java 拦截器和过滤器区别（转载）
1、拦截器是基于java的反射机制的，而过滤器是基于函数回调?
2、过滤器依赖与servlet容器，而拦截器不依赖与servlet容器?
3、拦截器只能对action请求起作用，而过滤器则可以对几乎所有的请求起作用?
4、拦截器可以访问action上下文、值栈里的对象，而过滤器不能?
5、在action的生命周期中，拦截器可以多次被调用，而过滤器只能在容器初始化时被调用一次?
???? 拦截器 ：是在面向切面编程的就是在你的service或者一个方法，前调用一个方法，或者在方法后调用一个方法比如动态代理就是拦截器的简单实现，在你调用方法前打印出字符串（或者做其它业务逻辑的操作），也可以在你调用方法后打印出字符串，甚至在你抛出异常的时候做业务逻辑的操作。?
下面通过实例来看一下过滤器和拦截器的区别：?
使用拦截器进行/admin 目录下jsp页面的过滤?
<package name="newsDemo" extends="struts-default"?
??????? namespace="/admin">?
??????? <interceptors>?
??????????? <interceptor name="auth" />?
??????????? <interceptor-stack name="authStack">?
??????????????? <interceptor-ref name="auth" />?
??????????? </interceptor-stack>?
??????? </interceptors>?
??????? <!-- action -->?
??????? <action name="newsAdminView!*" class="newsAction"?
??????????? method="{1}">?
??????????? <interceptor-ref name="defaultStack"/>?
??????????? <interceptor-ref name="authStack">?
??????????? </interceptor-ref>?
下面是我实现的Interceptor class:?
package com.test.news.util;?
import java.util.Map;?
import com.opensymphony.xwork2.ActionContext;?
import com.opensymphony.xwork2.ActionInvocation;?
import com.opensymphony.xwork2.interceptor.AbstractInterceptor;?
import com.test.news.action.AdminLoginAction;?
/**?
* @author chaoyin?
*/?
public class AccessInterceptor extends AbstractInterceptor {?
??? private static final long serialVersionUID = -4291195782860785705L;?
??? @Override?
??? public String intercept(ActionInvocation actionInvocation) throws Exception {?
???????? ActionContext actionContext = actionInvocation.getInvocationContext();?
???????? Map session = actionContext.getSession();?
????????
??????? //except login action?
???????? Object action = actionInvocation.getAction();?
??????? if (action instanceof AdminLoginAction) {?
??????????? return actionInvocation.invoke();?
???????? }?
??????? //check session?
??????? if(session.get("user")==null ){?
??????????? return "logout";?
???????? }?
??????? return actionInvocation.invoke();//go on?
???? }?
}?
?????? 过滤器：是在java web中，你传入的request,response提前过滤掉一些信息，或者提前设置一些参数，然后再传入servlet或者struts的 action进行业务逻辑，比如过滤掉非法url（不是login.do的地址请求，如果用户没有登陆都过滤掉）,或者在传入servlet或者 struts的action前统一设置字符集，或者去除掉一些非法字符.?
使用过滤器进行/admin 目录下jsp页面的过滤，首先在web.xml进行过滤器配置:?
??? <filter>?
??????? <filter-name>access filter</filter-name>?
??????? <filter-class>?
???????????? com.test.news.util.AccessFilter?
??????? </filter-class>?
??? </filter>?
??? <filter-mapping>?
??????? <filter-name>access filter</filter-name>?
??????? <url-pattern>/admin/*</url-pattern>?
??? </filter-mapping>?
下面是过滤的实现类:?
package com.test.news.util;?
import java.io.IOException;?
import javax.servlet.Filter;?
import javax.servlet.FilterChain;?
import javax.servlet.FilterConfig;?
import javax.servlet.ServletException;?
import javax.servlet.ServletRequest;?
import javax.servlet.ServletResponse;?
import javax.servlet.http.HttpServletRequest;?
import javax.servlet.http.HttpServletResponse;?
import javax.servlet.http.HttpSession;?
public class AccessFilter implements Filter {?
/**?
* @author chaoyin?
*/?
????
??? public void destroy() {?
???? }?
??? public void doFilter(ServletRequest arg0, ServletResponse arg1,?
???????????? FilterChain filterChain) throws IOException, ServletException {?
???????? HttpServletRequest request = (HttpServletRequest)arg0;?
???????? HttpServletResponse response = (HttpServletResponse)arg1;?
???????? HttpSession session = request.getSession();?
??????? if(session.getAttribute("user")== null && request.getRequestURI().indexOf("login.jsp")==-1 ){?
???????????? response.sendRedirect("login.jsp");?
??????????? return ;?
???????? }?
???????? filterChain.doFilter(arg0, arg1);?
???? }?
??? public void init(FilterConfig arg0) throws ServletException {?
???? }?
}
