Migration to JDK 11 has error occure “java.lang.NoClassDefFoundError: javax/activation/DataSource” (tomcat 9.0.12) [duplicate]

Answer 1

You seem to have included an incorrect artifact(external jar).

You should include javax.activation:javax.activation-api:1.2.0 as an external dependency to your project to explicitly access the class javax.activation.DataSource. Sample maven dependency for the same would be:

<dependency>
  <groupId>javax.activation</groupId>
  <artifactId>javax.activation-api</artifactId>
  <version>1.2.0</version>
</dependency>

Also, note if using modularised code (includes module-info.java), you must state a dependence on the library using declaration -

requires java.activation;