SpringBoot Anchors in YAML configuration files throw UnsupportedOperationException

SpringBoot Version: 3.0.0 SnakeYAML Version: 1.33

When using YAML achors in an application.yml configuration file to re-use configuration blocks, for example:

some:
  path: &anchor
    config: 
      key: value
  anotherpath: 
     << : *anchor

Spring Boot throws an UnsupportedOperationException within Snakeyaml's SafeConstructor class during start up due to a modification on a mutable collection (see below).

However, same configuration works fine with Spring Boot 2.7.5. (same snakeyaml version).

Thanks a lot in advance for any ideas.

java.lang.UnsupportedOperationException: null
    at java.base/java.util.ImmutableCollections.uoe(ImmutableCollections.java:142)
    at java.base/java.util.ImmutableCollections$ListItr.remove(ImmutableCollections.java:380)
    at org.yaml.snakeyaml.constructor.SafeConstructor.mergeNode(SafeConstructor.java:160)
    at org.yaml.snakeyaml.constructor.SafeConstructor.flattenMapping(SafeConstructor.java:83)
    at org.yaml.snakeyaml.constructor.SafeConstructor.flattenMapping(SafeConstructor.java:76)
    at org.yaml.snakeyaml.constructor.SafeConstructor.constructMapping2ndStep(SafeConstructor.java:212)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructMapping(BaseConstructor.java:557)
    at org.yaml.snakeyaml.constructor.SafeConstructor$ConstructYamlMap.construct(SafeConstructor.java:600)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructObjectNoCheck(BaseConstructor.java:270)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructObject(BaseConstructor.java:253)
    at org.springframework.boot.env.OriginTrackedYamlLoader$OriginTrackingConstructor.constructObject(OriginTrackedYamlLoader.java:118)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructMapping2ndStep(BaseConstructor.java:581)
    at org.yaml.snakeyaml.constructor.SafeConstructor.constructMapping2ndStep(SafeConstructor.java:213)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructMapping(BaseConstructor.java:557)
    at org.yaml.snakeyaml.constructor.SafeConstructor$ConstructYamlMap.construct(SafeConstructor.java:600)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructObjectNoCheck(BaseConstructor.java:270)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructObject(BaseConstructor.java:253)
    at org.springframework.boot.env.OriginTrackedYamlLoader$OriginTrackingConstructor.constructObject(OriginTrackedYamlLoader.java:118)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructMapping2ndStep(BaseConstructor.java:581)
    at org.yaml.snakeyaml.constructor.SafeConstructor.constructMapping2ndStep(SafeConstructor.java:213)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructMapping(BaseConstructor.java:557)
    at org.yaml.snakeyaml.constructor.SafeConstructor$ConstructYamlMap.construct(SafeConstructor.java:600)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructObjectNoCheck(BaseConstructor.java:270)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructObject(BaseConstructor.java:253)
    at org.springframework.boot.env.OriginTrackedYamlLoader$OriginTrackingConstructor.constructObject(OriginTrackedYamlLoader.java:118)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructMapping2ndStep(BaseConstructor.java:581)
    at org.yaml.snakeyaml.constructor.SafeConstructor.constructMapping2ndStep(SafeConstructor.java:213)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructMapping(BaseConstructor.java:557)
    at org.yaml.snakeyaml.constructor.SafeConstructor$ConstructYamlMap.construct(SafeConstructor.java:600)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructObjectNoCheck(BaseConstructor.java:270)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructObject(BaseConstructor.java:253)
    at org.springframework.boot.env.OriginTrackedYamlLoader$OriginTrackingConstructor.constructObject(OriginTrackedYamlLoader.java:118)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructMapping2ndStep(BaseConstructor.java:581)
    at org.yaml.snakeyaml.constructor.SafeConstructor.constructMapping2ndStep(SafeConstructor.java:213)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructMapping(BaseConstructor.java:557)
    at org.yaml.snakeyaml.constructor.SafeConstructor$ConstructYamlMap.construct(SafeConstructor.java:600)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructObjectNoCheck(BaseConstructor.java:270)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructObject(BaseConstructor.java:253)
    at org.springframework.boot.env.OriginTrackedYamlLoader$OriginTrackingConstructor.constructObject(OriginTrackedYamlLoader.java:118)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructDocument(BaseConstructor.java:207)
    at org.yaml.snakeyaml.constructor.BaseConstructor.getData(BaseConstructor.java:172)
    at org.springframework.boot.env.OriginTrackedYamlLoader$OriginTrackingConstructor.getData(OriginTrackedYamlLoader.java:98)
    at org.yaml.snakeyaml.Yaml$1.next(Yaml.java:499)
    at org.springframework.beans.factory.config.YamlProcessor.process(YamlProcessor.java:198)
    at org.springframework.beans.factory.config.YamlProcessor.process(YamlProcessor.java:166)
    at org.springframework.boot.env.OriginTrackedYamlLoader.load(OriginTrackedYamlLoader.java:83)
    at org.springframework.boot.env.YamlPropertySourceLoader.load(YamlPropertySourceLoader.java:50)
    at org.springframework.boot.context.config.StandardConfigDataLoader.load(StandardConfigDataLoader.java:54)
    at org.springframework.boot.context.config.StandardConfigDataLoader.load(StandardConfigDataLoader.java:36)
    at org.springframework.boot.context.config.ConfigDataLoaders.load(ConfigDataLoaders.java:95)
    at org.springframework.boot.context.config.ConfigDataImporter.load(ConfigDataImporter.java:128)
    at org.springframework.boot.context.config.ConfigDataImporter.resolveAndLoad(ConfigDataImporter.java:86)
    at org.springframework.boot.context.config.ConfigDataEnvironmentContributors.withProcessedImports(ConfigDataEnvironmentContributors.java:115)
    at org.springframework.boot.context.config.ConfigDataEnvironment.processInitial(ConfigDataEnvironment.java:242)
    at org.springframework.boot.context.config.ConfigDataEnvironment.processAndApply(ConfigDataEnvironment.java:229)
    at org.springframework.boot.context.config.ConfigDataEnvironmentPostProcessor.postProcessEnvironment(ConfigDataEnvironmentPostProcessor.java:96)
    at org.springframework.boot.context.config.ConfigDataEnvironmentPostProcessor.postProcessEnvironment(ConfigDataEnvironmentPostProcessor.java:89)
    at org.springframework.boot.env.EnvironmentPostProcessorApplicationListener.onApplicationEnvironmentPreparedEvent(EnvironmentPostProcessorApplicationListener.java:109)
    at org.springframework.boot.env.EnvironmentPostProcessorApplicationListener.onApplicationEvent(EnvironmentPostProcessorApplicationListener.java:94)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:176)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:169)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:143)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:131)
    at org.springframework.boot.context.event.EventPublishingRunListener.multicastInitialEvent(EventPublishingRunListener.java:136)
    at org.springframework.boot.context.event.EventPublishingRunListener.environmentPrepared(EventPublishingRunListener.java:81)
    at org.springframework.boot.SpringApplicationRunListeners.lambda$environmentPrepared$2(SpringApplicationRunListeners.java:64)
    at java.base/java.lang.Iterable.forEach(Iterable.java:75)
    at org.springframework.boot.SpringApplicationRunListeners.doWithListeners(SpringApplicationRunListeners.java:118)
    at org.springframework.boot.SpringApplicationRunListeners.doWithListeners(SpringApplicationRunListeners.java:112)
    at org.springframework.boot.SpringApplicationRunListeners.environmentPrepared(SpringApplicationRunListeners.java:63)
    at org.springframework.boot.SpringApplication.prepareEnvironment(SpringApplication.java:352)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:303)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1302)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1291)

Comment From: mhalbritter

Thanks for the report, fixed!

Comment From: himanshunp

Thanks for report and fix. I can’t wait for the new release.

Comment From: qugemingzi

I met the same question, how to fix this problem? Thanks - SpringBoot Version: 3.0.0 - SnakeYAML Version: 1.26

config:

defaults: &defaults
  adapter:  postgres
  host:     localhost

development:
  database: myapp_development
  <<: *defaults

error.log

20:10:27.189 [main] ERROR org.springframework.boot.SpringApplication - Application run failed
java.lang.UnsupportedOperationException: null
    at java.base/java.util.ImmutableCollections.uoe(ImmutableCollections.java:142)
    at java.base/java.util.ImmutableCollections$ListItr.remove(ImmutableCollections.java:380)
    at org.yaml.snakeyaml.constructor.SafeConstructor.mergeNode(SafeConstructor.java:160)
    at org.yaml.snakeyaml.constructor.SafeConstructor.flattenMapping(SafeConstructor.java:83)
    at org.yaml.snakeyaml.constructor.SafeConstructor.flattenMapping(SafeConstructor.java:76)
    at org.yaml.snakeyaml.constructor.SafeConstructor.constructMapping2ndStep(SafeConstructor.java:212)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructMapping(BaseConstructor.java:557)
    at org.yaml.snakeyaml.constructor.SafeConstructor$ConstructYamlMap.construct(SafeConstructor.java:600)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructObjectNoCheck(BaseConstructor.java:270)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructObject(BaseConstructor.java:253)
    at org.springframework.boot.env.OriginTrackedYamlLoader$OriginTrackingConstructor.constructObject(OriginTrackedYamlLoader.java:118)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructMapping2ndStep(BaseConstructor.java:581)
    at org.yaml.snakeyaml.constructor.SafeConstructor.constructMapping2ndStep(SafeConstructor.java:213)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructMapping(BaseConstructor.java:557)
    at org.yaml.snakeyaml.constructor.SafeConstructor$ConstructYamlMap.construct(SafeConstructor.java:600)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructObjectNoCheck(BaseConstructor.java:270)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructObject(BaseConstructor.java:253)
    at org.springframework.boot.env.OriginTrackedYamlLoader$OriginTrackingConstructor.constructObject(OriginTrackedYamlLoader.java:118)
    at org.yaml.snakeyaml.constructor.BaseConstructor.constructDocument(BaseConstructor.java:207)
    at org.yaml.snakeyaml.constructor.BaseConstructor.getData(BaseConstructor.java:172)
    at org.springframework.boot.env.OriginTrackedYamlLoader$OriginTrackingConstructor.getData(OriginTrackedYamlLoader.java:98)
    at org.yaml.snakeyaml.Yaml$1.next(Yaml.java:499)
    at org.springframework.beans.factory.config.YamlProcessor.process(YamlProcessor.java:198)
    at org.springframework.beans.factory.config.YamlProcessor.process(YamlProcessor.java:166)
    at org.springframework.boot.env.OriginTrackedYamlLoader.load(OriginTrackedYamlLoader.java:83)
    at org.springframework.boot.env.YamlPropertySourceLoader.load(YamlPropertySourceLoader.java:50)
    at org.springframework.boot.context.config.StandardConfigDataLoader.load(StandardConfigDataLoader.java:54)
    at org.springframework.boot.context.config.StandardConfigDataLoader.load(StandardConfigDataLoader.java:36)
    at org.springframework.boot.context.config.ConfigDataLoaders.load(ConfigDataLoaders.java:95)
    at org.springframework.boot.context.config.ConfigDataImporter.load(ConfigDataImporter.java:128)
    at org.springframework.boot.context.config.ConfigDataImporter.resolveAndLoad(ConfigDataImporter.java:86)
    at org.springframework.boot.context.config.ConfigDataEnvironmentContributors.withProcessedImports(ConfigDataEnvironmentContributors.java:115)
    at org.springframework.boot.context.config.ConfigDataEnvironment.processWithProfiles(ConfigDataEnvironment.java:313)
    at org.springframework.boot.context.config.ConfigDataEnvironment.processAndApply(ConfigDataEnvironment.java:234)
    at org.springframework.boot.context.config.ConfigDataEnvironmentPostProcessor.postProcessEnvironment(ConfigDataEnvironmentPostProcessor.java:96)
    at org.springframework.boot.context.config.ConfigDataEnvironmentPostProcessor.postProcessEnvironment(ConfigDataEnvironmentPostProcessor.java:89)
    at org.springframework.boot.env.EnvironmentPostProcessorApplicationListener.onApplicationEnvironmentPreparedEvent(EnvironmentPostProcessorApplicationListener.java:109)
    at org.springframework.boot.env.EnvironmentPostProcessorApplicationListener.onApplicationEvent(EnvironmentPostProcessorApplicationListener.java:94)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:176)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:169)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:143)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:131)
    at org.springframework.boot.context.event.EventPublishingRunListener.multicastInitialEvent(EventPublishingRunListener.java:136)
    at org.springframework.boot.context.event.EventPublishingRunListener.environmentPrepared(EventPublishingRunListener.java:81)
    at org.springframework.boot.SpringApplicationRunListeners.lambda$environmentPrepared$2(SpringApplicationRunListeners.java:64)
    at java.base/java.lang.Iterable.forEach(Iterable.java:75)
    at org.springframework.boot.SpringApplicationRunListeners.doWithListeners(SpringApplicationRunListeners.java:118)
    at org.springframework.boot.SpringApplicationRunListeners.doWithListeners(SpringApplicationRunListeners.java:112)
    at org.springframework.boot.SpringApplicationRunListeners.environmentPrepared(SpringApplicationRunListeners.java:63)
    at org.springframework.boot.SpringApplication.prepareEnvironment(SpringApplication.java:352)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:303)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1302)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1291)

Comment From: bclozel

@qugemingzi you will need to upgrade to a supported version as 3.0.x is not OSS supported anymore. See https://spring.io/projects/spring-boot#support

Comment From: qugemingzi

@qugemingzi you will need to upgrade to a supported version as 3.0.x is not OSS supported anymore. See https://spring.io/projects/spring-boot#support

@bclozel Thanks, I try version 3.0.1, then it works. But version 3.0.0 is failed