Spring报错：Bean property ‘per‘ is not writable or has an invalid setter method.

Caused by: org.springframework.beans.NotWritablePropertyException: Invalid property ‘per’ of bean class [com.zyq.service.impl.PersonServiceImpl]: Bean property ‘per’ is not writable or has an invalid setter method. Does the parameter type of the setter match the return type of the getter?

报错原因：
ApplicationContext.xml文件中

    <bean id="per" class="com.zyq.dao.impl.PersonDaoImpl"></bean>

<!--  PersonServiceImpl类中引用了personDao类  -->
    <bean id="personService" class="com.zyq.service.impl.PersonServiceImpl">
        <property name="per" ref="per"></property>
    </bean>
</beans>

property属性下name名称与Impl实现类中的setter()方法入参类型不对应:

<property name="per" ref="per"></property>

此处name="per"应该与

  public void setPersonDao(PersonDao person) {
        this.personDa = person;
    }

中PersonDao对应. 应改为name="personDao"或name="PersonDao".

实现类：

public class PersonServiceImpl implements PersonService {

    //原始new方法
//    PersonDao personDao = new PersonDaoImpl();

    //IOC方法 报空指针因为没有set方法 且PersonServiceImpl注入时要ref一下personDao类

    private PersonDao personDa;

    @Override
    public void say() {
        System.out.println("PersonService的say方法");
        personDa.eat();

    }

    public void setPersonDao(PersonDao person) {
        this.personDa = person;
    }
}

若此处报空指针异常错误，则大概率是Impl层没加Setter()方法.