RootCause:
As per Tomcat Wiki, Servlet 3.0 specification requires Jar scanning during server startup.
Tomcat is using org.apache.tomcat.util.scan.StandardJarScanner for this purpose.
From the javadoc of StandardJarScanner.
The default JarScanner implementation scans the WEB-INF/lib directory
followed by the provided classloader and then works up the classloader
hierarchy. This implementation is sufficient to meet the requirements
of the Servlet 3.0 specification as well as to provide a number of
Tomcat specific extensions. The extensions are:
Scanning the classloader hierarchy (enabled by default) Testing all files to see if they are JARs (disabled by default)
Testing all directories to see if they are exploded JARs (disabled by default)
All of the extensions may be controlled via configuration.
Solution1: Spring Boot specific.
We can disable this jar scanning.
I disabled it by adding below property in application-xxx.properties file. This property is Spring Boot specific.
# Comma-separated list of additional patterns that match jars to ignore for TLD scanning.
server.tomcat.additional-tld-skip-patterns=*.jar
You can find similar properties from Tomcat here.
These properties can be used to configure traditional tomcat (non-spring boot) applications.
Solution2: Spring specific
You can disable the JarScanner for manifest files as below.
@Bean
public EmbeddedServletContainerFactory embeddedServletContainerFactory() {
return new TomcatEmbeddedServletContainerFactory() {
@Override
protected void postProcessContext(Context context) {
((StandardJarScanner) context.getJarScanner()).setScanManifest(false);
}
};
}
Solution3 : Traditional Standalone Tomcat:
<Context>
...
<JarScanner scanManifest="false"/>
...
</Context>
Refer : The Jar Scanner Component.