Autofix for VocaDB API Java Client generated by OpenAPI

Just go to my sample VocaDB OpenAPI Java Client, and no need to read the rest of this doc 😁

1. install OpenAPI (see instruction)

   • optionally you can use docker to run OpenAPI generator, see instruction

2. grab the swagger.json from VocaDB API page

3. open bash and run these command

   openapi-generator-cli generate \
   --api-package <your package>.api \
   --model-package <your package>.model \
   --invoker-package <your package>.client \
   -i <location of the vocadb swagger.json file> \
   --group-id <your group-id> \
   --artifact-id <your artifact-id> \
   --artifact-version <your version> \
   -g java  \
      -p java8=true \
      -p dateLibrary=java8-localdatetime \
      -p useRuntimeException=true \
      -p useJakartaEe=true \
      -p openApiNullable=false \
      -p serializationLibrary=jackson \
      -p licenseName=<your license name> \
      -p licenseUrl=<your license url> \
   --library <any candidates other than okhttp-gson> \
   -o /local/sample-unfixed-client

   • available library candidates are specified in OpenAPI Java page
   • if you are using docker, make sure you modified the generator launch command, properly mounted the output directory, and modify the -o option to fit docker's environment

4. (if using resttemplate or webclient) resolve import conflict in UserApiApi.java

   1. remove import <your package>.model.MediaType;
   2. let apiUsersCurrentAlbumsAlbumIdPost() and apiUsersCurrentAlbumsAlbumIdPostWithHttpInfo() take the parameter of type <your package>.model.MediaType

5. (Optional) update some dependencies used by the client

   1. spring and Jackson related dependencies
   2. remove jackson-databind-nullable
   3. copy LICENSE, etc.

1. clone this project git clone --recurse-submodules -j8 https://github.com/CXwudi/vocadb-openapi-java-client-autofixer
2. open the my-config.yml file in ./vocadb-apiclient-fixer and edit it
   1. input directory is where your auto-generated client is
      • can be relative path from the ./vocadb-apiclient-fixer perspective
   2. relative path to model is the relative path from the input directory to path of --model-package on your openapi-generator-cli command
3. cd into ./vocadb-apiclient-fixer, run ./mvnw spring-boot:run '-Dspring-boot.run.arguments="--spring.config.import=file:my-config.yml"'
4. your client should be ready to use 😉

• OpenAPI is very fragile, so better stick with the command in the step to generate your client
• Gson is not working for parsing date, like Expected BEGIN_OBJECT but was STRING at line 1 column 109 path $.items[0].song.createDate
• when using Jackson, must put -p openApiNullable=false, otherwise parsing issue on list with com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of 'org.openapitools.jackson.nullable.JsonNullable<java.util.List<cx.mikufan.vocadbapiclient.model.SongInListForApiContract>>' out of START_ARRAY token. This is because with openApiNullable=true, your list is JsonNullable<List<>> instead of List<>
• as for data library, use java8-localdatetime
  • the default one threetenbp has parsing issue
  • the java-8 one use ZoneDateTime which requires an additional zone info in the string, but vocadb's date doesn't have it
• the my-config.yml file has some default config values filled in. It is used to autofix the sample-unfixed-client for demo purposes.
  • In fact, the sample VocaDB OpenAPI Java Client is fixed by this demo config

see notes in my sample client

This fixer will change all enum classes with suffixname of s into a class that can make Jackson JSON parser works for one-line multiple-value enum string.
For example, take a look at the SongForApiContract in the sample-unfixed-client. It has a field private PVServices pvServices;. Before fixing, PVServices is just an enum class. It can only accept one value for that field.
However, in reality, VocaDB could return multiple values for that field, separated by comma (like pvServers: "NicoNicoDouga, Youtube").
So the fixer will change each enum class like PVServices into a normal class that can accept such multiple values of the same enum.
And each new class will have customized @JsonCreator and @JsonValue annotations to stay compatible with the behavior of the old unfixed enum class.

This fixer also globally replaces all strings ApiApi to Api. If a file name contains such a string, the file is also renamed.