ConfigDataResourceNotFoundException incorrectly thrown for valid classpath locations

[bratkartoffel]

Hi,

after upgrading from spring boot 2.3.6 to 2.4.0 our application fails to startup. We tracked the error to our startup options, we use the following to setup the configuration resources paths:
--spring.config.location=classpath:/,file:../etc/

This results in the following error message:

***************************
APPLICATION FAILED TO START
***************************

Description:

Config data resource 'class path resource []' via location 'classpath:/' does not exist

Action:

Check that the value 'classpath:/' is correct, or prefix it with 'optional:'

07:53:54.024 [main] ERROR com.xxx.server.launcher.XxxServerApplication - Error starting up / running context
org.springframework.boot.context.config.ConfigDataResourceNotFoundException: Config data resource 'class path resource []' via location 'classpath:/' cannot be found
        at org.springframework.boot.context.config.ConfigDataResourceNotFoundException.withLocation(ConfigDataResourceNotFoundException.java:97)
        at org.springframework.boot.context.config.ConfigDataImporter.handle(ConfigDataImporter.java:133)
        at org.springframework.boot.context.config.ConfigDataImporter.resolve(ConfigDataImporter.java:104)
        at org.springframework.boot.context.config.ConfigDataImporter.resolve(ConfigDataImporter.java:93)
        at org.springframework.boot.context.config.ConfigDataImporter.resolveAndLoad(ConfigDataImporter.java:81)
        at org.springframework.boot.context.config.ConfigDataEnvironmentContributors.withProcessedImports(ConfigDataEnvironmentContributors.java:118)
        at org.springframework.boot.context.config.ConfigDataEnvironment.processInitial(ConfigDataEnvironment.java:230)
        at org.springframework.boot.context.config.ConfigDataEnvironment.processAndApply(ConfigDataEnvironment.java:217)
        at org.springframework.boot.context.config.ConfigDataEnvironmentPostProcessor.postProcessEnvironment(ConfigDataEnvironmentPostProcessor.java:88)
        at org.springframework.boot.context.config.ConfigDataEnvironmentPostProcessor.postProcessEnvironment(ConfigDataEnvironmentPostProcessor.java:80)
        at org.springframework.boot.env.EnvironmentPostProcessorApplicationListener.onApplicationEnvironmentPreparedEvent(EnvironmentPostProcessorApplicationListener.java:100)
        at org.springframework.boot.env.EnvironmentPostProcessorApplicationListener.onApplicationEvent(EnvironmentPostProcessorApplicationListener.java:86)
        at org.springframework.context.event.SimpleApplicationEventMulticaster.doInvokeListener(SimpleApplicationEventMulticaster.java:203)
        at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:196)
        at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:170)
        at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:148)
        at org.springframework.boot.context.event.EventPublishingRunListener.environmentPrepared(EventPublishingRunListener.java:82)
        at org.springframework.boot.SpringApplicationRunListeners.lambda$environmentPrepared$2(SpringApplicationRunListeners.java:63)
        at java.util.ArrayList.forEach(ArrayList.java:1257)
        at org.springframework.boot.SpringApplicationRunListeners.doWithListeners(SpringApplicationRunListeners.java:117)
        at org.springframework.boot.SpringApplicationRunListeners.doWithListeners(SpringApplicationRunListeners.java:111)
        at org.springframework.boot.SpringApplicationRunListeners.environmentPrepared(SpringApplicationRunListeners.java:62)
        at org.springframework.boot.SpringApplication.prepareEnvironment(SpringApplication.java:362)
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:320)
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1309)
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1298)
        at com.xxx.xxx.server.launcher.XxxServerApplication.main(XxxServerApplication.java:49)

The same setting works fine on the previous spring boot version.
We need this setting as we ship some default profiles within our jar, but also allow the user to use custom profiles within the "etc" folder.
Prefixing the "classpath:" with "optional:" doesn't print any error, but then the embedded profiles are not found.

Thanks,
Simon

[wilkinsona]

Thanks for the report, @bratkartoffel. I've tried to reproduce the behaviour that you have described but have been unable to do so. Specifying the root of the classpath as a spring.config.location works as expected for me both when running an application in my IDE and when packaged as a jar file.

If you would like us to spend some more time investigating, please spend some time providing a complete yet minimal sample that reproduces the problem. You can share it with us by pushing it to a separate repository on GitHub or by zipping it up and attaching it to this issue.

[bratkartoffel]

I've created a minimal example and could reproduce this. While testing I found out, that this only happens when running on Java 8. Using Java 11 is fine. Running in IntelliJ works also fine.
See the "reproduce.sh" script on how to reproduce.

GH24143.zip

[wilkinsona]

Thanks for the sample, @bratkartoffel. I've reproduced the problem.

The failure seems to be due to a difference in how the root of the classpath is resolved. As you have observed, this difference is specific to Java 8. It also only occurs when there are only jars on the classpath. If I modify the GH24143 script to add a directory to the classpath (I added .), the problem does not occur and the properties are resolved as expected:

./bin/GH24143 --spring.profiles.active=embedded,external --spring.config.location=classpath:/,file:../../../etc/


  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::                (v2.4.0)

2020-11-13 09:05:19.702  INFO 29925 --- [           main] org.example.TestApplication              : Starting TestApplication using Java 1.8.0_252 on wilkinsona-a01.vmware.com with PID 29925 (/Users/awilkinson/Downloads/GH24143/build/install/GH24143/lib/GH24143-1.0-SNAPSHOT.jar started by awilkinson in /Users/awilkinson/Downloads/GH24143/build/install/GH24143)
2020-11-13 09:05:19.704  INFO 29925 --- [           main] org.example.TestApplication              : The following profiles are active: embedded,external
2020-11-13 09:05:20.343  INFO 29925 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2020-11-13 09:05:20.351  INFO 29925 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2020-11-13 09:05:20.351  INFO 29925 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.39]
2020-11-13 09:05:20.394  INFO 29925 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2020-11-13 09:05:20.394  INFO 29925 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 656 ms
2020-11-13 09:05:20.514  INFO 29925 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
2020-11-13 09:05:20.639  INFO 29925 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2020-11-13 09:05:20.646  INFO 29925 --- [           main] org.example.TestApplication              : Started TestApplication in 1.242 seconds (JVM running for 1.522)
2020-11-13 09:05:20.648  INFO 29925 --- [           main] org.example.TestApplication              : example.embedded=1
2020-11-13 09:05:20.649  INFO 29925 --- [           main] org.example.TestApplication              : example.external=2
2020-11-13 09:05:20.715  INFO 29925 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Shutting down ExecutorService 'applicationTaskExecutor'

We'll continue to investigate to see what a potential fix may be.

Rather than adding a directory to the classpath, an alternative workaround is to enable legacy configuration file processing by setting spring.config.use-legacy-processing=true One way to do this is as a system property:

JAVA_OPTS=-Dspring.config.use-legacy-processing=true ./bin/GH24143 --spring.profiles.active=embedded,external --spring.config.location=classpath:/,file:../../../etc/

[wilkinsona]

The following references are being resolved:

• classpath:/application.properties
• classpath:/application.xml
• classpath:/application.yml
• classpath:/application.yaml

The directory for each of these is classpath:/ represented by a ClassPathResource with a path that's the empty string. The existence of these resources is checked by calling ClassLoader.getResource("") and requiring a non-null result. The result is null on Java 8 and non-null on Java 11.

Modifying the sample's main method to output the result of the getResource("") call produces jar:file:/Users/awilkinson/Downloads/GH24143/build/install/GH24143/lib/log4j-api-2.13.3.jar!/META-INF/versions/9/ with Java 11 and null with Java 8.

Modifying the sample to apply Spring Boot's plugin and building and running a fat jar produces jar:file:/Users/awilkinson/Downloads/GH24143/build/libs/GH24143-1.0-SNAPSHOT.jar!/BOOT-INF/classes!/ with both Java 8 and Java 11.

Modifying the sample to remove log4j-api-2.13.3.jar from the classpath causes it to fail with Java 11 (and continue to fail with Java 8). In other words, it only works with Java 11 when there's only jars on the classpath if one of those jars is a multi-release jar.

[wilkinsona]

I think we've been here before: spring-projects/spring-framework#16711.