将 Spring Boot 升级到 2.6.2 版本时出现 NullPointerException答案

【问题标题】：NullPointerException when upgrading Spring Boot to version 2.6.2将 Spring Boot 升级到 2.6.2 版本时出现 NullPointerException
【发布时间】：2022-01-05 07:52:01
【问题描述】：

我通过 Spring Boot 版本从 2.5.4 升级到 2.6.2。

现在我的应用由于这个错误而在启动时失败 - 见下文。

有什么解决办法吗？

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

【问题讨论】：

您是否相应地升级了其他依赖项，例如springfox 文档之一？看看这里，这有帮助吗：stackoverflow.com/questions/70059018/…?
@Thomas 我不知道我也应该升级其他东西。我还应该做什么？
请粘贴您的 swagger 依赖配置。这个问题应该是springboot2.6和swagger冲突。您可以尝试更新 swagger 版本。
我认为我的问题与此有关：stackoverflow.com/a/70037507/2300597

标签： java spring-boot swagger springfox

【解决方案1】：

使用 Spring Migrator 了解所有依赖项需要更新的内容

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

也适用于 Spring Fox - https://github.com/springfox/springfox/issues/3462

【讨论】：

【解决方案2】：

我知道这并不能直接解决您的问题，但请考虑转至 springdoc。 Springfox 在这一点上是如此的错误，以至于使用起来很痛苦。由于 Spring WebFlux 支持，我在 2 年前搬到了 springdoc，对此我感到非常高兴。此外，它还支持 Kotlin Coroutines，我不确定 Springfox 是否支持。

如果您决定迁移，springdoc 甚至还有 migration guide。

【讨论】：

【解决方案3】：

以下问题评论中提到的解决方法似乎也适用于使用弹簧执行器的人。

https://github.com/springfox/springfox/issues/3462#issuecomment-1010721223

【讨论】：