Where the Problem Started
Swagger failures often look like documentation-tool problems, but they frequently expose framework version mismatches, routing strategy changes, and security configuration at the same time. This post follows a SpringFox parse error in Spring Boot and records the compatibility points behind the fix.
I configured Swagger for detailed API documentation. We could have used it for pre-documentation to help collaboration and communication, but at the time we decided to organize the API in Notion, so I introduced it now that feature implementation is finished.
Integrating it with Spring Boot is a little tricky because the configuration differs by version.
Implementation Path
implementation 'io.springfox:springfox-boot-starter:3.0.0'
implementation 'io.springfox:springfox-swagger-ui:3.0.0'Start by adding the Swagger dependencies. Spring Boot has several Swagger/OpenAPI integration options, and Springfox was one of the common choices for this setup.
How I Verified It
After that, you need to create a Docket bean. This is from Baeldung’s official documentation. This is where the configuration changes depending on the Spring Boot version, and in the 2.7.x version currently used in this project, an error similar to the following appears.
00:50:54.956 [main] ERROR SpringApplication[reportFailure:830] - Application run failed
org.springframework.context.ApplicationContextException: Failed to start bean 'documentationPluginsBootstrapper'; nested exception is java.lang.NullPointerException: Cannot invoke "org.springframework.web.servlet.mvc.condition.PatternsRequestCondition.getPatterns()" because "this.condition" is null
at org.springframework.context.support.DefaultLifecycleProcessor.doStart(DefaultLifecycleProcessor.java:181)
at org.springframework.context.support.DefaultLifecycleProcessor.access$200(DefaultLifecycleProcessor.java:54)
at org.springframework.context.support.DefaultLifecycleProcessor$LifecycleGroup.start(DefaultLifecycleProcessor.java:356)
at java.base/java.lang.Iterable.forEach(Iterable.java:75)
at org.springframework.context.support.DefaultLifecycleProcessor.startBeans(DefaultLifecycleProcessor.java:155)
at org.springframework.context.support.DefaultLifecycleProcessor.onRefresh(DefaultLifecycleProcessor.java:123)
at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:935)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:586)
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:145)
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:740)
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:415)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:303)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1312)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1301)
at com.atlas.psp.AtlasRouterApplication.main(AtlasRouterApplication.java:53)
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)
at springfox.documentation.RequestHandler.sortedPaths(RequestHandler.java:113)
at springfox.documentation.spi.service.contexts.Orderings.lambda$byPatternsCondition$3(Orderings.java:89)
at java.base/java.util.Comparator.lambda$comparing$77a9974f$1(Comparator.java:473)
at java.base/java.util.TimSort.countRunAndMakeAscending(TimSort.java:355)
at java.base/java.util.TimSort.sort(TimSort.java:234)
at java.base/java.util.Arrays.sort(Arrays.java:1307)
at java.base/java.util.ArrayList.sort(ArrayList.java:1721)
at java.base/java.util.stream.SortedOps$RefSortingSink.end(SortedOps.java:392)
at java.base/java.util.stream.Sink$ChainedReference.end(Sink.java:258)
at java.base/java.util.stream.Sink$ChainedReference.end(Sink.java:258)
at java.base/java.util.stream.Sink$ChainedReference.end(Sink.java:258)
at java.base/java.util.stream.Sink$ChainedReference.end(Sink.java:258)
at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:510)
at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499)
at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:921)
at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
at java.base/java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:682)
at springfox.documentation.spring.web.plugins.WebMvcRequestHandlerProvider.requestHandlers(WebMvcRequestHandlerProvider.java:81)
at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:197)
at java.base/java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1625)
at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:509)
at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499)
at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:921)
at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
at java.base/java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:682)
at springfox.documentation.spring.web.plugins.AbstractDocumentationPluginsBootstrapper.withDefaults(AbstractDocumentationPluginsBootstrapper.java:107)
at springfox.documentation.spring.web.plugins.AbstractDocumentationPluginsBootstrapper.buildContext(AbstractDocumentationPluginsBootstrapper.java:91)
at springfox.documentation.spring.web.plugins.AbstractDocumentationPluginsBootstrapper.bootstrapDocumentationPlugins(AbstractDocumentationPluginsBootstrapper.java:82)
at springfox.documentation.spring.web.plugins.DocumentationPluginsBootstrapper.start(DocumentationPluginsBootstrapper.java:100)
at org.springframework.context.support.DefaultLifecycleProcessor.doStart(DefaultLifecycleProcessor.java:178)
... 14 common frames omittedApparently this happens because PathPatternParser changed with the Spring Boot 2.6 release, so this needs to be added to application.yaml.
spring.mvc.pathmatch.matching-strategy=ant_path_matcherYou also need to add the following Bean to SpringFoxConfig.
@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));
}The root cause is the PathPatternParser issue mentioned earlier. Swagger fails while scanning API endpoints and their metadata. PathPatternParser was designed for richer HTTP path matching, but that behavior does not line up cleanly with the Springfox scanning path used here.
After that, if Spring Security is configured, add the Swagger-related endpoints to antMatchers.
.antMatchers("/auth/signup","/profile", "/health","/swagger-ui/**", "/v3/api-docs", "/v2/api-docs").permitAll()Then if you go to v2/api-docs,
The JSON response appears from the docs endpoint, and swagger-ui renders that response into the familiar interactive API page.
Debugging Takeaway
The core of this issue was not Swagger itself, but the habit of suspecting version boundaries. When a library depends on framework internals, even a minor upgrade can affect routing, path matching, and security whitelists together. Reading the error log through to the end and checking the release change is what narrows the problem quickly.
The API endpoints are all collected like this, and you can also send requests directly from here.