浅谈SpringMVC HandlerInterceptor诡异问题排查

/**
 * 用户登录下上文
 *
 * @author : jamesfu
 * @date : 22/5/2019
 * @time : 9:18 AM
 */
@Data
public class UserContext {
  private final static ThreadLocal<UserContext> threadLocal = new ThreadLocal<>();

  private Long id;

  private String loginName;

  public static UserContext get() {
    UserContext context = threadLocal.get();
    if (context == null) {
      // TODO(james.h.fu):根据请求上下文获取token, 然后恢复用户登录下上文
      context = new UserContext() {{
        setId(1L);
        setLoginName("james.h.fu1");
      }};
      threadLocal.set(context);
    }

    return context;
  }

  public static void clear() {
    threadLocal.remove();
  }

  public static void set(UserContext context) {
    if (context != null) {
      threadLocal.set(context);
    }
  }
}

/**
 * 拦截器注册配置
 *
 * @author : jamesfu
 * @date : 22/5/2019
 * @time : 9:15 AM
 */
@Configuration
public class FilterConfig implements WebMvcConfigurer {
  @Autowired
  private JsonRpcInterceptor jsonRpcInterceptor;

  @Override
  public void addInterceptors(InterceptorRegistry registry) {
    registry.addInterceptor(jsonRpcInterceptor)
        .addPathPatterns("/json.rpc");
  }
}

/**
	 * Process the actual dispatching to the handler.
	 * <p>The handler will be obtained by applying the servlet's HandlerMappings in order.
	 * The HandlerAdapter will be obtained by querying the servlet's installed HandlerAdapters
	 * to find the first that supports the handler class.
	 * <p>All HTTP methods are handled by this method. It's up to HandlerAdapters or handlers
	 * themselves to decide which methods are acceptable.
	 * @param request current HTTP request
	 * @param response current HTTP response
	 * @throws Exception in case of any kind of processing failure
	 */
	protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception

/**
	 * Apply preHandle methods of registered interceptors.
	 * @return {@code true} if the execution chain should proceed with the
	 * next interceptor or the handler itself. Else, DispatcherServlet assumes
	 * that this interceptor has already dealt with the response itself.
	 */
	boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception {
		HandlerInterceptor[] interceptors = getInterceptors();
		if (!ObjectUtils.isEmpty(interceptors)) {
			for (int i = 0; i < interceptors.length; i++) {
				HandlerInterceptor interceptor = interceptors[i];
				if (!interceptor.preHandle(request, response, this.handler)) {
					triggerAfterCompletion(request, response, null);
					return false;
				}
				this.interceptorIndex = i;
			}
		}
		return true;
	}

/**
	 * Trigger afterCompletion callbacks on the mapped HandlerInterceptors.
	 * Will just invoke afterCompletion for all interceptors whose preHandle invocation
	 * has successfully completed and returned true.
	 */
	void triggerAfterCompletion(HttpServletRequest request, HttpServletResponse response, @Nullable Exception ex)
			throws Exception {

		HandlerInterceptor[] interceptors = getInterceptors();
		if (!ObjectUtils.isEmpty(interceptors)) {
			for (int i = this.interceptorIndex; i >= 0; i--) {
				HandlerInterceptor interceptor = interceptors[i];
				try {
					interceptor.afterCompletion(request, response, this.handler, ex);
				}
				catch (Throwable ex2) {
					logger.error("HandlerInterceptor.afterCompletion threw exception", ex2);
				}
			}
		}
	}