Hi
Looking after your explanation i beleive that you have a requirement for ESS/MSS.If yes, then It depends on the EHP level you are working. Till EHP 4 we have WDJ versions fully supporting for ESS/MSS. from EHP5 80-90% of applications are in ABAP. Most of the cases I've seen people still working on Java in EHP 5. In such case you will face problem in working with Travel Mgt services. SAP recommends to Migrate from JAVA to ABAP. Apart from these we are still using JAVA services for few more applications/services in EHP5&6 like
Who's who - WDJ
Change own data-WDJ
Sec 80 & 80C Deductions - WDJ
Hope this Info
will be useful
Cheers 
Pradyp