Can a field's transient property/flag be set through reflection in java?

Question

Is there a simple way to specify if a field should be transient or not in Java with reflection, similar to how a field's accessibility flag can be set with setAccessible()?

Answer 1

I cannot see any direct way to do this in the Java API, but it is possible with something like JRebel or LiveRebel http://www.zeroturnaround.com/jrebel/comparison/. You could use something like ASM from http://asm.ow2.org/ to rewrite the bytecode with transient modifiers on the relevant fields. Then trigger JRebel/LiveRebel to replace the runtime version of the class.

I haven't tried automating this with ASM, but I have used JRebel with IntelliJ IDEA to perform changes like this successfully during interactive development.

Answer 2

Reflection itself cannot alter code.

Java Agents should allow you to rewrite the class as it is loaded.

You can use reflection to alter serialPersistentFields if it exists (unlikely), before the serialisation mechanism caches the class data. You could use reflection in a highly version specific way to alter the data inside the serialisation mechanism.