefaultCase}}{{#allowableValues}}{{#enumVars}}{{#-last}}return {{{name}}};{{/-last}}{{/enumVars}}{{/allowableValues}}{{/enumUnknownDefaultCase}}{{^enumUnknownDefaultCase}}throw new IllegalArgumentException("Unexpected value '" + value + "'");{{/enumUnknownDefaultCase}}{{/isNullable}}
     }
   }

modules/openapi-generator/src/main/resources/JavaSpring/enumOuterClass.mustache

@@ -56,6 +56,6 @@ public enum {{{datatypeWithEnum}}}{{^datatypeWithEnum}}{{{classname}}}{{/datatyp
         return b;
       }
     }
-    {{#isNullable}}return null;{{/isNullable}}{{^isNullable}}throw new IllegalArgumentException("Unexpected value '" + value + "'");{{/isNullable}}
+    {{#isNullable}}return null;{{/isNullable}}{{^isNullable}}{{#enumUnknownDefaultCase}}{{#allowableValues}}{{#enumVars}}{{#-last}}return {{{name}}};{{/-last}}{{/enumVars}}{{/allowableValues}}{{/enumUnknownDefaultCase}}{{^enumUnknownDefaultCase}}throw new IllegalArgumentException("Unexpected value '" + value + "'");{{/enumUnknownDefaultCase}}{{/isNullable}}
   }
 }

modules/openapi-generator/src/test/java/org/openapitools/codegen/java/spring/SpringCodegenTest.java

@@ -4865,4 +4865,29 @@ public class SpringCodegenTest {
                 .toMethod()
                 .toFileAssert();
     }
+
+    @Test
+    public void testEnumUnknownDefaultCaseDeserializationTrue_issue13241() throws IOException {
+
+        SpringCodegen codegen = new SpringCodegen();
+        codegen.setLibrary(SPRING_BOOT);
+        codegen.additionalProperties().put(CodegenConstants.ENUM_UNKNOWN_DEFAULT_CASE, "true");
+
+        Map<String, File> files = generateFiles(codegen, "src/test/resources/bugs/issue_13241.yaml");
+
+        JavaFileAssert.assertThat(files.get("Color.java"))
+                .assertMethod("fromValue").bodyContainsLines("return UNKNOWN_DEFAULT_OPEN_API");
+    }
+
+    @Test
+    public void testEnumUnknownDefaultCaseDeserializationNotSet_issue13241() throws IOException {
+
+        SpringCodegen codegen = new SpringCodegen();
+        codegen.setLibrary(SPRING_BOOT);
+        Map<String, File> files = generateFiles(codegen, "src/test/resources/bugs/issue_13241.yaml");
+
+        JavaFileAssert.assertThat(files.get("Color.java"))
+                .assertMethod("fromValue").bodyContainsLines("throw new IllegalArgumentException(\"Unexpected value '\" + value + \"'\");");
+
+    }
 }

modules/openapi-generator/src/test/resources/bugs/issue_13241.yaml

@@ -0,0 +1,17 @@
+openapi: "3.0.0"
+info:
+  version: 2.0.0
+  title: test
+paths:
+  /pets:
+    get:
+      summary: List all pets
+      operationId: listPets
+      responses:
+        '200':
+          description: OK
+components:
+  schemas:
+    Color:
+      type: string
+      enum: [RED, BLUE, GREEN]