2.6 Migration Guide

The big OSGi bundle used in the Karaf features.xml has been replaced with the individual modules which are now all individual bundles. The big OSGi bundle is still built, but some features may not be available if that is used instead of the little bundles.
New ability to configure HTTP Conduits from the OSGi config:admin service
New ability to configure the CXF created HTTP Jetty ports from config:admin service
OAuth 2 support
STS updates to support Renew and Cancel as well as updates to support more pluggable token validations.

cxf-common-utilites was merged into cxf-api
cxf-rt-binding-http has been removed. It's been "deprecated" for a while and it's functionality has long been replaceable with the JAX-RS frontend.

All API's that take or return "generic" classes have been update to properly define the generic part. For example, methods like:
"Class getServiceClass()" have been updated to be "Class<?> getServiceClass()"
To resolve some of the "split-package" issues between jars, SOME (very few) classes did have their packages changed.
- org.apache.cxf.jaxb.JAXBUtils -> org.apache.cxf.common.jaxb.JAXBUtils (and a couple other classes in that jaxb package)
- Many of the internal "Impl" classes and "Managers" (like BindingFactoryManagerImpl, CXFBusLifeCycleManager, etc...) have moved into org.apache.cxf.bus.managers. Users should always rely on the interfaces they implement anyway.
The selectedConduit field of AbstractConduitSelector has been removed as a ConduitSelector may be used to select multiple conduits depending on scenarios and the selectedConduit field may not accurately reflect the conduit that had been selected depending on the state of the threads, clients, etc...

The org.apache.cxf.tools.* classes that were in cxf-api have been moved into cxf-tools-common or cxf-tools-validator.
The org.apache.cxf.ws.policy classes that were in cxf-api have been moved into cxf-rt-ws-policy.
cxf-common-utilities is no longer available. All the classes in there were moved into cxf-api to represent a complete "api".
Various classes in cxf-rt-core and cxf-rt-ws-addr have been moved up to cxf-api to resolve split-package issues. Dependencies on cxf-rt-core would have transitively brought in cxf-api anyway, so there should be little impact.
Spring is now an optional component of the http-jetty transports module and other modules. Applications that may have pulled in Spring transitively via CXF will be required to declare required spring dependencies in their own poms directly.
Most of the optional JAX-RS Providers have been moved out of the cxf-rt-frontend-jaxrs module and into a cxf-rt-rs-extension-providers module with the various dependencies marked optional/provided. Applications that use these optional providers will need to add the required dependencies. Also, the package names of many of those providers has changed to resolve split-package issues. Example: org.apache.cxf.jaxrs.provider.JSONProvider -> org.apache.cxf.jaxrs.provider.json.JSONProvider

The syntax of WS-SecurityPolicy policies is enforced more strictly. Some policies that worked with CXF < 2.6 will not load in CXF 2.6 as a result.
JMS Transport - when using TextMessage, CXF now leaves the contents as a String and uses java.io.Reader and java.io.Writer to boost performance. Previously, CXF would convert the Strings to/from byte[] requiring use of encoders, increasing memory usage, etc... However, some interceptors and functionality in CXF (or user interceptors) may expect or require they InputStream/OutputStreams, not Reader/Writer. In those cases, you may need to change to use a BytesMessage. For example, the FastInfoset feature and GZIP features expect to work on InputStream/OutputStream and thus would now work with TextMessage.