Spring(十七) Spring 拦截器

该例子结合Spring(十六）这篇文章来看，本人觉得其实Spring(十六）写的也是拦截器，都是AOP面向切面编程的知识点:

今天在SSH中用到spring拦截器,所以先在一个只有spring的测试项目中写了一个拦截器的一个简单例子,

结果还遇到了一点小错误,一下就按时间发展顺序记述.

Purview接口.

package aop; 

public interface Purview { 
    void checkLogin(); 
}
PurviesImpl类,Purview接口的实现类.

package aop; 

public class PurviewImpl implements Purview { 

    public void checkLogin() { 
        System.out.println("This is checkLogin method!"); 
    } 
} 

/**
* PurviewAdvice类,拦截器类,可以实现MethodBeforeAdvice, *AfterReturningAdvice, ThrowsAdvice接口，这里实现了MethodBeforeAdvice接口
*/
package aop; 

import java.lang.reflect.Method; 
import org.springframework.aop.MethodBeforeAdvice; 

public class PurviewAdvice implements MethodBeforeAdvice { 
    public void before(Method arg0, Object[] arg1, Object arg2) 
            throws Throwable { 
        System.out.println("This is before method!"); 
    } 
} 

//Test类,测试类.

package aop; 

import org.springframework.context.ApplicationContext; 
import org.springframework.context.support.ClassPathXmlApplicationContext; 

public class Test { 
    public static void main(String[] args) { 
        // TODO 自动生成方法存根 
        ApplicationContext ctx = new ClassPathXmlApplicationContext( 
                "applicationContext.xml"); 
        PurviewImpl purviewImpl = (PurviewImpl) ctx.getBean("purviewImpl"); 
        purviewImpl.checkLogin(); 

    } 

} 

applicationContext.xml配置文件.

    <bean id="purviewImpl" class="aop.PurviewImpl"></bean> 
    <bean id="purviewAdvice" class="aop.PurviewAdvice"></bean> 
    <bean id="purviewAdvisor" 
        class="org.springframework.aop.support.RegexpMethodPointcutAdvisor"> 
        <property name="advice"> 
            <ref local="purviewAdvice" /> 
        </property> 
        <property name="patterns"> 
            <list> 
                <value>.*checkLogin.*</value> 
            </list> 
        </property> 
    </bean> 

    <bean id="autoproxyaop" 
        class="org.springframework.aop.framework.autoproxy.BeanNameAutoProxyCreator"> 
        <property name="beanNames"> 
           <value>purviewImpl</value> //需要拦截的javaBean

        </property> 
        <property name="interceptorNames"> 
            <list> 
                  <value>purviewAdvisor</value>//拦截器列表，可以配置多个拦截器

            </list> 
        </property> 
    </bean>
运行结果报错,错误信息为:

Exception in thread "main" java.lang.ClassCastException: $Proxy1
 at aop.Test.main(Test.java:34)

将Test类中

PurviewImpl purviewImpl = (PurviewImpl) ctx.getBean("purviewImpl");

修改为

Purview purviewImpl = (Purview) ctx.getBean("purviewImpl");

程序运行结果为:

This is before method!
This is checkLogin method!

至此拦截器使用成功!

总结:用spring得到bean的时候,若该类实现了接口,则返回其接口类型的实例,

若直接返回该实现类类型的实例则会报错,错误信息如上所述.

评论

1 楼 se7en8974 2010-11-29  

不知道拦截flex的remoteobject调用的javabean可否，感觉应该可行。
Spring MVC的handler interceptor就没法做到拦截普通javabean