[WW-3599] Struts2 ignores 'final' modifier when backing form onto field

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Resolved
• Affects Version/s: 2.1.6
• Component/s: Core Actions
• Assignee: Unassigned
• Reporter: Jon
• Created: 23/Mar/11 14:33
• Updated: 21/Oct/22 07:43
• Resolved: 21/Oct/22 07:43

Description

I had a bean and nested enum defined like

public class SomeBean {
private Type type;
// getters+setters for type
public static enum Type {
UNSET(0),
USER(1),
GROUP(2);
public final short code;
private Type(short code)

{ this.code = code; }

}
}

We accidentally included the final field 'code' as the name of a field on a form that was backed by Struts. e.g. something like:

<s:select name="someBeanInstance.type.code" ... />

When this field was submitted, the final field 'code' was updated on the enum to match the value picked in the select box. This caused a huge amount of confusion for a time, as this field is marked final and so shouldn't ever be updated... presumably Struts is using reflection to bypass the JVM enforcement on finality?

Fix would be to check a public field isn't marked final, before backing a form onto it.