Spring中使用BeanPostProcessor需要注意的地方

Spring中Bean的实例化过程如下：

 

其中BeanPostProcessor的前置和后置处理的方法中都要返回该bean，不能是null，不然在getBean的时候获取不到。

public interface PasswordDecodable
{
	public String getEncodedPassword();
	
	public void setDecodedPassword(String password);
}

 

public class LoginModel implements PasswordDecodable
{

	private String password;
	
	public LoginModel()
	{
		
	}
	
	public LoginModel(String password)
	{
		this.password = password;
	}
	
	@Override
	public String getEncodedPassword()
	{
		// TODO Auto-generated method stub
		return this.password;
	}

	@Override
	public void setDecodedPassword(String password)
	{
		// TODO Auto-generated method stub
		this.password = password;
	}

}

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.BeanPostProcessor;

import com.uqee.spring.beans.PasswordDecodable;
import com.uqee.utils.Md5Token;

public class PasswordDecodePostProcessor implements BeanPostProcessor
{

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException
    {
        // TODO Auto-generated method stub
        return bean;
    }

    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException
    {
        // TODO Auto-generated method stub
        if(bean instanceof PasswordDecodable)
        {
            String encodedPassword = ((PasswordDecodable)bean).getEncodedPassword();
            String decodePassword = decodePassword(encodedPassword);
            ((PasswordDecodable)bean).setDecodedPassword(decodePassword);
        }
        return bean;
    }
    
    private String decodePassword(String encodePassword)
    {
        return Md5Token.getInstance().getLongToken(encodePassword);
    }
}

<bean id="loginModel" class="com.uqee.spring.beans.LoginModel">
        <constructor-arg index="0">
            <value>demo</value>
        </constructor-arg>
</bean>

PasswordDecodePostProcessor的postProcessAfterInitialization和postProcessBeforeInitialization均不能返回null，不然下列代码：

ConfigurableListableBeanFactory factory = new XmlBeanFactory(new ClassPathResource("applicationContext3.xml"));
		factory.addBeanPostProcessor(new PasswordDecodePostProcessor());
		PasswordDecodable passwordDecodable = (PasswordDecodable)factory.getBean("loginModel");

 

中passwordDecodable会是null引用。