Selectively publish through the gradle maven publishing plugin only when the version doesn’t exist in the repository.

withType<PublishToMavenRepository>().configureEach {
    onlyIf {
        logger.lifecycle("Checking published version of '${publication.groupId}:${publication.artifactId}' to '${publication.version}'")
        val dep = project.dependencies.create(group = publication.groupId, name = publication.artifactId, version = publication.version)
        val conf = rootProject.configurations.detachedConfiguration(dep)
        conf.isTransitive = false
        conf.resolutionStrategy.cacheDynamicVersionsFor(0, TimeUnit.SECONDS)
        conf.resolutionStrategy.cacheChangingModulesFor(0, TimeUnit.SECONDS)
        val lenientConfiguration = conf.resolvedConfiguration.lenientConfiguration
        if (lenientConfiguration.unresolvedModuleDependencies.isEmpty()) {
            val resolved = conf.resolvedConfiguration.firstLevelModuleDependencies.first()
            logger.lifecycle("Resolved published version of '${resolved.moduleGroup}:${resolved.moduleName}' to '${resolved.moduleVersion}'")
            false
        } else {
            logger.lifecycle("No published version of '${publication.groupId}:${publication.artifactId}' resolved to '${publication.version}'")
            true
        }
    }
}

publishing {
    publications {
        create<MavenPublication>("maven") {
            groupId = "com.example.client"
            artifactId = "example-client"
            version = "0.1.0"
            from(components["java"])
        }
    }
}

You can now replace the spring dependencies plugin with the native gradle platform bom support.

dependencies {
    implementation(platform("org.springframework.boot:spring-boot-dependencies:${Versions.springBoot}"))
}

To override a version though is a little less clean.

configurations {
  all {
    resolutionStrategy.eachDependency {
      if (this.requested.group == "redis.clients" && this.requested.name == "jedis") {
        this.useVersion(Versions.redis)
        this.because("issues with spring boot and library jedis versoin with >3")
      }
    }
  }
}

References:

• Spring Boot 2.4.4 BOM file
• Gradle Docs

Managing different kubectl and helm versions for different clusters can be a pain. Seems asdf is pretty cool for managing the versions and a simple shell alias can do all the setup.

alias k8s_local='asdf local kubectl 1.20.0 && \
asdf shell helm 3.4.2 && \
asdf current && \
kctx docker-desktop && \
kubeon'
alias k8s_ci='asdf local kubectl 1.19.4 && \
asdf shell helm 2.12.3 && \
asdf current && \
kctx ci && \
kubeon'

$ k8s_local
$ k8s_ci

Getting alt-left alt-right working between iTerm2, zsh, vim, tmux.

• iTerm2, setting the correct key bindings: Preferences -> Profile -> Keys ; Set preset to ‘Natural Text Editing’
• zsh, setting and consuming the correct key bindings: Enable zsh-vim-mode
• vim, overwrite f mapping with w, since f is sent for alt-right: .vimrc add line map f w

Using asciidoctor gradle plugin with spring restdocs extension and the gradle kotlin dsl.

plugins {
  id("org.asciidoctor.jvm.convert") version "3.2.0"
}

val asciidoctorExtensions by configurations.creating

dependencies {
  asciidoctorExtensions("org.springframework.restdocs:spring-restdocs-asciidoctor:2.0.5.RELEASE")
}

tasks {
  asciidoctor {
    dependsOn("test")
    inputs.dir(File("$buildDir/generated-snippets"))
    configurations("asciidoctorExtensions")
    asciidoctorj {
      baseDirFollowsSourceFile()
    }
    resources(delegateClosureOf<CopySpec> {
      from("src/docs/asciidoc") {
        include("**/img/**")
        include("**/data/**")
      }
    })
  }
}

Docker command to pull new images:

docker image ls --format "{{.Repository}}:{{.Tag}}" | xargs -I % sh -c "docker pull %"

@UniqueName
data class CreateRequest(
    val id: String = "",
    @get:NotBlank(message = "{req.name.blank}")
    val name: String = "",
    @get:NotBlank(message = "{req.description.blank}")
    val description: String = "",
    @get:Valid
    val nested: NestedClass = NestedClass("", ""),
)

data class NestedClass(
    @get:NotBlank(message = "{req.nested.something.blank}")
    val something: String,
    @get:NotBlank(message = "{req.nested.something_else.blank}")
    val somethingElse: String
)

@Target(AnnotationTarget.CLASS)
@Retention(AnnotationRetention.RUNTIME)
@Constraint(validatedBy = [UniqueNameValidator::class])
annotation class UniqueName(
    val message: String = "",
    val groups: Array<KClass<*>> = [],
    val payload: Array<KClass<out Payload>> = []
)

class UniqueNameValidator(
    private val sampleService: SampleService
) : ConstraintValidator<UniqueName, CreateRequest> {
    override fun isValid(request: CreateRequest, context: ConstraintValidatorContext): Boolean {
        val dupSample = sampleService.findByName(request.name)
        val result = !(dupSample != null && dupSample.id != project.id)
        if (!result) {
            context.disableDefaultConstraintViolation()
            context
                .buildConstraintViolationWithTemplate("{req.name.unique}")
                .addPropertyNode("name")
                .addConstraintViolation()
        }
        return result
    }
}

src/main/resources/ValidationMessages.properties

req.name.blank=Name is required.
req.name.unique=Name must be unique.
req.description.blank=Description is required.
req.nested.something.blank=Something is required.
req.nested.something_else.blank=Something Else is required.

Custom Response Messages

@ControllerAdvice
class ControllerAdvice {
    @ExceptionHandler(value = [MethodArgumentNotValidException::class])
    fun handleMethodArgumentNotValid(exception: MethodArgumentNotValidException): ResponseEntity<ValidationError> {
        val violations = exception.bindingResult.allErrors
            .mapNotNull { error ->
                when (error) {
                    is FieldError -> Violation(error.field.toSnakeCase(), error.defaultMessage ?: "")
                    is ObjectError -> Violation(error.objectName.toSnakeCase(), error.defaultMessage ?: "")
                    else -> null
                }
            }
            .toList()
        return ResponseEntity.status(BAD_REQUEST).body(ValidationError(errors = violations))
    }
}

class ValidationError(
    val status: String = BAD_REQUEST.toString(),
    val message: String = "Errors occurred during validation",
    val errors: List<Violation>
)
class Violation(val field: String, val message: String)

fun String.toSnakeCase(): String = Normalizer
    .normalize(this, Normalizer.Form.NFD)
    .replace("([A-Z]+)".toRegex(), "\\_\$1")
    .toLowerCase()

Controller

@PostMapping
fun create(@Valid @RequestBody body: CreateRequest): SampleDocument {
    return sampleService.save(body)
}

Sample Response

{
  "status": "400 BAD_REQUEST",
  "message": "Errors occurred during validation",
  "errors": [
    {
      "field": "nested.something_else",
      "message": "Something Else is required."
    },
    {
      "field": "name",
      "message": "Name must be unique."
    },
    {
      "field": "nested.something",
      "message": "Something is required."
    },
    {
      "field": "name",
      "message": "Name is required."
    },
    {
      "field": "description",
      "message": "Description is required."
    }
  ]
}

Spring boot (2.3.0+) tomcat access log configuration to log to stdout

server.tomcat.accesslog.enabled=true
server.tomcat.accesslog.directory=/dev
server.tomcat.accesslog.prefix=stdout
server.tomcat.accesslog.buffered=false
server.tomcat.accesslog.suffix=
server.tomcat.accesslog.file-date-format=
server.tomcat.accesslog.pattern=%{yyyy-MM-dd HH:mm:ss.SSS}t %r %s %b %T | %{Content-Type}i | %{Content-Type}o

Spring WebClient Exceeded limit on max bytes to buffer exception

Fix is to increase the max memory size for a specific codec or all codecs, for example: spring.codec.max-in-memory-size=20MB

2020-07-29 16:58:43.046  WARN 1 --- [or-http-epoll-2] reactor.netty.channel.FluxReceive        : [id: 0xca1ab03a, L:/x.x.x.x ! R:example.com/x.x.x.x:443] An exception has been observed post termination, use DEBUG level to see the full stack: io.netty.util.IllegalReferenceCountException: refCnt: 0, decrement: 1
2020-07-29 16:59:36.605  INFO 1 --- [or-http-epoll-3] com.example.RestProvider                 : retry rest call single commit request, retry [6], error [org.springframework.core.io.buffer.DataBufferLimitException: Exceeded limit on max bytes to buffer : 262144]
2020-07-29 16:59:36.607 ERROR 1 --- [or-http-epoll-3] r.n.channel.ChannelOperationsHandler     : [id: 0xb1b84f9b, L:/x.x.x.x ! R:example.com/x.x.x.x:443] Error was received while reading the incoming data. The connection will be closed.

io.netty.util.IllegalReferenceCountException: refCnt: 0, decrement: 1
	at io.netty.util.internal.ReferenceCountUpdater.toLiveRealRefCnt(ReferenceCountUpdater.java:74) ~[netty-common-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.util.internal.ReferenceCountUpdater.release(ReferenceCountUpdater.java:138) ~[netty-common-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.buffer.AbstractReferenceCountedByteBuf.release(AbstractReferenceCountedByteBuf.java:100) ~[netty-buffer-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.handler.codec.http.DefaultHttpContent.release(DefaultHttpContent.java:92) ~[netty-codec-http-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.util.ReferenceCountUtil.release(ReferenceCountUtil.java:88) ~[netty-common-4.1.49.Final.jar!/:4.1.49.Final]
	at reactor.netty.channel.FluxReceive.onInboundNext(FluxReceive.java:334) ~[reactor-netty-0.9.7.RELEASE.jar!/:0.9.7.RELEASE]
	at reactor.netty.channel.ChannelOperations.onInboundNext(ChannelOperations.java:352) ~[reactor-netty-0.9.7.RELEASE.jar!/:0.9.7.RELEASE]
	at reactor.netty.http.client.HttpClientOperations.onInboundNext(HttpClientOperations.java:629) ~[reactor-netty-0.9.7.RELEASE.jar!/:0.9.7.RELEASE]
	at reactor.netty.channel.ChannelOperationsHandler.channelRead(ChannelOperationsHandler.java:96) ~[reactor-netty-0.9.7.RELEASE.jar!/:0.9.7.RELEASE]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) ~[netty-transport-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) ~[netty-transport-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357) ~[netty-transport-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:103) ~[netty-codec-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) ~[netty-transport-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) ~[netty-transport-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357) ~[netty-transport-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.channel.CombinedChannelDuplexHandler$DelegatingChannelHandlerContext.fireChannelRead(CombinedChannelDuplexHandler.java:436) ~[netty-transport-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:324) ~[netty-codec-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:296) ~[netty-codec-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:251) ~[netty-transport-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) ~[netty-transport-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) ~[netty-transport-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357) ~[netty-transport-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.handler.ssl.SslHandler.unwrap(SslHandler.java:1518) ~[netty-handler-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.handler.ssl.SslHandler.decodeJdkCompatible(SslHandler.java:1267) ~[netty-handler-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.handler.ssl.SslHandler.decode(SslHandler.java:1314) ~[netty-handler-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:501) ~[netty-codec-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:440) ~[netty-codec-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:276) ~[netty-codec-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) ~[netty-transport-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) ~[netty-transport-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357) ~[netty-transport-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410) ~[netty-transport-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) ~[netty-transport-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) ~[netty-transport-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919) ~[netty-transport-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:792) ~[netty-transport-native-epoll-4.1.49.Final-linux-x86_64.jar!/:4.1.49.Final]
	at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:475) ~[netty-transport-native-epoll-4.1.49.Final-linux-x86_64.jar!/:4.1.49.Final]
	at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:378) ~[netty-transport-native-epoll-4.1.49.Final-linux-x86_64.jar!/:4.1.49.Final]
	at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989) ~[netty-common-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[netty-common-4.1.49.Final.jar!/:4.1.49.Final]
	at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) ~[netty-common-4.1.49.Final.jar!/:4.1.49.Final]
	at java.base/java.lang.Thread.run(Thread.java:834) ~[na:na]

Collections.unmodifiable* can throw StackOverflowError errors when used recursively. For example:

Exception in thread "main" java.lang.StackOverflowError
	at java.util.Collections$UnmodifiableCollection$1.<init>(Collections.java:1039)
	at java.util.Collections$UnmodifiableCollection.iterator(Collections.java:1038)
	at java.util.Collections$UnmodifiableCollection$1.<init>(Collections.java:1039)
	at java.util.Collections$UnmodifiableCollection.iterator(Collections.java:1038)
[...]

Reproducible Source:

List<Integer> list = Collections.unmodifiableList(Arrays.asList(0, 1, 2));
for (int i = 0; i < 10000; i++) {
    list = Collections.unmodifiableList(list);
}
for (int i : list) {
    System.out.println(i);
}

Just thought that was interesting.