迁移到 JDK 11 时出现错误“java.lang.NoClassDefFoundError: javax/activation/DataSource”（tomcat 9.0.12）
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Migration to JDK 11 has error occure "java.lang.NoClassDefFoundError: javax/activation/DataSource" (tomcat 9.0.12)
提问by SuperBeam
I'm migrating java project use JDK8 to use JDK 11 then has error occurred relate of javax activation. Following migration guide from Oracle, I see java.activation that module was removed from JDK 11.
我正在迁移 java 项目使用 JDK8 以使用 JDK 11 然后发生了与 javax 激活相关的错误。按照 Oracle 的迁移指南，我看到 java.activation 模块已从 JDK 11 中删除。
After that, I give a suggest to added third parties **activation-1.0.2.jar* but still, an error has occurred? Please give a suggestion about problem ? and could you tell me about experience of Migration source code use Java 8 to Java 11 (server with tomcat 9.0.12. compiler by Eclipse 2018-09(4.9.0)
之后，我建议添加第三方**activation-1.0.2.jar*，但仍然出现错误？请就问题提出建议？你能告诉我迁移源代码使用 Java 8 到 Java 11 的经验吗（带有 tomcat 9.0.12 的服务器。Eclipse 2018-09(4.9.0) 编译器）
This is detail error :
这是详细错误：
Caused by: java.lang.NoClassDefFoundError: javax/activation/DataSource
at java.base/java.lang.Class.getDeclaredMethods0(Native Method)
at java.base/java.lang.Class.privateGetDeclaredMethods(Class.java:3167)
at java.base/java.lang.Class.getDeclaredMethods(Class.java:2310)
at org.apache.catalina.util.Introspection.getDeclaredMethods(Introspection.java:133)
at org.apache.catalina.startup.WebAnnotationSet.loadMethodsAnnotation(WebAnnotationSet.java:285)
at org.apache.catalina.startup.WebAnnotationSet.loadApplicationServletAnnotations(WebAnnotationSet.java:138)
at org.apache.catalina.startup.WebAnnotationSet.loadApplicationAnnotations(WebAnnotationSet.java:69)
at org.apache.catalina.startup.ContextConfig.applicationAnnotationsConfig(ContextConfig.java:328)
at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:768)
at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:299)
at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:123)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5007)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:183)
回答by Naman
You seem to have included an incorrect artifact(external jar).
您似乎包含了一个不正确的工件（外部 jar）。
You should include javax.activation:javax.activation-api:1.2.0as an external dependency to your project to explicitly access the class javax.activation.DataSource. Sample maven dependency for the same would be:
您应该包含javax.activation:javax.activation-api:1.2.0作为项目的外部依赖项以显式访问该类javax.activation.DataSource。相同的示例 maven 依赖项将是：
<dependency>
<groupId>javax.activation</groupId>
<artifactId>javax.activation-api</artifactId>
<version>1.2.0</version>
</dependency>
Also, note ifusing modularised code (includes module-info.java), you must state a dependence on the library using declaration -
另外，请注意，如果使用模块化代码（包括module-info.java），则必须使用声明声明对库的依赖 -
requires java.activation;
