育才学习网1.怎么使用filter实现未登录用户自动跳转到登录页面
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
HttpServletRequest req = (HttpServletRequest)request;
if(req.getSession().getAttribute("user")==null){
req.setAttribute("error"， "请你先登录")；
//非法请求才会进到这里面，在这里保存请求的url地址，在成功登录后再进行跳转
req.getSession().setAttribute("goUrl", req.getRequestURL()+"?"+ req.getQueryString());
request.getRequestDispatcher("/ulogin.jsp").forward(request, response);
}
else{
chain.doFilter(request, response);
}
}
上面的代码是过滤器中的代码
下面的是servlet中的代码
if(request.getSession().getAttribute("goUrl")!=null){
String url = (String)request.getSession().getAttribute("goUrl");
response.sendRedirect(url);
}
else{
response.sendRedirect("/webshopping/index.jsp");
}
2.怎么使用filter实现未登录用户自动跳转到登录页面
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {HttpServletRequest req = (HttpServletRequest)request;if(req.getSession().getAttribute("user")==null){req.setAttribute("error"， "请你先登录")；//非法请求才会进到这里面，在这里保存请求的url地址，在成功登录后再进行跳转req.getSession().setAttribute("goUrl", req.getRequestURL()+"?"+ req.getQueryString());request.getRequestDispatcher("/ulogin.jsp").forward(request, response);}else{chain.doFilter(request, response)；}}上面的代码是过滤器中的代码下面的是servlet中的代码if(request.getSession().getAttribute("goUrl")!=null){String url = (String)request.getSession().getAttribute("goUrl");response.sendRedirect(url);}else{response.sendRedirect("/webshopping/index.jsp");}。
3.如何用Filter实现对注册用户是否登录的过滤
下面是我从前写的项目里用的用户过滤。供你参考。你可以去上看看，那儿有过滤器的视频教程。
package filter;
import java.io.*;
import javax.servlet.*;
import javax.servlet. ;charset=GBK");
request.setCharacterEncoding("GBK");
PrintWriter out=response.getWriter();
HttpServletRequest req=(HttpServletRequest)request;
HttpSession session=req.getSession();
//System.out.println(session.getAttribute("user"));
//user是用户登录后session.setAtrribute("user"，***)中的user
if(session.getAttribute("user")!=null){
chain.doFilter(request, response);
}
else{//未登录，后退
out.println("<script language='javascript'>alert（'你还未登录'）；"）；
out.println("history.go(-1);</script>");
}
}
//过滤器销毁
public void destroy(){}
}
4.如何使用filter实现未登录用户自动跳转到登录页面
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {HttpServletRequest req = (HttpServletRequest)request;if(req.getSession().getAttribute("user")==null){req.setAttribute("error"， "请你先登录")；//非法请求才会进到这里面，在这里保存请求的url地址，在成功登录后再进行跳转req.getSession().setAttribute("goUrl", req.getRequestURL()+"?"+ req.getQueryString());request.getRequestDispatcher("/ulogin.jsp").forward(request, response);}else{chain.doFilter(request, response)；}}上面的代码是过滤器中的代码下面的是servlet中的代码if(request.getSession().getAttribute("goUrl")!=null){String url = (String)request.getSession().getAttribute("goUrl");response.sendRedirect(url);}else{response.sendRedirect("/webshopping/index.jsp");}。
5.java过滤器怎么写 用的是SSH框架 主要目的是防止有些比如登录不填
在web.xml中配置过滤器
<filter>
<filter-name>encoding</filter-name>
<filter-class>；此处是自己已实现filter类的目录</filter-class>
<init-param>
<param-name>encoding</param-name>
<param-value>utf-8</param-value>
</init-param>
</filter>
<filter-mapping>
<url-pattern>；此处是要过滤的路径</url-pattern>
<filter-name>encoding</filter-name>
</filter-mapping>