How to Fix Spring Boot 2.6 Swagger NullPointerException by Switching to ant_path_matcher

Recently, after upgrading the Spring Boot version, a NullPointerException appeared when integrating Swagger, which many developers initially blamed on incorrect configuration.

The error stack trace is shown below:

Caused by: java.lang.NullPointerException: Cannot invoke "org.springframework.web.servlet.mvc.condition.PatternsRequestCondition.getPatterns()" because "this.condition" is null
    at springfox.documentation.spring.web.WebMvcPatternsRequestConditionWrapper.getPatterns(WebMvcPatternsRequestConditionWrapper.java:56) ~[springfox-spring-webmvc-3.0.0.jar:3.0.0]
    at spring... (stack trace continues)
    ... 14 common frames omitted

The problem is discussed in a closed Spring Boot issue and an active Springfox issue, and it mainly occurs in Spring Boot 2.6 and later because the new PathPatternParser replaces the old matching mechanism.

Two common solutions have emerged from the discussion:

Switch the path‑matching strategy back to ant_path_matcher by adding the following property:

spring.mvc.pathmatch.matching-strategy=ant_path_matcher

Add a custom @Bean that defines WebMvcEndpointHandlerMapping:

@Bean
public WebMvcEndpointHandlerMapping webEndpointServletHandlerMapping(WebEndpointsSupplier webEndpointsSupplier, ServletEndpointsSupplier servletEndpointsSupplier, ControllerEndpointsSupplier controllerEndpointsSupplier, EndpointMediaTypes endpointMediaTypes, CorsEndpointProperties corsProperties, WebEndpointProperties webEndpointProperties, Environment environment) {
    List<ExposableEndpoint<?>> allEndpoints = new ArrayList();
    Collection<ExposableWebEndpoint> webEndpoints = webEndpointsSupplier.getEndpoints();
    allEndpoints.addAll(webEndpoints);
    allEndpoints.addAll(servletEndpointsSupplier.getEndpoints());
    allEndpoints.addAll(controllerEndpointsSupplier.getEndpoints());
    String basePath = webEndpointProperties.getBasePath();
    EndpointMapping endpointMapping = new EndpointMapping(basePath);
    boolean shouldRegisterLinksMapping = this.shouldRegisterLinksMapping(webEndpointProperties, environment, basePath);
    return new WebMvcEndpointHandlerMapping(endpointMapping, webEndpoints, endpointMediaTypes, corsProperties.toCorsConfiguration(), new EndpointLinksResolver(allEndpoints, basePath), shouldRegisterLinksMapping, null);
}

private boolean shouldRegisterLinksMapping(WebEndpointProperties webEndpointProperties, Environment environment, String basePath) {
    return webEndpointProperties.getDiscovery().isEnabled() && (StringUtils.hasText(basePath) || ManagementPortType.get(environment).equals(ManagementPortType.DIFFERENT));
}

I applied the first solution by adding the property, and the issue was resolved. If you encounter the same problem, try switching the matching strategy or adding the bean as shown above.