How to Inject Null and Empty Values in Spring

<property name="a"><null/></property> 

<property name="b" value=""/> 

<beans xmlns="http://www.springframework.org/schema/beans"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
   xsi:schemaLocation="http://www.springframework.org/schema/beans
      http://www.springframework.org/schema/beans/spring-beans.xsd">
 
	<bean id="test" class="com.concretepage.Test">
	   <property name="a"> <null/></property>
           <property name="b" value=""/>
        </bean> 
 </beans> 

package com.concretepage;
public class Test {
	private Integer a;
	private String b;
	public Integer getA() {
		return a;
	}
	public void setA(Integer a) {
		this.a = a;
	}
	public String getB() {
		return b;
	}
	public void setB(String b) {
		this.b = b;
	}
}
 

package com.concretepage;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class SpringTest {
	public static void main(String[] args) {
	     ApplicationContext context = new ClassPathXmlApplicationContext("app-context.xml");
	     Test test=(Test)context.getBean("test");
	     if(test.getA()==null){
	    	 System.out.println("null value.");
	     }
	     if("".equals(test.getB())){
	    	 System.out.println("Empty value.");
	     }
	}
}