What breaks when upgrading Java 8 to 11?

• Removed modules: java.xml.bind (JAXB), java.xml.ws (JAX-WS/SOAP), java.activation (JAF), java.xml.ws.annotation (Common Annotations), java.corba (CORBA), java.transaction (JTA).
• Symptoms: ClassNotFoundException or NoClassDefFoundError for classes like javax.xml.bind.JAXBContext or javax.annotation.PostConstruct.
• Fix: add explicit Maven/Gradle dependencies for the Jakarta EE equivalents.
• Namespace migration: javax.* packages moved to jakarta.* in Jakarta EE 9+.
• Detection: run jdeps --jdk-internals your.jar before upgrading to find problematic dependencies.
• Spring Boot 3.x includes these as transitive dependencies, but standalone applications must add them manually.

What was removed?

Java 11 removed six modules that were deprecated for removal in Java 9 and deleted in Java 11.

| Module | Provides | Common Classes |
|--------|---------|----------------|
| java.xml.bind | JAXB (XML binding) | JAXBContext, Marshaller |
| java.xml.ws | JAX-WS (SOAP) | Service, @WebService |
| java.activation | JAF | DataHandler |
| java.xml.ws.annotation | Common Annotations | @PostConstruct, @Resource |
| java.corba | CORBA | ORB, IIOP |
| java.transaction | JTA | @Transactional (JTA version) |

What error do you see?

java.lang.ClassNotFoundException: javax.xml.bind.JAXBContext

or

java.lang.NoClassDefFoundError: javax/annotation/PostConstruct

How do you fix it?

Add explicit dependencies in your build file.

<!-- Maven: JAXB API + runtime --syn-kw">>
syn-kw"><dependencysyn-kw">>
    syn-kw"><groupIdsyn-kw">>jakarta.xml.bindsyn-kw"></groupIdsyn-kw">>
    syn-kw"><artifactIdsyn-kw">>jakarta.xml.bind-apisyn-kw"></artifactIdsyn-kw">>
    syn-kw"><versionsyn-kw">>4.0.2syn-kw"></versionsyn-kw">>
syn-kw"></dependencysyn-kw">>
syn-kw"><dependencysyn-kw">>
    syn-kw"><groupIdsyn-kw">>org.glassfish.jaxbsyn-kw"></groupIdsyn-kw">>
    syn-kw"><artifactIdsyn-kw">>jaxb-runtimesyn-kw"></artifactIdsyn-kw">>
    syn-kw"><versionsyn-kw">>4.0.5syn-kw"></versionsyn-kw">>
syn-kw"></dependencysyn-kw">>

<!-- Maven: Common Annotations (@PostConstruct) --syn-kw">>
syn-kw"><dependencysyn-kw">>
    syn-kw"><groupIdsyn-kw">>jakarta.annotationsyn-kw"></groupIdsyn-kw">>
    syn-kw"><artifactIdsyn-kw">>jakarta.annotation-apisyn-kw"></artifactIdsyn-kw">>
    syn-kw"><versionsyn-kw">>3.0.0syn-kw"></versionsyn-kw">>
syn-kw"></dependencysyn-kw">>

How do you detect problems before upgrading?

# Scan your JAR for removed API usage
jdeps --jdk-internals banking-service.jar

# Look for javax.xml.bind, javax.annotation, etc.

What about the javax to jakarta namespace change?

Jakarta EE 9+ changed the package namespace from javax.* to jakarta.*. If you upgrade to Jakarta EE 10 (used by Spring Boot 3.x), you must change all imports.

// Before (javax)
import javax.annotation.PostConstruct;
import javax.xml.bind.JAXBContext;

// After (jakarta)
import jakarta.annotation.PostConstruct;
import jakarta.xml.bind.JAXBContext;

What other changes affect the upgrade?

• Default GC changed from Parallel to G1 (since Java 9). Tuning parameters may differ.
• Some internal sun.* APIs are inaccessible under the module system.
• java.security.acl package was removed.
• Nashorn JavaScript engine was deprecated (removed in Java 15).

What are common mistakes?

WRONG: Adding the old javax.xml.bind:jaxb-api dependency instead of the Jakarta version.

WRONG: Not testing the full application after upgrading. Some failures only appear at runtime.

What should a senior engineer know?

• This is the single most common Java 8 to 11 migration issue.
• Spring Boot 2.x still uses javax.*. Spring Boot 3.x uses jakarta.*. Upgrading Spring Boot versions requires the namespace change.
• The --add-modules flag can temporarily re-add deprecated modules in Java 9 and 10, but this does not work in Java 11 because the modules are fully removed.
• For legacy systems that cannot change, consider using JDK 8 compatible JAXB implementations from Maven Central while keeping the javax.* imports.