什么是接口的幂等性，如何实现接口幂等性？，mongodb 实战第二版下载

@ControllerAdvice

public class MyControllerAdvice {

@ResponseBody

@ExceptionHandler(ServiceException.class)

public Response serviceExceptionHandler(ServiceException exception){

Response response=new Response(Integer.valueOf(exception.getCode()),exception.getMsg(),null);

return response;

}

}

3.3 编写创建 Token 和验证 Token 的接口以及实现类

@Service

public interface TokenService {

public Response createToken();

public Response checkToken(HttpServletRequest request);

}

具体实现类，核心的业务逻辑都写在注释中了

@Service

public class TokenServiceImpl implements TokenService {

@Autowired

private RedisTemplate redisTemplate;

@Override

public Response createToken() {

//生成 uuid 当作 token

String token = UUID.randomUUID().toString().replaceAll("-","");

//将生成的 token 存入 redis 中

redisTemplate.opsForValue().set(token,token);

//返回正确的结果信息

Response response=new Response(0,token.toString(),null);

return response;

}

@Override

public Response checkToken(HttpServletRequest request) {

//从请求头中获取 token

String token=request.getHeader("token");

if (StringUtils.isBlank(token)){

//如果请求头 token 为空就从参数中获取

token=request.getParameter("token");

//如果都为空抛出参数异常的错误

if (StringUtils.isBlank(token)){

throw new ServiceException(ResponseCode.ILLEGAL_ARGUMENT.getCode().toString(),ResponseCode.ILLEGAL_ARGUMENT.getMsg());

}

}

//如果 redis 中不包含该 token，说明 token 已经被删除了，抛出请求重复异常

if (!redisTemplate.hasKey(token)){

throw new ServiceException(ResponseCode.REPETITIVE_OPERATION.getCode().toString(),ResponseCode.REPETITIVE_OPERATION.getMsg());

}

//删除 token

Boolean del=redisTemplate.delete(token);

//如果删除不成功（已经被其他请求删除），抛出请求重复异常

if (!del){

throw new ServiceException(ResponseCode.REPETITIVE_OPERATION.getCode().toString(),ResponseCode.REPETITIVE_OPERATION.getMsg());

}

return new Response(0,"校验成功",null);

}

}

3.4 配置自定义注解

这是比较重要的一步，通过自定义注解在需要实现接口幂等性的方法上添加此注解，实现 token 验证

@Target({ElementType.METHOD})

@Retention(RetentionPolicy.RUNTIME)

public @interface ApiIdempotent {

}

接口拦截器

public class ApiIdempotentInterceptor implements HandlerInterceptor {

@Autowired

private TokenService tokenService;

@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();

ApiIdempotent methodAnnotation=method.getAnnotation(ApiIdempotent.class);

if (methodAnnotation != null){

// 校验通过放行，校验不通过全局异常捕获后输出返回结果

tokenService.checkToken(request);

}

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 {

}

}

3.5 配置拦截器以及 redis

配置 webConfig，添加拦截器

@Configuration

public class WebConfig implements WebMvcConfigurer {

@Override

public void addInterceptors(InterceptorRegistry registry) {

registry.addInterceptor(apiIdempotentInterceptor());

}

@Bean

public ApiIdempotentInterceptor apiIdempotentInterceptor() {

return new ApiIdempotentInterceptor();

}

}

配置 redis，使得中文可以正常传输

@Configuration

public class RedisConfig {

//自定义的 redistemplate

@Bean(name = "redisTemplate")

public RedisTemplate<String,Object> redisTemplate(RedisConnectionFactory factory){

//创建一个 RedisTemplate 对象，为了方便返回 key 为 string，value 为 Object

RedisTemplate<String,Object> template = new RedisTemplate<>();

template.setConnectionFactory(factory);

//设置 json 序列化配置

Jackson2JsonRedisSerializer jackson2JsonRedisSerializer=new

Jackson2JsonRedisSerializer(Object.class);

ObjectMapper objectMapper=new ObjectMapper();

objectMapper.setVisibility(PropertyAccessor.ALL, JsonAutoDetect.Visibility.ANY);

objectMapper.activateDefaultTyping(LaissezFaireSubTypeValidator.instance);

//string 的序列化

StringRedisSerializer stringRedisSerializer=new StringRedisSerializer();

//key 采用 string 的序列化方式

template.setKeySerializer(stringRedisSerializer);

//value 采用 jackson 的序列化方式

template.setValueSerializer(jackson2JsonRedisSerializer);

//hashkey 采用 string 的序列化方式

template.setHashKeySerializer(stringRedisSerializer);

//hashvalue 采用 jackson 的序列化方式

template.setHashValueSerializer(jackson2JsonRedisSerializer);

template.afterPropertiesSet();

return template;

}

}

最后是 controller

@RestController

@RequestMapping("/token")

public class TokenController {

@Autowired

private TokenService tokenService;

@GetMapping

public Response token(){

return tokenService.createToken();

}

@PostMapping("checktoken")

public Response checktoken(HttpServletRequest request){

return tokenService.checkToken(request);

}

}