chore: trying to generate like ts union types

build.gradle

@@ -28,6 +28,13 @@ def getCheckedOutGitCommitHash() {
 
 apply from: './publish-common.gradle'
 
+// Java toolchain configuration - Use Java 21 for modern features
+java {
+    toolchain {
+        languageVersion = JavaLanguageVersion.of(21)
+    }
+}
+
 def lombokVersion = '1.18.30'
 def lazysodiumVersion = '5.1.4'
 def jnaVersion = '5.15.0'
@@ -39,6 +46,8 @@ def jsonVersion = '20240303'
 def structuredFieldsVersion = '0.4'
 def jakartaAnnotationVersion = '2.1.1'
 def jacksonNullableVersion = '0.2.6'
+def jakartaValidationVersion = '3.0.2'
+def hibernateValidatorVersion = '8.0.1.Final'
 
 // test dependencies
 def testngVersion = '7.7.0'
@@ -62,6 +71,10 @@ dependencies {
     implementation "jakarta.annotation:jakarta.annotation-api:${jakartaAnnotationVersion}"
     implementation "org.openapitools:jackson-databind-nullable:${jacksonNullableVersion}"
 
+    // Jakarta Validation for generated models (required when useBeanValidation=true)
+    implementation "jakarta.validation:jakarta.validation-api:${jakartaValidationVersion}"
+    implementation "org.hibernate.validator:hibernate-validator:${hibernateValidatorVersion}"
+
     testImplementation platform("org.junit:junit-bom:${junitVersion}")
     testImplementation "org.junit.jupiter:junit-jupiter:${junitVersion}"
     testImplementation "com.squareup.okhttp3:mockwebserver:${mockwebVersion}"
@@ -214,10 +227,24 @@ tasks.openApiGenerate {
             serializationLibrary : "jackson",
             useJakartaEe         : "true",
             dateLibrary          : "java21",
-            sourceFolder         : "src/main/java"
+            sourceFolder         : "src/main/java",
+
+            // ====== oneOf Handling ======
+            // Generate interfaces for oneOf schemas - creates TypeScript-like union types
+            useOneOfInterfaces   : "true",      // Generates interfaces instead of flat classes (TypeScript-like)
+            legacyDiscriminatorBehavior: "false",
+
+            // ====== Reduce Boilerplate ======
+            hideGenerationTimestamp: "true",
+            openApiNullable      : "false",     // Don't use JsonNullable wrapper
+
+            // ====== Code Quality & Validation ======
+            generateConstructorWithAllArgs: "true",
+            performBeanValidation: "true",      // Requires jakarta.validation dependencies
+            useBeanValidation    : "true",      // Requires jakarta.validation dependencies
     ]
 
-    nameMappings.put("A", "AUpper")
+//    nameMappings.put("A", "AUpper")
 }
 
 tasks.register("prepareOpenApiSpec") {

src/main/java/org/cardanofoundation/signify/generated/keria/model/ACDCAttributes.java

@@ -27,6 +27,9 @@
 import com.fasterxml.jackson.annotation.JsonValue;
 import com.fasterxml.jackson.annotation.JsonPropertyOrder;
 import com.fasterxml.jackson.annotation.JsonTypeName;
+import jakarta.validation.constraints.*;
+import jakarta.validation.Valid;
+import org.hibernate.validator.constraints.*;
 
 /**
  * ACDCAttributes
@@ -36,7 +39,7 @@
   ACDCAttributes.JSON_PROPERTY_I,
   ACDCAttributes.JSON_PROPERTY_U
 })
-@jakarta.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen", date = "2025-11-27T15:07:13.177027+07:00[Asia/Ho_Chi_Minh]", comments = "Generator version: 7.16.0")
+@jakarta.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen", comments = "Generator version: 7.16.0")
 public class ACDCAttributes {
   public static final String JSON_PROPERTY_DT = "dt";
   @jakarta.annotation.Nullable
@@ -53,6 +56,15 @@ public class ACDCAttributes {
   public ACDCAttributes() {
   }
 
+  /**
+   * Constructor with all args parameters
+   */
+  public ACDCAttributes(@JsonProperty(JSON_PROPERTY_DT) String dt, @JsonProperty(JSON_PROPERTY_I) String i, @JsonProperty(JSON_PROPERTY_U) String u) {
+    this.dt = dt;
+    this.i = i;
+    this.u = u;
+  }
+
   public ACDCAttributes dt(@jakarta.annotation.Nullable String dt) {
 
     this.dt = dt;
@@ -64,6 +76,7 @@ public ACDCAttributes dt(@jakarta.annotation.Nullable String dt) {
    * @return dt
    */
   @jakarta.annotation.Nullable
+
   @JsonProperty(value = JSON_PROPERTY_DT, required = false)
   @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
 
@@ -89,6 +102,7 @@ public ACDCAttributes i(@jakarta.annotation.Nullable String i) {
    * @return i
    */
   @jakarta.annotation.Nullable
+
   @JsonProperty(value = JSON_PROPERTY_I, required = false)
   @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)
 
@@ -114,6 +128,7 @@ public ACDCAttributes u(@jakarta.annotation.Nullable String u) {
    * @return u
    */
   @jakarta.annotation.Nullable
+
   @JsonProperty(value = JSON_PROPERTY_U, required = false)
   @JsonInclude(value = JsonInclude.Include.USE_DEFAULTS)