"Unable to locate Spring NamespaceHandler for XML schema namespace[http://www.springframework.org/schema/tx]"
This happens when you include multiple Spring module dependencies in your pom.xml file and use Maven Shade or Assembly plugin to build a single JAR.
Since Spring can does not contain a single distribution jar (org.springframework:spring:jar), Spring namespace handlers, schema mappings and tooling information files are now present in multiple files with names:
In order to make it work in a single shaded JAR you need to merge contents of these files from different jars and place merged files into new JAR. More...