Do I need jsf-api or jsf-impl or both to start using JSF? Why are they not merged?

Question

I have started studying JSF and I would like to know what is the JAR to include within our classpath to start using JSF. Is it jsf-api or jsf-impl? Or we have to include both? And if it is both then why they are not merged?

Answer 1

I'll assume that you're not using a real Java EE application server like WildFly, TomEE, Payara, etc, but a barebones JSP/Servlet container like Tomcat which indeed doesn't ship with JSF out the box and you thus had to manually install it. Otherwise, all this fuss with JARs is unnecessary.

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Is it jsf-api or jsf-impl? Or we have to include both?

You need both. The jsf-api.jar contains the API, which exist of almost only abstract classes and interfaces. It are the javax.faces.* types which you are importing and using in your code. The jsf-impl.jar contains the implementation, which exist of the real hard working code. The implementation is internally loaded via factories in API. It are the com.sun.faces.* classes which you are not supposed to import and use directly in your code. If you do, then you wouldn't be able to switch to a different JSF implementation, such as MyFaces.

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And if it is both then why they are not merged?

There exist a merged JAR, the javax.faces.jar. You can pick this one instead of the two loose JARs.

See also:

• Our JSF wiki page
• JSF implementations and component libraries
• Difference between Mojarra and MyFaces
• In simplest terms, what is a factory?
• How to properly install and configure JSF libraries via Maven?