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用一个例子来说明，一个小网站，只有用户登录后才可访问，否则被拦截。
要定义拦截器，需要实现Spring的HandleIntercetor接口或者继承抽象类HanlerInterceptorAdater
中间有三个方法，通过例子说明：
public class AuthorizationInterceptor implements HandlerInterceptor { private static final String[] IGNGRE_URI={ "/loginForm","/login"}; /** * 该方法在Controller处理之前执行。当返回值为true才执行controller，否则不执行。 * @param httpServletRequest * @param httpServletResponse * @param o * @return * @throws Exception */ public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception { System.out.println("AuthorizationInterceptor preHandle --> "); boolean flag=false; String servletPath=httpServletRequest.getServletPath(); for(String s:IGNGRE_URI){ if(servletPath.contains(s)){ flag=true; break; } } if(!flag){ User user=(User)httpServletRequest.getSession().getAttribute("user"); if(user==null){ System.out.println("AuthorizationInterceptor 拦截请求："); httpServletRequest.setAttribute("message","请先登录再访问网站"); httpServletRequest.getRequestDispatcher("loginForm").forward(httpServletRequest,httpServletResponse); }else { System.out.println("AuthorizationInterceptor 放行请求："); flag=true; } } return flag; } /** * 在controller的方法调用之后执行，方法中可以多modelAndview进行操作 * @param httpServletRequest * @param httpServletResponse * @param o * @param modelAndView * @throws Exception */ public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception { System.out.println("AuthorizationInterceptor postHandle -->"); } /** * 该方法在整个请求完成之后执行，主要作用是用于清理资源 * @param httpServletRequest * @param httpServletResponse * @param o * @param e * @throws Exception */ public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception { System.out.println("AuthorizationInterceptor afterCompletion --> "); }}