I used,
bootstrap.addBundle(new AssetsBundle("/assets", "/", "a.js"));
bootstrap.addBundle(new MultiPartBundle());
but I need to serve a file say b.js on entering /b and c.js on entering /c.
How to do so?
You can map specific resources by specifying the resourcePath as the actual file. So, using the examples you have mentioned this is how you could achieve that:
bootstrap.addBundle(new AssetsBundle("/assets/a.js", "/a", null, "a"));
bootstrap.addBundle(new AssetsBundle("/assets/b.js", "/b", null, "b"));
bootstrap.addBundle(new AssetsBundle("/assets/c.js", "/c", null, "c"));
However, I think this is not a good practice and will become unmanageable over time, to keep a mapping of a URL per resource.
UPDATE For a more maintainable list of mappings I would recommend using something like the Configurable Assets Bundle for Dropwizard, where multiple mappings can be described on the configuration file. I have created a simple DW project which uses this lib and replicates the behaviour described on the question.