SpringMVC - 拦截器（08）

概述

Spring MVC的拦截器分为三种：访问controller前，访问controller后，页面渲染后。所有的拦截器都实现HandlerInterceptor接口，接口中包含三个类别的方法。也就是每个拦截器都会进行三次拦截处理。

多个拦截器的执行顺序

• postHandle按拦截器配置的逆序调用；
• postHandler按拦截器配置的逆序调用；
• afterCompletion按拦截器配置的逆序调用；
• postHandler在拦截器链内所有拦截器返成功调用；
• afterCompletion只有它的preHandle返回true才调用。
  至于为什么是这样，我也不清楚，还没读Spring MVC源码，等之后知道原理后会更新博文。

应用

  <mvc:interceptors>
   		<mvc:interceptor>
   			<!-- 现在是所有访问请求都会被拦截
					如果想拦截指定路径的请求，可以采用的方式如：/user/**
				-->
   			<mvc:mapping path="/**"/>
   			<bean class="com.first.mvc.MyInterceptor1"></bean>
   		</mvc:interceptor>
    </mvc:interceptors>

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

public class MyInterceptor1 implements HandlerInterceptor {

	@Override
	public void afterCompletion(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, Exception arg3)
			throws Exception {
		System.out.println("afterCompletion");
	}

	@Override
	public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, ModelAndView arg3)
			throws Exception {
		System.out.println("postHandle");
	}

	@Override
	public boolean preHandle(HttpServletRequest req, HttpServletResponse res, Object arg2) throws Exception {
		System.out.println("preHandle");
		if(req.getParameter("name") != null)
			return true;
		return false;
	}
}

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;

@Controller
public class MyFirst {
	
	@RequestMapping(value="/first.action")
	public ModelAndView first() {
		ModelAndView mv = new ModelAndView();
		System.out.println("第一次使用springmvc");
		mv.setViewName("newFile");
		return mv;
	}
}

案例

登陆之后才能访问其他功能，否则会被拦截到登陆界面。

public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object arg2) throws Exception {
	HttpSession session = request.getSession();
	String uri = request.getRequestURI();
	// 判断username是否为null
	if(!uri.contains("/login")){
		Object username = session.getAttribute("username");
		if(username == null){
			response.sendRedirect(request.getContextPath() + "/user/toLogin.action");
			return false;
		}
	}
	return true;
}