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fix(java): map OpenAPI 3.1 null type to Object to prevent ModelNull generation #23961

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fix(java): map OpenAPI 3.1 null type to Object to prevent ModelNull generation #23961

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c4c5c82
fix(java): map OpenAPI 3.1 null type to Object to prevent ModelNull g…
anupamchaubey Jun 6, 2026
ffac7aa
refactor(java): refine null-type handling and preserve fail-fast beha…
anupamchaubey Aug 9, 2026
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29 changes: 25 additions & 4 deletions ...enapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractJavaCodegen.java
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Original file line number Diff line number Diff line change
Expand Up @@ -1093,6 +1093,11 @@ public String toModelFilename(String name) {

@Override
public String getTypeDeclaration(Schema p) {
// Intercept "null" explicitly to prevent complex object resolution
if (p != null && "null".equalsIgnoreCase(p.getType())) {
return "Object";
}

Schema<?> schema = unaliasSchema(p);
Schema<?> target = ModelUtils.isGenerateAliasAsModel() ? p : schema;
if (ModelUtils.isArraySchema(target)) {
Expand Down Expand Up @@ -1866,16 +1871,32 @@ public String toExampleValue(Schema p) {

@Override
public String getSchemaType(Schema p) {
String openAPIType = super.getSchemaType(p);
if (p == null) {

@Mattias-Sehlstedt Mattias-Sehlstedt Jul 31, 2026

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Is this fallback necessary for the fix? To me it seems like a rather large change in behavior, and I fail to see why we would want to have a fallback with an error rather than a complete ceasing of processing? Surely something is very wrong if we get here (and this isn't the proper way to handle that)?

return super.getSchemaType(p);
}

// don't apply renaming on types from the typeMapping
if (typeMapping.containsKey(openAPIType)) {
return typeMapping.get(openAPIType);
// Intercept explicit OpenAPI 3.1 type: "null" immediately
if ("null".equalsIgnoreCase(p.getType())) {
return "Object";
}

String openAPIType = super.getSchemaType(p);

if (null == openAPIType) {
LOGGER.error("No Type defined for Schema {}", p);

@Mattias-Sehlstedt Mattias-Sehlstedt Jul 31, 2026

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Should we really log an error if this is an expected processing branch now?

return null;
}

// Intercept if openAPIType resolved to "null"
if ("null".equalsIgnoreCase(openAPIType)) {
return "Object";
}

// Don't apply renaming on types from the typeMapping
if (typeMapping.containsKey(openAPIType)) {
return typeMapping.get(openAPIType);
}

return toModelName(openAPIType);
}

Expand Down
9 changes: 9 additions & 0 deletions .../openapi-generator/src/test/java/org/openapitools/codegen/java/JavaClientCodegenTest.java
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Expand Up @@ -4556,6 +4556,15 @@ public void testSwagger2TagImportRestAssured() throws IOException {
assertThat(content)
.contains("import io.swagger.v3.oas.annotations.tags.*;")
.contains("@Tag(");

}

@Test
public void testNullTypeMapsToObject() {
final JavaClientCodegen codegen = new JavaClientCodegen();
Schema nullSchema = new Schema().type("null");
Assert.assertEquals(codegen.getSchemaType(nullSchema), "Object");
Assert.assertEquals(codegen.getTypeDeclaration(nullSchema), "Object");
}

}
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