"java.lang.NoClassDefFoundError: org/springframework/core/metrics/applicationstartup" is a runtime error indicating that the class "org.springframework.core.metrics.applicationstartup" cannot be found by the Java class loader. This can be caused by several reasons, including:

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The class is not on the classpath: Ensure that the required jar containing the class is included in the classpath.

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Class version mismatch: The class may have been compiled with a different version of the library.

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Dependency issue: The class may depend on another class that is not available.

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Try resolving the issue by adding the required jar to the classpath or ensuring that all dependencies are included in the classpath. If the issue still persists, try debugging the application to find the root cause of the error.

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