feat: use jackson in jvm factory of kotlin client

Author: PhilippHeuer

pkg/generator/openapi-kotlin/generator.go

@@ -223,7 +223,7 @@ func (g *KotlinGenerator) ToCodeType(schema *base.Schema, schemaType openapigene
 
 	// multiple types (e.g., ["string", "null"])
 	if util.CountExcluding(schema.Type, "null") > 1 {
-		return openapigenerator.CodeType{Name: "JsonElement"}, nil
+		return openapigenerator.CodeType{Name: "Any"}, nil
 	}
 
 	switch {
@@ -312,11 +312,11 @@ func (g *KotlinGenerator) ToCodeType(schema *base.Schema, schemaType openapigene
 		} else if schema.AdditionalProperties != nil && schema.AdditionalProperties.IsB() && schema.AdditionalProperties.B {
 			return openapigenerator.NewMapCodeType(
 				openapigenerator.NewSimpleCodeType("String", schema),
-				openapigenerator.NewSimpleCodeType("JsonElement", schema),
+				openapigenerator.NewSimpleCodeType("Any", schema),
 				schema,
 			), nil
 		} else if schema.AdditionalProperties == nil && schema.Properties == nil {
-			return openapigenerator.CodeType{Name: "JsonElement"}, nil
+			return openapigenerator.CodeType{Name: "Any"}, nil
 		} else {
 			if schema.Title == "" {
 				return openapigenerator.DefaultCodeType, fmt.Errorf("schema does not have a title. schema: %s", schema.Type)
@@ -336,7 +336,7 @@ func (g *KotlinGenerator) ToCodeType(schema *base.Schema, schemaType openapigene
 		if openapigenerator.HaveSameCodeTypeName(codeTypes) {
 			return codeTypes[0], nil
 		}
-		return openapigenerator.CodeType{Name: "JsonElement"}, nil
+		return openapigenerator.CodeType{Name: "Any"}, nil
 
 	default:
 		return openapigenerator.DefaultCodeType, fmt.Errorf("unhandled type. schema: %s, format: %s", schema.Type, schema.Format)

pkg/template/templates/openapi-kotlin-httpclient/api_factory.jvm.gohtml

@@ -21,16 +21,25 @@ import io.ktor.client.plugins.HttpTimeout
 import io.ktor.client.plugins.DefaultRequest
 import io.ktor.client.plugins.logging.LogLevel
 import io.ktor.client.request.header
+import io.ktor.http.ContentType
+import io.ktor.http.HttpHeaders
 import io.ktor.serialization.kotlinx.json.*
 import io.ktor.serialization.kotlinx.xml.*
-import io.ktor.http.HttpHeaders
+import io.ktor.serialization.jackson3.JacksonConverter
+import io.ktor.serialization.jackson3.jackson
+
 import io.opentelemetry.instrumentation.ktor.v3_0.KtorClientTelemetry
 
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.SupervisorJob
 import kotlinx.serialization.json.Json
 
+import tools.jackson.databind.DeserializationFeature
+import tools.jackson.databind.SerializationFeature
+import tools.jackson.module.kotlin.KotlinModule
+import tools.jackson.dataformat.xml.XmlMapper
+
 import org.slf4j.LoggerFactory
 
 object {{ .Metadata.Name }}Factory {
@@ -54,12 +63,31 @@ fun <T : Any> buildClient(api: KClass<T>, spec: Jvm{{ .Metadata.Name }}FactorySp
 
         // content negotiation
         install(ContentNegotiation) {
+            /*
             json(Json {
                 prettyPrint = true
                 isLenient = true
                 ignoreUnknownKeys = true
             })
             xml()
+            */
+
+            jackson {
+                enable(SerializationFeature.INDENT_OUTPUT)
+                configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false) // do not fail on new fields
+                configure(DeserializationFeature.ACCEPT_SINGLE_VALUE_AS_ARRAY, true) // allow single values to be read as array
+                configure(DeserializationFeature.FAIL_ON_INVALID_SUBTYPE, false) // do not fail on invalid polymorphic sub types
+                addModule(KotlinModule.Builder().build()) // kotlin support
+            }
+            register(
+                ContentType.Application.Xml, JacksonConverter(
+                    XmlMapper.builder()
+                        .enable(SerializationFeature.INDENT_OUTPUT)
+                        .configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false) // do not fail on new fields
+                        .addModule(KotlinModule.Builder().build()) // kotlin support
+                    .build()
+                )
+            )
         }
 
         // retry policy

pkg/template/templates/openapi-kotlin-httpclient/build.gradle.kts.core.gohtml

@@ -44,6 +44,12 @@ kotlin {
             // ktor jvm engine
             api(libs.ktor.client.cio)
 
+            // serialization
+            api(libs.ktor.serialization.jackson)
+            api(project.dependencies.platform(libs.jackson.bom))
+            api(libs.jackson.dataformat.xml)
+            api(libs.jackson.dataformat.yaml)
+
             // logging and tracing
             api(libs.opentelemetry.ktor)
 

pkg/template/templates/openapi-kotlin-httpclient/libs.versions.toml.gohtml

@@ -2,7 +2,8 @@
 {{- template "header-hash" }}
 
 [versions]
-ktor-version = "3.4.1"
+jackson-version = "3.1.1"
+ktor-version = "3.4.2"
 ktor-metrics-micrometer-version = "1.6.8"
 kotlin-version = "2.3.20"
 kotlinx-coroutines-version = "1.10.2"
@@ -12,9 +13,9 @@ opentelemetry-ktor-version = "2.26.1-alpha"
 jetbrains-annotations-version = "26.1.0"
 
 [libraries]
-openfeign-bom = { module = "io.github.openfeign:feign-bom", version = "13.6" }
-resilience4j-bom = { module = "io.github.resilience4j:resilience4j-bom", version = "2.3.0" }
-jackson-bom = { module = "com.fasterxml.jackson:jackson-bom", version = "2.20.0" }
+jackson-bom = { module = "tools.jackson:jackson-bom", version.ref = "jackson-version" }
+jackson-dataformat-xml = { module = "tools.jackson.dataformat:jackson-dataformat-xml" }
+jackson-dataformat-yaml = { module = "tools.jackson.dataformat:jackson-dataformat-yaml" }
 micrometer-bom = { module = "io.micrometer:micrometer-bom", version = "1.15.5" }
 micrometer-core = { module = "io.micrometer:micrometer-core" }
 slf4j-bom = { module = "org.slf4j:slf4j-bom", version = "2.0.17" }
@@ -30,6 +31,7 @@ ktor-client-core = { module = "io.ktor:ktor-client-core", version.ref = "ktor-ve
 ktor-client-content-negotiation = { module = "io.ktor:ktor-client-content-negotiation", version.ref = "ktor-version" }
 ktor-serialization-kotlinx-json = { module = "io.ktor:ktor-serialization-kotlinx-json", version.ref = "ktor-version" }
 ktor-serialization-kotlinx-xml = { module = "io.ktor:ktor-serialization-kotlinx-xml", version.ref = "ktor-version" }
+ktor-serialization-jackson = { module = "io.ktor:ktor-serialization-jackson3", version.ref = "ktor-version" }
 ktor-client-logging = { module = "io.ktor:ktor-client-logging", version.ref = "ktor-version" }
 ktor-client-tracing = { module = "io.ktor:ktor-client-tracing", version.ref = "ktor-version" }
 ktor-client-observer = { module = "io.ktor:ktor-client-observer", version.ref = "ktor-version" }