SpringBoot2.6中使用springfox报documentationPluginsBootstrapper问题
在最新的SpringBoot2.6中使用Swagger，引入springfox-swagger2后（版本2.9.2），启动项目报无法加载documentationPluginsBootstrapper：
ERROR [main][org.springframework.boot.SpringApplication]:819 - 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)
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:730)
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:412)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:302)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1301)
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1290)
at com.ikang.mis.sms.MisSmsApplication.main(MisSmsApplication.java:10)
Caused by: java.lang.NullPointerException: null
at springfox.documentation.spi.service.contexts.Orderings$8.compare(Orderings.java:112)
at springfox.documentation.spi.service.contexts.Orderings$8.compare(Orderings.java:109)
at com.google.common.collect.ComparatorOrdering.compare(ComparatorOrdering.java:37)
at java.base/java.util.TimSort.countRunAndMakeAscending(TimSort.java:355)
at java.base/java.util.TimSort.sort(TimSort.java:220)
at java.base/java.util.Arrays.sort(Arrays.java:1442)
at com.google.common.collect.Ordering.sortedCopy(Ordering.java:855)
at springfox.documentation.spring.web.plugins.WebMvcRequestHandlerProvider.requestHandlers(WebMvcRequestHandlerProvider.java:57)
at springfox.documentation.spring.web.plugins.DocumentationPluginsBootstrapper$2.apply(DocumentationPluginsBootstrapper.java:138)
at springfox.documentation.spring.web.plugins.DocumentationPluginsBootstrapper$2.apply(DocumentationPluginsBootstrapper.java:135)
at com.google.common.collect.Iterators$7.transform(Iterators.java:750)
at com.google.common.collect.TransformedIterator.next(TransformedIterator.java:47)
at com.google.common.collect.TransformedIterator.next(TransformedIterator.java:47)
at com.google.common.collect.MultitransformedIterator.hasNext(MultitransformedIterator.java:52)
at com.google.common.collect.MultitransformedIterator.hasNext(MultitransformedIterator.java:50)
at com.google.common.collect.ImmutableList.copyOf(ImmutableList.java:249)
at com.google.common.collect.ImmutableList.copyOf(ImmutableList.java:209)
at com.google.common.collect.FluentIterable.toList(FluentIterable.java:614)
at springfox.documentation.spring.web.plugins.DocumentationPluginsBootstrapper.defaultContextBuilder(DocumentationPluginsBootstrapper.java:111)
at springfox.documentation.spring.web.plugins.DocumentationPluginsBootstrapper.buildContext(DocumentationPluginsBootstrapper.java:96)
at springfox.documentation.spring.web.plugins.DocumentationPluginsBootstrapper.start(DocumentationPluginsBootstrapper.java:167)
at org.springframework.context.support.DefaultLifecycleProcessor.doStart(DefaultLifecycleProcessor.java:178)
... 14 common frames omitted
Process finished with exit code 1
出现以上错误，是由Springfox的一个bug引起的，这是在假设SpringMVC是如何建立的，但这并不总是成立的。具体来说，它假设MVC的路径匹配将使用基于Ant-based的路径匹配器，而不是基于PathPattern-based的匹配器。基于PathPattern-based的匹配已经是一个选项，并且是SpringBoot2.6的默认选项。
如Spring Boot 2.6发行说明中所述，您可以通过在application.properties文件中将Spring.mvc.pathmatch.matching-strategy设置为ant path matcher来恢复Springfox假定将使用的配置。请注意，只有在不使用Spring Boot的执行器时，此功能才起作用。无论配置的匹配策略如何，执行器始终使用基于路径模式的解析。如果您想在Spring Boot 2.6及更高版本中将其与执行器一起使用，则需要对Springfox进行更改。
