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RestTemplate is a synchronous Spring Framework client used to consume RESTful web services by simplifying HTTP communication. Synchronous Communication: It blocks the execution thread until a response is received.HTTP Methods: It provides built-in methods for standard operations like GET, POST, PUT, and DELETE.Automatic Mapping: It can automatically convert JSON or XML responses into Java domain objects using message converters.Status: While widely used, it is in maintenance mode. For new projects, Spring recommends using the modern RestClient or the reactive. Its an automate work. getForObject() Performs a GET request and returns the response body directly as an object. getForEntity() Performs a GET request and returns a ResponseEntity (includes status and headers). postForObject() Sends data via POST and returns the mapped response body. exchange() A general-purpose method for all HTTP verbs, offering full control over headers and request entities. getForObject- Controller Snippet Response is received in Object format. @RestController @RequestMapping("/api") public class ApiController { @Autowired private ApiService apiService; @GetMapping("/getUsers") public String users() { return apiService.getUsers(); } Service snippet: @Service public class ApiService { @Autowired private RestTemplate restTemplate; @Autowired UserApiRepo userApiRepo; public String getUsers() { String url = "https://jsonplaceholder.typicode.com/users"; String response = restTemplate.getForObject(url, String.class); return response; } Response: "id": 1, "name": "Leanne Graham", "username": "Bret", "email": "Sincere@april.biz", "address": { "street": "Kulas Light", "suite": "Apt. 556", "city": "Gwenborough", "zipcode": "92998-3874", "geo": { "lat": "-37.3159", "lng": "81.1496" } }, "phone": "1-770-736-8031 x56442", "website": "hildegard.org", "company": { "name": "Romaguera-Crona", "catchPhrase": "Multi-layered client-server neural-net", "bs": "harness real-time e-markets" } getForEntity() Respo

Java LLD: Designing a Thread-Safe Parking Lot with Strategy Pattern Designing a parking lot is a staple of Java LLD and machine coding interviews, yet most candidates fail to write production-grade code. As an ex-FAANG interviewer, I've seen countless designs fall apart under concurrent traffic or when asked to support multiple slot allocation algorithms. If you're prepping for interviews, I've been building javalld.com — real machine coding problems with full execution traces. The Mistake Most Candidates Make Monolithic locking on the entire ParkingLot class: Using a global synchronized keyword on the entry method, which serializes all gate entries and destroys system throughput. Hardcoding slot-finding logic: Mixing spatial layout algorithms (like nearest-to-entrance or smallest-available-fit) directly inside the ParkingLot or Gate classes, violating the Open-Closed Principle. Thread-safety as an afterthought: Relying on raw List<Slot> iterations without synchronization, causing race conditions where multiple cars are assigned to the exact same physical slot. The Right Approach Core mental model: Decouple capacity management from slot selection by using a Semaphore for gate-keeping and the Strategy Pattern for thread-safe slot allocation. Key entities: ParkingLot , Gate , Slot , Vehicle , ParkingStrategy ( SmallestFitStrategy , NearestEntranceStrategy ), and StrategyFactory . Why it beats the naive approach: It isolates concurrency concerns (preventing overbooking) from business rules (how we choose a slot), making the system highly performant and easily extensible. The Key Insight (Code) public class EntryGate { private final Semaphore semaphore ; private final ParkingStrategy strategy ; public EntryGate ( int capacity , ParkingStrategy strategy ) { this . semaphore = new Semaphore ( capacity ); this . strategy = strategy ; } public synchronized Ticket park ( Vehicle vehicle ) { if (! semaphore . tryAcquire ()) throw new ParkingFullException (); Slot slot = strat

You know that feeling when you join a new project or want to contribute to an open-source repo, and you spend the first two days just trying to figure out where everything is? I did. Every single time. Clone the repo. Open the files. Stare at 47 folders. Wonder which one actually matters. Grep for the entry point. Follow imports down a rabbit hole. Give up and ask someone. That's not learning. That's just wasted time. So I built CodeAutopsy. What it does Paste any GitHub URL. That's it. CodeAutopsy clones the repo, parses every file into an AST (Abstract Syntax Tree), traces every import and dependency, and gives you: An interactive dependency graph showing exactly what imports what The entry points — where execution actually starts A blast radius map — click any file and instantly see everything that breaks if you change it An AI-generated architectural summary explaining what the codebase does, how it's structured, and how to get started Live Health Telemetry: An Edge API that generates a live SVG health badge (A to F grade). Drop the markdown in your README once. Every time you refactor and re-scan, your badge updates everywhere instantly. My own CodeAutopsy repo just hit 99/100. Drop the markdown snippet once and forget about it. What used to take days now takes about 10 seconds. The real problem it solves Every developer has been here: You're onboarding at a new job. The codebase has 200 files. Your tech lead says "just read the code." You spend a week feeling lost. You want to contribute to an open-source project. The repo has no architecture docs. You don't know where to start. You're doing a code review on a PR that touches 15 files. You have no idea what the blast radius of those changes is. CodeAutopsy solves all three. The interesting engineering problems The hardest part wasn't the AST parsing — it was keeping it serverless without hitting Vercel's 504 timeout limits, while making the AI analysis feel instant. The Serverless Timeout Hack: Doing AST extra

The Care Quality Commission regulates 56,000+ healthcare and social care locations in England — care homes, GP surgeries, hospitals, dental practices, home care agencies. If you work in care sector tech, you've probably needed this data at some point. There's a CQC REST API, and I was planning to wrap it. Then I hit the auth wall. The API is now authenticated CQC migrated their API to api.service.cqc.org.uk and added bearer token authentication. You need to register at their developer portal, create an application, and include an Authorization: Bearer <token> header on every request. That's not a dealbreaker for enterprise use cases, but it creates friction for a data product — it means requiring users to register with CQC before they can run your actor. I checked the old API base ( api.cqc.org.uk/public/v1 ) as a fallback. HTTP 403. Fully blocked. The open-data file rescue CQC publishes a monthly open-data file called HSCA_Active_Locations.ods . It's a 23 MB OpenDocument Spreadsheet with every active regulated location in England — all 56,000 of them. Free, no auth, Open Government Licence. The URL is date-stamped and changes each month, but the transparency page always links to the current version. The approach: scrape the transparency page to find the current ODS URL, download the file, parse it, filter rows, push results. No API. No auth wall. The ODS parsing challenge ODS files ( .ods ) are ZIP archives containing XML. The standard tool for parsing them in Node.js is SheetJS ( xlsx package, v0.18.5 — the last Apache 2.0 release). The first surprise: the workbook has three sheets — README , HSCA_Active_Locations , and Dual_Registration_Locations . SheetJS defaults to the first sheet, which is the README with 34 rows. I added logic to find the sheet with the most rows. for ( const name of workbook . SheetNames ) { const probe = XLSX . utils . sheet_to_json ( sheet , { header : 1 }); if ( probe . length > bestCount ) { bestCount = probe . length ; bestSheet = shee

TRIESTE, Italy – For developers, system administrators, and digital hoarders alike, the daily struggle of locating a specific snippet of text buried deep inside hundreds of nested project files is a universal headache. While heavy-handed IDEs and clunky terminal commands exist, they often feel like using a sledgehammer to crack a nut. Enter FiXiY, a lightweight, blazing-fast utility designed to do exactly one thing flawlessly: scan a folder and find precisely what you’re looking for inside the files. Created by software engineer Lorenzo Battilocchi (known online as XeroHero), FiXiY has officially launched as a free, open-source project on GitHub. Simplicity Meets Speed Unlike built-in operating system searches that are notorious for missing code snippets or taking ages to index, FiXiY bypasses the bloat. It provides a localized, no-nonsense approach to file-content searching. Users simply point the tool to a folder, type in the phrase, string, or code block they need, and FiXiY maps out every instance across all supported file types within seconds. "As developers and creators, we waste an incredible amount of cumulative time just navigating our own file structures looking for a variable, a configuration line, or a specific piece of text," says creator Lorenzo Battilocchi. "FiXiY was built out of necessity. It’s a nimble, friction-free alternative for anyone who wants instant answers without waiting for a massive IDE to load or fighting with complex regex syntax in a terminal." Key Features of FiXiY: Deep Folder Scanning: Recursively searches through complex directory trees and nested folders seamlessly. Intelligent Text Matching: Pinpoints exact strings of text, code, or data buried within plain text, source code, scripts, and logs. Lightweight Footprint: Operates with zero background bloat, making it perfect for rapid-fire asset hunting on any machine. 100% Open Source: Built transparently for the community, ensuring full privacy with no data leaving your local mac

Last Friday at 4:30 PM, my product manager walked over: "Hey, can you grab the titles from the Hacker News homepage and send me an Excel file?" I thought: That's it? Five minutes tops. Two hours later, I was still debugging CSS selectors. How Things Spiraled Out of Control Step 1: Initialize the Project mkdir hacker-news-scraper && cd hacker-news-scraper npm init -y npm install puppeteer Hit enter, waited three minutes. Puppeteer needs to download a full Chromium browser — over 200 MB. I stared at the progress bar and started questioning my life choices. Step 2: Write the Code "It's just a document.querySelectorAll , right?" That's what I thought. Then I opened my editor: const puppeteer = require ( ' puppeteer ' ); ( async () => { const browser = await puppeteer . launch ({ headless : true , args : [ ' --no-sandbox ' , ' --disable-setuid-sandbox ' ] }); const page = await browser . newPage (); try { await page . goto ( ' https://news.ycombinator.com ' , { waitUntil : ' networkidle2 ' , timeout : 30000 }); await page . waitForSelector ( ' .titleline > a ' , { timeout : 10000 }); const titles = await page . evaluate (() => { const items = document . querySelectorAll ( ' .titleline > a ' ); return Array . from ( items ). map ( el => ({ title : el . textContent , url : el . href })); }); console . log ( JSON . stringify ( titles , null , 2 )); } catch ( err ) { console . error ( ' Scraping failed: ' , err . message ); } finally { await browser . close (); } })(); I counted: 27 lines. And this is the minimal version — no User-Agent spoofing, no retry logic, no proxy support, no concurrency control. Add all of that and you're well past 50 lines. Step 3: Run It node index.js Error: Navigation timeout of 30000 ms exceeded . Switched to domcontentloaded , got past that. But then waitForSelector timed out — because .titleline was a relatively new class name. Hacker News had silently changed it from .storylink at some point, and nobody sent me the memo. Step 4: Debug Set head

When Mozilla shut down Pocket in July 2025, I lost my favorite tool. Worse, none of the English alternatives (Instapaper, Readwise, Matter, Raindrop) had Japanese UI, and their article extraction was mediocre on Japanese pages. So I built one. It's called Readbox — Japanese-first, English-too, read-later as a PWA. Here's what I learned shipping it. The stack Next.js 15 App Router + TypeScript strict (no any ) Supabase (Postgres + Auth + RLS) Stripe (JPY + USD prices, locale-routed) Tailwind CSS Service Worker for PWA install + offline read Three things that bit me 1. Article extraction on Vercel serverless First attempt: Mozilla Readability + jsdom. Doesn't bundle on Vercel because of ESM compatibility issues and the 50MB serverless function size limit. I tried 6 approaches — Webpack externals, dynamic imports, edge runtime — none worked cleanly. Ended up using Jina Reader , which returns clean Markdown/HTML from any URL. Trade-off: third-party dependency, rate limits at scale. But it works today, and it's free. 2. Storing article body on-device I didn't want to host millions of articles' worth of HTML on Supabase (cost + privacy). Solution: extracted HTML lives in the browser's IndexedDB only (via Dexie); only metadata (URL, title, tags, read status) syncs to the server. Trade-off: cross-device sync of body content doesn't work seamlessly. Acceptable for a "read it later" workflow where you usually read on the device you saved on. 3. i18n routing — the silent sitemap killer For Japanese + English from one codebase: app/[locale]/ segment with /en prefix for English (default Japanese has no prefix, to preserve old URLs). Middleware detects cookie / Accept-Language and redirects accordingly. The gotcha (cost me a launch-day hour): middleware matcher excludes _next , api , image extensions — but if you forget .xml/.txt/.webmanifest , sitemap.xml and robots.txt get rewritten to /ja/sitemap.xml (which doesn't exist as a route → 404). Fix: export const config = { matcher

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Recently, Apache SeaTunnel welcomed several talented and highly motivated new Committers, and Wang Xuepeng is one of them. As a long-time contributor, Wang Xuepeng’s promotion to Committer was no coincidence. Over the years, he has quietly contributed a tremendous amount to the community, and everyone has witnessed his dedication. From first stepping into the open-source world to becoming a Committer of an Apache top-level project, he has accumulated plenty of stories and valuable insights along the way. What inspired his journey? What experiences and lessons does he want to share with the community? Let’s take a closer look at this exclusive interview with him! Personal Introduction Interview Transcript How long have you been involved in open source? What attracts you to open source? I started getting involved in open source in 2023. What attracts me most is the sense of achievement when the code I write can actually be used within the industry. When did you start contributing to SeaTunnel? What was the trigger? I joined WhaleOps in 2023, which was also when I first started engaging with open source. Now that you’ve been elected as a SeaTunnel Committer, could you summarize your contributions to the community, including both code and non-code contributions? Most of my major feature PRs have focused on building SeaTunnel’s metadata capabilities. When running SeaTunnel jobs and writing job configurations, users often need to manually enter datasource connection information. For file-based tasks, users also need to manually define field mappings. To address these issues, I designed an SPI interface called MetadataProvider . The interface mainly exposes two methods: Map<String, Object> datasourceMap(String connectorIdentifier, String metaDataDatasourceId); Optional<TableSchema> tableSchema(String metaDataTableId); Previously, some users in the community mentioned that datasource usernames and passwords were stored in Nacos with read-only access permissions. In scenario

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