From 3a80c205dd351a4372b5758f831009a53f3f0043 Mon Sep 17 00:00:00 2001
From: blaghed <17042053+blaghed@users.noreply.github.com>
Date: Mon, 17 Nov 2025 15:17:35 +0100
Subject: [PATCH] Fix Jackson Serialization of additionalProperties on java and
 jaxrs-spec

---
 .../Java/additional_properties.mustache       | 32 +++++++++++++++++++
 .../src/main/resources/Java/model.mustache    | 11 +++++++
 .../src/main/resources/Java/pojo.mustache     |  5 +++
 .../spec/additional_properties.mustache       | 32 +++++++++++++++++++
 .../resources/JavaJaxRS/spec/pojo.mustache    | 15 ++++++++-
 5 files changed, 94 insertions(+), 1 deletion(-)
 create mode 100644 modules/openapi-generator/src/main/resources/Java/additional_properties.mustache
 create mode 100644 modules/openapi-generator/src/main/resources/JavaJaxRS/spec/additional_properties.mustache

diff --git a/modules/openapi-generator/src/main/resources/Java/additional_properties.mustache b/modules/openapi-generator/src/main/resources/Java/additional_properties.mustache
new file mode 100644
index 000000000000..81af70c79ee0
--- /dev/null
+++ b/modules/openapi-generator/src/main/resources/Java/additional_properties.mustache
@@ -0,0 +1,32 @@
+{{#additionalPropertiesType}}
+  /**
+   * Set the additional (undeclared) property with the specified name and value.
+   * Creates the property if it does not already exist, otherwise replaces it.
+   * @param key the name of the property
+   * @param value the value of the property
+   * @return self reference
+   */
+  @JsonAnySetter
+  public {{classname}} putAdditionalProperty(String key, {{{.}}} value) {
+    this.put(key, value);
+    return this;
+  }
+
+  /**
+   * Return the additional (undeclared) properties.
+   * @return the additional (undeclared) properties
+   */
+  @JsonAnyGetter
+  public Map<String, {{{.}}}> getAdditionalProperties() {
+    return this;
+  }
+
+  /**
+   * Return the additional (undeclared) property with the specified name.
+   * @param key the name of the property
+   * @return the additional (undeclared) property with the specified name
+   */
+  public {{{.}}} getAdditionalProperty(String key) {
+    return this.get(key);
+  }
+{{/additionalPropertiesType}}
diff --git a/modules/openapi-generator/src/main/resources/Java/model.mustache b/modules/openapi-generator/src/main/resources/Java/model.mustache
index 8c8d3c2f4150..9cc53e077bcc 100644
--- a/modules/openapi-generator/src/main/resources/Java/model.mustache
+++ b/modules/openapi-generator/src/main/resources/Java/model.mustache
@@ -18,6 +18,17 @@ import java.io.Serializable;
 {{#jackson}}
 import com.fasterxml.jackson.annotation.JsonPropertyOrder;
 import com.fasterxml.jackson.annotation.JsonTypeName;
+{{#models}}
+{{#model}}
+{{#additionalPropertiesType}}
+import java.util.Map;
+import java.util.HashMap;
+import com.fasterxml.jackson.annotation.JsonAnySetter;
+import com.fasterxml.jackson.annotation.JsonAnyGetter;
+import com.fasterxml.jackson.annotation.JsonFormat;
+{{/additionalPropertiesType}}
+{{/model}}
+{{/models}}
 {{#withXml}}
 import com.fasterxml.jackson.dataformat.xml.annotation.*;
 {{/withXml}}
diff --git a/modules/openapi-generator/src/main/resources/Java/pojo.mustache b/modules/openapi-generator/src/main/resources/Java/pojo.mustache
index f0fecc192b96..0781cff67725 100644
--- a/modules/openapi-generator/src/main/resources/Java/pojo.mustache
+++ b/modules/openapi-generator/src/main/resources/Java/pojo.mustache
@@ -24,6 +24,9 @@
 @JsonTypeName("{{name}}")
 {{/hasDiscriminatorWithNonEmptyMapping}}
 {{/isClassnameSanitized}}
+{{#additionalPropertiesType}}
+@JsonFormat(shape=JsonFormat.Shape.OBJECT)
+{{/additionalPropertiesType}}
 {{/jackson}}
 {{>additionalModelTypeAnnotations}}{{>generatedAnnotation}}{{#discriminator}}{{>typeInfoAnnotation}}{{/discriminator}}{{>xmlAnnotation}}
 {{#vendorExtensions.x-class-extra-annotation}}
@@ -281,6 +284,8 @@ public class {{classname}} {{#parent}}extends {{{.}}} {{/parent}}{{#vendorExtens
   {{/isReadOnly}}
 
   {{/vars}}
+{{>additional_properties}}
+
   {{#parent}}
   {{#readWriteVars}}
   {{#isOverridden}}
diff --git a/modules/openapi-generator/src/main/resources/JavaJaxRS/spec/additional_properties.mustache b/modules/openapi-generator/src/main/resources/JavaJaxRS/spec/additional_properties.mustache
new file mode 100644
index 000000000000..7f59262156f1
--- /dev/null
+++ b/modules/openapi-generator/src/main/resources/JavaJaxRS/spec/additional_properties.mustache
@@ -0,0 +1,32 @@
+{{#additionalProperties}}
+  /**
+   * Set the additional (undeclared) property with the specified name and value.
+   * Creates the property if it does not already exist, otherwise replaces it.
+   * @param key the name of the property
+   * @param value the value of the property
+   * @return self reference
+   */
+  @JsonAnySetter
+  public {{classname}} putAdditionalProperty(String key, {{{datatypeWithEnum}}} value) {
+    this.put(key, value);
+    return this;
+  }
+
+  /**
+   * Return the additional (undeclared) properties.
+   * @return the additional (undeclared) properties
+   */
+  @JsonAnyGetter
+  public Map<String, {{{datatypeWithEnum}}}> getAdditionalProperties() {
+    return this;
+  }
+
+  /**
+   * Return the additional (undeclared) property with the specified name.
+   * @param key the name of the property
+   * @return the additional (undeclared) property with the specified name
+   */
+  public {{{datatypeWithEnum}}} getAdditionalProperty(String key) {
+    return this.get(key);
+  }
+{{/additionalProperties}}
diff --git a/modules/openapi-generator/src/main/resources/JavaJaxRS/spec/pojo.mustache b/modules/openapi-generator/src/main/resources/JavaJaxRS/spec/pojo.mustache
index 419f8b37ba03..632ba7bb9934 100644
--- a/modules/openapi-generator/src/main/resources/JavaJaxRS/spec/pojo.mustache
+++ b/modules/openapi-generator/src/main/resources/JavaJaxRS/spec/pojo.mustache
@@ -10,6 +10,13 @@ import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.annotation.JsonCreator;
 import com.fasterxml.jackson.annotation.JsonValue;
 import com.fasterxml.jackson.annotation.JsonTypeName;
+{{#additionalProperties}}
+import java.util.Map;
+import java.util.HashMap;
+import com.fasterxml.jackson.annotation.JsonAnySetter;
+import com.fasterxml.jackson.annotation.JsonAnyGetter;
+import com.fasterxml.jackson.annotation.JsonFormat;
+{{/additionalProperties}}
 {{/jackson}}
 {{#withXml}}
 import {{javaxPackage}}.xml.bind.annotation.XmlElement;
@@ -27,7 +34,12 @@ import {{javaxPackage}}.xml.bind.annotation.XmlEnumValue;
 {{#useSwaggerAnnotations}}{{#description}}@ApiModel(description = "{{{.}}}"){{/description}}{{/useSwaggerAnnotations}}{{#useSwaggerV3Annotations}}
 @Schema({{#title}}title="{{{.}}}", {{/title}}{{#description}}description="{{{.}}}"{{/description}}{{^description}}description=""{{/description}}){{/useSwaggerV3Annotations}}{{#useMicroProfileOpenAPIAnnotations}}
 @org.eclipse.microprofile.openapi.annotations.media.Schema({{#title}}title="{{{.}}}", {{/title}}{{#description}}description="{{{.}}}"{{/description}}{{^description}}description=""{{/description}}){{/useMicroProfileOpenAPIAnnotations}}
-{{#jackson}}@JsonTypeName("{{name}}"){{/jackson}}
+{{#jackson}}
+@JsonTypeName("{{name}}")
+{{#additionalProperties}}
+@JsonFormat(shape=JsonFormat.Shape.OBJECT)
+{{/additionalProperties}}
+{{/jackson}}
 {{>generatedAnnotation}}{{>additionalModelTypeAnnotations}}{{>xmlPojoAnnotation}}
 {{#vendorExtensions.x-class-extra-annotation}}
 {{{vendorExtensions.x-class-extra-annotation}}}
@@ -166,6 +178,7 @@ public class {{classname}} {{#parent}}extends {{{.}}}{{/parent}} {{#vendorExtens
   }
   {{/isMap}}
   {{/vars}}
+{{>additional_properties}}
 
   @Override
   public boolean equals(Object o) {