If you are seeing strange errors and/or warnings in your Spring Integration application context files, you likely have an old version of the schema cached in STS.

Try the following

Window | Preferences

Type 'cache' in the filter; in General | Network Connections | Cache, click 'Remove All'.

Also, be sure to enable 'Spring Project Nature' on the project (right click Spring Tools...).

Finally, ensure that 'Load NamespaceHandlers and XSDs from project's classpath' is checked in

Window | Preferences | Spring | Beans Support | Namespaces

and is not overridden in the project's properties.

You may need to clean all projects after making these changes.