拦截器的概念就不介绍了：
SpringMVC中拦截器的执行规则：
一个小示例展示：
我搞两个拦截器：
第一个：
package org.dreamtech.springmvc.interceptor; import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView; public class Interceptor1 implements HandlerInterceptor { @Override
public void afterCompletion(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, Exception arg3)
throws Exception {
System.out.println("页面渲染后1"); } @Override
public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, ModelAndView arg3)
throws Exception {
System.out.println("方法后1"); } @Override
public boolean preHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2) throws Exception {
System.out.println("方法前1");
return true;
} }
第二个：
package org.dreamtech.springmvc.interceptor; import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView; public class Interceptor2 implements HandlerInterceptor { @Override
public void afterCompletion(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, Exception arg3)
throws Exception {
System.out.println("页面渲染后2"); } @Override
public void postHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, ModelAndView arg3)
throws Exception {
System.out.println("方法后2"); } @Override
public boolean preHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2) throws Exception {
System.out.println("方法前2");
return true;
} }
然后把它配置到SpringMVC.xml中：
<!-- 配置拦截器 -->
<mvc:interceptors>
<!-- 配置多个拦截器 -->
<mvc:interceptor>
<!-- 拦截所有 -->
<mvc:mapping path="/**" />
<!-- 自定义拦截器类 -->
<bean class="org.dreamtech.springmvc.interceptor.Interceptor1" />
</mvc:interceptor>
<mvc:interceptor>
<!-- 拦截所有 -->
<mvc:mapping path="/**" />
<!-- 自定义拦截器类 -->
<bean class="org.dreamtech.springmvc.interceptor.Interceptor2s" />
</mvc:interceptor>
</mvc:interceptors>
执行之后：
然而我们如果把拦截器一的方法前不放行：
@Override
public boolean preHandle(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2) throws Exception {
System.out.println("方法前1");
return false;
}
这时候，发现控制台只是打印了：方法前1
但是，我们如果把拦截器二的方法前不放行：
打印的却是：
到这里就可以看出SpringMVC的执行规则了：
为了方便，我借用某博主的图片:
文字解释：
preHandler按拦截器定义顺序调用，
postHandler按拦截器定义逆序调用，
afterCompletion按拦截器定义逆序调用，
postHandler在所有的拦截器返回成功时候才会调用，
afterCompletion在preHandler返回true才会调用
应用：
登录功能：只有登录才能查看其他信息
限制：在非登陆状态下无法访问该网站任何一处
随意写一个登录页面：
<body>
<form action="${pageContext.request.contextPath }/login.action" method="post">
用户名：<input type="text" name="username">
<input type="submit" value="提交">
</form>
</body>
只用一个拦截器：
<mvc:interceptors>
<mvc:interceptor>
<mvc:mapping path="/**" />
<bean class="org.dreamtech.springmvc.interceptor.Interceptor2" />
</mvc:interceptor>
</mvc:interceptors>
拦截器：
package org.dreamtech.springmvc.interceptor; import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView; public class Interceptor2 implements HandlerInterceptor { @Override
public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object arg2, Exception arg3)
throws Exception { } @Override
public void postHandle(HttpServletRequest request, HttpServletResponse response, Object arg2, ModelAndView arg3)
throws Exception { } @Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object arg2) throws Exception {
String requestURI = request.getRequestURI();
/*
* URI:/login.action
* URL:http://xxx/xxx/login.action
*/
if(!requestURI.contains("/login")){
String username = (String) request.getSession().getAttribute("USER_SESSION");
if(username==null){
response.sendRedirect(request.getContextPath()+"/login.action");
return false;
}
}
return true;
} }
实现：
@RequestMapping(value = "/login.action", method = RequestMethod.GET)
public String login() {
return "login"; } @RequestMapping(value = "/login.action", method = RequestMethod.POST)
public String login(String username, HttpSession httpSession) {
httpSession.setAttribute("USER_SESSION", username);
return "redirect:/item/itemlist.action"; }
这里注意：我直接返回字符串：login是因为提前做了配置：
<bean
class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="prefix" value="/WEB-INF/jsp/" />
<property name="suffix" value=".jsp" />
</bean>