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🚀 Backend Java Developer Portfolio Projects

This document lists 10 potential portfolio projects designed to showcase backend Java development skills, including Spring Boot APIs, SQL/NoSQL databases, desktop applications, and Docker.

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1. Task Manager API

• Category: Spring Boot REST API
• Core Features: CRUD for tasks, user authentication, JWT, PostgreSQL persistence
• Skills Showcased: Spring Boot API design, SQL (Postgres), Dockerized local development

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LangGraph Advice for HTML-to-React Project

Why LangGraph > Prompts

• Modularity: Break your task into nodes (e.g., parse HTML, identify components, generate React code). Update one node for changes, not the whole prompt.
• State Tracking: Persist data (like parsed HTML) across nodes, avoiding repetitive context in prompts.
• Control Flow: Use conditional edges or loops to handle varied HTML structures, unlike linear prompts.
• Debugging: Inspect each node’s output with tools like LangSmith, easier than opaque prompt failures.
• Tool Integration: Add libraries (e.g., BeautifulSoup) or APIs (e.g., code validation) for robust workflows.

Getting Started

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scanf_s Family Functions Reference

Overview

The scanf_s family are secure versions of the standard scanf functions with enhanced security features to prevent buffer overruns. This guide focuses on sscanf_s and swscanf_s for parsing strings.

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Function Variants

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Windows API Time Structures Reference

Overview

Windows API provides two main structures for handling date and time: FILETIME and SYSTEMTIME. Each serves different purposes in time representation and manipulation.

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FILETIME Structure

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Tagging Langfuse Conversations for User + Site Conversions

This guide outlines how to tag Langfuse sessions or traces for a user and site when a conversion (e.g., moving from free to paid) occurs, allowing filtering of converted vs. non-converted conversations. Since Langfuse's API doesn't natively support key-based metadata filtering (e.g., site_id), we combine native filters with client-side processing.

Approach

1. Fetch sessions for a user in a time window (e.g., last 24 hours) using user_id and start_time_after.
2. Fetch traces for each session using session_id.
3. Filter traces client-side by metadata.site_id.
4. Apply a score (e.g., 24h_before_conversion=1) to matching traces or sessions for easy filtering in Langfuse.

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Debugging Serverless Lambda 500 Errors

1. Verify Basic Deployment and Connectivity

• Confirm Endpoints: After serverless deploy, run serverless info to list endpoints and stack outputs. Ensure the URLs match exactly, including the stage (e.g., /dev/).
• Test with Tools: Use curl -v https://your-endpoint.com/path or Postman to inspect response headers for clues (e.g., CORS or "Internal Server Error").
• AWS Console Check: Navigate to API Gateway > Your API > Stages and verify no deployment errors or invalid mappings.

2. Inspect Lambda Logs via CloudWatch

This is often the fastest way to identify errors, as 500s typically log stack traces.

• Enable Logging: In serverless.yml, ensure provider: logs: rest: true for API Gateway.

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Ticket 2: Implement StringToFileTime Helper Function

Description

Create a utility function to parse a date string in YYYY-MM-DD format into a FILETIME struct. This will be used for date filtering in later tickets. Test in main() with sample dates, converting and printing success/failure or verifying FILETIME values.

Acceptance Criteria

• Function signature: bool StringToFileTime(const std::wstring& dateStr, FILETIME& fileTime)
• Uses swscanf_s for parsing and SystemTimeToFileTime for conversion.
• Returns false on invalid format.
• In main(): Test valid and invalid date strings and print results.

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Documentation and Summary for std::wstring Constructor and MultiByteToWideChar

std::wstring(size_t count, wchar_t ch)

Summary

The std::wstring(size_t count, wchar_t ch) constructor is a member of the C++ Standard Library's std::basic_string class, specialized for wide characters (wchar_t) as std::wstring. It creates a wide string of length count, where each character is initialized to the specified wide character ch. In the provided code, it is used to allocate a std::wstring of size size - 1 filled with null characters (0) to prepare a buffer for the MultiByteToWideChar conversion.

Documentation

• Function Signature: std::wstring::basic_string(size_t count, wchar_t ch, const Allocator& alloc = Allocator())
• Parameters:

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FileSearch Application Recreation Tickets

• Ticket 1: Implement CharToWString Helper Function
  • Create a utility to convert char* to std::wstring using MultiByteToWideChar. Test in main() with sample inputs.
• Ticket 2: Implement StringToFileTime Helper Function
  • Create a utility to parse YYYY-MM-DD strings into FILETIME. Test valid/invalid dates in main().
• Ticket 3: Implement ParseAttributes Helper Function
  • Create a utility to parse comma-separated attribute strings (e.g., "hidden,readonly") into a DWORD. Test in main().
• Ticket 4: Implement Argument Parsing
• Parse command-line arguments into SearchCriteria struct and startDir. Display parsed values in main(). Depends on Tickets 1-3.

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Ticket 1: Implement CharToWString Helper Function

Description

Create a utility function to convert char* strings (from argv) to std::wstring. This is foundational for handling wide-character strings in Windows APIs. Test it in main() by converting sample argv-like inputs and printing them.

Acceptance Criteria

• Function signature: std::wstring CharToWString(const char* str)
• Handles null input gracefully (returns empty wstring).
• Uses MultiByteToWideChar with CP_ACP.
• In main(): Simulate argv, convert, and print to verify.