Filter与Servlet的区别和联系

偏执的太偏执、 2022-03-11 12:00 287阅读 0赞

<table style="direction:ltr; border-collapse:collapse; border-style:solid; border-color:#A3A3A3; border-width:1pt"> 
 <tbody> 
 <tr> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:1.102in; padding:4pt 4pt 4pt 4pt"> &nbsp; </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:3.5097in; padding:4pt 4pt 4pt 4pt"> Filter </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:3.8062in; padding:4pt 4pt 4pt 4pt"> Servlet </td> 
 </tr> 
 <tr> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:1.102in; padding:4pt 4pt 4pt 4pt"> 接口 </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:3.5097in; padding:4pt 4pt 4pt 4pt"> 实现Filter接口 </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:3.8062in; padding:4pt 4pt 4pt 4pt"> 实现Servlet接口 </td> 
 </tr> 
 <tr> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:1.102in; padding:4pt 4pt 4pt 4pt"> 使用步骤 </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:3.5097in; padding:4pt 4pt 4pt 4pt"> 1、创建类，继承接口 2、实现方法 init() doFilter() destroy() &nbsp; 3、配置WEB-INF/web.xml </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:3.8062in; padding:4pt 4pt 4pt 4pt"> 1、创建类，继承接口 2、实现方法 init() service() destroy() getServletConfig() getServletInfo() 3、配置WEB-INF/web.xml </td> 
 </tr> 
 <tr> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:1.102in; padding:4pt 4pt 4pt 4pt"> 初始化时间 </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:3.5097in; padding:4pt 4pt 4pt 4pt"> Servlet容器启动之后即初始化 </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:3.8062in; padding:4pt 4pt 4pt 4pt"> Servlet类被调用之后初始化、先于Filter调用。 初始化可以在容器启动后被调用但需要配置。 </td> 
 </tr> 
 <tr> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:1.102in; padding:4pt 4pt 4pt 4pt"> 调用顺序 </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:3.5097in; padding:4pt 4pt 4pt 4pt"> 1. 按照web.xml中的映射配置顺序按照配置条件从后向前调用 2. 层次调用doFilter()方法中FilterChain.doFilter（）之前的内容 3. 调用Servlet中的service()方法 4. service方法执行完毕后，层次调用doFilter()中FilterChain.doFilter()之后的方法，顺序与之前的相反 &nbsp; </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:3.8062in; padding:4pt 4pt 4pt 4pt"> 按照web.xml中的映射配置顺序按照配置条件从后向前调用第一个满足条件的Servlet，调用之前事先执行满足条件的Filter，不存在层次调用Servlet问题 </td> 
 </tr> 
 <tr> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:1.102in; padding:4pt 4pt 4pt 4pt"> 销毁 </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:3.5097in; padding:4pt 4pt 4pt 4pt"> 服务器停止后销毁，晚于Servlet销毁之后 </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:3.8062in; padding:4pt 4pt 4pt 4pt"> 服务器停止后销毁 </td> 
 </tr> 
 <tr> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:1.102in; padding:4pt 4pt 4pt 4pt"> 作用 </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:3.5097in; padding:4pt 4pt 4pt 4pt"> 1. 在HttpServletRequest到达Servlet之前，拦截客户的HttpServletRequest。 2. 根据需要检查HttpServletRequest，也可以修改HttpServletRequest头和数据。 3. 在HttpServletResponse到达客户端之前，拦截HttpServletResponse。 4. 根据需要检查HttpServletResponse，也可以修改HttpServletResponse头和数据。 </td> 
 <td style="border-style:solid; border-color:#A3A3A3; border-width:1pt; vertical-align:top; width:3.8062in; padding:4pt 4pt 4pt 4pt"> 主要是处理客户端的请求并将其结果发送到客户端。 </td> 
 </tr> 
 </tbody> 
</table>