Stop Hardcoding Prompts in Chat UIs: A Practical Guide to Google AI Studio for Java Developers

package com.example.toolia.api.controller;

import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import java.time.Instant;
import java.util.HashMap;
import java.util.Map;

@RestController
@RequestMapping("/api/v1")
public class TimeController {

    @GetMapping("/time")
    public ResponseEntity<Map<String, Object>> getCurrentTimestamp() {
        Map<String, Object> response = new HashMap<>();
        response.put("timestamp", Instant.now().toEpochMilli());
        response.put("status", "SUCCESS");
        return ResponseEntity.ok(response);
    }
}

curl https://generativelanguage.googleapis.com/v1beta/models/gemini-1.5-flash:generateContent \
  -X POST \
  -H "Content-Type: application/json" \
  -H "x-goog-api-key: ${GEMINI_API_KEY}" \
  -d '{
    "contents": [{"parts": [{"text": "Create a GET endpoint at /api/v1/time that returns the current Unix timestamp..."}]}],
    "generationConfig": {
      "temperature": 0.0,
      "responseMimeType": "text/plain"
    }
  }'

✔ [ MANDATORY ] Dependency Integrity: Ensure imported annotations (e.g., @RestController) perfectly match your local Spring Boot dependencies.
✔ [ MANDATORY ] Timezone & Clock Pitfalls: When computing epoch timestamps, account for localized UTC variances if your service runs across multi-region cloud nodes (like AWS or GCP).
✔ [ MANDATORY ] Thread Safety: If the model accidentally spins up static utility date formatters (like SimpleDateFormat), kill them immediately. They are notoriously thread-unsafe.
✔ [ OPTIONAL ] Exception Boundary Control: Ensure the endpoint does not leak raw internal exception stack traces to the client. Safely wrap execution failures with a global @ControllerAdvice handler.