spring 注入 dao，引用的时候为null

spring配置文件如下：
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">

default-autowire="no">

<bean id="IBdxmService" parent="baseTransactionProxy">
    <property name="target">
        <bean
            class="cn.com.ebidding.web.dljk.bdxm.service.impl.BdxmService">
            <property name="dao" ref="IBdxmDao" />
        </bean>
    </property>
</bean>

<bean id="IBdxmAuth" parent="baseTransactionProxy">
    <property name="target">
        <bean
            class="cn.com.ebidding.web.dljk.bdxm.auth.impl.BdxmAuth" singleton="false">
            <property name="dao" ref="IBdxmDao" />
        </bean>
    </property>
</bean>

<bean id="IBdxmBusiness" parent="baseTransactionProxy">
    <property name="target">
        <bean
            class="cn.com.ebidding.web.dljk.bdxm.business.impl.BdxmBusiness">
            <property name="dao" ref="IBdxmDao" />
        </bean>
    </property>
</bean>

<bean id="IBdxmValidate" parent="baseTransactionProxy">
    <property name="target">
        <bean
            class="cn.com.ebidding.web.dljk.bdxm.validate.impl.BdxmValidate">
            <property name="dao" ref="IBdxmDao" />
        </bean>
    </property>
</bean>

<bean id="IBdxmDao"
    class="cn.com.ebidding.web.dljk.bdxm.dao.impl.BdxmDao">
    <property name="sessionFactory" ref="sessionFactory" />
</bean> 

http://www.oschina.net/question/366783_132939?sort=time&p=1

 配置文件中没看到往bdxmservice中注入dao这个属性

你的spring中关于ISapDao的配置错误，你的class="cn.com.ebidding.web.wzjk.sap.dao.impl.SapDao">这个类是他的实现类吗？怎么看着像是接口类呢？