[REQ] Add support for Spring Boot 4 and Jackson 3 to kotlin generator and jvm-spring-restclient library

[olaisolheim]

Is your feature request related to a problem? Please describe.

The kotlin generator does not support Spring Boot 4 and Jackson 3 when used with the jvm-spring-restclient library.

Spring Boot 4 and Jackson 3 both came with changes that cause the generated code to now use deprecated and non-compiling code if used with Spring Boot 4 and Jackson 3.

Describe the solution you'd like

Add configuration options to instruct the generator to generate code that works with Spring Boot 4 and Jackson 3.

The spring generator was updated with new configuration options useSpringBoot4 and useJackson3 in #22854 which causes the generator to generate code compatible with the new versions. Perhaps the same options can be reused for this generator? 🙏

Describe alternatives you've considered

Until support is added, we will have to revert to generating clients in Java or add wiring to our build that swaps generated classes with our own.

Additional context

As far as I can see, in the generated code in our project, the issue is that the generated code uses MappingJackson2HttpMessageConverter (which is deprecated in Spring Boot 4). It also uses the package com.fasterxml.jackson (which moved to tools.jackson in Jackson 3).

As an alternative to adding support for useJackson3 as mentioned above, perhaps serializationLibrary could be extended with support for jackson3 instead of the existing jackson.

Related to #23098, but this adds support to kotlin-spring, which is typically used for the server-side and not the client-side (as is the case for kotlin generator in this issue).

[yonatankarp]

will be resolved by #23154

[yonatankarp]

Ah, sorry, this one is for my other pr 😄 #23161

[olaisolheim]

Thanks, highly appreciated!

Will #23161 add support to generate code compatible with Spring Boot 4 and Jackson 3 for the kotlin generator with the jvm-spring-restclient library, like our configuration?

            <plugin>
                <groupId>org.openapitools</groupId>
                <artifactId>openapi-generator-maven-plugin</artifactId>
                <executions>
                    <execution>
                        <id>generate-client</id>
                        <phase>generate-sources</phase>
                        <goals>
                            <goal>generate</goal>
                        </goals>
                        <configuration>
                            <inputSpec>openapi.yaml</inputSpec>
                            <packageName>${project.groupId}</packageName>
                            <modelPackage>${project.groupId}.model</modelPackage>
                            <apiPackage>${project.groupId}.client</apiPackage>
                            <generateModels>false</generateModels>
                            <generateApiTests>false</generateApiTests>
                            <generatorName>kotlin</generatorName>
                            <library>jvm-spring-restclient</library>
                            <configOptions>
                                <useSpringBoot3>true</useSpringBoot3>
                                <!-- <useSpringBoot4>true</useSpringBoot3> TODO use when supported -->
                                <!-- <useJackson3>true</useJackson3> TODO use when supported -->
                                <serializationLibrary>jackson</serializationLibrary>
                                <enumPropertyNaming>original</enumPropertyNaming>
                                <apiSuffix>HttpClient</apiSuffix>
                            </configOptions>
                        </configuration>
                    </execution>
                </executions>
            </plugin>

We also use the kotlin-spring generator with the spring-boot library in other projects.

[yonatankarp]

The kotlin-spring support for springboot 4 was merged today and will be included in the next release (7.21.0)

Also, be aware that useSpringBoot4 uses Jackson 3 by default per your config above ☝️

For kotlin generator - I need to check my pr - if not, I will open an additional pr (because the current one is already pretty huge)

[yonatankarp]

@olaisolheim It was the only one missed, so I'll add it to my PR. Be aware that you don't need the flag useJackson3 with useSpringBoot4 - because Jackson3 is the default for it

[olaisolheim]

@yonatankarp thanks for fixing all this—it helps us a lot.

I checked out and built your snapshot in #23161, and it seems to require the useJackson3=true option in order for the imports in the generated code to reference tools.jackson rather than com.fasterxml.jackson. The code itself is using Jackson 3, but with imports still on Jackson 2.

[Florenzen68]

@yonatankarp thanks for fixing all this—it helps us a lot.

I checked out and built your snapshot in #23161, and it seems to require the useJackson3=true option in order for the imports in the generated code to reference tools.jackson rather than com.fasterxml.jackson. The code itself is using Jackson 3, but with imports still on Jackson 2.

Hi guys, this is also an issue for java itself? I have now upgraded to SpringBoot4 at all and I am trying to make the openapi-generator work with Jackson3 too.
I added the following to my pom.xml:

            <plugin>
                <groupId>org.openapitools</groupId>
                <artifactId>openapi-generator-maven-plugin</artifactId>
                <version>${openapi-generator.version}</version> <!-- 7.20.0 -->
                <executions>
                    <execution>
                        <goals>
                            <goal>generate</goal>
                        </goals>
                        <configuration>
                            <inputSpec>${project.basedir}/src/main/resources/openapi/api.json</inputSpec>
                            <generatorName>java</generatorName>
                            <library>webclient</library>
                            <apiPackage>xy.api</apiPackage>
                            <modelPackage>xy.model</modelPackage>
                            <invokerPackage>xy.invoker</invokerPackage>
                            <templateDirectory>${project.basedir}/src/main/resources/templates/openapi-generator</templateDirectory>
                            <generateApiTests>false</generateApiTests>
                            <generateModelTests>false</generateModelTests>
                            <configOptions>
                                <useSpringBoot4>true</useSpringBoot4>
                                <dateLibrary>java8</dateLibrary>
                                <delegatePattern>false</delegatePattern>
                                <interfaceOnly>false</interfaceOnly>
                                <skipDefaultInterface>false</skipDefaultInterface>
                                <useJackson3>true</useJackson3>
                                <useJakartaEe>true</useJakartaEe>
                                <openApiNullable>false</openApiNullable>
                            </configOptions>
                        </configuration>
                    </execution>
                </executions>
            </plugin>

But it still generates jackson2 stuff... is there something wrong or incompatible within the config?

[yonatankarp]

@Florenzen68, I think that the Java support was fully implemented but not yet released (should be released in v7.21).

For more details see: #22294

[alehel]

Was this actually resolved by 7.21.0? I just patched our project to 7.21.0, but I'm still getting the following message with useSpringBoot4.

Caused by: java.lang.RuntimeException: This library must use Spring Boot 3. Try adding '--additional-properties useSpringBoot3=true' to your command.
        at org.openapitools.codegen.languages.KotlinClientCodegen.processJvmSpringRestClientLibrary(KotlinClientCodegen.java:868)
        at org.openapitools.codegen.languages.KotlinClientCodegen.processOpts(KotlinClientCodegen.java:529)
        at org.openapitools.codegen.DefaultGenerator.configureGeneratorProperties(DefaultGenerator.java:252)
        at org.openapitools.codegen.DefaultGenerator.generate(DefaultGenerator.java:1277)
        at org.openapitools.generator.gradle.plugin.tasks.GenerateTask.doWork(GenerateTask.kt:974)
        ... 135 more

If I also set useJackson3 to true, I get,
useJackson3 is not yet supported for kotlin-client. Jackson 3 support for kotlin-client will be added in a future release.

[yonatankarp]

@alehel the released changes are only for server side, client side is still under work