javaweb Filter过滤器

public class CharacterEncoding implements Filter {
    //初始化 web服务器启动，就已经初始化了，随时等待过滤对象出现
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("已经初始化了");
    }
//Chain链
    /*
    1.过滤中的所有代码，在过滤特定请求的时候都会执行
    2.必须要让过滤器继续通行
    filterChain.doFilter(servletRequest,servletResponse);
     */
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        servletRequest.setCharacterEncoding("utf-8");
        servletResponse.setCharacterEncoding("utf-8");
        servletResponse.setContentType("text/html;charset=UTF-8");
        System.out.println("CharacterEncodingFilter执行前...");
        filterChain.doFilter(servletRequest,servletResponse);//让我们的程序继续走。如果不写，程序到达这里就被拦截了
        System.out.println("CharacterEncodingFilter执行后...");
    }
    //销毁
    //web服务器关闭的时候，过滤器会销毁
    public void destroy() {
        System.out.println("已经销毁了");
    }
}

<filter>
        <filter-name>Filter</filter-name>
        <filter-class>com.kuang.filter.CharacterEncoding</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>Filter</filter-name>
<!--        只要是/servlet的任何请求，会经过这个过滤器-->
        <url-pattern>/servlet/*</url-pattern>
    </filter-mapping>