java_使用redis 进行请求限流
应用场景：在后端处理流程复杂，前端可能会高频点击的情况下，做请求限流来进行系统保护；
本文的应用场景为：前端请求导出excel,出现大数据量的情况下，限制每个ip 用户对于每个地区条件，一分钟内只能请求两次
思路：使用注解在对要限流的方法进行标识，自定义拦截器，在进入这个方法体之前，通过redis 获取缓存的key,该key 设置一个超时时间，该key 的value 为访问次数，每访问一次便+1，达到次数后则不进入方法体，直接返回请求已满，直到key 过期；
代码实现：
0.配置信息：
pom.xml :
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-redis</artifactId> <version>2.5.7</version></dependency>
1, 自定义注解 ======================================================
@Retention(RUNTIME)//运行时有效
@Target(ElementType.METHOD)//用在方法上
public @interface AccessLimit {
//时间范围(单位:秒)
int seconds();
//在这个时间范围内最大访问次数
int maxCount();
}
2.自定义拦截器============================================================
@Slf4j
@Component
public class ExportExcelLimitInterceptor implements HandlerInterceptor {
@Autowired
private RedisTemplate redisTemplate;
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
if (handler instanceof HandlerMethod) {
HandlerMethod hm = (HandlerMethod) handler;
//设置redisTemplate的序列化方式(必须设置为这种方式，因为要用到incr)
redisTemplate.setKeySerializer(new StringRedisSerializer());
redisTemplate.setValueSerializer(new StringRedisSerializer());
AccessLimit accessLimit = hm.getMethodAnnotation(AccessLimit.class);
if (null == accessLimit) {
return true;
}
int seconds = accessLimit.seconds();
int maxCount = accessLimit.maxCount();
String ipAddr = IpUtil.getIpAddr(request);
String key = request.getContextPath() + ":" + request.getServletPath() + "_exportExcel"+":" + ipAddr ;
String countStr = (String) redisTemplate.opsForValue().get(key);
Integer count = null;
//如果不是第一次访问，则把访问次数转换为integer类型
if(countStr != null){
count = Integer.valueOf(redisTemplate.opsForValue().get(key).toString());
}
log.info("count:{}",count);
//拿到访问次数的过期时间
Long keySeconds = redisTemplate.getExpire(key);
if (null == count || -1 == count) {
redisTemplate.opsForValue().set(key,String.valueOf(1));
//设置过期时间
redisTemplate.expire(key,seconds, TimeUnit.SECONDS);
return true;
}
if (count < maxCount) {
log.info("count:{}",count);
//访问次数+1
redisTemplate.opsForValue().increment(key,1);
//设置剩余过期时间(修改完该key的value值后，对应的过期时间会失效，需重新设置)
redisTemplate.expire(key,keySeconds, TimeUnit.SECONDS);
return true;
}
if (count >= maxCount) {
// response 返回 json 请求过于频繁请稍后再试
this.responseResult(response, new Result(500, "访问次数已超过限制，请稍后重试"));
return false;
}
}
return true;
}
void responseResult(HttpServletResponse response, Result result) throws IOException {
response.setHeader("Content-Type", "application/json;charset=utf8");
Writer writer = response.getWriter();
writer.write(JSONObject.toJSONString(result));
writer.close();
}
}
3.添加拦截器到webconfig ===============================================================================
@Configuration
public class WebMvcConfig implements WebMvcConfigurer {
@Autowired
private ExportExcelLimitInterceptor excelLimitInterceptor; // 访问限制拦截器
@Override
public void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor(excelLimitInterceptor)
.addPathPatterns("/qiannan/test");
}
}
4.添加注解到方法体===================================================================================
@AccessLimit(seconds=30,maxCount=2)
@GetMapping("/qiannan/test")
public Object test(String id) throws IOException {
return linkFeignClient.detail(id);
}
5. 用到的工具类：
public class IpUtil {
private IpUtil() { }
/**
* 获取登录用户的IP地址
* @param request
* @return
*/
public static String getIpAddr(HttpServletRequest request) {
String ip = request.getHeader("x-forwarded-for");
if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
ip = request.getHeader("Proxy-Client-IP");
}
if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
ip = request.getHeader("WL-Proxy-Client-IP");
}
if (ip == null || ip.length() == 0 || "unknown".equalsIgnoreCase(ip)) {
ip = request.getRemoteAddr();
}
if (ip.equals("0:0:0:0:0:0:0:1")) {
ip = "127.0.0.1";
}
if (ip.split(",").length > 1) {
ip = ip.split(",")[0];
}
return ip;
}
//ip转化为有序的长整形
public static long getIp2long(String ip) {
ip = ip.trim();
String[] ips = ip.split("\\.");
long ip2long = 0L;
for (int i = 0; i < 4; ++i) {
ip2long = ip2long << 8 | Integer.parseInt(ips[i]);
}
return ip2long;
}
}
