Problem Description

SpringBoot project has integrated springfox. After updating SpringBoot to 2.6.0 the application fails to start and throws an exception: Failed to start bean 'documentationPluginsBootstrapper'; nested exception is java.lang.NullPointerException.

The exception stack is as follows.

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Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2021-12-23 16:52:35.735 ERROR 15348 --- [           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)
    at org.springframework.context.support.DefaultLifecycleProcessor.access$200(DefaultLifecycleProcessor.java:54)
    at org.springframework.context.support.DefaultLifecycleProcessor$LifecycleGroup.start(DefaultLifecycleProcessor.java:356)
    at org.springframework.context.support.DefaultLifecycleProcessor$$Lambda$778/18341126.accept(Unknown Source)
    at java.lang.Iterable.forEach(Iterable.java:75)
    at org.springframework.context.support.DefaultLifecycleProcessor.startBeans(DefaultLifecycleProcessor.java:155)
    at org.springframework.context.support.DefaultLifecycleProcessor.onRefresh(DefaultLifecycleProcessor.java:123)
    at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:935)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:586)
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:145)
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:730)
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:412)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:302)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1301)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1290)
    at com.chqiuu.test.TestApplication.main(TestApplication.java:23)
Caused by: java.lang.NullPointerException: null
    at springfox.documentation.spring.web.WebMvcPatternsRequestConditionWrapper.getPatterns(WebMvcPatternsRequestConditionWrapper.java:56)
    at springfox.documentation.RequestHandler.sortedPaths(RequestHandler.java:113)
    at springfox.documentation.spi.service.contexts.Orderings.lambda$byPatternsCondition$3(Orderings.java:89)
    at springfox.documentation.spi.service.contexts.Orderings$$Lambda$796/7205235.apply(Unknown Source)
    at java.util.Comparator.lambda$comparing$77a9974f$1(Comparator.java:469)
    at java.util.Comparator$$Lambda$68/3330950.compare(Unknown Source)
    at java.util.TimSort.countRunAndMakeAscending(TimSort.java:351)
    at java.util.TimSort.sort(TimSort.java:230)
    at java.util.Arrays.sort(Arrays.java:1512)
    at java.util.ArrayList.sort(ArrayList.java:1454)
    at java.util.stream.SortedOps$RefSortingSink.end(SortedOps.java:387)
    at java.util.stream.Sink$ChainedReference.end(Sink.java:258)
    at java.util.stream.Sink$ChainedReference.end(Sink.java:258)
    at java.util.stream.Sink$ChainedReference.end(Sink.java:258)
    at java.util.stream.Sink$ChainedReference.end(Sink.java:258)
    at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:513)
    at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:502)
    at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708)
    at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
    at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499)
    at springfox.documentation.spring.web.plugins.WebMvcRequestHandlerProvider.requestHandlers(WebMvcRequestHandlerProvider.java:81)
    at springfox.documentation.spring.web.plugins.AbstractDocumentationPluginsBootstrapper$$Lambda$790/3038834.apply(Unknown Source)
    at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
    at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1374)
    at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:512)
    at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:502)
    at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708)
    at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
    at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499)
    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)
    ... 15 common frames omitted

Solution

This problem has plagued me for a long time, but also on the Internet to find a lot of information, but also some people say springboot version upgrade caused by the problem. There are two solutions found.

  1. downgrade springboot to 2.5.7, but this is only a temporary solution to the problem, not a permanent solution.
  2. migrate from SpringFox to SpringDoc, this way you can deal with the problem, but the amount of changes is still a bit large for the project that is already online.

Neither of these solutions is what I want the most, and I recently researched the documentation for Spring Boot 2.6.0. I found that 2.6.0 started using path matching based on PathPatternParser, while the Springfox version has not been updated or uses AntPathMatcher which causes this problem.

documentation for Spring Boot 2.6.0

Handling this issue is also very simple. Just modify the yaml file to change the SpringBoot path matching pattern to AntPathMatcher.

The configuration is as follows.

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spring:
  mvc:
    pathmatch:
      matching-strategy: ANT_PATH_MATCHER

Reference https://blog.csdn.net/QIU176161650/article/details/122111567