Day_09 Filter和监听器

文章目录

• • • 01-Filter概述(掌握)
    • 02-Filter入门案例(掌握)
    • 03-Filter执行流程(掌握)
    • 04-Filter生命周期(掌握)
    • 05-Filter相关配置(掌握)
    • 06-过滤器链(掌握)
    • 07-Filter拦截行为(掌握)
    • 08-Filter注解开发(掌握)
    • 09-监听器概述(掌握)
    • 10-一类监听器概述(掌握)
    • 11-一类监听器之ServletRequestListener(掌握)
    • 12-一类监听器之ServletContextListener(重点)
    • 13-二类监听器概述(掌握)
    • 14-二类监听器之ServletRequestAttributeListener(了解)
    • 15-三类监听器概述(了解)
    • 16-三类监听器之HttpSessionBindingListener(掌握)
    • 17-session钝化和活化(掌握)
    • 18-三类监听器之HttpSessionActivationListener(掌握)
    • 19-监听器的注解开发(掌握)

01-Filter概述(掌握)

• 概述

  A filter is an object that performs filtering tasks on either the request to a resource (a servlet or static content), or on the response from a resource, or both. 
  
  Filters perform filtering in the doFilter method. Every Filter has access to a FilterConfig object from which it can obtain its initialization parameters, and a reference to the ServletContext which it can use, for example, to load resources needed for filtering tasks. 
  
  Examples that have been identified for this design are: 
      Authentication Filters 
      Logging and Auditing Filters 
      Image conversion Filters 
      Data compression Filters 
      Encryption Filters 
      Tokenizing Filters 
      Filters that trigger resource access events 
      XSL/T filters 
      Mime-type chain Filter 
  

  • Filter对象可以用于过滤request和response;
  • Filter对象有一个FilterConfig对象，通过这个对象可以获取初始化参数，以及使用ServletContext对象；
  • 适用场景：Authentication Filters 、 Tokenizing Filters …

02-Filter入门案例(掌握)

• 开发步骤

  • ①定义FIlter类实现Filter接口
    • 重写方法
  • ②编写web.xml
    • 声明Filter类

• ①定义FIlter类实现Filter接口

  @WebServlet("/demo01")
  public class Demo01Servlet extends HttpServlet {
      protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          System.out.println("Demo01Servlet");
      }
  
      protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          doPost(request, response);
      }
  }
  

• ②编写web.xml

  <filter>
      <filter-name>Demo01Filter</filter-name>
      <filter-class>com.atguigu.filter.Demo01Filter</filter-class>
  </filter>
  <filter-mapping>
      <filter-name>Demo01Filter</filter-name>
      <url-pattern>/*</url-pattern>
  </filter-mapping>
  

03-Filter执行流程(掌握)

• 执行流程
  • 
• 注意事项
  • chain.doFilter只能执行一次。

04-Filter生命周期(掌握)

• 生命周期
  • 实例化
    • 服务器启动
  • 初始化
    • 服务器启动
  • 销毁
    • 服务器关闭

05-Filter相关配置(掌握)

• 相关配置

  • ①初始化参数
  • ②过滤路径
    • 2.1,完全匹配：以"/"开头
    • 2.2,目录匹配：以"/“开头，以”*"结尾
    • 2.3,后缀名匹配: 以"*"开头，以"后缀名"结尾
    • 2.4,过滤指定Servlet

• ①初始化参数

  <filter>
      <filter-name>Demo03Filter</filter-name>
      <filter-class>com.atguigu.filter.Demo03Filter</filter-class>
      <init-param>
          <param-name>encoding</param-name>
          <param-value>utf-8</param-value>
      </init-param>
  </filter>
  <filter-mapping>
      <filter-name>Demo03Filter</filter-name>
      <url-pattern>/*</url-pattern>
  </filter-mapping>
  

  public class Demo03Filter implements Filter {
  
      private String encoding;
  
  
      @Override
      public void init(FilterConfig filterConfig) throws ServletException {
          encoding = filterConfig.getInitParameter("encoding");
          System.out.println("encoding = " + encoding);
  
          Enumeration<String> initParameterNames = filterConfig.getInitParameterNames();
          while (initParameterNames.hasMoreElements()) {
              String initParameterName = initParameterNames.nextElement();
              String initParameterValue = filterConfig.getInitParameter(initParameterName);
              System.out.println("initParameterName = " + initParameterName + " , initParameterValue = " + initParameterValue);
  
          }
  
      }
  
      @Override
      public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
  
          System.out.println("encoding = " + encoding);
          chain.doFilter(request, response);//相当于执行Demo01Servlet
  
      }
  }
  

• ②过滤路径

  <filter>
      <filter-name>Demo04Filter</filter-name>
      <filter-class>com.atguigu.filter.Demo04Filter</filter-class>
  </filter>
  
  <!--2.1,完全匹配：以"/"开头-->
  <!--
  <filter-mapping>
      <filter-name>Demo04Filter</filter-name>
      <url-pattern>/demo01</url-pattern>
  </filter-mapping>
  -->
  <!--2.2,目录匹配：以"/"开头，以"*"结尾-->
  <!--
  <filter-mapping>
      <filter-name>Demo04Filter</filter-name>
      <url-pattern>/a/b/c/*</url-pattern>
  </filter-mapping>
  -->
  <!--2.3,后缀名匹配: 以"*"开头，以"后缀名"结尾-->
  <!--
  <filter-mapping>
      <filter-name>Demo04Filter</filter-name>
      <url-pattern>*.html</url-pattern>
  </filter-mapping>
  -->
  <!--2.4,过滤指定Servlet-->
  <filter-mapping>
      <filter-name>Demo04Filter</filter-name>
      <servlet-name>Demo01Servlet</servlet-name>
      <servlet-name>Demo02Servlet</servlet-name>
  </filter-mapping>
  

06-过滤器链(掌握)

• 概述

  • 由多个过滤器组成一个过滤链。
  • 只有当所有过滤器都放行，请求才能到达目标资源，如果有某一 个过滤器没有放行，那么请求则无法到达后续过滤器以及目标资源

• 执行顺序

  • 先配置，先过滤，后放行.

• 原因分析

  • 

• 代码实现

  public class Demo05Filter implements Filter {
  
  
  
      @Override
      public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
          System.out.println("Demo05Filter 过滤");
          chain.doFilter(request, response);//相当于执行Demo01Servlet
          System.out.println("Demo05Filter 放行");
  
      }
  }
  

  public class Demo06Filter implements Filter {
  
  
  
      @Override
      public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
          System.out.println("Demo06Filter 过滤");
          chain.doFilter(request, response);//相当于执行Demo01Servlet
          System.out.println("Demo06Filter 放行");
  
      }
  }
  

  <filter>
      <filter-name>Demo05Filter</filter-name>
      <filter-class>com.atguigu.filter.Demo05Filter</filter-class>
  </filter>
  <filter-mapping>
      <filter-name>Demo05Filter</filter-name>
      <url-pattern>/*</url-pattern>
  </filter-mapping>
  <filter>
      <filter-name>Demo06Filter</filter-name>
      <filter-class>com.atguigu.filter.Demo06Filter</filter-class>
  </filter>
  <filter-mapping>
      <filter-name>Demo06Filter</filter-name>
      <url-pattern>/*</url-pattern>
  </filter-mapping>
  

07-Filter拦截行为(掌握)

• 概述

  • Filter过滤器默认拦截的是请求，但是在实际开发中，我们还有请求转发和请求包含，以及由服务器触 发调用的全局错误页面。默认情况下过滤器是不参与过滤的，要想使用，就需要我们配置。

• 拦截行为

  • ①REQUEST : 默认值，过滤请求
  • ②ERROR : 过滤跳转全局错误页面
  • ③FORWARD ：过滤请求转发
  • ④INCLUDE : 过滤请求包含

• ①REQUEST : 默认值，过滤请求

  <!--①REQUEST : 默认值，过滤请求-->
  <filter-mapping>
      <filter-name>Demo07Filter</filter-name>
      <url-pattern>/*</url-pattern>
      <dispatcher>REQUEST</dispatcher>
  </filter-mapping>
  

• ②ERROR : 过滤跳转全局错误页面

  <!--②ERROR : 过滤跳转全局错误页面-->
  <filter-mapping>
      <filter-name>Demo07Filter</filter-name>
      <url-pattern>/*</url-pattern>
      <dispatcher>REQUEST</dispatcher>
      <dispatcher>ERROR</dispatcher>
  </filter-mapping>
  

• ③FORWARD ：过滤请求转发

  <!--③FORWARD ：过滤请求转发-->
  <filter-mapping>
      <filter-name>Demo07Filter</filter-name>
      <url-pattern>/*</url-pattern>
      <dispatcher>REQUEST</dispatcher>
      <dispatcher>FORWARD</dispatcher>
  </filter-mapping>
  

• ④INCLUDE : 过滤请求包含

  <!--④INCLUDE : 过滤请求包含-->
  <filter-mapping>
      <filter-name>Demo07Filter</filter-name>
      <url-pattern>/*</url-pattern>
      <dispatcher>REQUEST</dispatcher>
      <dispatcher>INCLUDE</dispatcher>
  </filter-mapping>
  

08-Filter注解开发(掌握)

• 概述

  • 使用@WebFilter注解替代XML配置。

• 源码

  @Target(ElementType.TYPE)
  @Retention(RetentionPolicy.RUNTIME)
  @Documented
  public @interface WebFilter {
  
      WebInitParam[] initParams() default {};
  
      String filterName() default "";
  
      String[] servletNames() default {};
  
      String[] value() default {};
  
      String[] urlPatterns() default {};
  
      DispatcherType[] dispatcherTypes() default {DispatcherType.REQUEST};
  
  }
  

• 代码实现1

  @WebFilter(
          filterName = "Demo08Filter",
          urlPatterns = {
                  "/demo01", "/demo02"
          },
          initParams = {
                  @WebInitParam(
                          name = "encoding", value = "utf-8"
                  ),
                  @WebInitParam(
                          name = "encoding2", value = "gbk"
                  )
          },
          dispatcherTypes = {
                  DispatcherType.REQUEST,
                  DispatcherType.FORWARD,
                  DispatcherType.INCLUDE,
                  DispatcherType.ERROR
          },
          servletNames = {
                  "Demo01Servlet", "Demo02Servlet"
          }
  
  )
  public class Demo08Filter implements Filter {
  
      @Override
      public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
          System.out.println("Demo08Filter 过滤");
          chain.doFilter(request, response);//相当于执行Demo01Servlet
          System.out.println("Demo08Filter 放行");
  
      }
  }
  

• 代码实现2

  @WebFilter("/*")
  public class Demo09Filter implements Filter {
  
      @Override
      public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
          System.out.println("Demo09Filter 过滤");
          chain.doFilter(request, response);//相当于执行Demo01Servlet
          System.out.println("Demo09Filter 放行");
  
      }
  }
  

09-监听器概述(掌握)

• 回顾
  • 事件源 : 事件发生的源头
  • 监听器 : 监听事件发生的组件
  • 事件绑定 : 将事件源和监听器关联起来
  • 事件 : 一件事
• Servlet事件
  • 事件源 : 三大域对象
  • 监听器 : 三类监听器
  • 事件绑定 : xml配置、注解配置
  • 事件 : 三大域对象内容发生改变
• 分类
  • 一类监听器
    • 监听三大域对象的状态改变(初始化、销毁)
  • 二类监听器
    • 监听三大域对象中的内容改变(添加、修改、移除)
  • 三类监听器
    • 监听三大域对象中的对象状态改变(绑定/解绑、钝化/活化)

10-一类监听器概述(掌握)

• 概述
  • 监听三大域对象的状态改变(初始化、销毁)
• 一类监听器
  • ServletRequestListener
    • 监听ServletRequest域对象的状态改变(初始化、销毁)
  • HttpSessionListener
    • 监听HttpSession域对象的状态改变(初始化、销毁)
  • ServletContextListener
    • 监听ServletContext域对象的状态改变(初始化、销毁)

11-一类监听器之ServletRequestListener(掌握)

• 概述

  • 监听ServletRequest域对象的状态改变(初始化、销毁)

• 代码实现

  public class MyServletRequestListener implements ServletRequestListener {
  
      @Override
      public void requestInitialized(ServletRequestEvent sre) {
          System.out.println("requestInitialized");
      }
  
      @Override
      public void requestDestroyed(ServletRequestEvent sre) {
          System.out.println("requestDestroyed");
      }
  
  
  }
  

  <listener>
      <listener-class>com.atguigu.listener1.MyServletRequestListener</listener-class>
  </listener>
  

12-一类监听器之ServletContextListener(重点)

• 概述

  • 监听ServletContext域对象的状态改变(初始化、销毁)

• 代码实现

  public class MyServletContextListener implements ServletContextListener {
  
      @Override
      public void contextInitialized(ServletContextEvent sce) {
          System.out.println("contextInitialized");
      }
  
      @Override
      public void contextDestroyed(ServletContextEvent sce) {
          System.out.println("contextDestroyed");
  
      }
  }
  

  <listener>
      <listener-class>com.atguigu.listener1.MyServletContextListener</listener-class>
  </listener>
  

13-二类监听器概述(掌握)

• 概述
  • 监听三大域对象中的内容改变(添加、修改、移除)
• 分类
  • ServletRequestAttributeListener
    • 监听ServletRequest域对象中的内容改变(添加、修改、移除)
  • HttpSessionAttributeListener
    • 监听HttpSession域对象中的内容改变(添加、修改、移除)
  • ServletContextAttributeListener
    • 监听ServletContext域对象中的内容改变(添加、修改、移除)

14-二类监听器之ServletRequestAttributeListener(了解)

• 概述

  • 监听ServletRequest域对象中的内容改变(添加、修改、移除)

• 代码实现

  public class MyServletRequestAttributeListener implements ServletRequestAttributeListener {
  
      @Override
      public void attributeAdded(ServletRequestAttributeEvent srae) {
          System.out.println("attributeAdded");
      }
  
      @Override
      public void attributeRemoved(ServletRequestAttributeEvent srae) {
          System.out.println("attributeRemoved");
  
      }
  
      @Override
      public void attributeReplaced(ServletRequestAttributeEvent srae) {
          System.out.println("attributeReplaced");
  
      }
  }
  

  <listener>
      <listener-class>com.atguigu.listener2.MyServletRequestAttributeListener</listener-class>
  </listener>
  

15-三类监听器概述(了解)

• 概述
  • 监听三大域对象中的对象状态改变(绑定/解绑、钝化/活化)
• 分类
  • HttpSessionBindingListener
    • 监听HttpSession域对象中的对象状态改变(绑定/解绑)
  • HttpSessionActivationListener
    • 监听HttpSession域对象中的对象状态改变(钝化/活化)

16-三类监听器之HttpSessionBindingListener(掌握)

• 概述

  • 监听HttpSession域对象中的对象状态改变(绑定/解绑)

• 代码实现

  public class Student  implements HttpSessionBindingListener {
  
      private Integer studentId;
      private String studentName;
  
      @Override
      public void valueBound(HttpSessionBindingEvent event) {
          System.out.println("Student绑定");
      }
  
      @Override
      public void valueUnbound(HttpSessionBindingEvent event) {
          System.out.println("Student解绑");
      }
  
  }
  

17-session钝化和活化(掌握)

• 概述

  • 当服务器突然宕机时，有一些需要长期使用的session数据会销毁，重启服务器后无法使用这些数据;
  • 因此，我们需要将这些session数据保留，并且下次重启之后可以使用。此时就可以考虑session的钝 化与活化

• 钝化

  • 序列化 : 当服务器关闭时，将session中的对象信息以字节的形式存储到缓存文件

• 活化

  • 反序列化 : 当服务器启动时，将缓存文件中的字节数据以对象的形式还原到session中

• 开发步骤

  • ①JavaBean实体类实现Serializable接口
  • ②编写tomcat的context.xml文件

• ①JavaBean实体类实现Serializable接口

  public class Teacher implements Serializable {
  
      private String teacherName;
  
  }
  

• ②编写tomcat的context.xml文件

  <Manager className="org.apache.catalina.session.PersistentManager" saveOnRestart="true" maxIdleSwap="1">
      <Store className="org.apache.catalina.session.FileStore" directory="E:\Program Files\apache-tomcat-9.0.56\conf\Session"/>
  </Manager>
  

18-三类监听器之HttpSessionActivationListener(掌握)

• 概述

  • 监听HttpSession域对象中的对象状态改变(钝化/活化)

• 代码实现

  public class Teacher implements Serializable , HttpSessionActivationListener {
  
      private String teacherName;
  
      @Override
      public void sessionWillPassivate(HttpSessionEvent se) {
          System.out.println("Teacher钝化");
      }
  
      @Override
      public void sessionDidActivate(HttpSessionEvent se) {
          System.out.println("Teacher活化");
  
      }
  }
  

19-监听器的注解开发(掌握)

• 概述

  • 使用@WebListener注解替代XML配置.

• 代码实现

  @WebListener
  public class MyHttpSessionAttributeListener implements HttpSessionAttributeListener {
  
      @Override
      public void attributeAdded(HttpSessionBindingEvent se) {
          System.out.println("attributeAdded");
      }
  
      @Override
      public void attributeRemoved(HttpSessionBindingEvent se) {
          System.out.println("attributeRemoved");
  
      }
  
      @Override
      public void attributeReplaced(HttpSessionBindingEvent se) {
          System.out.println("attributeReplaced");
  
      }
  }
  

标签：09,System,Filter,监听器,println,public,out
来源： https://blog.csdn.net/lbw18/article/details/123648743