Use Gradle to generate Java classes from a Swagger definition into a standalone JAR - gradle

Question

I am fairly new to both Gradle and Swagger code generator plugin for it (concretely the one that is linked from Swagger's website, i.e. https://github.com/thebignet/swagger-codegen-gradle-plugin), so I'm not sure whether my problem is with Gradle in general or with that particular plugin.
I've created a simple multi-module Spring Boot application (but the fact that I'm using Spring Boot or even Spring doesn't matter much). It's a console application; i.e. it doesn't start a webserver. In fact, it's actually a REST client consuming someone else's interface.
The application consists of four modules: spc-parent (which is just an envelope for the rest) containing spc-boot, spc-service, and spc-integration-model. Spc-boot contains just the starting point of the application, spc-service now contains a single Spring service, and spc-integration-model is meant to contain classes needed to consume the REST interface. The resulting structure will be much more complicated but I've tried to create a sort of a minimal example.
The problem lies within the spc-integration-model module. It consists of a single source file, petstore.json, and a build.gradle copied from https://github.com/thebignet/swagger-codegen-gradle-plugin (and only slightly modified). There are actually two problems (but they may have the same underlying cause).
When running gradle build (from spc-parent) for the very first time, it fails. Java sources are generated from petstore.json but they don't get compiled, which is why the service in spc-service doesn't see needed classes. However, running gradle build a second time fixes this (generated Java sources get compiled which makes it possible to compile spc-service, too).
The created JAR of spc-integration-model never contains anything besides Manifest.
My goal here is to persuade Gradle to compile the generated classes right away during the first build and also to put them into the JAR.
Now for some concrete Gradle tasks. The most interesting is spc-integration-model's build.gradle:
plugins {
id 'org.detoeuf.swagger-codegen' version '1.7.4'
id 'java'
}
apply plugin: 'org.detoeuf.swagger-codegen'
repositories {
mavenCentral()
jcenter()
}
swagger {
inputSpec = 'http://petstore.swagger.io/v2/swagger.json'
outputDir = file('build/swagger')
lang = 'java'
additionalProperties = [
'apiPackage' : 'ondra.spc.integration.client.api',
'dateLibrary' : 'java8',
'hideGenerationTimestamp': 'true',
'invokerPackage' : 'ondra.spc.integration.client',
'library' : 'resttemplate',
'modelNameSuffix' : 'Dto',
'modelPackage' : 'ondra.spc.integration.client.model'
]
importMappings = [
'Dog': 'io.swagger.petstore.client.model.Dog'
]
}
sourceSets {
swagger {
java {
srcDir file("${project.buildDir.path}/swagger/src/main/java")
}
}
}
classes.dependsOn('swagger')
ext {
spring_boot_version = springBootVersion
jackson_version = jacksonVersion
junit_version = jUnitVersion
swagger_annotations_version = swaggerAnnotationsVersion
swagger_codegen_version = swaggerCodegenVersion
}
dependencies {
swaggerCompile "org.springframework.boot:spring-boot-starter-web:$spring_boot_version"
swaggerCompile "io.swagger:swagger-annotations:$swagger_annotations_version"
compile sourceSets.swagger.output
compile "com.fasterxml.jackson.core:jackson-core:$jackson_version"
compile "com.fasterxml.jackson.core:jackson-annotations:$jackson_version"
compile "com.fasterxml.jackson.core:jackson-databind:$jackson_version"
compile "io.swagger:swagger-codegen:$swagger_codegen_version"
testCompile "junit:junit:$junit_version"
}
(Now that I'm re-reading my question I see that the local version of petstore.json is actually not used and an online version is used instead but let's leave that aside.)
The rest should be quite straightforward. spc-service:
dependencies {
compile "org.springframework:spring-context:$springVersion"
compile "org.springframework:spring-web:$springVersion"
compile project (":spc-integration-model")
}
spc-boot:
dependencies {
compile "org.springframework.boot:spring-boot:$springBootVersion"
compile "org.springframework.boot:spring-boot-autoconfigure:$springBootVersion"
compile "org.springframework:spring-web:$springVersion"
runtime "org.hibernate.validator:hibernate-validator:$hibernateVersion"
runtime "com.fasterxml.jackson.core:jackson-databind:$jacksonVersion"
compile project (":spc-service")
testCompile("org.junit.jupiter:junit-jupiter-api:$jUnitVersion")
testRuntime("org.junit.jupiter:junit-jupiter-engine:$jUnitVersion")
}
test {
useJUnitPlatform()
}
spc-parent:
subprojects {
apply plugin: 'java'
group 'ondra'
version '1.0-SNAPSHOT'
buildscript {
ext {
hibernateVersion = '6.0.9.Final'
jacksonVersion = '2.9.4'
springBootVersion = '2.0.0.RELEASE'
springVersion = '5.0.5.RELEASE'
swaggerAnnotationsVersion = '1.5.16'
swaggerCodegenVersion = '2.2.3'
jUnitVersion = '5.1.1'
}
repositories {
mavenCentral()
}
}
sourceCompatibility = 1.8
targetCompatibility = 1.8
repositories {
mavenCentral()
}
}
And spc-parent's settings.gradle:
rootProject.name = 'spc-parent'
include 'spc-boot'
include 'spc-service'
include 'spc-integration-model'
I've also put the whole application into a single archive: https://drive.google.com/open?id=1cOYIcaxnhik548w0wEGswgD2g4udATdD