NullPointerException when upgrading Spring Boot to version 2.6.2-CodePudding

I upgraded by Spring Boot version from 2.5.4 to 2.6.2.

Now my app fails at startup because of this error - see below.

Any ideas how to fix it?

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled. ||| 
2022-01-05 02:48:10.673 [main] ERROR org.springframework.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 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.cmp.tpe.rcf.MicroserviceApplication.main(MicroserviceApplication.java:19)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:49)
    at org.springframework.boot.loader.Launcher.launch(Launcher.java:108)
    at org.springframework.boot.loader.Launcher.launch(Launcher.java:58)
    at org.springframework.boot.loader.JarLauncher.main(JarLauncher.java:88)
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.util.TimSort.countRunAndMakeAscending(TimSort.java:355)
    at java.util.TimSort.sort(TimSort.java:220)
    at java.util.Arrays.sort(Arrays.java:1438)
    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)
    ... 22 common frames omitted

CodePudding user response：

Use Spring Migrator to know what all dependencies needs to be updated

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-properties-migrator</artifactId>
            <scope>compile</scope>
        </dependency>

Check this for more info - https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-2.6-Release-Notes

And also for Spring Fox - https://github.com/springfox/springfox/issues/3462

CodePudding user response：

I know this does not solve your problem directly, but consider moving to springdoc. Springfox is so buggy at this point that is a pain to use. I've moved to springdoc 2 years ago because of its Spring WebFlux support and I am very happy about it. Additionally, it also supports Kotlin Coroutines, which I am not sure Springfox does.

If you decide to migrate, springdoc even has a migration guide.