Produce valid JSON for Multi<String> return type in RESTEasy Reactive

[oliver-brm]

This is primarily meant to provide a fix for #18043. However, there were no integration-tests/resteasy-reactive yet, so I added them. I have a few questions with you to discuss:

Regarding my fix for the issue in StreamingUtil.java...

• is it safe for integration, regarding the UTF-8 charset and regarding the MediaType condition?
• the fix is a bit hack-ish; I think, if possible, it would be better to change those Jackson/JSONB writers, for example FullyFeaturedServerJacksonMessageBodyWriter; however, I wasn't sure how to test that for side-effects; probably running the RESTeasy TCK?

Regarding the integration tests for RESTeasy reactive
I added the project right under integration-tests and copied (YUK!) some classes from the resteasy-mutiny and resteasy-jackson integration tests. Would be better to share the classes, using a parent or shared project. However, I was not sure how much restructuring I would be allowed to do in this scope. You might like to have this done under a separate GitHub issue?

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[geoand]

Thanks!

Ping me when you are ready for a review

[oliver-brm]

Thanks!

Ping me when you are ready for a review

Ping! :-)

[geoand]

Thanks for this!

I would prefer if the PR didn't introduce a whole new project just for testing.
The PR could likely easily just add a new test in one of the json modules (and it doesn't need to be a integration test, it can be one a @QuarkusUnitTest)

[oliver-brm]

Hmm, I tried to move some of the tests to the quarkus-resteasy-reactive-jackson. However, I cannot get the test to run:

Caused by: io.quarkus.bootstrap.BootstrapException: Failed to create the application model for io.quarkus:quarkus-resteasy-reactive-jackson::jar:999-SNAPSHOT
	at io.quarkus.bootstrap.BootstrapAppModelFactory.resolveAppModel(BootstrapAppModelFactory.java:325)
	at io.quarkus.bootstrap.app.QuarkusBootstrap.bootstrap(QuarkusBootstrap.java:169)
	at io.quarkus.test.junit.QuarkusTestExtension.doJavaStart(QuarkusTestExtension.java:314)
	at io.quarkus.test.junit.QuarkusTestExtension.ensureStarted(QuarkusTestExtension.java:635)
	at io.quarkus.test.junit.QuarkusTestExtension.beforeAll(QuarkusTestExtension.java:682)
	at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$invokeBeforeAllCallbacks$8(ClassBasedTestDescriptor.java:368)
	at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
	at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.invokeBeforeAllCallbacks(ClassBasedTestDescriptor.java:368)
	at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.before(ClassBasedTestDescriptor.java:192)
	at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.before(ClassBasedTestDescriptor.java:78)
	at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:136)
	... 34 more
Caused by: io.quarkus.bootstrap.resolver.maven.BootstrapMavenException: Failed to resolve artifacts
	at io.quarkus.bootstrap.resolver.maven.MavenArtifactResolver.resolve(MavenArtifactResolver.java:172)
	at io.quarkus.bootstrap.resolver.BootstrapAppModelResolver.doResolveModel(BootstrapAppModelResolver.java:233)
	at io.quarkus.bootstrap.resolver.BootstrapAppModelResolver.resolveManagedModel(BootstrapAppModelResolver.java:147)
	at io.quarkus.bootstrap.BootstrapAppModelFactory.resolveAppModel(BootstrapAppModelFactory.java:311)
	... 44 more
Caused by: org.eclipse.aether.resolution.ArtifactResolutionException: Could not find artifact io.quarkus:quarkus-resteasy-reactive-server-spi-deployment:jar:999-SNAPSHOT
	at org.eclipse.aether.internal.impl.DefaultArtifactResolver.resolve(DefaultArtifactResolver.java:424)
	at org.eclipse.aether.internal.impl.DefaultArtifactResolver.resolveArtifacts(DefaultArtifactResolver.java:229)
	at org.eclipse.aether.internal.impl.DefaultRepositorySystem.resolveArtifacts(DefaultRepositorySystem.java:270)
	at io.quarkus.bootstrap.resolver.maven.MavenArtifactResolver.resolve(MavenArtifactResolver.java:170)
	... 47 more

[geoand]

I would suggest the following:

mvn -Dquickly to build all changes and then mvn test -f extensions/resteasy-reactive/quarkus-resteasy-reactive-jackson/deployment/ to run the tests in the jackson module.

see https://github.com/quarkusio/quarkus/blob/main/CONTRIBUTING.md#workflow-tips for more details

[oliver-brm]

Sorry, I messed up my fork. Had to re-create one and open a new PR. Please see #18401.