☕ Java后端开发者的一天(续) — 数据导出API全纪实

// Controller — 流式导出API package com.dataplatform.controller; @RestController @RequestMapping("/api/v1") public class ExportController { private final ExportService exportService; @PostMapping("/export") @RateLimit(key = "api_key", limit = 60, window = 60) public void export( @Valid @RequestBody ExportRequest req, @RequestHeader("X-API-Key") String apiKey, HttpServletResponse response) throws IOException { // 1. 自定义校验 if (!req.isValidTimeRange()) { response.setStatus(400); response.getWriter().write("{\"error\":\"时间范围不能超过90天\"}"); return; } // 2. 设置响应头 if ("csv".equals(req.getFormat())) { response.setContentType("text/csv; charset=UTF-8"); response.setHeader("Content-Disposition", "attachment; filename=export.csv"); } else { response.setContentType("application/json; charset=UTF-8"); } // 3. 流式写入（不加载全部到内存） exportService.exportData(req, response.getOutputStream()); } } // ──────────────────────────── // Service — MyBatis Cursor流式写入 // ──────────────────────────── @Service public class ExportService { private final EventDataMapper eventMapper; @Transactional(readOnly = true) // 只读事务 public void exportData(ExportRequest req, OutputStream out) throws IOException { PrintWriter writer = new PrintWriter( new OutputStreamWriter(out, StandardCharsets.UTF_8)); if ("csv".equals(req.getFormat())) { // CSV表头 writer.println("id,user_id,event_type,event_data,created_at"); } // Cursor逐行读取 → 逐行写入 → 零内存堆积 try (Cursor<EventData> cursor = eventMapper.scanByConditions( req.getStartTime(), req.getEndTime(), req.getUserId(), req.getEventType())) { for (EventData row : cursor) { // 每次迭代只取1行 if ("csv".equals(req.getFormat())) { writer.printf("%d,%s,%s,%s,%s%n", row.getId(), row.getUserId(), row.getEventType(), row.getEventData(), row.getCreatedAt()); } else { writer.println(toJsonString(row)); } writer.flush(); // 立即推送到客户端 } } // try-with-resources自动关闭Cursor } }

// 自定义注解：@RateLimit @Target(ElementType.METHOD) @Retention(RetentionPolicy.RUNTIME) public @interface RateLimit { String key(); // 限流维度：api_key / user_id / ip int limit() default 60; // 窗口内最大请求数 int window() default 60; // 窗口大小（秒） } // AOP切面：拦截@RateLimit注解的方法 @Aspect @Component public class RateLimitAspect { private final StringRedisTemplate redis; @Around("@annotation(rateLimit)") public Object checkRate(ProceedingJoinPoint pjp, RateLimit rateLimit) throws Throwable { // 1. 获取限流key（从请求头/参数中提取API Key） String apiKey = extractApiKey(pjp); // 反射获取 String redisKey = "rate_limit:" + apiKey; // 2. Redis INCR + EXPIRE（原子操作） Long count = redis.opsForValue().increment(redisKey); if (count == 1) { redis.expire(redisKey, rateLimit.window(), TimeUnit.SECONDS); } // 3. 超过限制 → 返回429 if (count > rateLimit.limit()) { throw new ResponseStatusException( HttpStatus.TOO_MANY_REQUESTS, "请求过于频繁，每" + rateLimit.window() + "秒限" + rateLimit.limit() + "次"); } // 4. 未超限 → 放行 return pjp.proceed(); } } // 使用方式：在Controller方法上加注解即可 @RateLimit(key = "api_key", limit = 60, window = 60) public void export(...) { ... }