Set up the contract-first API layer of a Spring Boot service — the single `apis/` directory at the repository root holding every contract (`apis/rest-server/` OpenAPI specs, `apis/grpc-server/` protobuf definitions, `apis/graphql-server/` SDL schemas, `apis/rest-client/<name>/`, `apis/grpc-client/<name>/` and `apis/graphql-client/<name>/` per downstream service, `apis/messaging/` AVRO schemas *and* the AsyncAPI specification that describes the topics carrying them), a starter spec for each one, and the code-generation plugin executions wired into the module that consumes each contract — `openapi-generator-maven-plugin` (Spring server interfaces + DTOs for the REST server, client + DTOs per REST client, and HTML documentation), `protobuf-maven-plugin` (gRPC service base classes and stubs, plus HTML documentation via `protoc-gen-doc`), `graphql-codegen-maven-plugin` (resolver interfaces + model types for the GraphQL server, request/response/projection classes per GraphQL client, plus the SDL copied onto the run
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Set up the contract-first API layer of a Spring Boot service — the single `apis/` directory at the repository root holding every contract (`apis/rest-server/` OpenAPI specs, `apis/grpc-server/` protobuf definitions, `apis/graphql-server/` SDL schemas, `apis/rest-client/<name>/`, `apis/grpc-client/<name>/` and `apis/graphql-client/<name>/` per downstream service, `apis/messaging/` AVRO schemas *and* the AsyncAPI specification that describes the topics carrying them), a starter spec for each one, and the code-generation plugin executions wired into the module that consumes each contract — `openapi-generator-maven-plugin` (Spring server interfaces + DTOs for the REST server, client + DTOs per REST client, and HTML documentation), `protobuf-maven-plugin` (gRPC service base classes and stubs, plus HTML documentation via `protoc-gen-doc`), `graphql-codegen-maven-plugin` (resolver interfaces + model types for the GraphQL server, request/response/projection classes per GraphQL client, plus the SDL copied onto the runtime classpath Spring for GraphQL loads it from, and `spectaql`/`graphql-voyager` run from the Maven build for its static HTML reference and schema graph), `avro-maven-plugin` (Java classes from the AVRO schemas), and `@asyncapi/html-template` run from the Maven build via `frontend-maven-plugin` (HTML documentation from the AsyncAPI specification). Adds a linting/compatibility check per contract kind and keeps generated sources out of version control and out of static analysis. Reads `springboot-stack.yml` for which contracts the service actually needs and writes no version numbers, inheriting them all from the root pom. Invoke as `/iru-setup-java-springboot-apis`, or with `args` (`stack-file:` line) when called from `iru-setup-java-springboot`. Use after the reactor and module sources exist, whenever a Spring Boot service needs its OpenAPI/protobuf/GraphQL/AVRO/AsyncAPI contracts and their generators set up instead of hand-configuring five code generators across several module poms.
model
sonnet
Setup Java Spring Boot APIs
Wire up the contract-first API layer. Two invariants:
Every contract lives under apis/ at the repository root — never inside a module's src/. One directory
is where a reviewer looks to see everything this service exposes and consumes, and it keeps a contract from
being coupled to the module that happens to implement it today. apis/ is not a Maven module.
Generated code is never committed and never hand-edited. It lands in each module's
target/generated-sources/, is git-ignored, and is excluded from Checkstyle/PMD/SpotBugs/JaCoCo/Sonar. If
something about the generated code is wrong, the fix is in the spec or the generator configuration.
Step 0 — Resolve inputs
Parse args for stack-file: <path>, defaulting to springboot-stack.yml. Read it and determine exactly which
contracts are needed:
Manifest field
Contract directory
Generated into
Generator
stack.restServer: true
apis/rest-server/
api/rest-server
openapi-generator-maven-plugin (spring generator)
stack.grpcServer: true
apis/grpc-server/
api/grpc-server
protobuf-maven-plugin
stack.graphqlServer: true
apis/graphql-server/ (SDL → code)
api/graphql-server
graphql-codegen-maven-plugin
stack.graphqlServer: true
apis/graphql-server/ (SDL → docs)
documentation only — no Java
spectaql (+ optional graphql-voyager) via frontend-maven-plugin
each stack.restClients[]
apis/rest-client/<name>/
infrastructure/clients/<name>
openapi-generator-maven-plugin (client generator)
each stack.grpcClients[]
apis/grpc-client/<name>/
infrastructure/clients/<name>
protobuf-maven-plugin
each stack.graphqlClients[]
apis/graphql-client/<name>/
infrastructure/clients/<name>
graphql-codegen-maven-plugin
stack.messaging.enabled: true
apis/messaging/ (AVRO schemas)
infrastructure/producers and/or api/consumers
avro-maven-plugin
stack.messaging.enabled: true
apis/messaging/ (AsyncAPI spec)
documentation only — no Java
@asyncapi/html-template via frontend-maven-plugin
If none apply, report that and stop — there's nothing to set up.
Verify the target module directories exist (from iru-setup-java-springboot-pom). If a module is missing, report it
and skip that contract rather than creating a module here.
Read the root pom.xml to confirm the generator plugins are already version-managed in <pluginManagement> (the
pom skill puts them there). Declare no <version> in any module pom below — if a version is missing from
pluginManagement, add it to the root pom rather than inline in the module.
apis/messaging/ holds two kinds of contract, not one: the AVRO schemas define the payloads, and the
AsyncAPI specification defines the interface — which topics exist, in which direction the service uses each one,
which message each one carries, and which server (broker) they live on. The AVRO schemas are what
avro-maven-plugin compiles into Java; the AsyncAPI document is what the documentation generators read. Keeping
them in one directory is deliberate: a new event means a new .avscand a new channel in the AsyncAPI file, and
a reviewer should see both in the same diff.
Create only the subdirectories the manifest calls for. Write apis/README.md explaining the layout, which module
each directory generates into, that generated code is never committed, and how to regenerate
(mvn generate-sources). This file is what stops the next developer from adding a spec in the wrong place.
Version contracts in the filename and in the path inside the contract, not by mutating a file in place: an
OpenAPI spec's paths carry /v1/..., a protobuf file declares package <service>.v1, an AVRO schema's namespace
ends in .v1, and a GraphQL SDL — which has no in-band version at all — is versioned by filename and by the
package its types generate into. A breaking change means a v2 file next to the v1 one, with both generating and both served
until v1 is retired. State this convention in apis/README.md.
Step 2 — REST server contract and generator
Write a starter OpenAPI 3.1 spec at apis/rest-server/<service>-api-v1.yaml covering one resource, and make it
complete enough to be a real template rather than a stub: info with a version and description, a server entry,
one tagged path with parameters and request/response bodies, components/schemas with per-field description
and required lists, and — importantly — a documented error schema plus 4xx/5xx responses that reference
it. If stack.security.enabled, add a securitySchemes entry (bearerFormat: JWT) and apply it.
Every field in every schema needs a description, and any field with a constraint needs it expressed in the spec
(maxLength, pattern, minimum, format) — those constraints become Bean Validation annotations on the
generated DTOs and they're what the documentation page reads. A spec without descriptions produces both
undocumented code and an undocumentable API.
Wire into api/rest-server/pom.xml:
<build>
<plugins>
<plugin>
<groupId>org.openapitools</groupId>
<artifactId>openapi-generator-maven-plugin</artifactId>
<executions>
<execution>
<id>generate-rest-server-v1</id>
<phase>generate-sources</phase>
<goals>
<goal>generate</goal>
</goals>
<configuration>
<inputSpec>${maven.multiModuleProjectDirectory}/apis/rest-server/<service>-api-v1.yaml</inputSpec>
<generatorName>spring</generatorName>
<apiPackage><base>.api.rest.v1.generated.api</apiPackage>
<modelPackage><base>.api.rest.v1.generated.model</modelPackage>
<configOptions>
<!-- interfaceOnly: generate the interfaces only; the controllers are hand-written and
implement them, so regeneration can never overwrite real logic. -->
<interfaceOnly>true</interfaceOnly>
<useSpringBoot3>true</useSpringBoot3>
<useTags>true</useTags>
<useJakartaEe>true</useJakartaEe>
<useBeanValidation>true</useBeanValidation>
<performBeanValidation>true</performBeanValidation>
<openApiNullable>false</openApiNullable>
<documentationProvider>none</documentationProvider>
<!-- reactive: true emits Mono/Flux signatures. Set from stack.concurrency. -->
<reactive><true-if-reactive></reactive>
<serializableModel>true</serializableModel>
<unhandledException>true</unhandledException>
</configOptions>
</configuration>
</execution>
<execution>
<id>generate-rest-server-docs</id>
<phase>generate-resources</phase>
<goals>
<goal>generate</goal>
</goals>
<configuration>
<inputSpec>${maven.multiModuleProjectDirectory}/apis/rest-server/<service>-api-v1.yaml</inputSpec>
<generatorName>html2</generatorName>
<output>${project.build.directory}/generated-docs/rest-server/v1</output>
<generateApiTests>false</generateApiTests>
<generateModelTests>false</generateModelTests>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
Notes:
interfaceOnly=true is the important setting. With it, the generator owns the interfaces and DTOs and the
hand-written @RestController implements them — so mvn generate-sources is always safe to re-run. Without it,
the generator emits controllers and every regeneration is a merge conflict.
reactive must match stack.concurrency. Getting it wrong produces signatures the controllers can't implement,
which surfaces as a confusing compile error rather than an obvious misconfiguration.
The html2 generator produces the standalone HTML documentation. It lands in
target/generated-docs/rest-server/v1 where the CI workflow can publish it to GitHub Pages next to the Antora
site — the documentation page then links to it rather than duplicating the endpoint list by hand.
Add one execution per version file. When v2 arrives, it gets its own execution and its own
apiPackage/modelPackage ending in .v2., and both keep generating.
Step 3 — gRPC server contract and generator
Write a starter .proto at apis/grpc-server/<service>_v1.proto: syntax = "proto3", package <service>.v1,
option java_package = "<base>.api.grpc.v1.generated", option java_multiple_files = true, one service with one
unary RPC and one server-streaming RPC, request/response messages, and an enum. Comment every message, every
field, and every RPC — protobuf comments are what protoc-gen-doc turns into the generated documentation, so an
uncommented field is an undocumented API field.
Field-number discipline belongs in the file as a comment: numbers are never reused or renumbered, a removed field
is marked reserved, and a deprecated field carries [deprecated = true] with the reason in its comment.
Wire into api/grpc-server/pom.xml, using the protobuf plugin groupId that the root pom manages — Spring
Boot 4's Initializr wires io.github.ascopes:protobuf-maven-plugin, while older setups used
org.xolstice.maven.plugins:protobuf-maven-plugin; the two have different configuration schemas, so read the root
pom to see which is in play and configure that one rather than assuming:
<plugin>
<groupId><protobuf-plugin-group></groupId>
<artifactId>protobuf-maven-plugin</artifactId>
<configuration>
<sourceDirectories>
<sourceDirectory>${maven.multiModuleProjectDirectory}/apis/grpc-server</sourceDirectory>
</sourceDirectories>
<!-- plus the grpc-java protoc plugin, so service base classes are generated and not just messages -->
</configuration>
<executions>
<execution>
<goals>
<goal>generate</goal>
</goals>
</execution>
</executions>
</plugin>
Consult the plugin's own current documentation for the exact element names (sourceDirectories vs
protoSourceRoot, how the grpc-java plugin is declared, whether protocVersion is needed) instead of guessing —
a wrong element name here fails the build with an unhelpful "unknown parameter" error. Verify by running
mvn generate-sources in Step 7.
For HTML documentation, add a second execution using the protoc-gen-doc protoc plugin
(io.github.pseudomuto:protoc-gen-doc) with --doc_opt=html,index.html, writing into
${project.build.directory}/generated-docs/grpc-server/v1. If the protobuf plugin in use can't invoke a custom
protoc plugin cleanly, fall back to a docker run pseudomuto/protoc-gen-doc step and say so in the report — don't
silently ship no gRPC documentation, since the documentation page is specified to link to it.
Step 3a — GraphQL server contract and generator
Only if stack.graphqlServer. Write a starter SDL at apis/graphql-server/<service>-v1.graphqls: one type for
the aggregate, an enum, an input type, a Query with one field, and a Mutation with one field. Give every
type, field, argument and enum value a description string ("""...""" or "..." above the element) — SDL
descriptions are what the generated Javadoc carries and what any schema explorer shows, so an undescribed field is
an undocumented API field, exactly as with OpenAPI.
Version by file and by type-name suffix rather than by mutating in place. GraphQL has no URL path to carry a
version, so a breaking change means a v2 SDL file whose types are generated into a .v2. package; both keep
generating and both stay served until v1 is retired. Say so in apis/README.md.
Wire into api/graphql-server/pom.xml:
<plugin>
<groupId>io.github.kobylynskyi</groupId>
<artifactId>graphql-codegen-maven-plugin</artifactId>
<executions>
<execution>
<id>generate-graphql-server-v1</id>
<phase>generate-sources</phase>
<goals>
<goal>generate</goal>
</goals>
<configuration>
<graphqlSchemaPaths>
<path>${maven.multiModuleProjectDirectory}/apis/graphql-server/<service>-v1.graphqls</path>
</graphqlSchemaPaths>
<outputDir>${project.build.directory}/generated-sources/graphql-server</outputDir>
<apiPackageName><base>.api.graphql.v1.generated.api</apiPackageName>
<modelPackageName><base>.api.graphql.v1.generated.model</modelPackageName>
<!-- Interfaces only, never implementations: the hand-written @Controller implements the
resolver interface, so regeneration can't overwrite real logic. Same reasoning as
interfaceOnly=true for the REST generator. -->
<generateApis>true</generateApis>
<generateClient>false</generateClient>
<!-- The default is javax.validation.constraints.NotNull, which does NOT exist on Spring
Boot 3+/Jakarta and fails compilation with "package javax.validation does not exist".
This override is required, not cosmetic. -->
<modelValidationAnnotation>jakarta.validation.constraints.NotNull</modelValidationAnnotation>
<!-- The @Generated annotation embeds a build timestamp, making output non-reproducible. -->
<addGeneratedAnnotation>false</addGeneratedAnnotation>
</configuration>
</execution>
</executions>
</plugin>
The generator emits a QueryResolver/MutationResolver interface plus one <Field><Operation>Resolver interface
per field, and the model classes. Implement the resolver interfaces from a hand-written @Controller using
@QueryMapping/@MutationMapping/@SchemaMapping.
Then copy the SDL onto the runtime classpath — this step is not optional. Spring for GraphQL reads the schema
at startup from spring.graphql.schema.locations, whose default is classpath:graphql/**/ with extensions
.graphqls/.gqls. The contract lives outside the module, so nothing puts it there by itself, and the failure
mode is a service that compiles perfectly and then refuses to start because the schema is empty:
Confirm in Step 7 that the file actually landed in target/classes/graphql/. If the service sets a non-default
spring.graphql.schema.locations, copy to wherever that points instead and note the divergence in the report.
Two more things worth setting and reporting:
spring.graphql.schema.inspection.enabled (on by default in recent Boot lines) reports schema fields with no
corresponding resolver at startup. Leave it on — it's how a field added to the SDL and never implemented gets
noticed at boot rather than as a runtime null.
Query depth and complexity limits. A GraphQL endpoint with neither lets any client issue a deeply nested
query that walks the object graph until the service dies — the standard denial-of-service shape for GraphQL, and
not a hypothetical one. There is no default limit. Add MaxQueryDepthInstrumentation and
MaxQueryComplexityInstrumentation beans, and say in the report that the chosen numbers are a starting point the
team must tune against their real schema.
Step 3b — GraphQL documentation generation, wired into the build
Only if api/graphql-server/ exists. graphql-codegen-maven-plugin generates code, not documentation, so unlike
REST (html2) and gRPC (protoc-gen-doc) the GraphQL contract would otherwise publish nothing. Close that gap the
same way apis/messaging/ does: an npm toolchain pinned beside the contract, driven from the Maven build by
frontend-maven-plugin, writing into target/generated-docs/ for the workflow to publish.
Tool
Produces
Role
spectaql
a single self-contained index.html reference
the primary reference — types, fields, arguments, enums, inputs and operations, with every SDL description rendered
graphql-voyager
an interactive schema graph
optional; answers "how do these types connect?", which a flat reference can't
The two are complements, not alternatives: SpectaQL is the page someone reads to integrate, Voyager is the picture
someone opens to understand the shape of the schema. Generate SpectaQL always; ask before adding Voyager, since it
roughly doubles the published bytes for that API.
Write apis/graphql-server/docs/package.json:
{
"name": "<service>-graphql-docs",
"private": true,
"version": "1.0.0",
"description": "GraphQL documentation toolchain. Not published; not a Maven module.",
"dependencies": {
"spectaql": "<latest 3.x>",
"graphql": "<latest 16.x>",
"graphql-voyager": "<latest 2.x>"
}
}
npm install there once and commit package-lock.json; add apis/graphql-server/docs/node_modules/ to
.gitignore. Drop graphql-voyager from the dependencies if Voyager wasn't wanted — graphql stays either way,
since the Voyager build script needs it and SpectaQL wants a matching version.
SpectaQL is configured by a YAML file per contract version, at apis/graphql-server/docs/spectaql-v1.yml:
spectaql:
targetDir: <replaced on the command line>
# One self-contained index.html, so publishing is a single file copy and the page
# works from any path on GitHub Pages.
oneFile: true
introspection:
# The SDL is the input — no running server and no introspection endpoint needed,
# which is what makes this work in CI.
schemaFile: ../<service>-v1.graphqls
info:
title: <Service> GraphQL API
description: The GraphQL interface exposed by this service.
version: "1.0.0"
x-url: <the deployed /graphql endpoint>
Voyager has no CLI and takes an introspection result rather than SDL, so it needs a small build script at
apis/graphql-server/docs/build-voyager.mjs. It stays offline by copying Voyager's own standalone bundle next to
the page rather than loading it from a CDN:
import { readFileSync, writeFileSync, mkdirSync, copyFileSync } from 'node:fs';
import { buildSchema, introspectionFromSchema } from 'graphql';
const [, , sdlPath, outDir, title] = process.argv;
// Voyager requires the `data` half of an introspection response — an object with a
// top-level __schema key, which is exactly what introspectionFromSchema returns.
const introspection = introspectionFromSchema(buildSchema(readFileSync(sdlPath, 'utf8')));
mkdirSync(outDir, { recursive: true });
for (const f of ['voyager.standalone.js', 'voyager.css']) {
copyFileSync(`node_modules/graphql-voyager/dist/${f}`, `${outDir}/${f}`);
}
writeFileSync(`${outDir}/index.html`, `<!doctype html>
<html><head><meta charset="utf-8"><title>${title}</title>
<link rel="stylesheet" href="voyager.css" />
<style>body,html,#voyager{height:100%;margin:0;overflow:hidden}</style>
</head><body>
<div id="voyager">Loading…</div>
<script src="voyager.standalone.js"></script>
<script>
GraphQLVoyager.renderVoyager(document.getElementById('voyager'), {
introspection: ${JSON.stringify(introspection)}
});
</script>
</body></html>
`);
Wire both into api/graphql-server/pom.xml with frontend-maven-plugin, exactly as Step 6b does for AsyncAPI —
same install-node-and-npm + npm ci prelude, same <skip> escape hatch (${graphql.docs.skip}), same
generate-resources phase as every other documentation generator in the reactor:
workingDirectory is ${maven.multiModuleProjectDirectory}/apis/graphql-server/docs and installDirectory is
${project.build.directory}, as in Step 6b. The layout that results —
generated-docs/graphql-server/v1/index.html with generated-docs/graphql-server/v1/voyager/index.html beneath
it — publishes to doc/api/graphql-server/v1/, next to doc/api/rest-server/v1/ and doc/api/grpc-server/v1/.
Add one pair of executions per SDL version file. Omit the Voyager execution entirely if it wasn't wanted rather
than leaving a disabled one behind.
Two things to confirm in Step 7 rather than assume:
The SpectaQL page shows the SDL descriptions. An SDL with no description strings produces a structurally
complete page that documents nothing — the same failure the OpenAPI spec has, and the reason Step 3a insists on
describing every element.
The Voyager page actually draws the graph. It is a client-side render, so a broken introspection payload
yields a blank page with a console error and no build failure at all. Open it and look; the bundled
voyager.standalone.js and voyager.css must sit beside index.html in the published output, since the page
loads them by relative path.
Step 4 — REST clients
Per entry in stack.restClients, put the downstream service's OpenAPI spec at
apis/rest-client/<name>/<name>-api.yaml. This is the downstream team's contract, not yours — the starter file
should be a minimal placeholder with a prominent comment saying to replace it with the real published spec, plus a
note in apis/README.md about keeping it in sync (ideally by pulling it from the downstream service's own
published artifact in CI rather than by hand).
<generator> follows stack.concurrency: java with library=restclient for blocking (matching the
spring-restclient starter), or java with library=webclient for reactive. Confirm the library name against
the generator's current option list rather than assuming — these names have changed across generator versions.
No HTML documentation execution is needed for clients: the contract belongs to the downstream service and is
documented there.
Give every operation at least one request/response example pair. This spec has a second consumer besides the
generator: the API mock in the compose stack (stack.apiMock — Microcks or WireMock, set up by
iru-setup-java-springboot-testcontainers) is built from this file, and it is the examples, not the schemas, that
become the mocked responses. A spec with complete schemas and no examples generates a perfectly good client and a
mock with nothing to say — which surfaces later as an integration test failing against an empty response body,
a long way from its cause. Name each example after the case it represents (found, not-found, rate-limited),
and cover the error responses too, since the adapter's exception translation is what most needs testing.
Step 5 — gRPC clients
Per entry in stack.grpcClients, put the downstream .proto at apis/grpc-client/<name>/<name>.proto, with the
same "this is someone else's contract" comment. Wire the protobuf plugin into
infrastructure/clients/<name>/pom.xml with java_package under
<base>.infrastructure.clients.<name>.generated, generating the stubs. Generate only the client stubs, not
service base classes.
This .proto is also what the compose stack's mock serves. A protobuf file has no examples section, so the
sample responses live alongside it — Microcks reads them from a companion examples artifact next to the .proto
in the same directory (a Postman collection or a Microcks-format YAML; check the pinned version's supported
formats), while WireMock's gRPC extension needs a descriptor set built from this file plus hand-written mappings.
Whichever stack.apiMock names, put those example files in this same directory, so a downstream contract and
the responses mocked for it are updated in one place.
Step 5a — GraphQL clients
Per entry in stack.graphqlClients, put the downstream service's SDL at
apis/graphql-client/<name>/<name>-api.graphqls, with the same "this is someone else's contract, replace it with
the real published schema" comment as the other client directories. A GraphQL server can produce its own SDL
(spring.graphql.schema.printer.enabled exposes it, and any introspection-enabled endpoint can be dumped with
gql-cli/apollo client:download-schema), so say in apis/README.md that this file should be refreshed from the
downstream service rather than hand-edited.
Wire into infrastructure/clients/<name>/pom.xml:
<configuration>
<graphqlSchemaPaths>
<path>${maven.multiModuleProjectDirectory}/apis/graphql-client/<name>/<name>-api.graphqls</path>
</graphqlSchemaPaths>
<outputDir>${project.build.directory}/generated-sources/graphql-client-<name></outputDir>
<apiPackageName><base>.infrastructure.clients.<name>.generated.api</apiPackageName>
<modelPackageName><base>.infrastructure.clients.<name>.generated.model</modelPackageName>
<!-- The mirror image of the server configuration: request/response and projection classes,
no resolver interfaces. -->
<generateApis>false</generateApis>
<generateClient>true</generateClient>
<modelValidationAnnotation>jakarta.validation.constraints.NotNull</modelValidationAnnotation>
<addGeneratedAnnotation>false</addGeneratedAnnotation>
</configuration>
Client generation needs a runtime dependency that server generation doesn't. The generated
<Op>Request/<Type>ResponseProjection classes extend base types from
io.github.kobylynskyi:graphql-java-codegen — the same artifact as the plugin, at the same version. Add it as a
compile dependency of the client module (version-managed in the root pom like everything else). Without it the
module generates and then fails to compile with cannot find symbol: class GraphQLResponseField, which reads like
a generator bug rather than a missing dependency.
The adapter itself uses Spring's HttpGraphQlClient (reactive) or HttpSyncGraphQlClient (blocking), matching
stack.concurrency; the generated request objects serialise the query and the projections declare which fields
come back.
This SDL is also what the compose stack's mock serves when stack.apiMock is Microcks, which reads GraphQL
schemas directly. Put the example responses in this same directory alongside the SDL, as for the other client
kinds — a downstream contract and the responses mocked for it belong in one place. If stack.apiMock is WireMock,
note in the report that GraphQL stubs must match on the request body rather than the path (every operation is a
POST /graphql) and that the SDL is not consumed by the mock at all, so the two can drift.
Step 6 — AVRO messaging schemas
Only if stack.messaging.enabled. Steps 6, 6a and 6b are all conditional on it.
Write one starter schema per event at
apis/messaging/<event-name>-v1.avsc: a record with namespace ending in .v1, a doc on the record and on
every field, and — critically — a default value on every optional field. Defaults are what make schema
evolution work: a field added without one is a backward-incompatible change that the registry will reject and that
breaks every existing consumer.
Wire into whichever of infrastructure/producers and api/consumers exist (both, if the service produces and
consumes):
stringType=String matters: the default (CharSequence) makes generated classes awkward to map with MapStruct.
The Confluent AVRO serializer resolves schemas through the schema registry at runtime, so also record in the
report that the registry's compatibility mode (BACKWARD is the usual choice) has to be configured in the
registry itself — neither this scaffold nor the poms can set it. If a subject naming strategy other than the
default is wanted (e.g. TopicRecordNameStrategy for multiple event types per topic), it must be configured in the
producer/consumer binding properties; note whether you set one.
Step 6a — The AsyncAPI specification
The AVRO schemas say what a message looks like. They say nothing about which topic carries it, in which
direction, under which consumer group, on which broker — so on their own they can't document the messaging
interface the way the OpenAPI spec documents the REST one. That's what the AsyncAPI document is for.
Write one at apis/messaging/<service>-async-api-v1.yaml, declaring the current AsyncAPI version — 3.1.0 at
the time of writing. Confirm what's current rather than copying that number: npx asyncapi validate <spec> reports
asyncapi-latest-version as an informational finding when a newer one exists, so the toolchain tells you directly.
asyncapi: 3.1.0
info:
title: <Service> Events API
version: 1.0.0
description: Events this service publishes and consumes.
servers:
kafka:
host: <broker-host>:9092
protocol: kafka
description: Kafka broker; schemas resolve through the Confluent Schema Registry.
channels:
orderCreated:
# `address` is the real topic name — it must match the
# `spring.cloud.stream.bindings.<binding>.destination` value, or the documentation
# describes a topic that doesn't exist. The channel *key* is just an internal id.
address: order.created.v1
description: Order lifecycle events.
messages:
OrderCreated:
$ref: '#/components/messages/OrderCreated'
operations:
sendOrderCreated:
# In AsyncAPI 3 the action is from THIS service's point of view:
# `send` = this service produces it, `receive` = this service consumes it.
action: send
summary: Publish an order-created event.
channel:
$ref: '#/channels/orderCreated'
messages:
- $ref: '#/channels/orderCreated/messages/OrderCreated'
components:
messages:
OrderCreated:
name: OrderCreated
title: Order created
contentType: application/avro
payload:
# Reference the .avsc, never restate it. One source of truth for the payload.
schemaFormat: application/vnd.apache.avro;version=1.9.0
schema:
$ref: './order-created-v1.avsc'
Three things to get right, each of which silently produces wrong documentation rather than an error:
action is written from this service's point of view.send is what the service produces, receive is what
it consumes. This is the one thing AsyncAPI 3 deliberately fixed from 2.x, where publish/subscribe meant the
opposite of what nearly everyone assumed. If you're adapting an older 2.x document, its subscribe becomes
send and its publish becomes receive — not the other way round.
Payloads are $refs to the .avsc files, under a schemaFormat + schema pair, resolved relative to the
AsyncAPI file — which is exactly why the two live in the same directory. Restating the fields inline creates a
second copy that drifts from the one the code is generated from.
address is the topic name from the binding configuration, not the channel key. Cross-check against
spring.cloud.stream.bindings.*.destination and say in the report if the bindings don't exist yet.
Cover both directions in this one file if the service both produces and consumes; it documents the service's whole
messaging interface, not one module's half of it. Give info.description, every channel, every operation
(summary), and every message a real description — as with the OpenAPI spec, the generated pages are only as good
as the text in the contract. Add a v2 file alongside when a breaking change arrives, following the same rule as
the other contracts.
Step 6b — AsyncAPI documentation generation, wired into the build
The official AsyncAPI HTML generator runs over the AsyncAPI file on every build, producing a static documentation
site published to GitHub Pages next to the REST and gRPC pages. It is driven by @asyncapi/cli, which bundles the
generator; @asyncapi/html-template is the template it renders with.
{
"name": "<service>-asyncapi-docs",
"private": true,
"version": "1.0.0",
"description": "AsyncAPI documentation toolchain. Not published; not a Maven module.",
"dependencies": {
"@asyncapi/cli": "<latest 6.x>",
"@asyncapi/html-template": "<latest 3.x>"
},
"overrides": {
"_comment": "@asyncapi/generator 3.4.0 depends on @asyncapi/generator-hooks 0.1.1, which was never published to npm; without this override `npm install` fails with ETARGET. Drop it once the upstream dependency resolves.",
"@asyncapi/generator-hooks": "0.1.0"
}
}
Check whether the overrides block is still needed before adding it — run npm install without it first and keep
it only if npm actually fails with ETARGET. A stale override silently pins a transitive dependency below what the
CLI expects.
Write it to apis/messaging/docs/package.json, run npm install there once, and commit the resulting
package-lock.json — it is what makes the documentation build reproducible and what lets CI use npm ci. Add
apis/messaging/docs/node_modules/ to .gitignore. Verify the install actually succeeds before moving on; if npm
reports ETARGET on a package other than generator-hooks, pin that one in overrides too and record it in the
report rather than leaving a build that only works on your machine.
Then wire the generator into Maven with frontend-maven-plugin, so mvn generate-resources produces the
documentation with no globally installed Node — the same guarantee the REST and gRPC documentation already have.
Put the executions in one module only: infrastructure/producers if it exists, otherwise api/consumers. The
AsyncAPI document describes the whole service, so generating it in both modules would just publish the same pages
twice under two paths.
<plugin>
<groupId>com.github.eirslett</groupId>
<artifactId>frontend-maven-plugin</artifactId>
<configuration>
<!-- package.json lives with the contract it documents, not in the module. -->
<workingDirectory>${maven.multiModuleProjectDirectory}/apis/messaging/docs</workingDirectory>
<!-- Node itself is a build artifact: keep it under target/, out of the source tree. -->
<installDirectory>${project.build.directory}</installDirectory>
<skip>${asyncapi.docs.skip}</skip>
<environmentVariables>
<!-- The CLI otherwise writes ~/.asyncapi-analytics and reports usage to New Relic on
every build. Pointing at a committed file with analyticsEnabled=false makes the
build silent and offline. (CI=true also suppresses it, but local builds aren't CI.) -->
<ASYNCAPI_METRICS_CONFIG_PATH>${maven.multiModuleProjectDirectory}/apis/messaging/docs/.asyncapi-analytics</ASYNCAPI_METRICS_CONFIG_PATH>
</environmentVariables>
</configuration>
<executions>
<execution>
<id>asyncapi-install-node</id>
<phase>generate-resources</phase>
<goals>
<goal>install-node-and-npm</goal>
</goals>
<configuration>
<nodeVersion>v<node-major>.<x>.<y></nodeVersion>
</configuration>
</execution>
<execution>
<id>asyncapi-install-toolchain</id>
<phase>generate-resources</phase>
<goals>
<goal>npm</goal>
</goals>
<configuration>
<!-- `ci`, not `install`: the committed lock file is the contract. -->
<arguments>ci --no-audit --no-fund</arguments>
</configuration>
</execution>
<execution>
<id>asyncapi-validate</id>
<phase>generate-resources</phase>
<goals>
<goal>npx</goal>
</goals>
<configuration>
<!-- Ahead of generation, so a malformed contract fails with a validation error
instead of an obscure generator crash. This resolves and type-checks the
referenced .avsc files too, so a missing or invalid AVRO schema fails here
(exit 1) rather than producing a page with empty payload tables. A merely
out-of-date `asyncapi:` version is reported as information and exits 0, so a
new specification release can never break the build on its own. -->
<arguments>asyncapi validate ${maven.multiModuleProjectDirectory}/apis/messaging/<service>-async-api-v1.yaml</arguments>
</configuration>
</execution>
<execution>
<id>asyncapi-docs-html</id>
<phase>generate-resources</phase>
<goals>
<goal>npx</goal>
</goals>
<configuration>
<!-- singleFile=true emits one self-contained index.html, so publishing is a single
file copy and the page works from any path on GitHub Pages. -->
<arguments>asyncapi generate fromTemplate ${maven.multiModuleProjectDirectory}/apis/messaging/<service>-async-api-v1.yaml @asyncapi/html-template -o ${project.build.directory}/generated-docs/messaging/v1 --force-write -p singleFile=true</arguments>
</configuration>
</execution>
</executions>
</plugin>
Declare <asyncapi.docs.skip>false</asyncapi.docs.skip> as a root-pom property so a developer with no network can
build with -Dasyncapi.docs.skip=true, and say so in the report — a build step that downloads Node and ~1600 npm
packages must have an escape hatch, and CI must not use it or the published documentation goes stale silently.
The executions bind to generate-resources, the same phase as the REST html2 and gRPC protoc-gen-doc
executions, so every API documentation artifact in the repository is produced by one predictable command. Add one
validate/generate pair per AsyncAPI version file, writing into .../messaging/v2/ when v2 arrives.
Version numbers: frontend-maven-plugin goes in the root pom's <pluginManagement> like every other plugin —
add it there (see iru-setup-java-springboot-pom) rather than inline here. The npm package versions are the one
exception to this repository's no-inline-versions rule, because they live in package.json, not in a pom; pin them
to exact currently-published versions and let the committed lock file do the rest.
Step 7 — Verify generation actually works
Delegate to iru-gate-runner:
mvn -q clean generate-sources # every generator runs
mvn -q clean compile # hand-written code compiles against the generated code
Then confirm by inspection:
generated sources exist under each expected module's target/generated-sources/;
the packages match what Steps 2–6 configured, so the hand-written mappers and controllers resolve;
if GraphQL is enabled, target/classes/graphql/ actually contains the SDL, and no generated file imports
javax.validation — both are silent-at-generation, loud-later failures (a service that won't start, and a
module that won't compile);
if GraphQL is enabled, generated-docs/graphql-server/v1/index.html exists and shows the SDL descriptions, and
(when Voyager was wanted) generated-docs/graphql-server/v1/voyager/index.html exists with
voyager.standalone.js and voyager.css beside it;
generated HTML documentation exists under target/generated-docs/, including
generated-docs/messaging/v1/index.html if messaging is enabled;
that page actually lists the AVRO field names and their doc text. The asyncapi-validate execution catches the
usual causes before generation — a $ref to a missing .avsc and an .avsc that isn't valid AVRO both fail it
with asyncapi-document-resolved errors, since the validator resolves and type-checks the referenced schema —
so an empty payload table here means something subtler, most often a message declared in components but never
wired to a channel or an operation.
A generator that runs but produces nothing usually means a wrong inputSpec/sourceDirectory path — remember
these are absolute via ${maven.multiModuleProjectDirectory}, because the contract lives outside the module.
Fix whatever fails. This is the step most likely to need real iteration, particularly the protobuf plugin's
configuration schema and the OpenAPI generator's library option names — check the plugin's actual documentation
rather than trying variations.
Step 8 — Keep generated output out of git and out of analysis
Confirm .gitignore covers target/ (which already covers generated-sources and generated-docs). If any
generator was configured to write outside target/, either change it to write inside target/ — strongly
preferred — or add an explicit ignore entry and explain why in the report.
Add apis/graphql-server/docs/node_modules/ to .gitignore if the GraphQL documentation toolchain was set up;
its package.json, package-lock.json, spectaql-*.yml and build-voyager.mjs are committed.
Add apis/messaging/docs/node_modules/ to .gitignore if the AsyncAPI toolchain was set up — it's the one
generated directory that can't live under target/, because npm requires it beside its package.json. Its
package.json, package-lock.json, and .asyncapi-analyticsare committed; nothing else in that directory
is.
Confirm the root pom's Checkstyle sourceDirectories, PMD excludeRoots, SpotBugs excludeFilterFile, JaCoCo
excludes, and sonar.exclusions all cover the generated packages. iru-setup-java-springboot-pom sets these
up; verify they match the package names actually configured here, and correct them if the generated packages
ended up somewhere the exclusions don't reach. Thousands of findings on generated DTOs is how a team learns to
ignore the quality report entirely.
Step 9 — Contract linting (recommended)
Add a lightweight check per contract kind so a malformed contract fails in CI rather than at generation time, and
report what you added:
OpenAPI — the generator's own validateSpec option (on by default) catches structural errors. For style and
breaking-change detection, note Spectral (@stoplight/spectral-cli) and oasdiff as the tools to add to CI;
wire one in if the user wants it now.
protobuf — buf lint and buf breaking are the standard; adding a buf.yaml is cheap and catches
field-number reuse, which is otherwise a silent wire-compatibility break.
AVRO — schema compatibility is checked by the registry. Note that
io.confluent:kafka-schema-registry-maven-plugin can run test-compatibility against a real registry in CI,
which catches an incompatible schema before deploy rather than at first publish.
GraphQL — the generator parses the SDL, so a syntactically broken schema already fails the build. For style
and breaking-change detection, note GraphQL Inspector (@graphql-inspector/cli, with a diff command that
classifies each change as breaking, dangerous, or safe) and graphql-schema-linter as the tools to add to CI;
wire one in if the user wants it now. Breaking-change detection matters more here than for REST, because GraphQL
has no URL version to hide behind — removing a field breaks every client that selected it.
AsyncAPI — already wired in Step 6b as the asyncapi-validate execution, so a malformed contract fails with
a validation error rather than an obscure generator crash. asyncapi validate also reports
asyncapi-latest-version informationally when a newer specification version is available, which is the cheapest
way to notice the document has fallen behind. Note asyncapi diff as the breaking-change check to add to CI
later.
Step 10 — Report
Summarize:
Every contract file created, with its path and what it describes.
Every generator execution added, to which module pom, generating into which package, and where its HTML
documentation lands.
The reactive/library settings resolved from stack.concurrency, and the protobuf plugin flavour detected.
For GraphQL: where the SDL is copied to for runtime loading, that modelValidationAnnotation was set to the
jakarta annotation, whether graphql-java-codegen was added to each GraphQL client module, the query
depth/complexity limits chosen, whether Voyager was generated alongside SpectaQL, and the published paths of
both.
For messaging: the AsyncAPI version declared, which module hosts the documentation executions, the exact npm
package versions pinned in apis/messaging/docs/package.json, whether npm install needed any overrides at
all, and the Node version pinned in frontend-maven-plugin.
The result of Step 7, including whether HTML documentation was actually produced for REST, gRPC, GraphQL and
messaging, whether the messaging page's payload tables came out populated rather than empty, and whether the
GraphQL pages showed real descriptions and a drawn schema graph.
Whether the analysis exclusions in Step 8 already covered the generated packages or had to be corrected.
What linting was wired versus merely recommended.
Warn explicitly:
The client specs under apis/rest-client/ and apis/grpc-client/ are placeholders for someone else's
contract — they must be replaced with the downstream service's real published spec before the client adapters
mean anything, and kept in sync afterwards. They have two consumers, not one: the client generator and the
compose stack's API mock (stack.apiMock), so a spec left as a placeholder produces both a useless client and a
mock that agrees with it. Report which client specs still carry no examples, since those mock nothing.
Generated code must never be committed or edited. Fix the spec or the generator configuration instead.
A GraphQL endpoint has no depth or complexity limit by default, and the numbers set here are a guess until
someone tunes them against the real schema. Until then a single nested query can exhaust the service. This is the
one item in this skill's output that is a live availability risk rather than a tidiness concern.
The GraphQL SDL is read twice — at build time and at startup. Changing where it lives, or the
spring.graphql.schema.locations property, breaks the second one only, and only at runtime.
The AVRO registry compatibility mode and the gRPC field-numbering discipline are enforced outside this
repository (in the registry, and by review or buf breaking) — the scaffold can't enforce either.
Adding an event means editing the .avscand the AsyncAPI file. An .avsc added alone compiles to a Java
class that appears in no documentation at all, and nothing in the build will say so. State which direction
(send/receive) each operation documents, since an inverted action is the one error here that produces a
confident, wrong diagram rather than a failure.
Every contract's descriptions and constraints feed the documentation pages, so an under-described spec produces
under-described documentation. /iru-update-java-springboot-documentation reads these files.
