For years, I chased the dream of running macOS in a virtual machine<\/strong>. Whenever I wanted to make a very small edit on my Debian laptop, crop a screenshot, add a quick arrow, or block out a small area, the system only had GIMP for editing images. Powerful, but heavy and slow for tiny, frequent tasks. I wanted something nimble: quick to open, easy to use, and focused on the common one-off edits people do dozens of times a day.<\/p>"},{"title":"GraalVM Native Image Agent - reachability metadata: how to run it, where files go","link":"https:\/\/ozkanpakdil.github.io\/posts\/my_collections\/2025\/09-16-graalvm-native-image-agent\/","pubDate":"Tue, 16 Sep 2025 00:00:00 +0000","guid":"https:\/\/ozkanpakdil.github.io\/posts\/my_collections\/2025\/09-16-graalvm-native-image-agent\/","description":"How to run the agent (generic Java) and where the metadata is used"},{"title":"The Pagination Pitfall: A React + Spring Boot Cautionary Tale","link":"https:\/\/ozkanpakdil.github.io\/posts\/my_collections\/2025\/pagination-pitfall-react-springboot\/","pubDate":"Thu, 07 Aug 2025 00:00:00 +0000","guid":"https:\/\/ozkanpakdil.github.io\/posts\/my_collections\/2025\/pagination-pitfall-react-springboot\/","description":"Why using client-side pagination for unknown data sizes in a React + Spring Boot app can backfire - and how to fix it with proper server-side pagination."},{"title":"A Retrospective on High-Traffic Systems, Garbage Collection Battles, and the Rise of G1","link":"https:\/\/ozkanpakdil.github.io\/posts\/my_collections\/2025\/2025-05-04-turkcell\/","pubDate":"Sun, 04 May 2025 00:00:30 +0000","guid":"https:\/\/ozkanpakdil.github.io\/posts\/my_collections\/2025\/2025-05-04-turkcell\/","description":" It was 2012. Turkcell, Turkey\u2019s largest mobile operator, had 15 million subscribers, and the pressure was on. As part of the operations team for www.turkcell.com.tr<\/a>, I managed a labyrinth of infrastructure: 10 strong\nlinux servers which had Weblogic installed humming behind Apache mod_weblogic proxies, serving dynamic requests while Apache handled static content. The e-commerce platform, Turkcell Shop, was my responsibility-where a\nsingle GC pause during peak traffic could mean thousands of failed transactions and angry customers.<\/p>"},{"title":"Handling Concurrent API Calls in Spring Boot","link":"https:\/\/ozkanpakdil.github.io\/posts\/my_collections\/2025\/2025-02-20-handling-concurrent-api-calls-in-spring-boot\/","pubDate":"Thu, 20 Feb 2025 00:00:30 +0000","guid":"https:\/\/ozkanpakdil.github.io\/posts\/my_collections\/2025\/2025-02-20-handling-concurrent-api-calls-in-spring-boot\/","description":" When building Spring Boot applications, handling concurrent API calls efficiently is crucial to ensure optimal performance and scalability. Here are a few approaches to manage concurrent read and write operations:<\/p>\n Using Spring WebFlux’s WebClient allows for reactive programming, making it easier to handle multiple API calls.<\/p>"},{"title":"What is load balancing and how to do it on client side","link":"https:\/\/ozkanpakdil.github.io\/posts\/my_collections\/2025\/2025-01-09-client-load-balancing\/","pubDate":"Thu, 09 Jan 2025 00:00:30 +0000","guid":"https:\/\/ozkanpakdil.github.io\/posts\/my_collections\/2025\/2025-01-09-client-load-balancing\/","description":" “Load balancing” can be explained as maintaining any workload. For example if you have to serve 1000 breakfast in the morning you can divide the work among 2-3 or more caterers to lower the delivery\/preparation time.<\/p>\n In the computer world, same logic applies, if you want to deliver fast, you can divide the work, for example for a website we can have 5-10 webserver, this way website will be delivered faster(especially during high traffic), this is server side.<\/p>"},{"title":"How to find java app hosting(ISP) or How to deploy Spring Boot website to Koyeb","link":"https:\/\/ozkanpakdil.github.io\/posts\/my_collections\/2025\/2025-01-01-deploy-spring-boot-to-cloud-koyeb\/","pubDate":"Wed, 01 Jan 2025 00:00:30 +0000","guid":"https:\/\/ozkanpakdil.github.io\/posts\/my_collections\/2025\/2025-01-01-deploy-spring-boot-to-cloud-koyeb\/","description":" Spring boot is the most famous java framework, and I have been looking for a simple way to serve a java app on a hosting service(not dedicated which is very expensive not AWS\/Azure which are too complicated), Most shared hosting does not support java apps, they support php or asp or perl here<\/a> is the table for godaddy webhosting supported tech.<\/p>\n I will explain how to deploy from dockerhub to Koyeb, or we can deploy from github repository too.<\/p>"},{"title":"HashMap collisions and how JDK handles it","link":"https:\/\/ozkanpakdil.github.io\/posts\/my_collections\/2024\/2024-11-27-java-hashmap-collisions\/","pubDate":"Wed, 27 Nov 2024 00:00:30 +0000","guid":"https:\/\/ozkanpakdil.github.io\/posts\/my_collections\/2024\/2024-11-27-java-hashmap-collisions\/","description":" I was thinking on this question On a final note, from Java 8, the linked lists are dynamically replaced with balanced binary search trees in collision resolution after the number of collisions in a given bucket location exceed a certain threshold.<\/p><\/blockquote>\n Than I wonder how it works and went and found the source code of hash map<\/a> in openjdk. It is a very long class, almost 2600 lines, but so many comments \ud83e\udd13 it is not very common to see this much comment in a java code, anyway then I start reading it and wanted to note down how it behaves on collusion<\/p>"},{"title":"FFM (Foreign Function and Memory) Stdlib Example","link":"https:\/\/ozkanpakdil.github.io\/posts\/my_collections\/2024\/2024-11-11-java-ffm-stdlib\/","pubDate":"Mon, 11 Nov 2024 00:00:30 +0000","guid":"https:\/\/ozkanpakdil.github.io\/posts\/my_collections\/2024\/2024-11-11-java-ffm-stdlib\/","description":" FFM is the new API trying to replace JNI and jep is here<\/a> It is basically calling functions outside of JVM or accessing memory not managed by JVM. I wanted to test can FFM beat regular Java API, below you can find a simple test doing math sin with FFM and with regular And result is<\/p>"},{"title":"How to publish JetBrains Rider plugin for opentelemetry\/honeycomb","link":"https:\/\/ozkanpakdil.github.io\/posts\/my_collections\/2024\/2024-10-06-how-to-publish-jetbrains-plugin\/","pubDate":"Sun, 06 Oct 2024 00:00:30 +0000","guid":"https:\/\/ozkanpakdil.github.io\/posts\/my_collections\/2024\/2024-10-06-how-to-publish-jetbrains-plugin\/","description":" I had the chance to work with honeycomb.io 2 weeks ago, mainly I was changing the code which sends data too appinsights azre now needed to send data to honeycomb too. It was not too complex but it is hard to catch those\nlog lines and make sure if we called the endpoint correctly and what data we sent. There is wonderful plugin for that for appinsights https:\/\/github.com\/Socolin\/ApplicationInsightsRiderPlugin<\/a> but there was no plugin whcih can show opentelemetry calls, yes honeycomb.io uses OTEL protocol meaning opentelemetry which is kind of industry standard now for observability.<\/p>"},{"title":"Creating Installers for Java Applications with jpackage","link":"https:\/\/ozkanpakdil.github.io\/posts\/my_collections\/2024\/2024-06-29-jpackager\/","pubDate":"Sat, 29 Jun 2024 00:00:30 +0000","guid":"https:\/\/ozkanpakdil.github.io\/posts\/my_collections\/2024\/2024-06-29-jpackager\/","description":" Jpackage, a powerful tool introduced in Java 14. In this blog post, I’ll explore how to use jpackage to create installers for different operating systems, with a focus on creating an MSI installer for Windows.<\/p>\n jpackage<\/a> is a packaging tool that comes bundled with the Java Development Kit (JDK) since version 14. It allows developers to package Java applications into platform-specific packages that can be easily distributed and installed. It contains the JRE in the generated package and one trigger executable for specified platform. jpackage supports creating various types of installers, including:<\/p>"},{"title":"Spring boot 3 RestClient and RestTemplate logging http requests and response","link":"https:\/\/ozkanpakdil.github.io\/posts\/my_collections\/2024\/2024-05-18-http-logging\/","pubDate":"Sat, 18 May 2024 00:00:30 +0000","guid":"https:\/\/ozkanpakdil.github.io\/posts\/my_collections\/2024\/2024-05-18-http-logging\/","description":" In Spring boot(SB) 2 the configuration was different, now in SB3 we need to configure the rest client differently. Before SB3 there was RestTemplate now there is new Rest api coming in spring world. Find more details here<\/a>.<\/p>\n Adding the required dependency which will do the real http logging here.<\/p>\n The big difference is properties configuration, it is changed and not documented on spring site<\/p>\n Using only “wire” will give request\/response dump. And that extra http=DEBUG will give connection and more debug log, find it at the end of the page.<\/p>"},{"title":"How to use resources(file and memory) in try","link":"https:\/\/ozkanpakdil.github.io\/posts\/my_collections\/2024\/2024-04-18-use-resources-in-try\/","pubDate":"Thu, 18 Apr 2024 00:00:30 +0000","guid":"https:\/\/ozkanpakdil.github.io\/posts\/my_collections\/2024\/2024-04-18-use-resources-in-try\/","description":" I wrote a small piece of code to do some pdf encryption with openpdf, and intellij`s sonarlint was complaining about “Resources should be closed” more details here<\/a><\/p>\n
\nOn Windows, I tried VMware and VirtualBox countless times with different tutorials and blogs. Each attempt ended in frustration: crashes, unsupported hardware, endless configuration rabbit holes. It felt like a goal always just out of reach. And finally I found https:\/\/github.com\/kholia\/OSX-KVM<\/a> it has the readme which explains the steps for setting up.<\/p>"},{"title":"Paint, a lightweight image editor for quick edits","link":"https:\/\/ozkanpakdil.github.io\/posts\/my_collections\/2025\/paint-lightweight-image-editor\/","pubDate":"Wed, 12 Nov 2025 00:00:00 +0000","guid":"https:\/\/ozkanpakdil.github.io\/posts\/my_collections\/2025\/paint-lightweight-image-editor\/","description":"Why I built Paint<\/h2>\n
Prologue: The Era of WebLogic and Apache Mod_WebLogic<\/h2>\n
Handling Concurrent Read API Calls<\/h3>\n
Asynchronous Methods<\/h4>\n
@Async<\/code> at @Service<\/code> annotation and enabling asynchronous processing can help handle multiple API calls concurrently.<\/p>\n@Async<\/span>\n<\/span><\/span>public<\/span> CompletableFuture<<\/span>String><\/span> asyncMethod<\/span>() {\n<\/span><\/span> \/\/ Call external API<\/span>\n<\/span><\/span> return<\/span> CompletableFuture.completedFuture<\/span>("Result"<\/span>);\n<\/span><\/span>}\n<\/span><\/span><\/code><\/pre><\/div>WebClient with Reactor<\/h4>\n
How does HashMap handle collisions internally? What changes were introduced in Java 8 for its implementation?<\/code>\nand reading this blog<\/a> says<\/p>\n\n
Math.sin<\/code><\/p>\nimport<\/span> java.lang.foreign.FunctionDescriptor;\n<\/span><\/span>import<\/span> java.lang.foreign.Linker;\n<\/span><\/span>import<\/span> java.lang.foreign.MemorySegment;\n<\/span><\/span>import<\/span> java.lang.foreign.SymbolLookup;\n<\/span><\/span>import<\/span> java.lang.foreign.ValueLayout;\n<\/span><\/span>\n<\/span><\/span>public<\/span> class<\/span> FFMSinTest<\/span> {\n<\/span><\/span> public<\/span> static<\/span> void<\/span> main<\/span>(String[]<\/span> args) throws<\/span> Throwable {\n<\/span><\/span> Linker linker =<\/span> Linker.nativeLinker<\/span>();\n<\/span><\/span> SymbolLookup stdlib =<\/span> linker.defaultLookup<\/span>();\n<\/span><\/span>\n<\/span><\/span> \/\/ Locate the "sin" function in the C math library<\/span>\n<\/span><\/span> MemorySegment sinAddress =<\/span> stdlib.find<\/span>("sin"<\/span>).orElseThrow<\/span>();\n<\/span><\/span> FunctionDescriptor descriptor =<\/span> FunctionDescriptor.of<\/span>(ValueLayout.JAVA_DOUBLE<\/span>, ValueLayout.JAVA_DOUBLE<\/span>);\n<\/span><\/span> var<\/span> sinHandle =<\/span> linker.downcallHandle<\/span>(sinAddress, descriptor);\n<\/span><\/span>\n<\/span><\/span> double<\/span> angle =<\/span> Math.PI<\/span> \/<\/span> 4; \/\/ 45 degrees in radians<\/span>\n<\/span><\/span>\n<\/span><\/span> \/\/ Timing Java's Math.sin()<\/span>\n<\/span><\/span> long<\/span> javaStartTime =<\/span> System.nanoTime<\/span>();\n<\/span><\/span> for<\/span> (int<\/span> i =<\/span> 0; i <<\/span> 1_000_000; i++<\/span>) {\n<\/span><\/span> double<\/span> result =<\/span> Math.sin<\/span>(angle);\n<\/span><\/span> }\n<\/span><\/span> long<\/span> javaEndTime =<\/span> System.nanoTime<\/span>();\n<\/span><\/span> long<\/span> javaDuration =<\/span> javaEndTime -<\/span> javaStartTime;\n<\/span><\/span>\n<\/span><\/span> \/\/ Timing C sin via FFM<\/span>\n<\/span><\/span> long<\/span> ffmStartTime =<\/span> System.nanoTime<\/span>();\n<\/span><\/span> for<\/span> (int<\/span> i =<\/span> 0; i <<\/span> 1_000_000; i++<\/span>) {\n<\/span><\/span> double<\/span> result =<\/span> (double<\/span>) sinHandle.invoke<\/span>(angle);\n<\/span><\/span> }\n<\/span><\/span> long<\/span> ffmEndTime =<\/span> System.nanoTime<\/span>();\n<\/span><\/span> long<\/span> ffmDuration =<\/span> ffmEndTime -<\/span> ffmStartTime;\n<\/span><\/span>\n<\/span><\/span> System.out<\/span>.println<\/span>("Java Math.sin() took: "<\/span> +<\/span> javaDuration \/<\/span> 1_000_000.0<\/span> +<\/span> " ms"<\/span>);\n<\/span><\/span> System.out<\/span>.println<\/span>("C sin (FFM) took: "<\/span> +<\/span> ffmDuration \/<\/span> 1_000_000.0<\/span> +<\/span> " ms"<\/span>);\n<\/span><\/span> }\n<\/span><\/span>}\n<\/span><\/span><\/code><\/pre><\/div>What is jpackage?<\/h2>\n
implementation 'org.apache.httpcomponents.client5:httpclient5:5.3.1'<\/span>\n<\/span><\/span><\/code><\/pre><\/div>logging.level.org.apache.hc.client5.http.wire<\/span>=<\/span>DEBUG<\/span>\n<\/span><\/span>logging.level.org.apache.hc.client5.http<\/span>=<\/span>DEBUG<\/span>\n<\/span><\/span><\/code><\/pre><\/div>non compliant<\/h1>\n
public<\/span> class<\/span> PasswordProtectedPDF<\/span> {\n<\/span><\/span> private<\/span> static<\/span> final<\/span> Logger logger =<\/span> Logger.getLogger<\/span>(PasswordProtectedPDF.class<\/span>.getName<\/span>());\n<\/span><\/span>