演示FilterConfig接口的getInitParameter(String name)方法

一、创建MyFilter03

public class MyFilter03 implements Filter {
	private String characterEncoding;
	FilterConfig fc;
	public void init(FilterConfig fConfig) throws ServletException {
		// 获取FilterConfig对象
		this.fc = fConfig;
	}
	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		// 输出参数信息
		characterEncoding=fc.getInitParameter("encoding");
		System.out.println("encoding初始化参数的值为："+characterEncoding);
		chain.doFilter(request, response);
	}
	public void destroy() {
	}
}

二、配置filter，并放在web.xml最前面

  <filter>
    <filter-name>MyFilter03</filter-name>
    <filter-class>cn.itcast.chapter08.filter.MyFilter03</filter-class>
    <init-param>
      <param-name>encoding</param-name>
      <param-value>GBK</param-value>
    </init-param>
  </filter>
  <filter-mapping>
    <filter-name>MyFilter03</filter-name>
    <url-pattern>/MyServlet</url-pattern>
  </filter-mapping>

注解开发的话，这么设置初始化参数

@WebFilter(value= "/MyServlet",initParams={@WebInitParam(name="encoding",value="GBk")}) 

三、重启tomcat

http://localhost:8080/chapter08/MyServlet，查看控制台