Servlet（五）web.xml常用的一些配置

（1）lode-on-startup，該Servlet會在項目啓動時被調用（主要調用起init方法，爲安全着想，一般不應該爲該Servlet建立URL映射），一般用作預處理一些數據，或者配合多線程建立定時任務

    <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 表示多個預處理Servlet的啓動順序--> <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");獲取web.xml中encoding值utf-8

    2.1 多個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爲每個init-param名字
      	String name=names.nextElement();
      }

（3）context-param，全局配置信息，可在多個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");獲取到日期