servlet中ServletConfig实例

先在web.xml为servlet参见初始化参数，用init-param标签

 <servlet>
    <description></description>
    <display-name>ServletDemo3</display-name>
    <servlet-name>ServletDemo3</servlet-name>
    <servlet-class>cn.itcast.ServletDemo3</servlet-class>
    <init-param>
    <param-name>data</param-name>
    <param-value>what</param-value>
    </init-param>
  </servlet>
  <servlet-mapping>
    <servlet-name>ServletDemo3</servlet-name>
    <url-pattern>/ServletDemo3</url-pattern>
  </servlet-mapping>

在3个方法上分别写上

public void init(ServletConfig config) throws ServletException {
		this.config = config;
	
	}

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		String value = config.getInitParameter("data");
		System.out.println(value);
	
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		doGet(request,response);
	}

运行访问后，会在控制台看见what，即所配置的初始值