java - JAX-RS in relation to Jersey and JSRs

Question

I'm trying to get my head around some concepts in Java:

1. JSR(s): describe specifications, but carry no actual implementations. E.g. http://jsr311.java.net/ is the "home" for "Java? API for RESTful Web Services". It serves as a common reference for all implementations of JSR-311.
2. One can download the interfaces (?) of JSR-311 from http://mvnrepository.com/artifact/javax.ws.rs/jsr311-api, however, unless you are implementing JSR-311 by yourself these have no particular value?
3. JSR(s) will usually/always have a reference implementation. To find it you'll have to google "JSR XXX reference implementation" or see the specifications home page (e.g. http://jsr311.java.net/)
4. For JSR-311 this reference implementation is Jersey. Using maven you can get the jersey server from http://mvnrepository.com/artifact/com.sun.jersey/jersey-server/1.9. Since Jersey provides an implementation according to the interfaces found in http://mvnrepository.com/artifact/javax.ws.rs/jsr311-api, you only need to add Jersey as a dependency in your project and not the jsr311-api itself. (this applies to all JSR technologies?)
5. Putting both http://mvnrepository.com/artifact/javax.ws.rs/jsr311-api and http://mvnrepository.com/artifact/com.sun.jersey/jersey-server/1.9 as dependencies in your project will possibly cause classpath problems?

Am I completely off or onto someting?

Answer 1

1. Yes, this isn't anything new. Think about JDBC, java provides the interfaces (Connection, Statement, ResultSet etc) but it is up to database vendors to provide implementations.

2. If you're using a JSR-311 implementation like Jersey or Apache CXF then you'll annotate your classes with the javax.ws.rs annotations, such as @Path, @GET, @Produces etc. This is why you need to explicitly have JSR-311 as a maven dependency.

3. Yes, usually. Have a look at the JSR list on wiki.

4. You need both the JSR and the implementation. The annotations are in the JSR, the implementation provides supporting classes, such as com.sun.jersey.spi.container.servlet.ServletContainer.

5. No, it is necessary to have both as dependencies (see point 4); you won't get classpath conflicts.