1. re:Invent 2024 conference news
2. Corrections to the calculation of the cost of Kubernetes in the 128th episode (I was too optimistic)
3. Which technology to choose for native clients?
4. Java LLM recap
5. Steve Jobs and Enterprise Java
6. BCE: the location of repositories
7. BCE: organization of the MP Rest Client and its parameters
8. What is SecureRandom?
9. Graylog? ELK? LGTM (Loki for logs, Grafana for visualization, Tempo for traces, and Mimir for metrics)?
10. What is the best approach for bean validation on JPA Entities and 400
11. LangGraph4J vs. LangChain4J

Any questions left? Ask now: https://gist.github.com/AdamBien/355fd0bebcfd5865464cbaf32b0e3e5a and get the answers at the next airhacks.tv. Some questions are also answered with a short video: 60 seconds or less with Java

Ask questions during the show via twitter mentioning me: https://twitter.com/AdamBien (@AdamBien),using the hashtag: #airhacks or built-in chat at: airhacks.tv. You can join the Q&A session live each first Monday of month, 8 P.M at airhacks.tv

1. K8 cost estimation
2. UUID generation for persistence
3. Thoughts on: How to migrate from EJB to CDI?
4. the 100-episodes back time machine. Questions from: 28th airhacks.tv:

   "Java EE 8 News, New server (the real hardware): the part list. Oracle says it is 'commmitted' to Java EE 8 microprofile.io announcement Wildfly-Swarm, Payara Micro and the relation to microservices Dynamic injection into @Stateless EJBs Handling ViewExpiredException in JSF Managing JAX-RS clients on servers Accessing GlassFish / Payara logifles from the browser Is overusing CDI a code smell? JAX-RS MessageBodyWriter and Singleton challenges How to approach logging in microservices? Monitoring Java EE methods"

Any questions left? Ask now: and get the answers at the next airhacks.tv. Some questions are also answered with a short video: 60 seconds or less with Java

Ask questions during the show via twitter mentioning me: https://twitter.com/AdamBien (@AdamBien),using the hashtag: #airhacks or built-in chat at: airhacks.tv. You can join the Q&A session live each first Monday of month, 8 P.M at airhacks.tv

The talk "The Best of Java Shorts Show: 100 Snippets in 50 Minutes" at Devoxx 2024 Belgium was recorded with a selection of the most interesting or popular shorts:

From REST API and SDKs to langchain4j to fully managed cloud solutions to local integration with jlama and llama3.java of open source foundation models. In this session I will present architectures, ideas, hacks, and workarounds for integrating LLM with Java enterprise applications. I will illustrate the concepts with Java 21, Quarkus / MicroProfile code and integrate the latest Claude, ChatGPT, llama and AWS Bedrock models. Your questions will be given priority and answered interactively.

How to: run Java as a shell script, run a Java app without compiling, print an emoji, run an HTTP dev server, use libraries without compiling, colorful logs, access LLMs,run timer jobs, access the clipboard, implement a file watch, main in interfaces, easy file parsing (...) and ~100 other popular Java snippets from youtube.com/bienadam/shorts. No builds, no Maven, no dependencies, just javac and Visual Studio code.

"String.join() is 30% faster than Collectors.joining(), JMH not always necessary for high-level benchmarking, interfaces slightly faster than abstract classes but the difference is negligible, Quarkus requires no installation - just use the POM file, Quarkus tests are integration tests and should be used sparingly, use shutdown hooks or @PreDestroy for clean connection closure in Lambdas, GraalVM shines in CLI tools and polyglot applications, simple export method for Java version management, JavaFX on mobile is challenging but viable with Gluon, EJBs and some Java EE concepts are outdated, but interceptors and dependency injection are still relevant"

...is ready to watch:

See you every first Monday of the month at https://airhacks.tv 8pm CET (UTC+1:00). Show is also announced at: meetup.com/airhacks.

Any questions left? Ask now: gist.github.com/AdamBien/26939d9a232bd0c3b79fd6149bc0815b

1. performance: abstract class vs. interface Hi, I got an interview question as to which one is faster Abstract class or Interface ? Can you explain please. What is Faster: String.join or Collectors.joining?
2. DB connections and lambda shutdown
3. performance measurement with or without JMH: "PLEASE use the microbenchmark harness in future videos. I have the impression, that this suggests that performance measurements with after-minus-before is a good idea." from: What is Faster: String.join or Collectors.joining?
4. the 100-episodes back time machine. Questions from: 27th airhacks.tv:

   "Interceptors and Dependency Injection Singleton EJBs, CDI and concurrency BCE in Eclipse and can Boundary communicate with Entity? Stateful EJBs vs. SessionScoped"

Any questions left? Ask now: https://gist.github.com/AdamBien/0e1193cd4697658cd226e4c370bec94d and get the answers at the next airhacks.tv. Some questions are also answered with a short video: 60 seconds or less with Java

Ask questions during the show via twitter mentioning me: https://twitter.com/AdamBien (@AdamBien),using the hashtag: #airhacks or built-in chat at: airhacks.tv. You can join the Q&A session live each first Monday of month, 8 P.M at airhacks.tv

"JSON validation using JSONPath and custom validators, running Jakarta EE apps on OpenShift, comparing JBoss EAP and Quarkus applications, cross-platform GUI development options, constructor injection vs field injection debate, integrating Microprofile with Java 21, rebuilding blog engine with Quarkus and Microprofile, JSON vs DTOs, Lombok vs plain Java Record Classes, Jakarta EE, MicroProfile vs plain Java 21"

...is ready to watch:

See you every first Monday of the month at https://airhacks.tv 8pm CET (UTC+1:00). Show is also announced at: meetup.com/airhacks.

Are you nice? :-) Then checkout: the airhacks discord server

Any questions left? Ask now: gist.github.com/AdamBien/95544fc7692e0ce518ffb17573507443and get the answers at the next airhacks.tv. Some questions are also answered with a short video: 60 seconds or less with Java

Any questions left? Ask now: gist.github.com/AdamBien/edbfe339f2f1fbc7e5e2b219d51d5735 and get the answers at the next airhacks.tv. Some questions are also answered with a short video: 60 seconds or less with Java

Ask questions during the show via twitter mentioning me: https://twitter.com/AdamBien (@AdamBien),using the hashtag: #airhacks or built-in chat at: airhacks.tv. You can join the Q&A session live each first Monday of month, 8 P.M at airhacks.tv

1. How to deal with EJB passivation in CDI
2. How to deal with EJB pooling in CDI
3. Migration from CMP Entities to recent Jakarta EE / MicroProfile
4. GeeCON session "Containerless, Bloatless, YAML-less, Serverless Java #slideless" questions

   Why is Kubernetes recommended in private dc but not in public cloud? Why one should not mvn clean? Can you show what is actually inside function.zip file? Why maven not gradle? Is it a good idea to building lambda as a quarkus native image? As the bucket's name is generated, would the bucket be recreated after every deploy of the lambda? What vscode plugins are you using for this kind of development in Java? How to manage multiple environments in this setup ( staging | prod ) How to share s3 information with another project for example lambda? How are you versioning and deploying the app for green/blue deployments to run two versions at a time?

5. Time machine / questions from 24th airhacks.tv:

   Is Java EE Dying? Cross-component business transactions and BCE Webjars?! Content negotiation Concurrency, SLSB and throttling Runtime pluggability and Java EE, CDI, OSGi Groovy-based DSL for configurability? Caches in crippled network environments DAOs, Entities, CRUD and duplication CDI in EAR Portlets vs. Single Page apps Annotation-based configuration Managing common data with REST (aka microservices) Streams vs. old collections How to deal with abstract classes in BCE?

Any questions left? Ask now: https://gist.github.com/AdamBien/463d60f4fa37489120df7816d74ff3b3 and get the answers at the next airhacks.tv. Some questions are also answered with a short video: 60 seconds or less with Java

Ask questions during the show via twitter mentioning me: https://twitter.com/AdamBien (@AdamBien),using the hashtag: #airhacks or built-in chat at: airhacks.tv. You can join the Q&A session live each first Monday of month, 8 P.M at airhacks.tv

I used the following template in this talk as base for the examples: aws-functionurl-cdk-only. However, most of my real-world projects rely on the: aws-quarkus-lambda-cdk-plain project.

The abstract:

Serverless is the least complex, most secure, cost-effective (or even free) architecture for most enterprise applications and is compatible with the "Green IT" premises. In this session, I will explain the inner workings of a serverless application from a code perspective with IaC provisioning with Java, real-world MicroProfile code, and live deployments. I will answer your questions in real-time.

1. Conferences attended: jCon and GeekOn
2. Time machine show reviewing questions from 2016
3. Upcoming courses on serverless NoSQL with Java and using LLMs in enterprise
4. Interesting podcast episodes on Kotlin, LLM integration with Java, and JVector database
5. Various ways for AWS Lambda functions to communicate with each other and external services [from: https://discord.gg/airhacks]
6. llama2.java--Llama 2 in With One Pure Java 21 File [video: https://youtu.be/71t5vjSbfsI]

Any questions left? Ask now: https://gist.github.com/AdamBien/0909ac2cbae6781b868d3e1c00ac4e4c and get the answers at the next airhacks.tv. Some questions are also answered with a short video: 60 seconds or less with Java

Ask questions during the show via twitter mentioning me: https://twitter.com/AdamBien (@AdamBien),using the hashtag: #airhacks or built-in chat at: airhacks.tv. You can join the Q&A session live each first Monday of month, 8 P.M at airhacks.tv

1. History of airhacks.tv and airhacks.com workshops
2. Migrating JAX-RS to serverless using Quarkus: Quarkus translates JSON HTTP events to JAX-RS invocations
3. Difference between Quarkus and Micronaut: Build-time deployment and extensions in Quarkus
4. Using Lambda for load balancing in front of backend cloud services
5. Java performance and energy efficiency compared to other languages based on a study
6. Parallel streams and CompletableFuture for optimizing access to DynamoDB and S3
7. Purpose of Serializable marker interface in Java
8. Using Epsilon GC (no-op garbage collector) in Java for serverless
9. Comparing Java EE and Spring performance from 8 years ago

See you every first Monday of the month at https://airhacks.tv 8pm CET (UTC+1:00). Show is also announced at: meetup.com/airhacks.

Are you nice? :-) Then checkout: the airhacks discord server

1. Serverless: Quarkus vs. plain Java [from: https://discord.gg/airhacks]
2. Serverless: Java vs. Python [from: https://discord.gg/airhacks]
3. Lambda as Load Balancer?
4. Parallel execution without reactive frameworks
5. The purpose of Serializable interface
6. How to learn Quarkus [video: https://youtu.be/H7O7mIJCLFY]

Any questions left? Ask now: https://gist.github.com/AdamBien/39f104488136a52d16221a310f4581d1 and get the answers at the next airhacks.tv. Some questions are also answered with a short video: 60 seconds or less with Java

Ask questions during the show via twitter mentioning me: https://twitter.com/AdamBien (@AdamBien),using the hashtag: #airhacks or built-in chat at: airhacks.tv. You can join the Q&A session live each first Monday of month, 8 P.M at airhacks.tv

You can switch to Java 8 by running j8 in your terminal. (Quickly switching to Java 8 is especially useful for code archealogists and historians.)

A Maven configuration for a simple Java SE project is twice as long.

Also checkout the airhacks.fm podcast: "No Dependencies--Or How Rife 2 and Bld Happened"

bld is a pure Java build tool that uses Java as the configuration:

Also checkout the airhacks.fm podcast episode: "No Dependencies--Or How Rife 2 and Bld Happened" with Geert Bevin, the creator of bld.

1. > 500 Java Shorts: youtube.com/bienadam/shorts
2. How to System Test Jakarta EE / MicroProfile applications?
3. Applets, WASM, and PWAs
4. How far you can get without big frameworks
5. ...only Java 22 can do that

Any questions left? Ask now: https://gist.github.com/AdamBien/c5193c88f02250bba0b2995b567228c7 and get the answers at the next airhacks.tv. Some questions are also answered with a short video: 60 seconds or less with Java

Ask questions during the show via twitter mentioning me: https://twitter.com/AdamBien (@AdamBien),using the hashtag: #airhacks or built-in chat at: airhacks.tv. You can join the Q&A session live each first Monday of month, 8 P.M at airhacks.tv

1. Why do you waste your time/energy by using Vscode instead of IntelliJ IDEA?
2. Is Java EE falling out of favour?
3. Real World Java EE Patterns-Rethinking Best Practices in 2024
4. Thoughts about the Kubernetes "engine"
5. How far you can get without big frameworks in professional Java Enterprise?
6. Time machine (Nov 03, 2015):
   1. How do you compare OOP with Functional programming and increasing trend with Functional ?
   2. Database access in a SaaS-Environment (JavaEE). One database per user. Best way to add dynamically database conf/connections for new users?
   3. Recommendations to ensure the high-performance & high-availability in Java EE applications?
   4. SOAP and duplicated namespaces after server upgrade
   5. REST with proxies and JSON over DTOs
   6. A beginners guide to application servers
   7. How to separate Control from Boundary on a real world example
   8. How I use Maven release plugin and possible strategies
   9. SessionId mechanism between a WebApp and JavaScript client
   10. How to kickstart Hazelcast in Java EE
   11. My view on OOP and trending functional languages. From JavaOne Airhacks BoF
   12. Database access in a SaaS-Environment (JavaEE). One database per user. Best way to add dynamically database conf/connections for new users? JavaOne Airhacks BoF
   13. Mixing Primefaces with various JavaScript frameworks. From Effective Java EE comment

Ask questions during the show via twitter mentioning me: https://twitter.com/AdamBien (@AdamBien),using the hashtag: #airhacks or built-in chat at: airhacks.tv. You can join the Q&A session live each first Monday of month, 8 P.M at airhacks.tv

Any questions left? Ask now: https://gist.github.com/AdamBien/fbf7291d3af942be1c92f163564d0e9c and get the answers at the next airhacks.tv. Some questions are also answered with a short video: 60 seconds or less with Java

1. Authentication with Quarkus using OpenID Connect
2. The complexity of OpenID Connect
3. Proposing new Java features
4. Comparing Quarkus with Open Liberty and Helidon
5. WASM and Java isolation techniques
6. Running Java programs as Windows services
7. Persisting data with Eclipse Microstream
8. Microstream vs. relational databases
9. Tools for generating architecture diagrams
10. Clustering, Consistency and Scalability
11. Managing secrets on AWS
12. Events routing vs data streaming on AWS

Discussed technologies:

Quarkus, Open Liberty, Helidon, Eclipse MicroProfile, Tanuki, OpenID Connect, OAuth, AWS CodeArtifact, AWS EventBridge, AWS Kinesis, HashiCorp Vault, DynamoDB, S3, Postgres, Keycloak, Cognito, Microstream, Eclipse Store, DrawIO, MagicDraw, PlantUML, yUML, Lucidcharts

Any questions left? Ask now: gist.github.com/AdamBien/fbf7291d3af942be1c92f163564d0e9c and get the answers at the next airhacks.tv. Some questions are also answered with a short video: 60 seconds or less with Java

See you every first Monday of the month at https://airhacks.tv 8pm CET (UTC+1:00). Show is also announced at: meetup.com/airhacks.

Are you nice? :-) Then checkout: the airhacks discord server

1. WASM vs. Java restrictions and isolation
2. Java as Windows Service
3. How to propose new Java features
4. How to draw architectural diagrams--the uncanny valley
5. How to deal with secrets in the cloud (...People tend to feel comfortable with some cloud provided vault that gives you environment variables that I believe is quite promiscuous as anybody can issue an env command and see them all...) from: discord.gg/airhacks
6. The time machine: relevant questions from the 19th airhacks.tv (2015):

   Practices for securing 3rd-party API credentials, Is it really needed for a professional java developer to read a whole book on IDE? Or a beginner to spend so much time to understand an IDE rather than focusing on the language?, Can be something 6.4x more productive than Java EE?, How to implement authentication in Java EE applications?, ResourceBundle injection in Java EE, What are JavaBeans, Enterprise JavaBeans, ManagedBeans and BackingBeans?, Staging Java EE applications with docker, Pros and Cons of EJBs and clustering, Encapsulation violation: with or without DTOs, Thoughts on TDD

Ask questions during the show via twitter mentioning me: https://twitter.com/AdamBien (@AdamBien),using the hashtag: #airhacks or built-in chat at: airhacks.tv. You can join the Q&A session live each first Monday of month, 8 P.M at airhacks.tv

Any questions left? Ask now: gist.github.com/AdamBien/fe338c0d125676255c5cfc4f0dc5dea8 and get the answers at the next airhacks.tv. Some questions are also answered with a short video: 60 seconds or less with Java

1. Is Java good for game development?
2. Thoughts on Optional
3. Paper Engine vs. Spigot
4. Time Machine: 100 episodes back:

   How to replace the Java EE Principal?,NPE issue in afterburner.fx?,Java EE in a movie streaming startup?,What is InjectionPoint and Produces?,Opinion about dukescript.com,MVC vs. ECB, data model vs. view model and what is a component?,How to build your custom server?,Pros and Cons of ESBs and the relation to Java EE,Does Java FX follow the Passive View MVP Pattern?,Java Mission Control and webapps trouble shooting,EJB vs. CDI,Exposing public and private JAX-RS APIs,Reactive programming and Java EE,Microservice integration with or without a Service Bus

5. Thoughts on JSF, JSPs and Java

Ask questions during the show via twitter mentioning me: https://twitter.com/AdamBien (@AdamBien),using the hashtag: #airhacks or built-in chat at: airhacks.tv. You can join the Q&A session live each first Monday of month, 8 P.M at airhacks.tv

Any questions left? Ask now: gist.github.com/AdamBien/732d40904a07286deeb2e90e6df9014c and get the answers at the next airhacks.tv. Some questions are also answered with a short video: 60 seconds or less with Java

1. Java monoliths as Lambda
2. Cost Driven Architectures challenges
3. Hypermedia Systems
4. Java Template Engine
5. Lambda Snapstart Experiences
6. Per user Locale scope and CDI
7. Service service = new ServiceImpl()
8. Time travelling or the 17th airhacks.tv: 50 MB WARs, Kafka, threading and akka

Ask questions during the show via twitter mentioning me: https://twitter.com/AdamBien (@AdamBien),using the hashtag: #airhacks or built-in chat at: airhacks.tv. You can join the Q&A session live each first Monday of month, 8 P.M at airhacks.tv

Any questions left? Ask now: gist.github.com/AdamBien/24c8c38937cfa43c25676076c231896c and get the answers at the next airhacks.tv. Some questions are also answered with a short video: 60 seconds or less with Java

1. conference news and updates
2. Quarkus and CraC (from: https://discord.gg/airhacks by jarry_dk)
3. Machine to Machine authentication on AWS
4. Access to external resources to AWS
5. Documentation with antora
6. Time machine: "JavaScript and MVVM, cross concern and technical BCE, DTOs and REST, unit testing servers, service to service testing, sending messages to a phone,"

Ask questions during the show via twitter mentioning me: https://twitter.com/AdamBien (@AdamBien),using the hashtag: #airhacks or built-in chat at: airhacks.tv. You can join the Q&A session live each first Monday of month, 8 P.M at airhacks.tv

Any questions left? Ask now: gist.github.com/AdamBien/31e84638e4a97a3ebb4074dc3b8118bb and get the answers at the next airhacks.tv. Some questions are also answered with a short video: 60 seconds or less with Java

See you every first Monday of the month at https://airhacks.tv 8pm CET (UTC+1:00). Show is also announced at: meetup.com/airhacks.

Are you nice? :-) Then checkout: the airhacks discord server

"Is it possible to migrate Java EE / J2EE monoliths ...to AWS Lambda? How to package an AWS Lambda application efficiently? Relying on Java's superpower: how to reuse IaC / CDK constructs with Java? How to create a self-provisioned serverless application with Java? What is the granularity of a function? What is the difference between a function and a microservice? Are synchronous functions an anti-pattern? How to efficiently structure Java applications' business and IaC code. I will discuss "working" practices and patterns with code and live deployments in this code-focused session. Attendees' questions are highly appreciated!"

...as always the abstract was just a suggestion and I also enjoyed the questions and discussions before (we had a short pre-show :-)), during and after the talk.

The talk was recorded and is available on:

All examples were based on: https://github.com/AdamBien/aws-quarkus-lambda-cdk-plain

1. The airhacks.tv time travelling: 15th airhacks.tv (8 years ago)
2. A standard Money and Currency implementation
3. Authorization and authentication with Jakarta EE and Microprofile
4. Virtual Threads and JPA
5. Java Formatters
6. Jakarta Data and BCE
7. PostgreSQL with AWS Lambdas
8. Composite keys and REST API
9. UUIDs vs. ULIDs
10. DocumentDB vs. DynamoDB vs. AuroraV2
11. SQS vs. SNS vs. Kinesis vs. EventBridge

Ask questions during the show via twitter mentioning me: https://twitter.com/AdamBien (@AdamBien),using the hashtag: #airhacks or built-in chat at: airhacks.tv. You can join the Q&A session live each first Monday of month, 8 P.M at airhacks.tv

Any questions left? Ask now: https://gist.github.com/AdamBien/132643f891e116fe0d0e0722f63fb7d5 and get the answers at the next airhacks.tv. Some questions are also answered with a short video: 60 seconds or less with Java

1. Implementing Sockets and Java
2. What does your test stack look like on AWS?
3. Does it make any difference cloud vs. on premises?
4. What are you using for load testing?
5. What are you using for end-to-end tests where you simulate users/clients?
6. Do you have experience with Grafana k6 and if yes, what is your experience?
7. And where do you run client simulators, on AWS EC2 instances or on a runner/agent in your pipeline?
8. What is your strategy for setting up test data for end-to-end tests?
9. How do you reset data before you run next test for end-to-end tests? Would you recommend creating VM snapshots and how to do that?
10. Best way to integrate a non xa resource into container managed transactions of stateless EJBs (wildfly)
11. CI/CD on AWS example
12. Experiences with trunk based development
13. Handling persistence (JPA) exceptions
14. RequestScope, long running transactions and JWT

Any questions left? Ask now: https://gist.github.com/AdamBien/0088a3d6964ebdae9b59693400747106 and get the answers at the next airhacks.tv. Some questions are also answered with a short video: 60 seconds or less with Java

See you every first Monday of the month at https://airhacks.tv 8pm CET (UTC+1:00). Show is also announced at: meetup.com/airhacks.

Are you nice? :-) Then checkout: the airhacks discord server

1. What are you using for modularization of your monolithic Java backend? by @kriehzoo
2. What is your experience with project jigsaw, do you use it for your projects? by @kriehzoo
3. Real world BCE article
4. Kogito vs. Camunda by @dempile
5. Minio integration ideas by @dempile
6. "time travelling / episode 13: JPA and schema evolution, multi tenancy, deltaspike, picketlink, JSR-375, onion architecture, RPC communication, zero downtime, JDBC configuration, singleton JPA Entity"

Any questions left? Ask now: gist.github.com/AdamBien/d6c474fe8869b2c278ab6dbd4d03afaf and get the answers at the next airhacks.tv. Some questions are also answered with a short video: 60 seconds or less with Java

See you every first Monday of the month at https://airhacks.tv 8pm CET (UTC+1:00). Show is also announced at: meetup.com/airhacks.

Are you nice? :-) Then checkout: the airhacks discord server

Ten years later, in 2022, I was invited again and delivered a session with the title "Java EE 6 and the Future Is Now, and now we got.. clouds", in which I discussed a migration path to a serverless architecture:

During the talk, I didn't managed to migrate the application to modern Java and clouds, but promised to record a screencast, which is also available:

"Microservices vs. Monoliths, Schedulers, Lightweight vs. Heavyweight, Time Derived Properties, Groovy, JavaScript":

...is ready to watch:

See you every first Monday of the month at https://airhacks.tv 8pm CET (UTC+1:00). Show is also announced at: meetup.com/airhacks.

Are you nice? :-) Then checkout: the airhacks discord server

Any questions left? Ask now: gist.github.com/AdamBien/62791e98ed40d1d2b13801e3e717a949 and get the answers at the next airhacks.tv. Some questions are also answered with a short video: 60 seconds or less with Java

1. Microservices vs. Monoliths
2. Best way to schedule a repeated task in an application scoped cdi bean
3. Airhacks Time Machine
4. The Airhacks Time Machine:

   Microservices and Java EE, Lightweight vs. Heavyweight, OSGi, time derived properties, JRebel, security between microservices, debug docker apps, batch processing, Groovy, JavaScript, Java, websockets and scalability, seceond level cache.

Any questions left? Ask now: gist.github.com/AdamBien/a97ce552e3f784721dda8054ab1871f2 and get the answers at the next airhacks.tv. Some questions are also answered with a short video: 60 seconds or less with Java

See you every first Monday of the month at https://airhacks.tv 8pm CET (UTC+1:00). Show is also announced at: meetup.com/airhacks.

Also checkout: the airhacks discord server

See you at these upcoming conferences and workshops:

1. Code Europe Conference: Dissecting Serverless Java on AWS
   conference session Code Europe Conference Cracow 23 May 2023
   https://www.codeeurope.pl/en/agenda
2. InfoShare: The Java Shorts Animation Show: 100 Snippets in 40 Minutes
   conference session InfoShare Gdansk 24 May 2023
   https://infoshare.pl
3. Code Europe Conference: Keynote: Dissecting Serverless Java on AWS
   keynote conference session Code Europe Conference Warsaw 25 May 2023
   https://www.codeeurope.pl/en/agenda
4. InfoShare: The Future of Java in the Cloud and on Premises
   conference session InfoShare Gdansk 25 May 2023
   https://infoshare.pl
5. online: AWS Java Bootstrap [online event]
   airhacks.live workshops 15 Jun 2023
   https://workshops.adam-bien.com/aws-java-bootstrap.htm
6. Jcon Europe: "Serverless" Is What J2EE Was Meant To Be
   conference session Jcon Europe Cologne 20 Jun 2023
   https://2023.europe.jcon.one
7. online: Cost Driven Architectures with Java on AWS [online event]
   airhacks.live workshops 22 Jun 2023
   https://workshops.adam-bien.com/aws-cost-driven-architectures.htm

1. Follow up: my interview questions
2. Programmatic and portable JAX-RS endpoint registration
3. Time machine, the 10th episode: "Java EE Favourites, SPA technologies, complex JSON strategies, CDI scope management"
4. Are shared deployments back?
5. Are there any reason for reactive programming left?
6. About OpenJ9 JVM, or which JDK to pick
7. Jakarta gRPC, Google gRPC
8. Do application servers make sense?
9. Thoughts on Ansible deployments
10. Thoughts on 12 factors and cloud native

Any questions left? Ask now: gist.github.com/AdamBien/6147ea9d4d354b5cae3cb3726b1db0de and get the answers at the next airhacks.tv. Some questions are also answered with a short video: 60 seconds or less with Java

See you every first Monday of the month at https://airhacks.tv 8pm CET (UTC+1:00). Show is also announced at: meetup.com/airhacks.

Are you nice? :-) Then checkout: the airhacks discord server

1. Test Driven Development
2. Maven vs. Gradle
3. Serverless Enterprise Java

Time machine 100 episodes ago 8th airhacks.tv episode: 31st, October, 2014

resilience and discovery, OData vs. JSON, Lazy OneToMany and JAX-RS serialization problems, simple reporting solutions, API Gateways and Java EE, centralized API management solutions, enum serialization options, row-level authorization and Java EE

batch processing over ejb scheduler, access to user-specific database for caller/user?, you can deploy Spring on any container, managing deployed microservices (status, healthchecks, restarting), local and production Docker setup, JSF and JavaScript frameworks, javax.persistence.OptimisticLockException recovery automation, session storage and Jakarta EE

Any questions left? Ask now: https://gist.github.com/AdamBien/ab8b773336a30dd543af03b62c4a2a0d and get the answers at the next airhacks.tv. Some questions are also answered with a short video: 60 seconds or less with Java

See you every first Monday of the month at https://airhacks.tv 8pm CET (UTC+1:00). Show is also announced at: meetup.com/airhacks.

Are you nice? :-) Then checkout: the airhacks discord server

In Java naming is not hard, you can conveniently name everything var:

class Var {
    String var;
    
    public Var() {
        this.var = "duke is varvar!";
    }
    
    record VAR(Var var){
        public String getVar(){
        return this.var.var;
        }
    }
    
    public static void main(String... args) {
        var var = new VAR(new Var());
        System.out.println(var.getVar());
    }
}

Events are also announced at meetup.com/airhacks/ and discord.gg/airhacks

"Flutter / Dart opinions, splitting read / writes, Leaving Clouds, Http Client, Liskov Principle, JAX-RS Response and AutoCloseable, monolithic AWS Lambda limitations, Update Strategies and Quarkus":

...is ready to watch:

See you every first Monday of the month at https://airhacks.tv 8pm CET (UTC+1:00). Show is also announced at: meetup.com/airhacks.

Are you nice? :-) Then checkout: the airhacks discord server

Any questions left? Ask now: gist.github.com/AdamBien/ab8b773336a30dd543af03b62c4a2a0d and get the answers at the next airhacks.tv. Some questions are also answered with a short video: 60 seconds or less with Java: youtube.com/@bienadam/shorts

1. LTS clarifications: There seems to be a widespread misconception that only LTS releases are suitable for production. That non-LTS releases are experimental, unstable, or otherwise unsuitable. [from discord.gg/airhacks]
2. Dart / Flutter opinions
3. Leaving clouds? Thoughts on article: world.hey.com/dhh/why-we-re-leaving-the-cloud-654b47e0
4. HttpClient and Response as JSON
5. What is "Liskov substitution principle"
6. Why JAX-RS Response is AutoCloseable?
7. The name of the current method
8. Update strategies and Quarkus

Any questions left? Ask now: gist.github.com/AdamBien/3eba2c0cee3c6e2722cd6c3d440d9bef and get the answers at the next airhacks.tv. Some questions are also answered with a short video: 60 seconds

See you every first Monday of the month at https://airhacks.tv 8pm CET (UTC+1:00). Show is also announced at: meetup.com/airhacks.

Are you nice? :-) Then checkout: the airhacks discord server

In this CJUG session, I will create a Java service from scratch, run and test it locally, in container environments, and as AWS Lambda. Same code base, minimal code, no YAML, and the same APIs on different runtimes. I will focus on structure, maintainability, and the "no-dependencies" approach. Your questions are highly appreciated, and I will answer them in real time.

...is available:

"Java is fast, productive, comes with excellent tooling, and runs well on next-generation cloud-native runtimes. I would like to discuss unconventional and pragmatic serverless Java architectures with lots of code, live deployments, and measurements in this interactive session. Your questions are, as always, highly welcome and will be answered in real-time."

...is available:

"Dead OneToMany, Docker, Thin-, Fat-, Jars, Hot Redeployment and the clouds, Strategies for Multi Tenancy, Horizontal vs. Deep Learning, what is cloud native?, cloud vs. on--premise architectures":

...is ready to watch:

See you every first Monday of the month at https://airhacks.tv 8pm CET (UTC+1:00). Show is also announced at: meetup.com/airhacks.

Are you nice? :-) Then checkout: the airhacks discord server

Any questions left? Ask now: gist.github.com/AdamBien/3eba2c0cee3c6e2722cd6c3d440d9bef and get the answers at the next airhacks.tv. Some questions are also answered with a short video: 60 seconds with Java

1. Time travel: topics from 100 episodes back (October 2014): SessionScoped, Stateful, RequestScoped, avoiding OneToMany JPA, stateless session beans
2. Thoughts on docker, layered images, Thin Jars, Fat Jars, Jakarta EE server
3. Challenges and strategies for application hot redeployment
4. Strategies for multi tenant applications
5. Thoughts on learning: horizontal knowledge vs. deep dive

Any questions left? Ask now: gist.github.com/AdamBien/d5e03decb40c390ff44c1a41de52657c and get the answers at the next airhacks.tv. Some questions are also answered with a short video: 60 seconds

See you every first Monday of the month at https://airhacks.tv 8pm CET (UTC+1:00). Show is also announced at: meetup.com/airhacks.

Are you nice? :-) Then checkout: the airhacks discord server

import javax.enterprise.concurrent.ManagedExecutorService;
public class EventSource {

    
    @Resource
    ManagedExecutorService threadPool;
(...)
}

In pure MicroProfile environments these API is not available but can be replaced with ManagedExecutor from MicroProfile Context Propagation:

import org.eclipse.microprofile.context.ManagedExecutor;
public class EventSource {

    @Inject
    ManagedExecutor executor;
}

Both injected instances are inheriting from ExecutorService. Migration from javax.enterprise.concurrent.ManagedExecutorService to org.eclipse.microprofile.context.ManagedExecutor should be matter of replacing @Resource with @Inject, renaming the injected classes and fixing the imports.

"Lambda Extensions, token cache with DynamoDB, Java EE vs. PlayFramework popularity, Kotlin, Rust, Optional use cases, Java Modules":

...is ready to watch:

See you every first Monday of the month at https://airhacks.tv 8pm CET (UTC+1:00). Show is also announced at: meetup.com/airhacks.

Some questions are also answered with a short video: one minute with...

News: the airhacks discord server is available: https://discord.gg/BpMGmxvRDb

1. Time travel: 100 episodes ago: Play Framework vs. Java EE, reading a network file, ID generation, stateful calculations, JSF and Bootstrap, structuring huge applications, mixing storage and transfer concerns (...)
2. 2022 observations
3. Strategies for updating tokens of AWS Lambda's
4. the state of airhacks industries :-)

See you every first Monday of the month at https://airhacks.tv 8pm CET (UTC+1:00). Show is also announced at: meetup.com/airhacks.

Any questions left? Ask now: gist.github.com/AdamBien/d60f7b91dc0e897915c083de35edef72 and get the answers at the next airhacks.tv.

Some questions are also answered with a short (video): one minute with... on www.youtube.com/bienadam

"CraC, SnapStart, AWS Lambda, structuring micro services, REST or not, Change Data Capture in the clouds, CraC vs. GraalVM, managing certificates, monolithic lambda deployments, asynchronous lambdas packaging":

...is ready to watch:

See you every first Monday of the month at https://airhacks.tv 8pm CET (UTC+1:00). Show is also announced at: meetup.com/airhacks.

Some questions are also answered with a short video: one minute with...

1. 100 episodes ago: stateful microservices, BCE design, how to learn Java, .NET vs. Java EE, REST, Layers, micro services, GoF and Java EE (...)
2. CraC / SnapStart and Monolithic Lambdas
3. Opinion: the state of Java documentation
4. AWS Lambda and REST Endpoints
5. Non AWS Endpoints
6. Packaging serverless applications

See you every first Monday of the month at https://airhacks.tv 8pm CET (UTC+1:00). Show is also announced at: meetup.com/airhacks.

Any questions left? Ask now: gist.github.com/AdamBien/dc9b58e2c5e4a3232cb8df8fa8ba7fc7 and get the answers at the next airhacks.tv.

Some questions are also answered with a short video: one minute with...

SnapStart / CraC was also covered at the: airhacks.fm podcast episode with the title: "Java, CraC and Reducing Cold Start Duration with AWS Lambda SnapStart"

Clustered annotation corrections, blocking lambdas, quarkus, resteasy vs. jersey, modern Java challenges, off-heap memory, boundary control entity structure, AWS SDKs

...is ready to watch:

See you every first Monday of the month at https://airhacks.tv 8pm CET (UTC+1:00). Show is also announced at: meetup.com/airhacks.

Any questions left? Ask now: https://gist.github.com/AdamBien/dc9b58e2c5e4a3232cb8df8fa8ba7fc7 and get the answers at the next airhacks.tv.

Some questions are also answered with a short video: one minute with...]]> https://adambien.blog/roller/abien/entry/blocking_lambdas_off_heap_memory Thu, 10 Nov 2022 03:33:04 +0000 https://adambien.blog/roller/abien/entry/blocking_lambdas_off_heap_memory I took Java 6 / Java EE 6 sample / GlassFish application created live at the JDD 2012 conference (Java EE: Future Is Now, But It Is Not Evenly Distributed Yet) and migrated it to MicroProfile and deployed as AWS Lambda (in 18 mins):

1. airhacks.tv time machine. Reviewing content from 100 episodes ago: exposed DB objects, vanilla Java EE, shared classes, BCE and *Resources, uploading large files, maven lifecycle hooks (...)
2. What if a lambda needs to call an external api, I.e. Wait for a reply?
3. I'm moving from Payara to Quarkus but I can't make sense of the CXF plugin for Quarkus(...)
4. Would you include a dependency to your project even if you only need a small portion of functionality or dev/copy this single function on your own?
5. Java Releases now seem to have the tend to add more and more syntax sugars to the language (modules, var, records,…). Whats your opinion on that? Will it help the language to grow or does it make it more unaccessible for inexperienced developers?
6. Recent Java additions (Off-Heap-Memory, SIMD) seem to offer a memory mgmt. outside of the GC or a vendor specific instruction set. Given those new possibilities in Java do you think it will introduce new complexity for JDK/GC developers to introduce improvements since those features are outside the range of a managed environment?
7. Do you use the AWS SDK clients, models etc. when you want to access AWS services like S3, DynamoDB etc? If not, how do you create the requests (JASON) and how do you do the authentication?
8. announcement: "for short questions - you don't have to wait a month"

See you every first Monday of the month at https://airhacks.tv 8pm CET (UTC+1:00). Show is also announced at: meetup.com/airhacks.

Any questions left? Ask now: gist.github.com/AdamBien/ad7ced219e3f9224866de30a6bbb347d and get the answers at the next airhacks.tv.

"In this webinar, Adam Bien (@AdamBien) will give you insight on approaches to create, structure, build, test, and survive serverside Java projects. He will set up a few Java SE, Quarkus, Jakarta EE, and MicroProfile projects "from scratch," explain the principles with (hopefully) working code and answer your questions in real-time."

Clustered, Distributed Events, System.out.println for logging, NoSQL mapping strategies, BCE, Jakarta EE vs. Quarkus, long running processes with Lambda, caching in Lambda, VSC vs. IntelliJ

...is ready to watch:

See you every first Monday of the month at https://airhacks.tv 8pm CET (UTC+1:00). Show is also announced at: meetup.com/airhacks.

Any questions left? Ask now: https://gist.github.com/AdamBien/ad7ced219e3f9224866de30a6bbb347d and get the answers at the next airhacks.tv.

Some questions are also answered with a short video: one minute with...

1. airhacks.tv time machine. Reviewing content from 100 episodes ago: cross-cutting concerns, horizontal vs. vertical splitting, mockito, configuration (...)
2. @Clustered vs. Hazelcast and distributed events
3. data in NoSQL storage
4. Quarkus vs. Jakarta EE
5. System.out.println vs. logging
6. BCE pattern and builders
7. Is System.out.println too complex and verbose?
8. announcement: "for short questions - you don't have to wait a month"

See you every first Monday of the month at https://airhacks.tv 8pm CET (UTC+1:00). Show is also announced at: meetup.com/airhacks.

Any questions left? Ask now: gist.github.com/AdamBien/877ce9c05f8eaeaf1dda2ba2df7eddd0 and get the answers at the next airhacks.tv.

Launching the web server in verbose mode with: jwebserver -o verbose, outputs the incoming headers after executing: curl http://localhost:8000:

> Accept: */*
> Host: localhost:8000
> User-agent: curl/7.79.1

The following Java HttpClient:

import java.net.http.HttpResponse.BodyHandlers;
import java.net.http.*;

var client = HttpClient.newHttpClient();
var request = HttpRequest.newBuilder(URI.create("http://localhost:8000"))
                .GET()
                .build();
var response = client.send(request,BodyHandlers.ofString())

generates these headers:

> Connection: Upgrade, HTTP2-Settings
> Http2-settings: AAEAAEAAAAIAAAABAAMAAABkAAQBAAAAAAUAAEAA
> Host: localhost:8000
> User-agent: Java-http-client/19
> Upgrade: h2c

See it in action and in less than 1 min:

Abstract:

"Serverless Java applications are stateless and store their data in a range of cloud persistence stores, from relational databases, like Aurora, over file-based block storage like S3 to persistent event stores like Kinesis.

In this keynote, I will focus on the characteristics and challenges of serverless Lambda and Fargate Java application's data access layer and discuss the impact on authentication, authorization, connection handling or scalability, data mapping, portability, and costs. Your questions are highly welcome!"

import static org.junit.jupiter.api.Assertions.assertNotNull;
import javax.inject.Inject;
import org.eclipse.microprofile.rest.client.inject.RestClient;
import org.junit.jupiter.api.Test;
import io.quarkus.test.junit.QuarkusTest;

@QuarkusTest
public class AutocloseableResponseIT {

    @Inject
    @RestClient
    WebsiteClient client;

    @Test
    void closeExplicitly(){
        var response = this.client.getContent();
        var content = response.readEntity(String.class);
        response.close();
        assertNotNull(content);
    }

    @Test
    void autoClose(){
        try(var response = this.client.getContent()){
            var content = response.readEntity(String.class);
            assertNotNull(content);
        }
    }
}

The corresponding client (Rest Client for MicroProfile) used in this example is:

import javax.ws.rs.GET;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;

import org.eclipse.microprofile.rest.client.inject.RegisterRestClient;

@RegisterRestClient(baseUri = "http://localhost:8080")
public interface WebsiteClient {
    
    @GET
    @Produces(MediaType.TEXT_PLAIN)
    Response getContent();
}

Too many "open" Responses may lead to blocking behavior.

"J2EE, Java EE, Jakarta EE migration projects, NetBeans vs. VSC, custom Bean Validators, JPA and JSON-B data mapping, fault tolerance and retry-able transactions, HTTP/2 use cases, too long URIs"

is ready:

See you every first Monday of the month at https://airhacks.tv 8pm CET (UTC+1:00). Show is also announced at: meetup.com/airhacks.

Any questions left? Ask now: https://gist.github.com/AdamBien/877ce9c05f8eaeaf1dda2ba2df7eddd0 and get the answers at the next airhacks.tv.

1. The time machine or topics from 100 episodes ago (the 2nd airhacks.tv)
2. J2EE, Java EE and Jakarta EE upgrades
3. NetBeans and Visual Studio Code
4. The single Jakarta EE dependency
5. Installation of custom Bean Validators
6. Date conversions with JPA and JSON-B
7. The "retriable transaction" annotation
8. Use cases for http 2 server push
9. Dealing with 414 (Request-URI Too Large)

See you every first Monday of the month at https://airhacks.tv 8pm CET (UTC+1:00). Show is also announced at: meetup.com/airhacks.

Any questions left? Ask now: gist.github.com/AdamBien/49efb5c357b19ad2bdde82ea026db803 and get the answers at the next airhacks.tv.

@RegisterRestClient(baseUri = "http://localhost:8000")
public interface WebsiteClient {
    
    @GET
    @Produces(MediaType.TEXT_PLAIN)
    Response getContent();
}

...injected to Quarkus JAX-RS resource:

import javax.inject.Inject;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.core.Response;

import org.eclipse.microprofile.rest.client.inject.RestClient;

@Path("website")
public class WebsiteResource {


    @Inject
    @RestClient
    WebsiteClient firstClient;

    @Inject
    @RestClient
    WebsiteClient secondClient;

    @GET
    public String injected() {
        for (int i = 0; i < 500; i++) {
            Response firstResponse = this.firstClient.getContent();
            Response secondResponse = this.secondClient.getContent();
            System.out.println(i);
        }
        return "+";
    }    
}

will block after 50 iterations.

Reason: the exhaustion of the underlying HTTP connection pool. See stack trace:

org.apache.http.pool.AbstractConnPool.getPoolEntryBlocking(AbstractConnPool.java:393)
org.apache.http.pool.AbstractConnPool.access$300(AbstractConnPool.java:70)
org.apache.http.pool.AbstractConnPool$2.get(AbstractConnPool.java:253)
org.apache.http.pool.AbstractConnPool$2.get(AbstractConnPool.java:198)
org.apache.http.impl.conn.PoolingHttpClientConnectionManager.leaseConnection(PoolingHttpClientConnectionManager.java:306)
org.apache.http.impl.conn.PoolingHttpClientConnectionManager$1.get(PoolingHttpClientConnectionManager.java:282)
org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:190)
org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:186)
org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:89)
org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:110)
org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:185)
org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:83)
org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:56)
org.jboss.resteasy.client.jaxrs.engines.ManualClosingApacheHttpClient43Engine.invoke(ManualClosingApacheHttpClient43Engine.java:302)

The underlying resources are freed with the Response#close call, now all 500 iterations are performed without blocking:

@GET
public String injected() {
    for (int i = 0; i < 500; i++) {
        Response firstResponse = this.firstClient.getContent();
        firstResponse.close();
        Response secondResponse = this.secondClient.getContent();
        firstResponse.close();
        System.out.println(i);
    }
    return "+";
}    

The blocking behaviour depends on the JAX-RS / MicroProfile Rest Client implementation. RESTEasy requires an explicit Response#close call, Jersey does not.

import java.time.Duration;
import java.time.Instant;
import java.util.concurrent.TimeUnit;
import org.junit.jupiter.api.Test;

public class DurationToStringTest {

    void slow(){
        try {
            TimeUnit.SECONDS.sleep(1);
        } catch (InterruptedException e) {}
    }

    @Test
    public void durationToString() throws InterruptedException {
        var start = Instant.now();
        this.slow();
        var duration = Duration.between(start, Instant.now());
        var durationAsString = duration.toString();  //ISO-8601
        System.out.println(durationAsString);
    }
}

The method Duration#toString returns a combined representation of hours, minutes, seconds and fractional seconds, standardized by ISO-8601.

The above example produces the following output: PT1.001087S.

import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.assertEquals;

import java.util.List;
import jakarta.json.Json;
import jakarta.json.JsonValue;
import jakarta.json.JsonValue.ValueType;

public class PatternMatchingTest {

    JsonValue javaToJson(Object javaType){
        if (javaType instanceof String string) {
            return Json.createValue(string);
        } else if (javaType instanceof Integer integer) {
            return Json.createValue(integer);
        } else if (javaType instanceof Boolean bool) {
            return bool? JsonValue.TRUE : JsonValue.FALSE;
        }
        return Json.createValue(javaType.toString());
    }

}   

Now a List of various Java types can be converted to the corresponding JSON-P (Jakarta JSON Processing) values:

@Test
public void instanceOfWithoutCasting() {
    var mix = List.of("duke",42,true);

    assertEquals(ValueType.STRING, javaToJson(mix.get(0)).getValueType());
    assertEquals(ValueType.NUMBER, javaToJson(mix.get(1)).getValueType());
    assertEquals(ValueType.TRUE, javaToJson(mix.get(2)).getValueType());
}   

As an example, the following test converts three seconds to milliseconds:

@Test
public void secondsToMs() {
    var expected = 3 * 1000;
    var actual = TimeUnit.SECONDS.toMillis(3);
    assertEquals(expected, actual);
}

Now from milliseconds to minutes:

@Test
public void msToMinutes() {
    var expected = 3;
    var actual = TimeUnit.MILLISECONDS.toMinutes(180000);
    assertEquals(expected, actual);
}

With TimeUnit we can even wait for the next vacations:

@Test
public void sleepWithTimeUnitForThreeSeconds() throws InterruptedException {
    long start = System.currentTimeMillis();
    
    TimeUnit.SECONDS.sleep(3);
    //TimeUnit.DAYS.sleep(300); :-)

    var duration = System.currentTimeMillis() - start;
    assertTrue(duration >= 3000);
}

import javax.ws.rs.DefaultValue;
import javax.ws.rs.GET;
import javax.ws.rs.HeaderParam;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;

@Path("/hello")
public class GreetingResource {

    @GET
    @Produces(MediaType.TEXT_PLAIN)
    public String hello(@DefaultValue("james") @HeaderParam("firstName") String firstName,
                        @DefaultValue("duke") @HeaderParam("lastName") String lastName) {
        return firstName + " " + lastName;
    }
}

...is accessible via a Rest Client for MicroProfile interface with overloaded methods:

import javax.ws.rs.GET;
import javax.ws.rs.HeaderParam;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;

import org.eclipse.microprofile.rest.client.inject.RegisterRestClient;

@Path("/hello")
@Produces(MediaType.TEXT_PLAIN)
@RegisterRestClient(baseUri = "http://localhost:8080")
public interface GreetingResourceClient {

    @GET
    public String hello(@HeaderParam("firstName") String firstName, @HeaderParam("lastName") String lastName);

    @GET
    public String hello(@HeaderParam("firstName") String firstName);

    @GET
    public String hello();
    
}

Now the client can be injected and the overloaded methods conveniently called:

import static org.junit.jupiter.api.Assertions.assertEquals;

import javax.inject.Inject;

import org.eclipse.microprofile.rest.client.inject.RestClient;
import org.junit.jupiter.api.Test;

import io.quarkus.test.junit.QuarkusTest;

@QuarkusTest
public class GreetingResourceTest {

    @Inject
    @RestClient
    GreetingResourceClient client;

    @Test
    void helloWithoutParameters(){
        var hello = this.client.hello();
        assertEquals(hello, "james duke");
    }

    @Test
    void helloWithFirstName(){
        var hello = this.client.hello("john");
        assertEquals(hello, "john duke");
    }

    @Test
    void helloWithFirstNameAndLastName(){
        var hello = this.client.hello("john","dukem");
        assertEquals(hello, "john dukem");
    }  
}

import java.util.Collections;
import java.util.List;

import org.junit.jupiter.api.Test;

public class EmptyListsTest {

    //Java 9+
    @Test
    public void listOf() {
        var emptyList = List.<String>of();
        assertTrue(emptyList.isEmpty());
    }
}    

    //Java 5+
    @Test
    public void emptyList() {
        var emptyList = Collections.<String>emptyList();
        assertTrue(emptyList.isEmpty());
    }