java - Spring bean field (which is instantiated explicitly) is assigned to null sometimes -

one day faced incident application started crashing because of npe. found place crashing, cannot sure why happen.

roughly speaking lets assume have class a appears spring bean @ same time. class has field property instantiated explicitly (yes, know how sounds like) , method propertyuser uses field:

class {    private objectclass property = new objectclass();    public void propertyuser() {       property.action();    }       ....    getter\setter property } 

and after time of usual work, property field has become null has resulted in npe propertyuser method. changed legacy code , property assigned via spring container either, need sure reason of error appearance.

so pleased if give me hint.