每一次进行幂等校验之前先获取token，因为token的时效性只有1次，我们每次获得的token在幂等操作后就无效了，所以一个token不需要长期保存在redis中。
@RestController
public class TokenController {
@Autowired
private RedisService redisService;
@GetMapping("/users-anon/gettoken")
public Map getToken(@RequestParam("url") String url) {
Map<String,String> tokenMap = new HashMap();
String tokenValue = UUID.randomUUID().toString();
tokenMap.put(url + tokenValue, tokenValue);
redisService.set(url + tokenValue, tokenValue);
return tokenMap;
}}
获取token后，访问该url的接口，此时我们使用拦截器进行拦截(/add/**可表示为所有有新增操作的接口)
@SpringBootConfiguration
public class TokenInterceptorConfig extends WebMvcConfigurerAdapter {
@Autowired
private TokenInterceptor tokenInterceptor;
@Override
public void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor(tokenInterceptor).addPathPatterns("/add/**");
}}
拦截器的具体内容为
@Slf4j
@Component
public class TokenInterceptor implements HandlerInterceptor {
@Autowired
private RedisService redisService;
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
String tokenName = request.getRequestURI() + request.getParameter("token_value");
String tokenValue = request.getParameter("token_value");
if (tokenValue != null && !tokenValue.equals("")) {
log.info("tokenName:{},tokenValue:{}",tokenName,tokenValue);
return handleToken(request,response,handler);
}
return false;
}
@Override
public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, @Nullable ModelAndView modelAndView) throws Exception {
if (redisService.exists(request.getParameter("token_value"))) {
RedisTool.releaseDistributedLock(redisService, request.getParameter("token_value"), request.getParameter("token_value"));
}
}
@Override
public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, @Nullable Exception ex) throws Exception {
}
/**
* 分布式锁处理
* @param request
* @param response
* @param handler
* @return
* @throws Exception
*/
private boolean handleToken(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
//当大量高并发下所有带token参数的请求进来时，进行分布式锁定,允许某一台服务器的一个线程进入，锁定时间3分钟
if (RedisTool.tryGetDistributedLock(redisService,request.getParameter("token_value"),request.getParameter("token_value"),180)) {
if (redisService.exists(request.getRequestURI() + request.getParameter("token_value"))) {
//当请求的url与token与redis中的存储相同时
if (redisService.get(request.getRequestURI() + request.getParameter("token_value")).equals(request.getParameter("token_value"))) {
//放行的该线程删除redis中存储的token
redisService.del(request.getRequestURI() + request.getParameter("token_value"));
//放行
return true;
}
}
//当请求的url与token与redis中的存储不相同时，解除锁定
RedisTool.releaseDistributedLock(redisService,request.getParameter("token_value"),request.getParameter("token_value"));
//进行拦截
return false;
}
return false;
}直到后续controller操作执行完毕后释放分布式锁,见postHandle。
分布式锁的具体实现为
package com.cloud.user.config.redis;
/**
- Created by Administrator on 2018-08-05.
*/
public class RedisTool {
private static final String LOCK_SUCCESS = "OK";
private static final Long RELEASE_SUCCESS = 1L;
/**
* 尝试获取分布式锁
* @param lockKey 锁
* @param requestId 请求标识
* @param expireTime 超期时间
* @return 是否获取成功
*/
public static boolean tryGetDistributedLock(RedisService redisService, String lockKey, String requestId, int expireTime) {
String result = redisService.set(lockKey, requestId, expireTime);
if (LOCK_SUCCESS.equals(result)) {
return true;
}
return false;
}
/**
* 释放分布式锁
* @param lockKey 锁
* @param requestId 请求标识
* @return 是否释放成功
*/
public static boolean releaseDistributedLock(RedisService redisService, String lockKey, String requestId) {
Object result = redisService.eval(lockKey,requestId);
if (RELEASE_SUCCESS.equals(result)) {
return true;
}
return false;
}}
在RedisServiceImpl实现类中，以上set跟eval的具体实现为
private static final String SET_IF_NOT_EXIST = "NX";
private static final String SET_WITH_EXPIRE_TIME = "PX";
@Autowired
private JedisPool jedisPool;
public T execute(RedisFunction fun) {
Jedis jedis = null;
try {
jedis = jedisPool.getResource();
return (T)fun.callback(jedis);
}catch (Exception e) {
logger.error(e.getMessage());
return null;
}finally {
if (jedis != null) {
jedis.close();
}
}}
@Override
public String set(String lockKey, String requestId, int expireTime) {
return execute(new RedisFunction<String, Jedis>() {
@Override
public String callback(Jedis jedis) {
return jedis.set(lockKey,requestId,SET_IF_NOT_EXIST,SET_WITH_EXPIRE_TIME,expireTime);
}
});}
@Override
public Object eval(String lockKey, String requestId) {
return execute(new RedisFunction<String, Jedis>() {
@Override
public Object callback(Jedis jedis) {
String script = "if redis.call('get', KEYS[1]) == ARGV[1] then return redis.call('del', KEYS[1]) else return 0 end";
return jedis.eval(script, Collections.singletonList(lockKey),Collections.singletonList(requestId));
}
});}
public interface RedisFunction {
Object callback(E jedis);}
