一、通过过滤器可以做什么
1 对请求进行统一编码
2 对请求进行认证
包 javax.servlet.Filter
1作用:把某些信息过滤掉
2实现 Filter 接口.
1public void doFilter (ServletRequest, ServletResponse, FilterChain)该方法完成实际的过滤操作，当客户端请求方法与过滤器设置匹配的URL时，Servlet容器将先调用过滤器的doFilter方法。FilterChain用户访问后续过滤器。
2public void init(FilterConfig filterConfig)
3public void destroy()
4web.xml中配置
<filter>
<filter-name>qq</filter-name>
<filter-class>con.hw.controller.EncodingFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>qq</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
乱码处理
public void doFilter(ServletRequest arg0, ServletResponse arg1,
FilterChain arg2) throws IOException, ServletException {
HttpServletRequest request=(HttpServletRequest) arg0;
HttpServletResponse response=(HttpServletResponse) arg1;
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
response.setCharacterEncoding("utf-8");
arg2.doFilter(request, response);//通过验证
}
非法字段
public void doFilter(ServletRequest arg0, ServletResponse arg1,
FilterChain arg2) throws IOException, ServletException {
HttpServletRequest request=(HttpServletRequest) arg0;
HttpServletResponse response=(HttpServletResponse) arg1;
String jl = request.getParameter("jl");
if(jl!=null&&jl.indexOf("小狗")!=-1){
response.sendRedirect("filter.jsp");
}else{
arg2.doFilter(request, response);//放行
}
}
验证登录
public void doFilter(ServletRequest request1, ServletResponse response1,FilterChain chain) throws IOException, ServletException {HttpServletRequest request=(HttpServletRequest) request1;HttpServletResponse response=(HttpServletResponse) response1; HttpSession session = request.getSession(); if(session.getAttribute("user")!=null){ chain.doFilter(request, response);//放行 }else{ response.sendRedirect(request.getContextPath()+"/login.jsp"); }}f3com.filter.LoginFilterf3/PersonListServlet
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