How to Debug Spring Boot Controllers: Logging, Timing, and 404 Handling

1. Controller Interface Debugging

Logging request parameters, headers, and responses is essential for troubleshooting, security auditing, and monitoring. In most cases, detailed logs help quickly locate errors or verify backend logic.

Problem Diagnosis: View request data to pinpoint incorrect or missing parameters and verify response correctness.

Security Auditing: Record detailed information to trace sensitive data flow and detect potential vulnerabilities.

Monitoring & Alerts: Integrate logs with monitoring systems to trigger alerts on abnormal behavior.

In a Spring Boot project, set the logging level to TRACE for the web package:

logging:
  level:
    web: TRACE

Example controller:

@GetMapping("/index")
public Object index(Long id, String kw) {
  HttpHeaders headers = new HttpHeaders();
  headers.add("x-version", "1.0.0");
  ResponseEntity<Object> response = new ResponseEntity<>(
        String.format("【id = %d, kw = %s】", id, kw),
        headers,
        HttpStatusCode.valueOf(200));
  return response;
}

After enabling log-request-details: true, the logs include full request and response details, which is invaluable for debugging (not recommended for production).

spring:
  mvc:
    log-request-details: true

2. Measuring Interface Duration

Tracking request processing time aids performance monitoring and fault diagnosis. Common approaches include AOP, interceptors, and external monitoring tools, each with pros and cons.

AOP – Advantages: decoupled code, reusable, easy maintenance. Disadvantages: added complexity, slight performance overhead. Interceptor – Advantages: simple integration with Spring MVC. Disadvantages: limited to web layer. Performance Monitoring Tools – Advantages: comprehensive features, strong visualization. Disadvantages: external dependencies, higher cost.

The article demonstrates a lightweight Spring‑provided solution using ServletRequestHandledEvent:

@Component
public class TimeCountListener implements ApplicationListener<ServletRequestHandledEvent> {
    @Override
    public void onApplicationEvent(ServletRequestHandledEvent event) {
        Throwable failureCause = event.getFailureCause();
        if (failureCause != null) {
            System.err.printf("错误原因: %s%n", failureCause.getMessage());
        }
        System.err.println("========================================");
        System.err.printf(
            "请求客户端地址：%s
请求URL: %s
请求Method: %s
请求耗时: %d毫秒%n",
            event.getClientAddress(),
            event.getRequestUrl(),
            event.getMethod(),
            event.getProcessingTimeMillis()
        );
        System.err.println("========================================");
    }
}

Testing the same /index endpoint shows accurate timing information:

3. Handling Unpleasant 404 Errors

When a request targets a non‑existent endpoint, Spring Boot returns an error page whose format depends on the Accept header. To unify the response format, replace the default DefaultHandlerExceptionResolver.

Configuration (Spring Boot 3.x):

# Throw exception when no handler is found (will be removed in 3.4)
spring.mvc.throw-exception-if-no-handler-found
# Disable static resource mapping
spring.web.resources.add-mappings

Adjust static resource pattern if needed:

spring:
  mvc:
    static-path-pattern: /static/**

Custom exception resolver:

@Component
public class ExceptionResolverConfig implements WebMvcConfigurer {
    @Override
    public void extendHandlerExceptionResolvers(List<HandlerExceptionResolver> resolvers) {
        resolvers.remove(resolvers.size() - 1);
        resolvers.add(new DefaultHandlerExceptionResolver() {
            @Override
            protected ModelAndView handleNoHandlerFoundException(NoHandlerFoundException ex,
                    HttpServletRequest request, HttpServletResponse response, Object handler) throws IOException {
                ModelAndView mv = new ModelAndView(new View() {
                    @Override
                    public void render(Map<String, ?> model, HttpServletRequest request, HttpServletResponse response) throws Exception {
                        response.getWriter().println(ex.getMessage());
                    }
                });
                return mv;
            }
        });
    }
}

Resulting unified JSON error response:

Other solutions exist; choose the one that fits your project requirements.