1. If you don't have the access to your XI/PI server at the directory level
2. If you don't have access to Market place download  

Use the below procedure to get the aii_map_api.jar file,

If your machine is running on windows operating system,(remember your machine means from where you work on Repository and Directory Frameworks)

Then look in this folder,

>:\Documents and Settings\\Application Data\Sun\Java\Deployment\javaws\cache\http\D\P\DMrep\DMrepository

where - host name of XI server.
- J2EE dispatcherport of XI servergenerally it will be 50000 if instance number is 00 or it will 50000+(100 X Instance number)

- the userprofile with which your are working on your machine.

in the directory you will find "RMaii_map_api.jar". Copy this to your working directory for java mapping class program and set in classpath. You can also rename this jar file as the original name is "aii_map_api.jar".

I really appreciate if some body  explores on different OS (LINUX etc...) environments to get aii_map_api.jar file, since the client files will cached into the user profiles when we first log into Repository & Directory frameworks.