Java Static final alternatives for use with Spring DI

Question

I have a class that I wanted to have static final variables.

public static final Map<String, Long> ID_MAP; 

I wanted to be able to inject the map via Spring. This can't be done b/c it is a static final . My alternative was to declare it as static and use Spring with a setter. Something like

public void setIDMapSpring (long iDMapSpring){
   ID_MAP = iDMapSpring; 

This, however, means that another class can come change the value. Are there any alternatives that I can try. I was thinking of having a Singleton with the Map as a final field but I've still to figure out how to pass the Map, and possibly other variables I want marked final , to the getInstance method. Also, I struggle to find the simplest and least complex solution.

Answer 1

将地图设为字段并注入单例。

Answer 2

If you're concerned about an outside class changing the value after Spring sets it, you could integrate a flag into your class that only lets the field be set once. Say you initialize a static AtomicBoolean called "CAN_SET_ID_MAP" to true. Then, in the map's setter:

if (CAN_SET_ID_MAP.compareAndSet (true, false)) {
  ID_MAP = iDMapSpring;
} else {
  throw new IllegalStateException ("ID_MAP already set");
}

There are other ways to do it. You probably want to use a thread-safe form of protection regardless.