幂等性,就是只多次操作的结果是一致的。这里可能有人会有疑问。
问:为什么要多次操作结果都一致呢?比如我查询数据,每次查出来的都一样,即使我修改了每次查出来的也都要一样吗?
答:我们说的多次,是指同一次请求中的多次操作。这个多次操作可能会在如下情况发生:
经过上面的描述,相信大家已经清楚了什么叫接口幂等性及其重要性。那么如何设计呢?大致有以下几种方案:
token机制
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: 6666
spring:
application:
name: idempotent-api
redis:
host: 192.168.2.43
port: 6379
3、业务代码:
@Getter
@AllArgsConstructor
public 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;
}
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();
}
}
}
@Component
public 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);
}
}
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;
}
}
}
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface NeedIdempotent {
}
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) {
}
}
@Configuration
public class InterceptorConfig implements WebMvcConfigurer {
@Override
public void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor(idempotentInterceptor())
.addPathPatterns("/**");
}
@Bean
public IdempotentInterceptor idempotentInterceptor() {
return new IdempotentInterceptor();
}
}
@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。