When a SpringBoot high version project introduces swagger version 2.9.2, an error is reported when starting the project.

as a result of:

After springboot version 2.6.0, the default path matching policy of spring MVC was changed from antpathmatcher to pathpatternparser, resulting in an error! (the lower version of swagger is not compatible with the higher version of springboot)

The solution is to switch back to the original AntPathMatcher and configure it in the configuration file

spring.mvc.pathmatch.matching-strategy = ant_path_matcher

2022-04-01 10:59:37.480 ERROR 5252 --- [           main] o.s.boot.SpringApplication               : Application run failed

org.springframework.context.ApplicationContextException: Failed to start bean 'documentationPluginsBootstrapper'; nested exception is java.lang.NullPointerException
	at org.springframework.context.support.DefaultLifecycleProcessor.doStart(DefaultLifecycleProcessor.java:181) ~[spring-context-5.3.13.jar:5.3.13]
	at org.springframework.context.support.DefaultLifecycleProcessor.access$200(DefaultLifecycleProcessor.java:54) ~[spring-context-5.3.13.jar:5.3.13]
	at org.springframework.context.support.DefaultLifecycleProcessor$LifecycleGroup.start(DefaultLifecycleProcessor.java:356) ~[spring-context-5.3.13.jar:5.3.13]
	at java.lang.Iterable.forEach(Iterable.java:75) ~[na:1.8.0_271]
	at org.springframework.context.support.DefaultLifecycleProcessor.startBeans(DefaultLifecycleProcessor.java:155) ~[spring-context-5.3.13.jar:5.3.13]
	at org.springframework.context.support.DefaultLifecycleProcessor.onRefresh(DefaultLifecycleProcessor.java:123) ~[spring-context-5.3.13.jar:5.3.13]
	at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:935) ~[spring-context-5.3.13.jar:5.3.13]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:586) ~[spring-context-5.3.13.jar:5.3.13]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:145) ~[spring-boot-2.6.1.jar:2.6.1]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:730) [spring-boot-2.6.1.jar:2.6.1]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:412) [spring-boot-2.6.1.jar:2.6.1]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:302) [spring-boot-2.6.1.jar:2.6.1]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1301) [spring-boot-2.6.1.jar:2.6.1]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1290) [spring-boot-2.6.1.jar:2.6.1]
	at com.ji.Springboot09SwaggerApplication.main(Springboot09SwaggerApplication.java:10) [classes/:na]
Caused by: java.lang.NullPointerException: null
	at springfox.documentation.spring.web.WebMvcPatternsRequestConditionWrapper.getPatterns(WebMvcPatternsRequestConditionWrapper.java:56) ~[springfox-spring-webmvc-3.0.0.jar:3.0.0]
	at springfox.documentation.RequestHandler.sortedPaths(RequestHandler.java:113) ~[springfox-core-3.0.0.jar:3.0.0]
	at springfox.documentation.spi.service.contexts.Orderings.lambda$byPatternsCondition$3(Orderings.java:89) ~[springfox-spi-3.0.0.jar:3.0.0]
	at java.util.Comparator.lambda$comparing$77a9974f$1(Comparator.java:469) ~[na:1.8.0_271]
	at java.util.TimSort.countRunAndMakeAscending(TimSort.java:355) ~[na:1.8.0_271]
	at java.util.TimSort.sort(TimSort.java:220) ~[na:1.8.0_271]
	at java.util.Arrays.sort(Arrays.java:1512) ~[na:1.8.0_271]
	at java.util.ArrayList.sort(ArrayList.java:1464) ~[na:1.8.0_271]
	at java.util.stream.SortedOps$RefSortingSink.end(SortedOps.java:387) ~[na:1.8.0_271]
	at java.util.stream.Sink$ChainedReference.end(Sink.java:258) ~[na:1.8.0_271]
	at java.util.stream.Sink$ChainedReference.end(Sink.java:258) ~[na:1.8.0_271]
	at java.util.stream.Sink$ChainedReference.end(Sink.java:258) ~[na:1.8.0_271]
	at java.util.stream.Sink$ChainedReference.end(Sink.java:258) ~[na:1.8.0_271]
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:483) ~[na:1.8.0_271]
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:472) ~[na:1.8.0_271]
	at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708) ~[na:1.8.0_271]
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) ~[na:1.8.0_271]
	at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499) ~[na:1.8.0_271]
	at springfox.documentation.spring.web.plugins.WebMvcRequestHandlerProvider.requestHandlers(WebMvcRequestHandlerProvider.java:81) ~[springfox-spring-webmvc-3.0.0.jar:3.0.0]
	at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193) ~[na:1.8.0_271]
	at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1384) ~[na:1.8.0_271]
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:482) ~[na:1.8.0_271]
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:472) ~[na:1.8.0_271]
	at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708) ~[na:1.8.0_271]
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) ~[na:1.8.0_271]
	at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499) ~[na:1.8.0_271]
	at springfox.documentation.spring.web.plugins.AbstractDocumentationPluginsBootstrapper.withDefaults(AbstractDocumentationPluginsBootstrapper.java:107) ~[springfox-spring-web-3.0.0.jar:3.0.0]
	at springfox.documentation.spring.web.plugins.AbstractDocumentationPluginsBootstrapper.buildContext(AbstractDocumentationPluginsBootstrapper.java:91) ~[springfox-spring-web-3.0.0.jar:3.0.0]
	at springfox.documentation.spring.web.plugins.AbstractDocumentationPluginsBootstrapper.bootstrapDocumentationPlugins(AbstractDocumentationPluginsBootstrapper.java:82) ~[springfox-spring-web-3.0.0.jar:3.0.0]
	at springfox.documentation.spring.web.plugins.DocumentationPluginsBootstrapper.start(DocumentationPluginsBootstrapper.java:100) ~[springfox-spring-web-3.0.0.jar:3.0.0]
	at org.springframework.context.support.DefaultLifecycleProcessor.doStart(DefaultLifecycleProcessor.java:178) ~[spring-context-5.3.13.jar:5.3.13]
	... 14 common frames omitted