Filter学习

Filter: 过滤器，用来过滤网站的数据；（减少重复代码）

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Filter开发步骤
1.导包,实现filter接口，重写方法
2.编写过滤器

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("过滤器执行前...");
        filterChain.doFilter(servletRequest,servletResponse);//让我们的请求继续走，如果不写servlet就被拦截
        System.out.println("过滤器执行后...");
   

}3.在web.xml中配置Filter

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