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javaspring-bootnullpointerexceptionswaggerspring-boot-actuator

Spring Boot Rest API failed to run if actuator dependency is added to pom.xml

I have a simple spring boot application with just one GET endpoint for testing purpose. The endpoint works fine as far as I don't add the actuator dependency to my project. However, as soon as I add the actuator dependency, it stops running and throws the following error which is surprisingly for swagger I believe.

So I am not understanding why this error is appearing if I have swagger already enabled and working.

Error:

2022-10-02 22:48:26.558  WARN 14872 --- [           main] ConfigServletWebServerApplicationContext : Exception encountered during context initialization - cancelling refresh attempt: org.springframework.context.ApplicationContextException: Failed to start bean 'documentationPluginsBootstrapper'; nested exception is java.lang.NullPointerException
2022-10-02 22:48:26.739  INFO 14872 --- [           main] o.apache.catalina.core.StandardService   : Stopping service [Tomcat]
2022-10-02 22:48:26.754  INFO 14872 --- [           main] ConditionEvaluationReportLoggingListener : 

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2022-10-02 22:48:26.769 ERROR 14872 --- [           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) ~[spring-context-5.3.23.jar:5.3.23]
    at org.springframework.context.support.DefaultLifecycleProcessor.access$200(DefaultLifecycleProcessor.java:54) ~[spring-context-5.3.23.jar:5.3.23]
    at org.springframework.context.support.DefaultLifecycleProcessor$LifecycleGroup.start(DefaultLifecycleProcessor.java:356) ~[spring-context-5.3.23.jar:5.3.23]
    at java.base/java.lang.Iterable.forEach(Iterable.java:75) ~[na:na]
    at org.springframework.context.support.DefaultLifecycleProcessor.startBeans(DefaultLifecycleProcessor.java:155) ~[spring-context-5.3.23.jar:5.3.23]
    at org.springframework.context.support.DefaultLifecycleProcessor.onRefresh(DefaultLifecycleProcessor.java:123) ~[spring-context-5.3.23.jar:5.3.23]
    at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:935) ~[spring-context-5.3.23.jar:5.3.23]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:586) ~[spring-context-5.3.23.jar:5.3.23]
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:147) ~[spring-boot-2.7.4.jar:2.7.4]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:734) ~[spring-boot-2.7.4.jar:2.7.4]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:408) ~[spring-boot-2.7.4.jar:2.7.4]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:308) ~[spring-boot-2.7.4.jar:2.7.4]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1306) ~[spring-boot-2.7.4.jar:2.7.4]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1295) ~[spring-boot-2.7.4.jar:2.7.4]
    at com.example.playground.PlaygroundApplication.main(PlaygroundApplication.java:10) ~[classes/:na]
Caused by: java.lang.NullPointerException: null
    at springfox.documentation.spi.service.contexts.Orderings$8.compare(Orderings.java:112) ~[springfox-spi-2.9.2.jar:null]
    at springfox.documentation.spi.service.contexts.Orderings$8.compare(Orderings.java:109) ~[springfox-spi-2.9.2.jar:null]
    at com.google.common.collect.ComparatorOrdering.compare(ComparatorOrdering.java:37) ~[guava-20.0.jar:na]
    at java.base/java.util.TimSort.countRunAndMakeAscending(TimSort.java:355) ~[na:na]
    at java.base/java.util.TimSort.sort(TimSort.java:220) ~[na:na]
    at java.base/java.util.Arrays.sort(Arrays.java:1441) ~[na:na]
    at com.google.common.collect.Ordering.sortedCopy(Ordering.java:855) ~[guava-20.0.jar:na]
    at springfox.documentation.spring.web.plugins.WebMvcRequestHandlerProvider.requestHandlers(WebMvcRequestHandlerProvider.java:57) ~[springfox-spring-web-2.9.2.jar:null]
    at springfox.documentation.spring.web.plugins.DocumentationPluginsBootstrapper$2.apply(DocumentationPluginsBootstrapper.java:138) ~[springfox-spring-web-2.9.2.jar:null]
    at springfox.documentation.spring.web.plugins.DocumentationPluginsBootstrapper$2.apply(DocumentationPluginsBootstrapper.java:135) ~[springfox-spring-web-2.9.2.jar:null]
    at com.google.common.collect.Iterators$7.transform(Iterators.java:750) ~[guava-20.0.jar:na]
    at com.google.common.collect.TransformedIterator.next(TransformedIterator.java:47) ~[guava-20.0.jar:na]
    at com.google.common.collect.TransformedIterator.next(TransformedIterator.java:47) ~[guava-20.0.jar:na]
    at com.google.common.collect.MultitransformedIterator.hasNext(MultitransformedIterator.java:52) ~[guava-20.0.jar:na]
    at com.google.common.collect.MultitransformedIterator.hasNext(MultitransformedIterator.java:50) ~[guava-20.0.jar:na]
    at com.google.common.collect.ImmutableList.copyOf(ImmutableList.java:249) ~[guava-20.0.jar:na]
    at com.google.common.collect.ImmutableList.copyOf(ImmutableList.java:209) ~[guava-20.0.jar:na]
    at com.google.common.collect.FluentIterable.toList(FluentIterable.java:614) ~[guava-20.0.jar:na]
    at springfox.documentation.spring.web.plugins.DocumentationPluginsBootstrapper.defaultContextBuilder(DocumentationPluginsBootstrapper.java:111) ~[springfox-spring-web-2.9.2.jar:null]
    at springfox.documentation.spring.web.plugins.DocumentationPluginsBootstrapper.buildContext(DocumentationPluginsBootstrapper.java:96) ~[springfox-spring-web-2.9.2.jar:null]
    at springfox.documentation.spring.web.plugins.DocumentationPluginsBootstrapper.start(DocumentationPluginsBootstrapper.java:167) ~[springfox-spring-web-2.9.2.jar:null]
    at org.springframework.context.support.DefaultLifecycleProcessor.doStart(DefaultLifecycleProcessor.java:178) ~[spring-context-5.3.23.jar:5.3.23]
    ... 14 common frames omitted

Here is this sample project in the github that you can clone and run to replicate this error: https://github.com/syednoman84/playground/

Few points about this sample project:

  1. It is using actuator, lombok, swagger2, swagger-ui and swagger-bean-validators
  2. I have this spring.mvc.pathmatch.matching-strategy=ANT_PATH_MATCHER in my application.properties
  3. I have a SwaggerConfig defined in SwaggerConfig.java
  4. I have a DocketApiBean defined as DocketApiBean.java

Just to reiterate, as soon as I remove the actuator dependency from my pom.xml, everything works fine. However, if I add the actuator dependency and then run the app, it fails to start.

Thanks for the help in advance.

Solution

  • Swaggerfox is not compatible with the newer Spring Boot versions.

    Try Springdoc instead https://springdoc.org/:

    <dependency>
      <groupId>org.springdoc</groupId>
      <artifactId>springdoc-openapi-ui</artifactId>
      <version>1.6.11</version>
 </dependency>

    You can access the Swagger UI: http://localhost:8080/swagger-ui/index.html