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问题描述

• 项目能正常启动，但是启动过程中swagger报空指针异常，swagger文档无法打开

解决方案

一、实体修饰符错误

• 情况：实体A和实体B相互引用（见下方代码说明）
• 解决方案：检查相互引用的地方，是否修饰符误写成了
  
public

• 代码说明：

  @ApiModel("A")
  class A{
      @ApiModelProperty("B")
      @Transient
      private B b;//如果为public则会出现上述情况
  }
  /**********************/
  @ApiModel("B")
  class B{
      @ApiModelProperty("A")
      @Transient
      private A a;//如果为public则会出现上述情况
  }
  

附录

完整报错信息

java.lang.NullPointerException: null
	at springfox.documentation.schema.Example.equals(Example.java:131) ~[springfox-core-3.0.0.jar:3.0.0]
	at java.util.Objects.equals(Objects.java:59) ~[na:1.8.0_191]
	at springfox.documentation.service.RequestParameter.equals(RequestParameter.java:132) ~[springfox-core-3.0.0.jar:3.0.0]
	at java.util.HashMap.putVal(HashMap.java:648) ~[na:1.8.0_191]
	at java.util.HashMap.put(HashMap.java:612) ~[na:1.8.0_191]
	at java.util.HashSet.add(HashSet.java:220) ~[na:1.8.0_191]
	at java.util.stream.ReduceOps$3ReducingSink.accept(ReduceOps.java:169) ~[na:1.8.0_191]
	at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193) ~[na:1.8.0_191]
	at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:175) ~[na:1.8.0_191]
	at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193) ~[na:1.8.0_191]
	at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1382) ~[na:1.8.0_191]
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481) ~[na:1.8.0_191]
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471) ~[na:1.8.0_191]
	at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708) ~[na:1.8.0_191]
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) ~[na:1.8.0_191]
	at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499) ~[na:1.8.0_191]
	at springfox.documentation.spring.web.readers.operation.OperationParameterReader.apply(OperationParameterReader.java:93) ~[springfox-spring-web-3.0.0.jar:3.0.0]
	at springfox.documentation.spring.web.plugins.DocumentationPluginsManager.operation(DocumentationPluginsManager.java:144) ~[springfox-spring-web-3.0.0.jar:3.0.0]
	at springfox.documentation.spring.web.readers.operation.ApiOperationReader.read(ApiOperationReader.java:72) ~[springfox-spring-web-3.0.0.jar:3.0.0]
	at springfox.documentation.spring.web.scanners.CachingOperationReader.lambda$new$0(CachingOperationReader.java:43) ~[springfox-spring-web-3.0.0.jar:3.0.0]
	at java.util.HashMap.computeIfAbsent(HashMap.java:1127) ~[na:1.8.0_191]
	at springfox.documentation.spring.web.scanners.CachingOperationReader.read(CachingOperationReader.java:48) ~[springfox-spring-web-3.0.0.jar:3.0.0]
	at springfox.documentation.spring.web.scanners.ApiDescriptionReader.read(ApiDescriptionReader.java:72) ~[springfox-spring-web-3.0.0.jar:3.0.0]
	at springfox.documentation.spring.web.scanners.ApiListingScanner.scan(ApiListingScanner.java:169) ~[springfox-spring-web-3.0.0.jar:3.0.0]
	at springfox.documentation.spring.web.scanners.ApiDocumentationScanner.scan(ApiDocumentationScanner.java:67) ~[springfox-spring-web-3.0.0.jar:3.0.0]
	at springfox.documentation.spring.web.plugins.AbstractDocumentationPluginsBootstrapper.scanDocumentation(AbstractDocumentationPluginsBootstrapper.java:96) [springfox-spring-web-3.0.0.jar:3.0.0]
	at springfox.documentation.spring.web.plugins.AbstractDocumentationPluginsBootstrapper.bootstrapDocumentationPlugins(AbstractDocumentationPluginsBootstrapper.java:82) [springfox-spring-web-3.0.0.jar:3.0.0]
	at springfox.documentation.spring.web.plugins.DocumentationPluginsBootstrapper.start(DocumentationPluginsBootstrapper.java:100) [springfox-spring-web-3.0.0.jar:3.0.0]
	at org.springframework.context.support.DefaultLifecycleProcessor.doStart(DefaultLifecycleProcessor.java:178) [spring-context-5.3.15.jar:5.3.15]
	at org.springframework.context.support.DefaultLifecycleProcessor.access$200(DefaultLifecycleProcessor.java:54) [spring-context-5.3.15.jar:5.3.15]
	at org.springframework.context.support.DefaultLifecycleProcessor$LifecycleGroup.start(DefaultLifecycleProcessor.java:356) [spring-context-5.3.15.jar:5.3.15]
	at java.lang.Iterable.forEach(Iterable.java:75) ~[na:1.8.0_191]
	at org.springframework.context.support.DefaultLifecycleProcessor.startBeans(DefaultLifecycleProcessor.java:155) [spring-context-5.3.15.jar:5.3.15]
	at org.springframework.context.support.DefaultLifecycleProcessor.onRefresh(DefaultLifecycleProcessor.java:123) [spring-context-5.3.15.jar:5.3.15]
	at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:935) ~[spring-context-5.3.15.jar:5.3.15]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:586) ~[spring-context-5.3.15.jar:5.3.15]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:145) ~[spring-boot-2.6.3.jar:2.6.3]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:732) ~[spring-boot-2.6.3.jar:2.6.3]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:414) ~[spring-boot-2.6.3.jar:2.6.3]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:302) ~[spring-boot-2.6.3.jar:2.6.3]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1303) ~[spring-boot-2.6.3.jar:2.6.3]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1292) ~[spring-boot-2.6.3.jar:2.6.3]
	at com.xyx.GroupServer.main(GroupServer.java:30) ~[classes/:na]