Why is Java 8 JDK recommended for GlassFish 4.1?

So I'm wondering why it is recommended to use it under JDK 8, since GlassFish 4.1 is a Java EE 7 application server?

I think they just recommend using the latest compatible non-beta Java, which in this case is Java 8. The version of the Java EE specification (in this case Java EE 7), which is implemented by Glassfish 4 and a JDK version that (or which may be used) to start the server are two different things.

Also note that Java 7 has EOL (End of Life) in April 2015 . There will be no more updates for Java 7, so at some point you will have to switch to Java 8 anyway.

Is it just because I will be able to use the new Java 8 functionality?

This might be one of the reasons for using JDK 8.

Or there are deeper reasons for this, such as stability, knowing bugs, etc.

I think there might be some bugs in JDK 7 that are fixed or not found in JDK 8, but that shouldn't be critical. In terms of stability, I think the values ​​are the same if they don't match.

So does GlassFish actually perform better on JDK 8 than on JDK 7, or can I ignore this statement and just install it in JDK 7 if I'm not using the new features provided in Java SE 8?

I wouldn't say Glassfish performs better, but I would also recommend using the latest compatible Java version. But you can also safely ignore the instruction and use JDK 7.

For more information, this spring.io blog post has a good summary of Java 8 in enterprise projects and with various application servers.