Spring Boot2.6之后，swagger的包，WebMvcPatternsRequestConditionWrapper.getPatterns NPE 异常

文章目录

• Spring Boot2.6之后，swagger的包，WebMvcPatternsRequestConditionWrapper.getPatterns NPE 异常
• 报错现象
• • 堆栈
  • 截图
• 排查过程
• 解决方案

报错现象

堆栈

2022-03-13 02:40:28.000 ERROR [16312] --- [           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 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:740)
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:415)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:303)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1312)
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1301)
	at com.example.demo1.Demo1Application.main(Demo1Application.java:22)
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$3(Orderings.java:89)
	at java.base/java.util.Comparator.lambda$comparing$77a9974f$1(Comparator.java:469)
	at java.base/java.util.TimSort.countRunAndMakeAscending(TimSort.java:355)
	at java.base/java.util.TimSort.sort(TimSort.java:234)
	at java.base/java.util.Arrays.sort(Arrays.java:1515)
	at java.base/java.util.ArrayList.sort(ArrayList.java:1750)
	at java.base/java.util.stream.SortedOps$RefSortingSink.end(SortedOps.java:392)
	at java.base/java.util.stream.Sink$ChainedReference.end(Sink.java:258)
	at java.base/java.util.stream.Sink$ChainedReference.end(Sink.java:258)
	at java.base/java.util.stream.Sink$ChainedReference.end(Sink.java:258)
	at java.base/java.util.stream.Sink$ChainedReference.end(Sink.java:258)
	at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:485)
	at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:474)
	at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:913)
	at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.base/java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:578)
	at springfox.documentation.spring.web.plugins.WebMvcRequestHandlerProvider.requestHandlers(WebMvcRequestHandlerProvider.java:81)
	at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:195)
	at java.base/java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1655)
	at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:484)
	at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:474)
	at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:913)
	at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.base/java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:578)
	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)
	... 14 common frames omitted

截图

排查过程

首先在NPE地方打断点，发现是 this.condition 为 null 导致的，那就看它哪里set了

Ctrl + F 搜一下发现只有构造方法有赋值语句，那就在这里打断点吧，然后重启debug，再次来到这里

• 顺着堆栈往上找，发现是springfox.documentation.spring.web.plugins.WebMvcRequestHandlerProvider在返回 requestHandlers 时赋值的。
• 我们来看这个值来源是什么，顺着stream的代码，找到了原来时取handlerMappings中的字段，发现是org.springframework.web.servlet.mvc.method.RequestMappingInfo#pathPatternsCondition 字段
  
• 这个类是Spring的代码，我们直接看定义处，发现本身就可能为空，说明这是SpringFox代码的一个bug
  
• 使用这么广的开源软件居然有bug，怀疑是没及时更新导致，看了一下最新的3.0.0其实是2020.7发布的，怪不得和spring boot最新版不兼容
  - 再来看为啥2.6之前就没事呢？去 spring 官网看看2.6的更新，其中有一条

请求路径与 Spring MVC 处理映射匹配的默认策略已从AntPathMatcher更改为PathPatternParser。
你可以设置spring.mvc.pathmatch.matching-strategy为ant-path-matcher来改变它。

原来是默认的 path 解析策略调整了，所以我列了以下几个解决方案

解决方案