Here is a working solution to the generic post ordering issue.
Steve Muench has an article "Forcing a New Dept to Post Before a New Emp Without Composition", which presented two ways to solve the post ordering contraints:
1. Override postChanges() method in the detail/child entity object Implementation java file. For example, if Dept and Emp table, then write below codes in EmpImpl.java file:
2. An even simpler way:
Steve also has a very good article on "Most Commonly Used Methods in ADF Business Components" which lists all common used methods in EO, VO, AM, etc.