1、pom.xml：主要是引入了redis相关依赖
<dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId></dependency><!-- spring-boot-starter-data-redis --><dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-redis</artifactId></dependency><dependency> <groupId>org.apache.commons</groupId> <artifactId>commons-pool2</artifactId></dependency><!-- jedis --><dependency> <groupId>redis.clients</groupId> <artifactId>jedis</artifactId></dependency><dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> <optional>true</optional></dependency><dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope></dependency><!-- commons-lang3 --><dependency> <groupId>org.apache.commons</groupId> <artifactId>commons-lang3</artifactId></dependency><!-- org.json/json --><dependency> <groupId>org.json</groupId> <artifactId>json</artifactId> <version>20190722</version></dependency>
2、application.yml：主要是配置redis
server: port: 6666spring: application: name: idempotent-api redis: host: 192.168.2.43 port: 6379
3、业务代码：
•新建一个枚举，列出常用返回信息，如下：
@Getter@AllArgsConstructorpublic enum ResultEnum { REPEATREQUEST(405, "重复请求"), OPERATEEXCEPTION(406, "操作异常"), HEADERNOTOKEN(407, "请求头未携带token"), ERRORTOKEN(408, "token正确") ; private Integer code; private String msg;}
•新建一个JsonUtil，当请求异常时往页面中输出json：
public class JsonUtil { private JsonUtil() {} public static void writeJsonToPage(HttpServletResponse response, String msg) { PrintWriter writer = null; response.setCharacterEncoding("UTF-8"); response.setContentType("text/html; charset=utf-8"); try { writer = response.getWriter(); writer.print(msg); } catch (IOException e) { } finally { if (writer != null) writer.close(); } }}
•新建一个RedisUtil，用来操作redis：
@Componentpublic class RedisUtil {
private RedisUtil() {}
private static RedisTemplate redisTemplate;
@Autowired public void setRedisTemplate(@SuppressWarnings("rawtypes") RedisTemplate redisTemplate) { redisTemplate.setKeySerializer(new StringRedisSerializer()); //设置序列化Value的实例化对象 redisTemplate.setValueSerializer(new GenericJackson2JsonRedisSerializer()); RedisUtil.redisTemplate = redisTemplate; }
/** * 设置key-value，过期时间为timeout秒 * @param key * @param value * @param timeout */ public static void setString(String key, String value, Long timeout) { redisTemplate.opsForValue().set(key, value, timeout, TimeUnit.SECONDS); }
/** * 设置key-value * @param key * @param value */ public static void setString(String key, String value) { redisTemplate.opsForValue().set(key, value); }
/** * 获取key-value * @param key * @return */ public static String getString(String key) { return (String) redisTemplate.opsForValue().get(key); }
/** * 判断key是否存在 * @param key * @return */ public static boolean isExist(String key) { return redisTemplate.hasKey(key); }
/** * 删除key * @param key * @return */ public static boolean delKey(String key) { return redisTemplate.delete(key); }}
•新建一个TokenUtil，用来生成和校验token：生成token没什么好说的，这里为了简单直接用uuid生成，然后放入redis中。校验token，如果用户没有携带token，直接返回false；如果携带了token，但是redis中没有这个token，说明已经被删除了，即已经访问了，返回false；如果redis中有，但是redis中的token和用户携带的token不一致，也返回false；有且一致，说明是第一次访问，就将redis中的token删除，然后返回true。
public class TokenUtil {
private TokenUtil() {}
private static final String KEY = "token"; private static final String CODE = "code"; private static final String MSG = "msg"; private static final String JSON = "json"; private static final String RESULT = "result";
/** * 生成token并放入redis中 * @return */ public static String createToken() { String token = UUID.randomUUID().toString(); RedisUtil.setString(KEY, token, 60L); return RedisUtil.getString(KEY); }
/** * 校验token * @param request * @return * @throws JSONException */ public static Map<String, Object> checkToken(HttpServletRequest request) throws JSONException { String headerToken = request.getHeader(KEY); JSONObject json = new JSONObject(); Map<String, Object> resultMap = new HashMap<>(); // 请求头中没有携带token，直接返回false if (StringUtils.isEmpty(headerToken)) { json.put(CODE, ResultEnum.HEADERNOTOKEN.getCode()); json.put(MSG, ResultEnum.HEADERNOTOKEN.getMsg()); resultMap.put(RESULT, false); resultMap.put(JSON, json.toString()); return resultMap; }
if (StringUtils.isEmpty(RedisUtil.getString(KEY))) { // 如果redis中没有token，说明已经访问成功过了，直接返回false json.put(CODE, ResultEnum.REPEATREQUEST.getCode()); json.put(MSG, ResultEnum.REPEATREQUEST.getMsg()); resultMap.put(RESULT, false); resultMap.put(JSON, json.toString()); return resultMap; } else { // 如果redis中有token，就删除掉，删除成功返回true，删除失败返回false String redisToken = RedisUtil.getString(KEY); boolean result = false; if (!redisToken.equals(headerToken)) { json.put(CODE, ResultEnum.ERRORTOKEN.getCode()); json.put(MSG, ResultEnum.ERRORTOKEN.getMsg()); } else { result = RedisUtil.delKey(KEY); String msg = result ? null : ResultEnum.OPERATEEXCEPTION.getMsg(); json.put(CODE, 400); json.put(MSG, msg); } resultMap.put(RESULT, result); resultMap.put(JSON, json.toString()); return resultMap; } }}
新建一个注解，用来标注需要进行幂等的接口：
@Target(ElementType.METHOD)@Retention(RetentionPolicy.RUNTIME)public @interface NeedIdempotent {} 接着要新建一个拦截器，对有@NeedIdempotent注解的方法进行拦截，进行自动幂等。
public class IdempotentInterceptor implements HandlerInterceptor{
@Override public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse,Object object) throws JSONException { // 拦截的不是方法，直接放行 if (!(object instanceof HandlerMethod)) { return true; } HandlerMethod handlerMethod = (HandlerMethod) object; Method method = handlerMethod.getMethod(); // 如果是方法，并且有@NeedIdempotent注解，就自动幂等 if (method.isAnnotationPresent(NeedIdempotent.class)) { Map<String, Object> resultMap = TokenUtil.checkToken(httpServletRequest); boolean result = (boolean) resultMap.get("result"); String json = (String) resultMap.get("json"); if (!result) { JsonUtil.writeJsonToPage(httpServletResponse, json); } return result; } else { return true; } }
@Override public void postHandle(HttpServletRequest httpServletRequest,HttpServletResponse httpServletResponse, Object o,ModelAndView modelAndView) { }
@Override public void afterCompletion(HttpServletRequest httpServletRequest,HttpServletResponse httpServletResponse,Object o, Exception e) { }}
然后将这个拦截器配置到spring中去： @Configurationpublic class InterceptorConfig implements WebMvcConfigurer {
@Override public void addInterceptors(InterceptorRegistry registry) { registry.addInterceptor(idempotentInterceptor()) .addPathPatterns("/**"); } @Bean public IdempotentInterceptor idempotentInterceptor() { return new IdempotentInterceptor(); }
}
•最后新建一个controller，就可以愉快地进行测试了：
@RestController@RequestMapping("/idempotent")public class IdempotentApiController {
@NeedIdempotent @GetMapping("/hello") public String hello() { return "are you ok?"; }
@GetMapping("/token") public String token() { return TokenUtil.createToken(); }}
访问/token，不需要什么校验，访问/hello，就会自动幂等，每一次访问都要先获取token，一个token不能用两次。