>如果有下一個Filter時，將請求轉發給下一個Filter
>如果無下一個Filter時，將請求轉發給Web資源(serlvet/jsp/html)
d)可以將web資源中的一些公共代碼，提取出來，放入Filter中

`<filter>
    <filter-name>FilterDemo1</filter-name>
    <filter-class>cn.web.servlet.filter.FilterDemo1</filter-class>
</filter>
<filter-mapping>
    <filter-name>FilterDemo1</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

<filter>
    <filter-name>FilterDemo2</filter-name>
    <filter-class>cn.web.servlet.filter.FilterDemo2</filter-class>
</filter>
<filter-mapping>
    <filter-name>FilterDemo2</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>
`

`import java.io.IOException;
 

import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ShowServlet extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    response.setContentType("text/html; charset=UTF-8");
    response.getWriter().write("歡迎學習Servlet下篇");
}
 

}`

import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class FilterDemo2 implements Filter {

    public void destroy() {
    }
    public void doFilter(ServletRequest request, ServletResponse response,FilterChain chain) throws IOException, ServletException {
        response.setContentType("text/html;charset=UTF-8");
        System.out.println("第二個攔截器：Filter2");
        //放行請求[調用]
        chain.doFilter(request,response);
    }
    public void init(FilterConfig filterConfig) throws ServletException {
    }

}
 

過濾器鏈-學習筆記