Servlet（五）web.xml常用的一些配置

（1）lode-on-startup，该Servlet会在项目启动时被调用（主要调用起init方法，为安全着想，一般不应该为该Servlet建立URL映射），一般用作预处理一些数据，或者配合多线程建立定时任务

<servlet><pre name="code" class="html"><span style="font-family:Arial, Helvetica, sans-serif;"> </span><span style="font-family:SimSun;font-size:12px;"> <servlet-name>FirstServlet</servlet-name></span> <servlet-class>com.hunhun.FirstServlet</servlet-class> <!-- 1 表示多个预处理Servlet的启动顺序--> <lode-on-startup>1</lode-on-startup> </servlet>

（2）init-param，可用做Servlet的一些配置信息

<servlet>
<servlet-name>FirstServlet</servlet-name>
<servlet-class>com.hunhun.FirstServlet</servlet-class>
<init-param>
<param-name>encoding</param-name>
<param-value>utf-8</param-value>
</init-param>
</servlet>

可以在FirstServlet的do*方法中使用this.getServletConfig().getInitParameter("encoding");获取web.xml中encoding值utf-8
    2.1 多个init-param

<servlet>
<servlet-name>FirstServlet</servlet-name>
<servlet-class>com.hunhun.FirstServlet</servlet-class>
<init-param>
<param-name>encoding</param-name>
<param-value>utf-8</param-value>
</init-param>
<init-param>
<param-name>author</param-name>
<param-value>hunhun</param-value>
</init-param>
<init-param>
<param-name>versioon</param-name>
<param-value>1.0</param-value>
</init-param>
</servlet>

可以在FirstServlet的do*方法中
  Enumeration<String> names = this.getServletConfig().getInitParameterNames();
while(names.hasMoreElements()){
//name为每个init-param名字
String name=names.nextElement();
}（3）context-param，全局配置信息，可在多个Servlet中使用
<servlet>
<servlet-name>FirstServlet</servlet-name>
<servlet-class>com.hunhun.FirstServlet</servlet-class>
<init-param>
<param-name>encoding</param-name>
<param-value>utf-8</param-value>
</init-param>
<init-param>
<param-name>author</param-name>
<param-value>hunhun</param-value>
</init-param>
<init-param>
<param-name>versioon</param-name>
<param-value>1.0</param-value>
</init-param>
</servlet>
<context-param>
<param-name>date</param-name>
<param-value>2011-12-3 10:30:24</param-value>
</context-param>

可以在*Servlet的do*方法中使用String date = this.getServletContext().getInitParameter("date");获取到日期