1六、SpringMVC拦截器

时间  2020-03-23
标签 springmvc 拦截 栏目 Spring 繁體版
原文   原文链接

拦截定义

定义拦截器，实现HandlerInterceptor接口。接口中提供三个方法。java

public class HandlerInterceptor1 implements HandlerInterceptor{

    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        //return false表示拦截，不向下执行
        //return true表示放行
        return false;
    }

    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
    }

    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
    }
}

能够从名称和参数看出各个接口的顺序和做用:web

  • public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception
    • 参数最少，只有三个
    • 进入 Handler方法以前执行
    • 用于身份认证、身份受权。好比身份认证，若是认证不经过表示当前用户没有登录，须要此方法拦截再也不向下执行
  • public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception
    • 多了一个modelAndView参数
    • 进入Handler方法以后，返回modelAndView以前执行
    • 应用场景从modelAndView出发：将公用的模型数据(好比菜单导航)在这里传到视图，也能够在这里统一指定视图
  • public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception
    • 多了一个Exception的类型的参数
    • 执行Handler完成执行此方法
    • 应用场景：统一异常处理，统一日志处理

拦截器配置

针对HandlerMapping配置

springmvc拦截器针对HandlerMapping进行拦截设置，若是在某个HandlerMapping中配置拦截，通过该HandlerMapping映射成功的handler最终使用该拦截器。spring

<bean
	class="org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping">
	<property name="interceptors">
		<list>
			<ref bean="handlerInterceptor1"/>
			<ref bean="handlerInterceptor2"/>
		</list>
	</property>
</bean>
<bean id="handlerInterceptor1" class="com.tianlang.intercapter.HandlerInterceptor1"/>
<bean id="handlerInterceptor2" class="com.tianlang.intercapter.HandlerInterceptor2"/>

通常不推荐使用。session

相似全局的拦截器

springmvc配置相似全局的拦截器，springmvc框架将配置的相似全局的拦截器注入到每一个HandlerMapping中。mvc

<!--拦截器 -->
<mvc:interceptors>
    <!--多个拦截器,顺序执行 -->
    <mvc:interceptor>
        <!-- /**表示全部url包括子url路径 -->
        <mvc:mapping path="/**"/>
        <bean class="com.tianlang.interceptor.HandlerInterceptor1"></bean>
    </mvc:interceptor>
    <mvc:interceptor>
        <mvc:mapping path="/**"/>
        <bean class="com.tianlang.interceptor.HandlerInterceptor2"></bean>
    </mvc:interceptor>
</mvc:interceptors>

拦截测试

测试多个拦截器各个方法执行时机app

访问/items/queryItems.action框架

  • 1.两个拦截器都放行
DEBUG [http-apr-8080-exec-1] - DispatcherServlet with name 'springmvc' processing GET request for [/ssm1/items/queryItems.action]
DEBUG [http-apr-8080-exec-1] - Looking up handler method for path /items/queryItems.action
DEBUG [http-apr-8080-exec-1] - Returning handler method [public org.springframework.web.servlet.ModelAndView com.iot.learnssm.firstssm.controller.ItemsController.queryItems(javax.servlet.http.HttpServletRequest,com.iot.learnssm.firstssm.po.ItemsQueryVo) throws java.lang.Exception]
DEBUG [http-apr-8080-exec-1] - Returning cached instance of singleton bean 'itemsController'
DEBUG [http-apr-8080-exec-1] - Last-Modified value for [/ssm1/items/queryItems.action] is: -1
HandlerInterceptor1...preHandle
HandlerInterceptor2...preHandle
DEBUG [http-apr-8080-exec-1] - Fetching JDBC Connection from DataSource
DEBUG [http-apr-8080-exec-1] - Registering transaction synchronization for JDBC Connection
DEBUG [http-apr-8080-exec-1] - Returning JDBC Connection to DataSource
HandlerInterceptor2...postHandle
HandlerInterceptor1...postHandle
DEBUG [http-apr-8080-exec-1] - Rendering view [org.springframework.web.servlet.view.JstlView: name 'items/itemsList'; URL [/WEB-INF/jsp/items/itemsList.jsp]] in DispatcherServlet with name 'springmvc'
DEBUG [http-apr-8080-exec-1] - Added model object 'itemtypes' of type [java.util.HashMap] to request in view with name 'items/itemsList'
DEBUG [http-apr-8080-exec-1] - Added model object 'itemsQueryVo' of type [com.iot.learnssm.firstssm.po.ItemsQueryVo] to request in view with name 'items/itemsList'
DEBUG [http-apr-8080-exec-1] - Added model object 'org.springframework.validation.BindingResult.itemsQueryVo' of type [org.springframework.validation.BeanPropertyBindingResult] to request in view with name 'items/itemsList'
DEBUG [http-apr-8080-exec-1] - Added model object 'itemsList' of type [java.util.ArrayList] to request in view with name 'items/itemsList'
DEBUG [http-apr-8080-exec-1] - Forwarding to resource [/WEB-INF/jsp/items/itemsList.jsp] in InternalResourceView 'items/itemsList'
HandlerInterceptor2...afterCompletion
HandlerInterceptor1...afterCompletion
DEBUG [http-apr-8080-exec-1] - Successfully completed request

总结：preHandle方法按顺序执行，postHandle和afterCompletion按拦截器配置的逆向顺序执行。jsp

2.拦截器1放行，拦截器2不放行post

DEBUG [http-apr-8080-exec-8] - DispatcherServlet with name 'springmvc' processing GET request for [/ssm1/items/queryItems.action]
DEBUG [http-apr-8080-exec-8] - Looking up handler method for path /items/queryItems.action
DEBUG [http-apr-8080-exec-8] - Returning handler method [public org.springframework.web.servlet.ModelAndView com.iot.learnssm.firstssm.controller.ItemsController.queryItems(javax.servlet.http.HttpServletRequest,com.iot.learnssm.firstssm.po.ItemsQueryVo) throws java.lang.Exception]
DEBUG [http-apr-8080-exec-8] - Returning cached instance of singleton bean 'itemsController'
DEBUG [http-apr-8080-exec-8] - Last-Modified value for [/ssm1/items/queryItems.action] is: -1
HandlerInterceptor1...preHandle
HandlerInterceptor2...preHandle
HandlerInterceptor1...afterCompletion
DEBUG [http-apr-8080-exec-8] - Successfully completed request

总结：测试

  • 拦截器1放行，拦截器2 preHandle才会执行。
  • 拦截器2 preHandle不放行，拦截器2 postHandle和afterCompletion不会执行。
  • 只要有一个拦截器不放行，postHandle不会执行。

3.两个拦截器都不放

DEBUG [http-apr-8080-exec-9] - DispatcherServlet with name 'springmvc' processing GET request for [/ssm1/items/queryItems.action]
DEBUG [http-apr-8080-exec-9] - Looking up handler method for path /items/queryItems.action
DEBUG [http-apr-8080-exec-9] - Returning handler method [public org.springframework.web.servlet.ModelAndView com.iot.learnssm.firstssm.controller.ItemsController.queryItems(javax.servlet.http.HttpServletRequest,com.iot.learnssm.firstssm.po.ItemsQueryVo) throws java.lang.Exception]
DEBUG [http-apr-8080-exec-9] - Returning cached instance of singleton bean 'itemsController'
DEBUG [http-apr-8080-exec-9] - Last-Modified value for [/ssm1/items/queryItems.action] is: -1
HandlerInterceptor1...preHandle
DEBUG [http-apr-8080-exec-9] - Successfully completed request

总结：

  • 拦截器1 preHandle不放行，postHandle和afterCompletion不会执行。
  • 拦截器1 preHandle不放行，拦截器2不执行。

4.拦截器1不放行，拦截器2放行

DEBUG [http-apr-8080-exec-8] - DispatcherServlet with name 'springmvc' processing GET request for [/ssm1/items/queryItems.action]
DEBUG [http-apr-8080-exec-8] - Looking up handler method for path /items/queryItems.action
DEBUG [http-apr-8080-exec-8] - Returning handler method [public org.springframework.web.servlet.ModelAndView com.iot.learnssm.firstssm.controller.ItemsController.queryItems(javax.servlet.http.HttpServletRequest,com.iot.learnssm.firstssm.po.ItemsQueryVo) throws java.lang.Exception]
DEBUG [http-apr-8080-exec-8] - Returning cached instance of singleton bean 'itemsController'
DEBUG [http-apr-8080-exec-8] - Last-Modified value for [/ssm1/items/queryItems.action] is: -1
HandlerInterceptor1...preHandle
DEBUG [http-apr-8080-exec-8] - Successfully completed request

和两个拦截器都不行的结果一致，由于拦截器1先执行，没放行

  • 小结

根据测试结果，对拦截器应用。

好比：统一日志处理拦截器，须要该拦截器preHandle必定要放行，且将它放在拦截器连接中第一个位置。

好比：登录认证拦截器，放在拦截器连接中第一个位置。权限校验拦截器，放在登录认证拦截器以后。（由于登录经过后才校验权限，固然登陆认证拦截器要放在统一日志处理拦截器后面）

拦截器应用(实现登录认证)

登录controller方法

@Controller
public class LoginController {
    // 登录
    @RequestMapping("/login")
    public String login(HttpSession session, String username, String password)
            throws Exception {
        // 在session中保存用户身份信息
        session.setAttribute("username", username);
        // 重定向到商品列表页面
        return "redirect:/items/queryItems.action";
    }

    // 退出
    @RequestMapping("/logout")
    public String logout(HttpSession session) throws Exception {
        // 清除session
        session.invalidate();
        // 重定向到商品列表页面
        return "redirect:/items/queryItems.action";
    }
}

登录认证拦截实现

  • 代码实现
/**
 * 登录认证拦截器
 */
public class LoginInterceptor implements HandlerInterceptor {

    public boolean preHandle(HttpServletRequest request,
                             HttpServletResponse response, Object handler) throws Exception {
        //获取请求的url
        String url = request.getRequestURI();
        //判断url是不是公开地址（实际使用时将公开 地址配置配置文件中）
        if(url.indexOf("login.action")>=0){
            //若是进行登录提交，放行
            return true;
        }
        //判断session
        HttpSession session  = request.getSession();
        //从session中取出用户身份信息
        String username = (String) session.getAttribute("username");
        if(username != null){
            //身份存在，放行
            return true;
        }
        //执行这里表示用户身份须要认证，跳转登录页面
        request.getRequestDispatcher("/WEB-INF/jsp/login.jsp").forward(request, response);
        return false;
    }

    public void postHandle(HttpServletRequest request,
                           HttpServletResponse response, Object handler,
                           ModelAndView modelAndView) throws Exception {
        System.out.println("LoginInterceptor...postHandle");
    }

    public void afterCompletion(HttpServletRequest request,
                                HttpServletResponse response, Object handler, Exception ex)
            throws Exception {
        System.out.println("LoginInterceptor...afterCompletion");
    }
}
  • 拦截器配置
<!--拦截器 -->
<mvc:interceptors>
    <!--多个拦截器,顺序执行 -->
    <!-- 登录认证拦截器 -->
    <mvc:interceptor>
        <mvc:mapping path="/**"/>
        <bean class="com.tianlang.interceptor.LoginInterceptor"></bean>
	</mvc:interceptor>  
</mvc:interceptors>
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