[jaxrs-spec] Add @JsonIgnoreProperties on the discriminator to avoid duplicated keys during serialisation

modules/openapi-generator/src/main/resources/JavaJaxRS/spec/typeInfoAnnotation.mustache

@@ -1,4 +1,8 @@
 {{#jackson}}
+@JsonIgnoreProperties(
+  value = "{{{discriminator.propertyBaseName}}}", // ignore manually set {{{discriminator.propertyBaseName}}}, it will be automatically generated by Jackson during serialization
+  allowSetters = true // allows the {{{discriminator.propertyBaseName}}} to be set during deserialization
+)
 @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "{{{discriminator.propertyBaseName}}}", visible = true)
 @JsonSubTypes({
   {{#discriminator.mappedModels}}

modules/openapi-generator/src/test/java/org/openapitools/codegen/java/jaxrs/JavaJAXRSSpecServerCodegenTest.java

@@ -1289,6 +1289,88 @@ public void testDiscriminatorMappingUsedInJsonTypeName() throws Exception {
                 .fileDoesNotContain("@JsonTypeName(\"DogRequest\")");
     }
 
+    /**
+     * A model with a discriminator must emit {@code @JsonIgnoreProperties} on the discriminator
+     * property so Jackson does not serialize that property twice (once for the manually declared
+     * field and once for the {@code @JsonTypeInfo} type id), which produces a duplicate key in the
+     * response body. {@code allowSetters = true} preserves the field during deserialization.
+     */
+    @Test
+    public void testDiscriminatorEmitsJsonIgnorePropertiesToAvoidDuplicateKey() throws Exception {
+        File output = Files.createTempDirectory("test").toFile().getCanonicalFile();
+        output.deleteOnExit();
+
+        OpenAPI openAPI = new OpenAPIParser()
+                .readLocation("src/test/resources/3_0/jaxrs/petstore.yaml", null, new ParseOptions()).getOpenAPI();
+
+        codegen.setOutputDir(output.getAbsolutePath());
+
+        ClientOptInput input = new ClientOptInput()
+                .openAPI(openAPI)
+                .config(codegen);
+
+        DefaultGenerator generator = new DefaultGenerator();
+        Map<String, File> files = generator.opts(input).generate().stream()
+                .collect(Collectors.toMap(File::getName, Function.identity()));
+
+        // The parent model (which carries the discriminator) must ignore the manually declared
+        // discriminator property during serialization while still allowing it to be set during
+        // deserialization. The discriminator property in this spec is "petType".
+        JavaFileAssert.assertThat(files.get("PetRequest.java"))
+                .hasImports("com.fasterxml.jackson.annotation.JsonIgnoreProperties")
+                .fileContains(
+                        "@JsonIgnoreProperties(",
+                        "value = \"petType\"",
+                        "allowSetters = true")
+                // @JsonIgnoreProperties must precede @JsonTypeInfo on the class declaration.
+                .fileContainsPattern("@JsonIgnoreProperties\\([\\s\\S]*?@JsonTypeInfo");
+
+        // Child models do not carry the discriminator, so they must not receive the annotation.
+        JavaFileAssert.assertThat(files.get("CatRequest.java"))
+                .fileDoesNotContain("@JsonIgnoreProperties");
+        JavaFileAssert.assertThat(files.get("DogRequest.java"))
+                .fileDoesNotContain("@JsonIgnoreProperties");
+    }
+
+    /**
+     * With {@code legacyDiscriminatorBehavior=false} the discriminator is propagated from the
+     * parent onto every child reachable through the discriminator mapping, so each child also
+     * emits {@code @JsonTypeInfo}. The {@code @JsonIgnoreProperties} fix must therefore apply to
+     * the children too, otherwise they would serialize the discriminator property twice.
+     */
+    @Test
+    public void testDiscriminatorJsonIgnorePropertiesPropagatesToChildren_whenLegacyBehaviorDisabled() throws Exception {
+        File output = Files.createTempDirectory("test").toFile().getCanonicalFile();
+        output.deleteOnExit();
+
+        Map<String, Object> properties = new HashMap<>();
+        properties.put("legacyDiscriminatorBehavior", "false");
+
+        final CodegenConfigurator configurator = new CodegenConfigurator()
+                .setGeneratorName("jaxrs-spec")
+                .setAdditionalProperties(properties)
+                .setInputSpec("src/test/resources/3_0/jaxrs-spec/discriminator-mapping-children.yaml")
+                .setOutputDir(output.getAbsolutePath().replace("\\", "/"));
+
+        DefaultGenerator generator = new DefaultGenerator();
+        Map<String, File> files = generator.opts(configurator.toClientOptInput()).generate().stream()
+                .collect(Collectors.toMap(File::getName, Function.identity()));
+
+        // The parent and every mapped child must ignore the manually declared discriminator
+        // property during serialization (it is written once by @JsonTypeInfo) while still
+        // allowing it to be set during deserialization. The discriminator property is "petType".
+        for (String modelFile : new String[]{"PetResponse.java", "CatResponse.java", "DogResponse.java"}) {
+            JavaFileAssert.assertThat(files.get(modelFile))
+                    .hasImports("com.fasterxml.jackson.annotation.JsonIgnoreProperties")
+                    .fileContains(
+                            "@JsonIgnoreProperties(",
+                            "value = \"petType\"",
+                            "allowSetters = true")
+                    // @JsonIgnoreProperties must precede @JsonTypeInfo on the class declaration.
+                    .fileContainsPattern("@JsonIgnoreProperties\\([\\s\\S]*?@JsonTypeInfo");
+        }
+    }
+
     @Test
     public void testGenerateJsonNullableListFieldsHelperMethodReferences_issue23251() throws Exception {
         Map<String, Object> properties = new HashMap<>();

modules/openapi-generator/src/test/resources/3_0/jaxrs-spec/discriminator-mapping-children.yaml

@@ -0,0 +1,53 @@
+openapi: 3.0.3
+info:
+  title: Discriminator mapping with allOf children
+  description: >
+    Minimal spec reproducing a discriminated polymorphic response where the
+    discriminator declares an explicit mapping to child schemas. With
+    legacyDiscriminatorBehavior=false the discriminator is propagated onto the
+    mapped children, so the @JsonIgnoreProperties / @JsonTypeInfo annotations
+    must be emitted on both the parent and the children.
+  version: 1.0.0
+paths:
+  /pets:
+    get:
+      operationId: getPet
+      responses:
+        '200':
+          description: A pet
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/PetResponse'
+components:
+  schemas:
+    PetResponse:
+      type: object
+      required:
+        - petType
+      properties:
+        petType:
+          type: string
+        name:
+          type: string
+      discriminator:
+        propertyName: petType
+        mapping:
+          CAT: '#/components/schemas/CatResponse'
+          DOG: '#/components/schemas/DogResponse'
+    CatResponse:
+      description: Response payload for a cat resource
+      allOf:
+        - $ref: '#/components/schemas/PetResponse'
+        - type: object
+          properties:
+            declawed:
+              type: boolean
+    DogResponse:
+      description: Response payload for a dog resource
+      allOf:
+        - $ref: '#/components/schemas/PetResponse'
+        - type: object
+          properties:
+            bark:
+              type: boolean

samples/server/petstore/jaxrs-spec-jakarta/src/gen/java/org/openapitools/model/Animal.java

@@ -17,6 +17,10 @@
 import com.fasterxml.jackson.annotation.JsonTypeName;
 import org.openapitools.jackson.nullable.JsonNullable;
 
+@JsonIgnoreProperties(
+  value = "className", // ignore manually set className, it will be automatically generated by Jackson during serialization
+  allowSetters = true // allows the className to be set during deserialization
+)
 @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "className", visible = true)
 @JsonSubTypes({
   @JsonSubTypes.Type(value = BigCat.class, name = "BigCat"),

samples/server/petstore/jaxrs-spec-quarkus-mutiny/src/gen/java/org/openapitools/model/Animal.java

@@ -14,6 +14,10 @@
 import com.fasterxml.jackson.annotation.JsonTypeName;
 import org.openapitools.jackson.nullable.JsonNullable;
 
+@JsonIgnoreProperties(
+  value = "className", // ignore manually set className, it will be automatically generated by Jackson during serialization
+  allowSetters = true // allows the className to be set during deserialization
+)
 @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "className", visible = true)
 @JsonSubTypes({
   @JsonSubTypes.Type(value = Cat.class, name = "CAT"),

samples/server/petstore/jaxrs-spec-quarkus-mutiny/src/gen/java/org/openapitools/model/ParentWithNullable.java

@@ -15,6 +15,10 @@
 import com.fasterxml.jackson.annotation.JsonTypeName;
 import org.openapitools.jackson.nullable.JsonNullable;
 
+@JsonIgnoreProperties(
+  value = "type", // ignore manually set type, it will be automatically generated by Jackson during serialization
+  allowSetters = true // allows the type to be set during deserialization
+)
 @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "type", visible = true)
 @JsonSubTypes({
   @JsonSubTypes.Type(value = ChildWithNullable.class, name = "ChildWithNullable"),

samples/server/petstore/jaxrs-spec-swagger-annotations/src/gen/java/org/openapitools/model/Animal.java

@@ -17,6 +17,10 @@
 import com.fasterxml.jackson.annotation.JsonTypeName;
 import org.openapitools.jackson.nullable.JsonNullable;
 
+@JsonIgnoreProperties(
+  value = "className", // ignore manually set className, it will be automatically generated by Jackson during serialization
+  allowSetters = true // allows the className to be set during deserialization
+)
 @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "className", visible = true)
 @JsonSubTypes({
   @JsonSubTypes.Type(value = Cat.class, name = "CAT"),

samples/server/petstore/jaxrs-spec-swagger-annotations/src/gen/java/org/openapitools/model/ParentWithNullable.java

@@ -18,6 +18,10 @@
 import com.fasterxml.jackson.annotation.JsonTypeName;
 import org.openapitools.jackson.nullable.JsonNullable;
 
+@JsonIgnoreProperties(
+  value = "type", // ignore manually set type, it will be automatically generated by Jackson during serialization
+  allowSetters = true // allows the type to be set during deserialization
+)
 @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "type", visible = true)
 @JsonSubTypes({
   @JsonSubTypes.Type(value = ChildWithNullable.class, name = "ChildWithNullable"),

samples/server/petstore/jaxrs-spec-swagger-v3-annotations-jakarta/src/gen/java/org/openapitools/model/Animal.java

@@ -15,6 +15,10 @@
 import com.fasterxml.jackson.annotation.JsonTypeName;
 import org.openapitools.jackson.nullable.JsonNullable;
 
+@JsonIgnoreProperties(
+  value = "className", // ignore manually set className, it will be automatically generated by Jackson during serialization
+  allowSetters = true // allows the className to be set during deserialization
+)
 @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "className", visible = true)
 @JsonSubTypes({
   @JsonSubTypes.Type(value = Cat.class, name = "CAT"),

samples/server/petstore/jaxrs-spec-swagger-v3-annotations-jakarta/src/gen/java/org/openapitools/model/ParentWithNullable.java

@@ -16,6 +16,10 @@
 import com.fasterxml.jackson.annotation.JsonTypeName;
 import org.openapitools.jackson.nullable.JsonNullable;
 
+@JsonIgnoreProperties(
+  value = "type", // ignore manually set type, it will be automatically generated by Jackson during serialization
+  allowSetters = true // allows the type to be set during deserialization
+)
 @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "type", visible = true)
 @JsonSubTypes({
   @JsonSubTypes.Type(value = ChildWithNullable.class, name = "ChildWithNullable"),

samples/server/petstore/jaxrs-spec-swagger-v3-annotations/src/gen/java/org/openapitools/model/Animal.java

@@ -15,6 +15,10 @@
 import com.fasterxml.jackson.annotation.JsonTypeName;
 import org.openapitools.jackson.nullable.JsonNullable;
 
+@JsonIgnoreProperties(
+  value = "className", // ignore manually set className, it will be automatically generated by Jackson during serialization
+  allowSetters = true // allows the className to be set during deserialization
+)
 @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "className", visible = true)
 @JsonSubTypes({
   @JsonSubTypes.Type(value = Cat.class, name = "CAT"),

samples/server/petstore/jaxrs-spec-swagger-v3-annotations/src/gen/java/org/openapitools/model/ParentWithNullable.java

@@ -16,6 +16,10 @@
 import com.fasterxml.jackson.annotation.JsonTypeName;
 import org.openapitools.jackson.nullable.JsonNullable;
 
+@JsonIgnoreProperties(
+  value = "type", // ignore manually set type, it will be automatically generated by Jackson during serialization
+  allowSetters = true // allows the type to be set during deserialization
+)
 @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "type", visible = true)
 @JsonSubTypes({
   @JsonSubTypes.Type(value = ChildWithNullable.class, name = "ChildWithNullable"),

samples/server/petstore/jaxrs-spec-withxml/src/gen/java/org/openapitools/model/Animal.java

@@ -24,6 +24,10 @@
 import javax.xml.bind.annotation.XmlEnum;
 import javax.xml.bind.annotation.XmlEnumValue;
 
+@JsonIgnoreProperties(
+  value = "className", // ignore manually set className, it will be automatically generated by Jackson during serialization
+  allowSetters = true // allows the className to be set during deserialization
+)
 @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "className", visible = true)
 @JsonSubTypes({
   @JsonSubTypes.Type(value = Cat.class, name = "CAT"),

samples/server/petstore/jaxrs-spec-withxml/src/gen/java/org/openapitools/model/ParentWithNullable.java

@@ -25,6 +25,10 @@
 import javax.xml.bind.annotation.XmlEnum;
 import javax.xml.bind.annotation.XmlEnumValue;
 
+@JsonIgnoreProperties(
+  value = "type", // ignore manually set type, it will be automatically generated by Jackson during serialization
+  allowSetters = true // allows the type to be set during deserialization
+)
 @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "type", visible = true)
 @JsonSubTypes({
   @JsonSubTypes.Type(value = ChildWithNullable.class, name = "ChildWithNullable"),

samples/server/petstore/jaxrs-spec/src/gen/java/org/openapitools/model/Animal.java

@@ -17,6 +17,10 @@
 import com.fasterxml.jackson.annotation.JsonTypeName;
 import org.openapitools.jackson.nullable.JsonNullable;
 
+@JsonIgnoreProperties(
+  value = "className", // ignore manually set className, it will be automatically generated by Jackson during serialization
+  allowSetters = true // allows the className to be set during deserialization
+)
 @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "className", visible = true)
 @JsonSubTypes({
   @JsonSubTypes.Type(value = Cat.class, name = "CAT"),

samples/server/petstore/jaxrs-spec/src/gen/java/org/openapitools/model/ParentWithNullable.java

@@ -18,6 +18,10 @@
 import com.fasterxml.jackson.annotation.JsonTypeName;
 import org.openapitools.jackson.nullable.JsonNullable;
 
+@JsonIgnoreProperties(
+  value = "type", // ignore manually set type, it will be automatically generated by Jackson during serialization
+  allowSetters = true // allows the type to be set during deserialization
+)
 @JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.PROPERTY, property = "type", visible = true)
 @JsonSubTypes({
   @JsonSubTypes.Type(value = ChildWithNullable.class, name = "ChildWithNullable"),