Posts

Non-business day table design in Oracle for business day calculations — weekend strategy, unique constraints, and code taxonomy.

Business day calculation done right: why a non-business day table beats a holiday-only table, plus batch sync with a government holiday API.

Fix favicon.ico 404 or 500 errors in Spring Boot when a catch-all controller hijacks static resource requests. Diagnosis and Filter-based solution.

Fix SVN E155015 remains in conflict error caused by tree conflicts. Step-by-step resolution via terminal and IntelliJ.

When building Spring MVC features that accept a resource ID as a URL parameter, IDOR vulnerabilities are easy to miss. Here's how to catch and fix them.

How to build Ajax-powered search pages in Spring MVC with Thymeleaf — fragment separation, the replaceWith() bug, DAO/DTO split, and MyBatis dynamic queries.

Learn how to quickly check your installed Java version using the terminal with simple commands for developers.

How to convert a single-record Oracle SQL query into a per-entity aggregate for list views. Practical patterns with MyBatis and CTEs.

String comparison, array membership checks, and static constants — the three places where JS-to-Java conversions quietly break.

How I designed a feature letting approvers view requesters' budgets in a B2B e-commerce platform, with lessons on scope control.

Oracle YYYYMMDD date strings can be compared without TO_DATE. Learn why lexicographic order equals chronological order and how to avoid ORA-01839.

Add a favicon to your Spring Boot Thymeleaf project — from generation to Security config to fixing manifest BOM errors.

Spring Session throws OutOfMemoryError during Redis deserialization. Here's why it happens and how to fix it permanently with serializer changes and session trimming.

Three Thymeleaf patterns for displaying a product's selected option next to its name in a cart list — with proper null handling.

A step-by-step breakdown of a real Java cart DTO assembly method: multi-type branching, external API calls in loops, and delivery fee calculation strategy.

Stop wasting resources on unreasonable log retrieval requests. Learn how to professionally push back by leveraging privacy policies and system design.

How a shared Thymeleaf layout caused unnecessary DB queries and resource loading on a login page, and the simple layout split that fixed it.

Can CSS group elements into one container? Learn the difference between DOM structure and CSS, and how to properly group elements in real projects.

Confused about DAO vs DTO in Java? Learn the difference, common mistakes, and the exact naming conventions your team expects.

Learn how to search logs with grep in Linux, including file patterns, useful options, and real-world debugging techniques.

MyBatis #{param} fails in IntelliJ Database Console because it's not real SQL. Learn how to fix it using ? parameter binding correctly.

Oracle hierarchy query using CONNECT BY solves menu sorting issues that ORDER BY cannot handle. Learn the correct pattern for tree-structured data.

Learn how to query Oracle synonyms and find their target tables using ALL_SYNONYMS, including how to detect broken synonyms.

Spring exception logging explained. Learn how to use stack traces and traceId to quickly find the root cause in production systems.

Thymeleaf null boolean error happens when SpEL cannot convert null to boolean. Learn the root cause and how to fix it properly.