瞬間幾千次的重復提交，我用?SpringBoot Redis?扛住了！
時間：2021-09-13 13:59:16
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[導讀]來源：jianshu.com/p/c806003a8530前言:在實際的開發(fā)項目中,一個對外暴露的接口往往會面臨很多次請求，我們來解釋一下冪等的概念：任意多次執(zhí)行所產生的影響均與一次執(zhí)行的影響相同。按照這個含義，最終的含義就是對數(shù)據(jù)庫的影響只能是一次性的，不能重復處理。如何保證其...
來源：jianshu.com/p/c806003a8530前言:
在實際的開發(fā)項目中,一個對外暴露的接口往往會面臨很多次請求，我們來解釋一下冪等的概念：任意多次執(zhí)行所產生的影響均與一次執(zhí)行的影響相同。按照這個含義，最終的含義就是 對數(shù)據(jù)庫的影響只能是一次性的，不能重復處理。如何保證其冪等性，通常有以下手段：- 數(shù)據(jù)庫建立唯一性索引，可以保證最終插入數(shù)據(jù)庫的只有一條數(shù)據(jù)
- token機制，每次接口請求前先獲取一個token，然后再下次請求的時候在請求的header體中加上這個token，后臺進行驗證，如果驗證通過刪除token，下次請求再次判斷token
- 悲觀鎖或者樂觀鎖，悲觀鎖可以保證每次for update的時候其他sql無法update數(shù)據(jù)(在數(shù)據(jù)庫引擎是innodb的時候,select的條件必須是唯一索引,防止鎖全表)
- 先查詢后判斷，首先通過查詢數(shù)據(jù)庫是否存在數(shù)據(jù)，如果存在證明已經請求過了，直接拒絕該請求，如果沒有存在，就證明是第一次進來，直接放行。
一：搭建redis的服務Api
1:首先是搭建redis服務器。2:引入springboot中到的redis的stater，或者Spring封裝的jedis也可以，后面主要用到的api就是它的set方法和exists方法,這里我們使用springboot的封裝好的redisTemplate/**
?*?redis工具類
?*/
@Component
public?class?RedisService?{
????@Autowired
????private?RedisTemplate?redisTemplate;
????/**
?????*?寫入緩存
?????*?@param?key
?????*?@param?value
?????*?@return
?????*/
????public?boolean?set(final?String?key,?Object?value)?{
????????boolean?result?=?false;
????????try?{
????????????ValueOperationsObject>?operations?=?redisTemplate.opsForValue();
????????????operations.set(key,?value);
????????????result?=?true;
????????}?catch?(Exception?e)?{
????????????e.printStackTrace();
????????}
????????return?result;
????}
????/**
?????*?寫入緩存設置時效時間
?????*?@param?key
?????*?@param?value
?????*?@return
?????*/
????public?boolean?setEx(final?String?key,?Object?value,?Long?expireTime)?{
????????boolean?result?=?false;
????????try?{
????????????ValueOperationsObject>?operations?=?redisTemplate.opsForValue();
????????????operations.set(key,?value);
????????????redisTemplate.expire(key,?expireTime,?TimeUnit.SECONDS);
????????????result?=?true;
????????}?catch?(Exception?e)?{
????????????e.printStackTrace();
????????}
????????return?result;
????}
????/**
?????*?判斷緩存中是否有對應的value
?????*?@param?key
?????*?@return
?????*/
????public?boolean?exists(final?String?key)?{
????????return?redisTemplate.hasKey(key);
????}
????/**
?????*?讀取緩存
?????*?@param?key
?????*?@return
?????*/
????public?Object?get(final?String?key)?{
????????Object?result?=?null;
????????ValueOperationsObject>?operations?=?redisTemplate.opsForValue();
????????result?=?operations.get(key);
????????return?result;
????}
????/**
?????*?刪除對應的value
?????*?@param?key
?????*/
????public?boolean?remove(final?String?key)?{
????????if?(exists(key))?{
????????????Boolean?delete?=?redisTemplate.delete(key);
????????????return?delete;
????????}
????????return?false;
????}
}
二：自定義注解AutoIdempotent
自定義一個注解，定義此注解的主要目的是把它添加在需要實現(xiàn)冪等的方法上，凡是某個方法注解了它，都會實現(xiàn)自動冪等。后臺利用反射如果掃描到這個注解，就會處理這個方法實現(xiàn)自動冪等，使用元注解ElementType.METHOD表示它只能放在方法上，etentionPolicy.RUNTIME表示它在運行時@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public?@interface?AutoIdempotent?{
??
}
三：token創(chuàng)建和檢驗
1:token服務接口我們新建一個接口，創(chuàng)建token服務，里面主要是兩個方法，一個用來創(chuàng)建token，一個用來驗證token。創(chuàng)建token主要產生的是一個字符串，檢驗token的話主要是傳達request對象，為什么要傳request對象呢？主要作用就是獲取header里面的token,然后檢驗，通過拋出的Exception來獲取具體的報錯信息返回給前端public?interface?TokenService?{
????/**
?????*?創(chuàng)建token
?????*?@return
?????*/
????public??String?createToken();
????/**
?????*?檢驗token
?????*?@param?request
?????*?@return
?????*/
????public?boolean?checkToken(HttpServletRequest?request)?throws?Exception;
}
2:token的服務實現(xiàn)類token引用了redis服務，創(chuàng)建token采用隨機算法工具類生成隨機uuid字符串,然后放入到redis中(為了防止數(shù)據(jù)的冗余保留,這里設置過期時間為10000秒,具體可視業(yè)務而定)，如果放入成功，最后返回這個token值。checkToken方法就是從header中獲取token到值(如果header中拿不到，就從paramter中獲取)，如若不存在,直接拋出異常。這個異常信息可以被攔截器捕捉到，然后返回給前端。@Service
public?class?TokenServiceImpl?implements?TokenService?{
????@Autowired
????private?RedisService?redisService;
????/**
?????*?創(chuàng)建token
?????*
?????*?@return
?????*/
????@Override
????public?String?createToken()?{
????????String?str?=?RandomUtil.randomUUID();
????????StrBuilder?token?=?new?StrBuilder();
????????try?{
????????????token.append(Constant.Redis.TOKEN_PREFIX).append(str);
????????????redisService.setEx(token.toString(),?token.toString(),10000L);
????????????boolean?notEmpty?=?StrUtil.isNotEmpty(token.toString());
????????????if?(notEmpty)?{
????????????????return?token.toString();
????????????}
????????}catch?(Exception?ex){
????????????ex.printStackTrace();
????????}
????????return?null;
????}
????/**
?????*?檢驗token
?????*
?????*?@param?request
?????*?@return
?????*/
????@Override
????public?boolean?checkToken(HttpServletRequest?request)?throws?Exception?{
????????String?token?=?request.getHeader(Constant.TOKEN_NAME);
????????if?(StrUtil.isBlank(token))?{//?header中不存在token
????????????token?=?request.getParameter(Constant.TOKEN_NAME);
????????????if?(StrUtil.isBlank(token))?{//?parameter中也不存在token
????????????????throw?new?ServiceException(Constant.ResponseCode.ILLEGAL_ARGUMENT,?100);
????????????}
????????}
????????if?(!redisService.exists(token))?{
????????????throw?new?ServiceException(Constant.ResponseCode.REPETITIVE_OPERATION,?200);
????????}
????????boolean?remove?=?redisService.remove(token);
????????if?(!remove)?{
????????????throw?new?ServiceException(Constant.ResponseCode.REPETITIVE_OPERATION,?200);
????????}
????????return?true;
????}
}
四：攔截器的配置
1:web配置類，實現(xiàn)WebMvcConfigurerAdapter，主要作用就是添加autoIdempotentInterceptor到配置類中，這樣我們到攔截器才能生效，注意使用@Configuration注解，這樣在容器啟動是時候就可以添加進入context中@Configuration
public?class?WebConfiguration?extends?WebMvcConfigurerAdapter?{
????@Resource
???private?AutoIdempotentInterceptor?autoIdempotentInterceptor;
????/**
?????*?添加攔截器
?????*?@param?registry
?????*/
????@Override
????public?void?addInterceptors(InterceptorRegistry?registry)?{
????????registry.addInterceptor(autoIdempotentInterceptor);
????????super.addInterceptors(registry);
????}
}
2:攔截處理器：主要的功能是攔截掃描到AutoIdempotent到注解到方法,然后調用tokenService的checkToken()方法校驗token是否正確，如果捕捉到異常就將異常信息渲染成json返回給前端/**
?*?攔截器
?*/
@Component
public?class?AutoIdempotentInterceptor?implements?HandlerInterceptor?{
????@Autowired
????private?TokenService?tokenService;
????/**
?????*?預處理
?????*
?????*?@param?request
?????*?@param?response
?????*?@param?handler
?????*?@return
?????*?@throws?Exception
?????*/
????@Override
????public?boolean?preHandle(HttpServletRequest?request,?HttpServletResponse?response,?Object?handler)?throws?Exception?{
????????if?(!(handler?instanceof?HandlerMethod))?{
????????????return?true;
????????}
????????HandlerMethod?handlerMethod?=?(HandlerMethod)?handler;
????????Method?method?=?handlerMethod.getMethod();
????????//被ApiIdempotment標記的掃描
????????AutoIdempotent?methodAnnotation?=?method.getAnnotation(AutoIdempotent.class);
????????if?(methodAnnotation?!=?null)?{
????????????try?{
????????????????return?tokenService.checkToken(request);//?冪等性校驗,?校驗通過則放行,?校驗失敗則拋出異常,?并通過統(tǒng)一異常處理返回友好提示
????????????}catch?(Exception?ex){
????????????????ResultVo?failedResult?=?ResultVo.getFailedResult(101,?ex.getMessage());
????????????????writeReturnJson(response,?JSONUtil.toJsonStr(failedResult));
????????????????throw?ex;
????????????}
????????}
????????//必須返回true,否則會被攔截一切請求
????????return?true;
????}
????@Override
????public?void?postHandle(HttpServletRequest?request,?HttpServletResponse?response,?Object?handler,?ModelAndView?modelAndView)?throws?Exception?{
????}
????@Override
????public?void?afterCompletion(HttpServletRequest?request,?HttpServletResponse?response,?Object?handler,?Exception?ex)?throws?Exception?{
????}
????/**
?????*?返回的json值
?????*?@param?response
?????*?@param?json
?????*?@throws?Exception
?????*/
????private?void?writeReturnJson(HttpServletResponse?response,?String?json)?throws?Exception{
????????PrintWriter?writer?=?null;
????????response.setCharacterEncoding("UTF-8");
????????response.setContentType("text/html;?charset=utf-8");
????????try?{
????????????writer?=?response.getWriter();
????????????writer.print(json);
????????}?catch?(IOException?e)?{
????????}?finally?{
????????????if?(writer?!=?null)
????????????????writer.close();
????????}
????}
}
五：測試用例
1:模擬業(yè)務請求類首先我們需要通過/get/token路徑通過getToken()方法去獲取具體的token，然后我們調用testIdempotence方法，這個方法上面注解了@AutoIdempotent，攔截器會攔截所有的請求，當判斷到處理的方法上面有該注解的時候，就會調用TokenService中的checkToken()方法，如果捕獲到異常會將異常拋出調用者，下面我們來模擬請求一下：@RestController
public?class?BusinessController?{
????@Resource
????private?TokenService?tokenService;
????@Resource
????private?TestService?testService;
????@PostMapping("/get/token")
????public?String??getToken(){
????????String?token?=?tokenService.createToken();
????????if?(StrUtil.isNotEmpty(token))?{
????????????ResultVo?resultVo?=?new?ResultVo();
????????????resultVo.setCode(Constant.code_success);
????????????resultVo.setMessage(Constant.SUCCESS);
????????????resultVo.setData(token);
????????????return?JSONUtil.toJsonStr(resultVo);
????????}
????????return?StrUtil.EMPTY;
????}
????@AutoIdempotent
????@PostMapping("/test/Idempotence")
????public?String?testIdempotence()?{
????????String?businessResult?=?testService.testIdempotence();
????????if?(StrUtil.isNotEmpty(businessResult))?{
????????????ResultVo?successResult?=?ResultVo.getSuccessResult(businessResult);
????????????return?JSONUtil.toJsonStr(successResult);
????????}
????????return?StrUtil.EMPTY;
????}
}
2:使用postman請求首先訪問get/token路徑獲取到具體到token：
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