[BUG][java]Additional properties in multipart requests generates invalid code

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

Using a multipart request body which has additional-properties as part generates invalid code for the java-resttemplate client. It was introduced in version 7.5.0 before this version it worked correctly

Spec below creates following for example:

package org.openapitools.client.api;

import org.openapitools.client.ApiClient;
import org.openapitools.client.BaseApi;

import java.io.File;
import org.openapitools.client.model.StructuredType;

import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.stream.Collectors;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
import org.springframework.web.client.RestClientException;
import org.springframework.web.client.HttpClientErrorException;
import org.springframework.core.ParameterizedTypeReference;
import org.springframework.core.io.FileSystemResource;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;

@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen", comments = "Generator version: 7.19.0-SNAPSHOT")
public class FileApi extends BaseApi {

    public FileApi() {
        super(new ApiClient());
    }

    public FileApi(ApiClient apiClient) {
        super(apiClient);
    }

    /**
     * 
     * 
     * <p><b>201</b> - File created successfully
     * @param documentBytes  (required)
     * @param documentType  (required)
     * @param properties  (required)
     * @param structured  (optional)
     * @throws RestClientException if an error occurs while attempting to invoke the API
     */
    public void createFile(File documentBytes, String documentType, Map<String, String> properties, StructuredType structured) throws RestClientException {
        createFileWithHttpInfo(documentBytes, documentType, properties, structured);
    }

    /**
     * 
     * 
     * <p><b>201</b> - File created successfully
     * @param documentBytes  (required)
     * @param documentType  (required)
     * @param properties  (required)
     * @param structured  (optional)
     * @return ResponseEntity&lt;Void&gt;
     * @throws RestClientException if an error occurs while attempting to invoke the API
     */
    public ResponseEntity<Void> createFileWithHttpInfo(File documentBytes, String documentType, Map<String, String> properties, StructuredType structured) throws RestClientException {
        Object localVarPostBody = null;
        
        // verify the required parameter 'documentBytes' is set
        if (documentBytes == null) {
            throw new HttpClientErrorException(HttpStatus.BAD_REQUEST, "Missing the required parameter 'documentBytes' when calling createFile");
        }
        
        // verify the required parameter 'documentType' is set
        if (documentType == null) {
            throw new HttpClientErrorException(HttpStatus.BAD_REQUEST, "Missing the required parameter 'documentType' when calling createFile");
        }
        
        // verify the required parameter 'properties' is set
        if (properties == null) {
            throw new HttpClientErrorException(HttpStatus.BAD_REQUEST, "Missing the required parameter 'properties' when calling createFile");
        }
        

        final MultiValueMap<String, String> localVarQueryParams = new LinkedMultiValueMap<String, String>();
        final HttpHeaders localVarHeaderParams = new HttpHeaders();
        final MultiValueMap<String, String> localVarCookieParams = new LinkedMultiValueMap<String, String>();
        final MultiValueMap<String, Object> localVarFormParams = new LinkedMultiValueMap<String, Object>();

        if (documentBytes != null)
            localVarFormParams.add("documentBytes", new FileSystemResource(documentBytes));
        if (documentType != null)
            localVarFormParams.add("documentType", documentType);
        if (structured != null)
            localVarFormParams.add("structured", structured);
        if (properties != null)
            localVarFormParams.addAll("properties", properties);

        final String[] localVarAccepts = {  };
        final List<MediaType> localVarAccept = apiClient.selectHeaderAccept(localVarAccepts);
        final String[] localVarContentTypes = { 
            "multipart/form-data"
         };
        final MediaType localVarContentType = apiClient.selectHeaderContentType(localVarContentTypes);

        String[] localVarAuthNames = new String[] {  };

        ParameterizedTypeReference<Void> localReturnType = new ParameterizedTypeReference<Void>() {};
        return apiClient.invokeAPI("/api/v1/file", HttpMethod.POST, Collections.<String, Object>emptyMap(), localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localReturnType);
    }

    @Override
    public <T> ResponseEntity<T> invokeAPI(String url, HttpMethod method, Object request, ParameterizedTypeReference<T> returnType) throws RestClientException {
        String localVarPath = url.replace(apiClient.getBasePath(), "");
        Object localVarPostBody = request;

        final Map<String, Object> uriVariables = new HashMap<String, Object>();
        final MultiValueMap<String, String> localVarQueryParams = new LinkedMultiValueMap<String, String>();
        final HttpHeaders localVarHeaderParams = new HttpHeaders();
        final MultiValueMap<String, String> localVarCookieParams = new LinkedMultiValueMap<String, String>();
        final MultiValueMap<String, Object> localVarFormParams = new LinkedMultiValueMap<String, Object>();

        final String[] localVarAccepts = {  };
        final List<MediaType> localVarAccept = apiClient.selectHeaderAccept(localVarAccepts);
        final String[] localVarContentTypes = { 
            "multipart/form-data"
         };
        final MediaType localVarContentType = apiClient.selectHeaderContentType(localVarContentTypes);

        String[] localVarAuthNames = new String[] {  };

        return apiClient.invokeAPI(localVarPath, method, uriVariables, localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, returnType);
    }
}

but should look like

package org.openapitools.client.api;

import org.openapitools.client.ApiClient;
import org.openapitools.client.BaseApi;

import java.io.File;
import org.openapitools.client.model.StructuredType;

import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.stream.Collectors;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
import org.springframework.web.client.RestClientException;
import org.springframework.web.client.HttpClientErrorException;
import org.springframework.core.ParameterizedTypeReference;
import org.springframework.core.io.FileSystemResource;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;

@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen", comments = "Generator version: 7.19.0-SNAPSHOT")
public class FileApi extends BaseApi {

    public FileApi() {
        super(new ApiClient());
    }

    public FileApi(ApiClient apiClient) {
        super(apiClient);
    }

    /**
     * 
     * 
     * <p><b>201</b> - File created successfully
     * @param documentBytes  (required)
     * @param documentType  (required)
     * @param properties  (required)
     * @param structured  (optional)
     * @throws RestClientException if an error occurs while attempting to invoke the API
     */
    public void createFile(File documentBytes, String documentType, Map<String, String> properties, StructuredType structured) throws RestClientException {
        createFileWithHttpInfo(documentBytes, documentType, properties, structured);
    }

    /**
     * 
     * 
     * <p><b>201</b> - File created successfully
     * @param documentBytes  (required)
     * @param documentType  (required)
     * @param properties  (required)
     * @param structured  (optional)
     * @return ResponseEntity&lt;Void&gt;
     * @throws RestClientException if an error occurs while attempting to invoke the API
     */
    public ResponseEntity<Void> createFileWithHttpInfo(File documentBytes, String documentType, Map<String, String> properties, StructuredType structured) throws RestClientException {
        Object localVarPostBody = null;
        
        // verify the required parameter 'documentBytes' is set
        if (documentBytes == null) {
            throw new HttpClientErrorException(HttpStatus.BAD_REQUEST, "Missing the required parameter 'documentBytes' when calling createFile");
        }
        
        // verify the required parameter 'documentType' is set
        if (documentType == null) {
            throw new HttpClientErrorException(HttpStatus.BAD_REQUEST, "Missing the required parameter 'documentType' when calling createFile");
        }
        
        // verify the required parameter 'properties' is set
        if (properties == null) {
            throw new HttpClientErrorException(HttpStatus.BAD_REQUEST, "Missing the required parameter 'properties' when calling createFile");
        }
        

        final MultiValueMap<String, String> localVarQueryParams = new LinkedMultiValueMap<String, String>();
        final HttpHeaders localVarHeaderParams = new HttpHeaders();
        final MultiValueMap<String, String> localVarCookieParams = new LinkedMultiValueMap<String, String>();
        final MultiValueMap<String, Object> localVarFormParams = new LinkedMultiValueMap<String, Object>();

        if (documentBytes != null)
            localVarFormParams.add("documentBytes", new FileSystemResource(documentBytes));
        if (documentType != null)
            localVarFormParams.add("documentType", documentType);
        if (structured != null)
            localVarFormParams.add("structured", structured);
        if (properties != null)
            localVarFormParams.add("properties", properties);

        final String[] localVarAccepts = {  };
        final List<MediaType> localVarAccept = apiClient.selectHeaderAccept(localVarAccepts);
        final String[] localVarContentTypes = { 
            "multipart/form-data"
         };
        final MediaType localVarContentType = apiClient.selectHeaderContentType(localVarContentTypes);

        String[] localVarAuthNames = new String[] {  };

        ParameterizedTypeReference<Void> localReturnType = new ParameterizedTypeReference<Void>() {};
        return apiClient.invokeAPI("/api/v1/file", HttpMethod.POST, Collections.<String, Object>emptyMap(), localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, localReturnType);
    }

    @Override
    public <T> ResponseEntity<T> invokeAPI(String url, HttpMethod method, Object request, ParameterizedTypeReference<T> returnType) throws RestClientException {
        String localVarPath = url.replace(apiClient.getBasePath(), "");
        Object localVarPostBody = request;

        final Map<String, Object> uriVariables = new HashMap<String, Object>();
        final MultiValueMap<String, String> localVarQueryParams = new LinkedMultiValueMap<String, String>();
        final HttpHeaders localVarHeaderParams = new HttpHeaders();
        final MultiValueMap<String, String> localVarCookieParams = new LinkedMultiValueMap<String, String>();
        final MultiValueMap<String, Object> localVarFormParams = new LinkedMultiValueMap<String, Object>();

        final String[] localVarAccepts = {  };
        final List<MediaType> localVarAccept = apiClient.selectHeaderAccept(localVarAccepts);
        final String[] localVarContentTypes = { 
            "multipart/form-data"
         };
        final MediaType localVarContentType = apiClient.selectHeaderContentType(localVarContentTypes);

        String[] localVarAuthNames = new String[] {  };

        return apiClient.invokeAPI(localVarPath, method, uriVariables, localVarQueryParams, localVarPostBody, localVarHeaderParams, localVarCookieParams, localVarFormParams, localVarAccept, localVarContentType, localVarAuthNames, returnType);
    }
}

openapi-generator version

7.17.0

OpenAPI declaration file content or url

openapi: 3.0.3
info:
  title: Minimal
  description: Api to reproduce bug
  version: 0.5.1-SNAPSHOT.0
tags:
  - name: test
servers:
  - url: http://localhost:8080
paths:
  "/api/v1/file":
    post:
      tags:
        - file
      operationId: createFile
      requestBody:
        required: true
        content:
          multipart/form-data:
            schema:
              $ref: "#/components/schemas/FileUploadRequest"
            encoding:
              documentBytes:
                contentType: "*/*"
              properties:
                contentType: application/json
      responses:
        "201":
          description: File created successfully
components:
  schemas:
    FileUploadRequest:
      type: object
      properties:
        documentBytes:
          type: string
          format: binary
        documentType:
          type: string
        properties:
          $ref: '#/components/schemas/TypeMap'
      required:
        - documentBytes
        - documentType
        - properties
    TypeMap:
        type: object
        additionalProperties:
          type: string

<--
(for YAML code) or

(here your code)

(for JSON code), so it becomes more readable. If it is longer than about ten lines,
please create a Gist (https://gist.github.com) or upload it somewhere else and
link it here.
-->

Generation Details

{
  "$schema": "https://raw.githubusercontent.com/OpenAPITools/openapi-generator-cli/refs/heads/master/apps/generator-cli/src/config.schema.json",
  "spaces": 2,
  "generator-cli": {
    "version": "7.18.0",
    "generators": {
      "java-client-sdk": {
        "generatorName": "java",
        "library": "resttemplate",
        "inputSpec": "api-specification.yml",
        "output": "#{cwd}/sdks/java-client-sdk",
        "globalProperty": {
          "apiTests": false,
          "apiDocs": false,
          "modelTests": false,
          "modelDocs": false
        },
        "additionalProperties": {
          "serializationLibrary": "jackson",
          "useJakartaEe": true,
          "hideGenerationTimestamp": true,
          "useAbstractionForFiles": true,
          "sourceFolder": "src/gen/java",
          "booleanGetterPrefix": "is",
          "enumUnknownDefaultCase": true
        }
      }
    }
  }
}

npx @openapitools/openapi-generator-cli generate

Steps to reproduce

See config and spec above.

Related issues/PRs

Suggest a fix

I am going to prepare a PR.

Reproduce the issue with a multipart request containing an additional-properties part and generate the Java resttemplate client shown in the report. Compare the generated FileApi output with the expected example, then add coverage for this case in the generator's Java client tests; done means the generated client is valid and handles the properties map correctly.