Spring 实现给Bean属性注入null值

<bean class="ExampleBean">
  <property name="email"><value/></property>
</bean>

<bean class="ExampleBean">
  <property name="email"><null/></property>
</bean>

@Component("countFunction")
public class CountFunction implements AviatorFunction {    
    @Resource(name = "mongoLogInfoDAO")
    private MongoLogInfoDAO mongoLogInfoDAO;
 
    @Override
    public String getName() {
        return "count";
    }

AviatorEvaluator.addFunction(new CountFunction());

@Component("functionExecutor")
public class FunctionExecutor {
    protected static final Loggerx LOGGER = Loggerx.getLogger("system");
 
    @Resource(name = "mongoDAO")
    private MongoDAO mongoDAO;
 
    @Resource(name = "prism4001Producer")
    private SmartMQProducer prism4001Producer;
    
    @Resource(name = "whereGreaterThenFunction")
    private  WhereGreaterThenFunction whereGreaterThenFunction;
    
    @Resource(name = "countFunction")
    private  CountFunction countFunction;
    
    @Resource(name = "devideFunction")
    private  DevideFunction devideFunction;
    
    @Resource(name = "selectFunction")
    private  SelectFunction selectFunction;
    
    @Resource(name = "whereEqualFunction")
    private  WhereEqualFunction whereEqualFunction;
    
    @Resource(name = "timeFunction")
    private  TimeFunction timeFunction;
    
    @Resource(name = "whereLessThenFunction")
    private  WhereLessThenFunction whereLessThenFunction;
    
    @Resource(name = "whereGreaterThenEqualFunction")
    private  WhereGreaterThenEqualFunction whereGreaterThenEqualFunction;
    
    @Resource(name = "whereInFunction")
    private  WhereInFunction whereInFunction;
    
    @Resource(name = "greaterThenFunction")
    private  GreaterThenFunction greaterThenFunction;
    
    @Resource(name = "regexFunction")
    private  RegexFunction regexFunction;
    
    @Resource(name = "maxFunction")
    private  MaxFunction maxFunction;
    
    @Resource(name = "minFunction")
    private  MinFunction minFunction;
    
    @Resource(name = "equalFunction")
    private  EqualFunction equalFunction;
    
    @Resource(name = "lessThenEqualFunction")
    private  LessThenEqualFunction lessThenEqualFunction;
    
    @Resource(name = "lessThenFunction")
    private  LessThenFunction lessThenFunction;
    
    @Resource(name = "plusFunction")
    private  PlusFunction plusFunction;
    
    @Resource(name = "multiFunction")
    private  MultiFunction multiFunction;
    
    @Resource(name = "notEqualFunction")
    private  NotEqualFunction notEqualFunction;
    
    @Resource(name = "whereNotInFunction")
    private  WhereNotInFunction whereNotInFunction;
    
    @Resource(name = "sumFunction")
    private  SumFunction sumFunction;
    
    @Resource(name = "minusFunction")
    private  MinusFunction minusFunction;
    
   {
        AviatorEvaluator.addFunction(whereGreaterThenFunction);
        AviatorEvaluator.addFunction(countFunction);
        AviatorEvaluator.addFunction(devideFunction);
        AviatorEvaluator.addFunction(selectFunction);
        AviatorEvaluator.addFunction(whereEqualFunction);
        AviatorEvaluator.addFunction(timeFunction);
        AviatorEvaluator.addFunction(whereLessThenFunction);
        AviatorEvaluator.addFunction(whereGreaterThenEqualFunction);
        AviatorEvaluator.addFunction(whereInFunction);
        AviatorEvaluator.addFunction(greaterThenFunction);
        AviatorEvaluator.addFunction(regexFunction);
        AviatorEvaluator.addFunction(maxFunction);
        AviatorEvaluator.addFunction(minFunction);
        AviatorEvaluator.addFunction(equalFunction);
        AviatorEvaluator.addFunction(lessThenEqualFunction);
        AviatorEvaluator.addFunction(lessThenFunction);
        AviatorEvaluator.addFunction(plusFunction);
        AviatorEvaluator.addFunction(multiFunction);
        AviatorEvaluator.addFunction(notEqualFunction);
        AviatorEvaluator.addFunction(whereNotInFunction);
        AviatorEvaluator.addFunction(sumFunction);
        AviatorEvaluator.addFunction(minusFunction);
    }