Obviously it is also an implementation of Jakarta Faces specification implemented by Eclipse EE4J as well
No, it is not.
Follow the https://mvnrepository.com/artifact/jakarta.faces/jakarta.faces-api link and download the JAR file and inspect its contents using any zip tool. You'll see that it contains only jakarta.* classes. It does not contain classes from the implementation package such as com.sun.faces.* (Mojarra) or org.apache.myfaces.* (MyFaces). In other words, it only contains the API classes not the impl classes.
This JAR file is essentially the "Jakarta Faces specification" part of your first statement:
I know that Mojarra is Eclipse EE4J implementation of the Jakarta Faces specification.
As to,
So, are they same project or not
no, the Mojarra project is here https://github.com/eclipse-ee4j/mojarra and the Mojarra dependency is here:
<!-- https://mvnrepository.com/artifact/org.glassfish/jakarta.faces -->
<dependency>
<groupId>org.glassfish</groupId>
<artifactId>jakarta.faces</artifactId>
<version>4.0.0-M1</version>
</dependency>
Download the JAR file and inspect its contents. You'll see that it contains jakarta.* classes and com.sun.faces.* classes.
what is the difference between them?
The API can be included as <scope>provided</scope> in projects targeting a full fledged Jakarta EE server which already ships with API+impl out the box. You'll then be able to import jakarta.faces.* classes in your code. For those servers, you only need to include the impl (Mojarra or MyFaces) as <scope>provided</scope> if you wish to be able to step through the source code in IDE's debugger and/or if you wish to monkeypatch some implementation classes.
But in barebones servletcontainers such as Tomcat, the API dependency as <scope>compile</scope> won't work because the implementation is missing. You'll need the impl dependency instead.
See also:
