Refer to this tech article: https://www.ibm.com/developerworks/websphere/library/techarticles/1306_chakraborty/1306_chakraborty.html
Some code need to be revised for dynamic aggregation to work properly. You can see completely working code which has been tested with IIB 10.0.0.19 in this project.
Note: Please be aware that XML domain is deprecated. But this is just an example for understanding dynamic aggregation. The production code should be use XMLNSC and convert only control message to XML domain.