如何在将升级到 Java 11 的 Java 8 项目中运行新功能？

Question

I'm supposed to upgrade a Java project from 8 to 11. I've been told to add some features initially to test if the server runs but it doesn't. This is what I did. In pom.xml, I changed

<jdk.version>1.8</jdk.version>

to

<jdk.version>11</jdk.version>

And in the feature set xml file (RestProject/src/main/liberty/config/include/feature-set-ee8.xml) of Liberty Server, I changed the following:

<server>
    <featureManager>
        <feature>webProfile-8.0</feature>
        <feature>jms-2.0</feature>
        <feature>jaxb-2.2</feature>
        <feature>localConnector-1.0</feature>
    </featureManager>
</server>

to

<server>
    <featureManager>
        <feature>webProfile-9.1</feature>
        <feature>xmlBinding-3.0</feature>
        <feature>messaging-3.0</feature>
    </featureManager>
</server>

But when I run the server, I get the following error:

[ERROR   ] CWWKF0044E: The webProfile-9.1 and com.ibm.websphere.appserver.builtinAuthentication-1.0 features cannot be loaded at the same time. The webProfile-9.1 feature of Jakarta EE 9 is incompatible with the com.ibm.websphere.appserver.builtinAuthentication-1.0 feature of Java EE 6. The webProfile-9.1 and webProfile-9.1 configured features include an incompatible combination of features. Your configuration is not supported. Update the configuration to use features that support either the Jakarta EE or Java EE programming models, but not both.
[ERROR   ] CWWKF0033E: The singleton features servlet-5.0 and servlet-4.0 cannot be loaded at the same time.  The configured features webProfile-9.1 and jaxrs-2.1 include one or more features that cause the conflict. Your configuration is not supported; update server.xml to remove incompatible features.

I tried copying over some stuff from the default server's server.xml to this project's server.xml but it keeps resetting whenever I run the server. Am I supposed to use a specific version of these features?

Answer 1

These features aren't tied to the Java version, they're tied to the server version. While you can still upgrade Java from 8 to 11, you can't upgrade Java/Jakarta EE to version 9 yet. The problem with that is that the package names have changed - in Java EE and in Jakarta EE 8, packages started with javax . In Jakarta 9 and later, packages start with jakarta . That makes them 100% incompatible.

So until you have to update the server as well, just keep the old feature versions.