AFTER upgrade from Spring boot 1.2 to 1.5.2, FileNotFoundException during Tomcat 8.5 Startup

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.

Just to improve Sundaraj's findings... disabling TLD scanning completely will break JSP/JSTL support.

The issue is that the classpath itself is OK, only Tomcat additionally scans the manifest files of each Jar, and since with Maven each Jar is in its own directory, that generates meaningless paths (probably running from Eclipse?).

So if you want to keep using JSP with JSTL, you should disable just the manifest scanning.

For Spring Boot 2.0, add this to your application's configuration:

  @Bean
  public TomcatServletWebServerFactory tomcatFactory() {
    return new TomcatServletWebServerFactory() {
      @Override
      protected void postProcessContext(Context context) {
        ((StandardJarScanner) context.getJarScanner()).setScanManifest(false);
      }
    };
  }