What is 'weaving'?

Question

I've seen this term when read about how Spring works and I've just read the article about JPA implementation performance and it has the next statistics:

EclipseLink                                                           3215 ms
(Run-time weaver - Spring ReflectiveLoadTimeWeaver weaver  )
EclipseLink (Build-time weaving)                                      3571 ms
EclipseLink (No weaving)                                              3996 ms

So, could someone explain in plain English, what is weaving?

Thanks!

Answer 1

Weaving is generating or editing code by directly modifying existing .class (byte-code) files. This can occur at different points in the application life cycle.

1. Outside of JVM at compile time at packaging time
2. Inside a JVM at class load time. after a class has been loaded.

Spring Framework uses this for AOP functionality. Eclipselink uses weaving for lazy loading or change tracking.

Answer 2

From here:

In Spring AOP makes it possible to modularize and separate logging, transaction like services and apply them declaratively to the components Hence programmer can focus on specific concerns. Aspects are wired into objects in the spring XML file in the way as JavaBean. This process is known as 'Weaving'.