Java

A practical guide to completing your TLS certificate chainTL;DRSpring Boot Admin showed my application as REGISTERED → OFFLINE because the server certificate I presented during the health‑check was missing the intermediate CA.Re‑exporting the keystore (PKCS #12 / JKS) with the full chain—leaf + intermediate (+ root)—cleared the error and the instance now sits happily in the UP state.The SymptomRight after deployment my Spring Boot app registered...

https://speakerdeck.com/vitalieb/efficient-logs-with-elastic-stackDemo code available at https://github.com/vitalieb/ElasticStackPresentation

IntroductionChannels are used for routing messages to endpoints.Channels do the routing and endpoints perform the operations.Spring Integration (SI) provides numerous adapters for communication between different systems.SI uses 3 types of components to construct its messaging architecture:MessageChannelEndpointEndpoint > Channel (passes a Message) > EndpointSpring Integration mirrors everything from "Enterprise Integration Patterns"; so If you're familiar with those you can easily...

Advanced class design: Anonymous classes are implicitly final and it can never be static.static method > default methoddefault method > abstract methoddefault method > default method (re-declared with different implementation)default method > static methodstatic method > non-static methodnon-static method > static methodStatic methods can never be abstract.Static interface methods must be invoked using the interface name instead of reference variable - otherwise...

I want to share with you my Spring Core Certification notes I took.Here they are:

What is Spring Boot? Spring Boot is a set of preconfigured framework that works on top of Spring Framework and simplifies configuring a Spring application. What are the advantages of using Spring Boot? Most important advantage is easy configuration of Spring application.Additional to this it provides something more:Integrated web containers that allow for easy testing Starters - sets of dependencies that help...

What does REST stand for? REST stands for REpresentational State Transfer. What is a resource? Anything that can be named is a resource. Usually that nouns that define our model. What are safe REST operations? Safe operations are operations that don't change things. These are: GET HEAD OPTIONSWhat are idempotent operations? Why is idempotency important? Idempotent operations are operations that always return the same result....

What is the delegating filter proxy? Delegating filter proxy is a servlet filter registered with the web container that delegates the requests to a Filter implementation on the Spring context side. That is there a 2 places servlet filters are attached to:Web container  Spring contextAs of Spring Security all requests pass through delegating filter proxy that is registered with the container...

Hibernate is an ORM framework that implements Java Persistence API (JPA).For Hibernate to work we need 3 things:Hibernate configuration (hibernate.properties or hibernate.cfg.xml) Mapping metadata (XML or annotation-based) - info for instructing Hibernate on how the entities have to be mapped to DB tables. Mapping metadata contains persistence unit info. Persistence unit - per database mapping configuration + some other...

What is the difference between checked and unchecked exceptions? Checked exceptions are exceptions that are checked at compile time - that fact enforces the developer to either catch it and handle or declare as being thrown and it will be propagated in call stack. Unchecked exceptions are not checked at compile time. Why do we (in Spring) prefer unchecked exceptions? Spring prefers...