[10] 过滤器 Filter

• Filter
  
• FilterChain （在Filter中init方法作为参数）
  
• FilterConfig （在Filter中doFilter方法作为参数）

• getInitParameter(String name)
• 该方法用来获取过滤器的初始化参数，这个初始化参数在web.xml中进行配置，方式和Servlet初始化参数类似

public class TimeFilter implements Filter {
    private int start = 0;
    private int end = 24;
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("TimeFilter初始化，开始抓取初始化参数");
        start = Integer.parseInt(filterConfig.getInitParameter("start"));
        end = Integer.parseInt(filterConfig.getInitParameter("end"));
    }
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        System.out.println("TimeFilter过滤");
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(new Date());
        int curHour = calendar.get(Calendar.HOUR_OF_DAY);
        if (curHour >= end || curHour < start) {
            request.setAttribute("start", start);
            request.setAttribute("end", end);
            request.getRequestDispatcher("/WEB-INF/notice.jsp").forward(request, response);
        }
        
        chain.doFilter(request, response);
    }
    public void destroy() {
        System.out.println("TimeFilter爆炸");
    }
}

<filter>
    <filter-name>timeFilter</filter-name>
    <filter-class>com.zker.TimeFilter</filter-class>
    <init-param>
        <param-name>start</param-name>
        <param-value>15</param-value>
    </init-param>
    <init-param>
        <param-name>end</param-name>
        <param-value>22</param-value>
    </init-param>
</filter>
<filter-mapping>
    <filter-name>timeFilter</filter-name>
    <url-pattern>/limit/*</url-pattern>
</filter-mapping>

<filter-mapping>
    <filter-name>timeFilter</filter-name>
    <url-pattern>/limit/*</url-pattern>
    <dispatcher>REQUEST</dispatcher>
    <dispatcher>FORWARD</dispatcher>
    <dispatcher>INCLUDE</dispatcher>
    <dispatcher>ERROR</dispatcher>
</filter-mapping>