求助有关页面的跳转

我们在一般论坛点击页面的时候，如果没有登录，就会跳转到其他页面，
这是怎么实现的？
可以用Struts1的action实现吗？

解决方案 »

免费领取超大流量手机卡，每月29元包185G流量+100分钟通话, 中国电信官方发货

在web.xml中进行如下设置<filter>
   <filter-name>access</filter-name>
   <filter-class>net.resume.web.AccessFilter</filter-class>
   <init-param>
   <param-name>access.config</param-name>
   <param-value>WEB-INF/access-config.properties</param-value>
   </init-param>
  </filter>
  <filter-mapping>
   <filter-name>access</filter-name>
   <url-pattern>/*</url-pattern>
  </filter-mapping>
AccessFilter 类继承了 javax.servlet.Filter，下面是具体实现。。
关键是doFilter类，其他的可根据个人习惯及想法实现。import java.io.FileInputStream;
import java.io.IOException;
import java.util.Properties;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import net.resume.Contants;
import net.resume.model.User;
import net.resume.service.ServiceException;
import net.resume.service.ServiceFactory;
import net.resume.service.ServicesConfigException;
import net.resume.service.ServicesInstanceExcepption;
import net.resume.service.UserServices;public class AccessFilter implements Filter {

private Properties config ; public AccessFilter() {
super();
// TODO 自动生成构造函数存根
} public void init(FilterConfig cfg) throws ServletException {
config = new Properties();
String filename = cfg.getInitParameter("access.config");
filename = cfg.getServletContext().getRealPath(filename);

try {
config.load(new FileInputStream(filename));
} catch (Exception e) {
e.printStackTrace();
throw new ServletException(e);
} } public void doFilter(ServletRequest req, ServletResponse res,
FilterChain chain) throws IOException, ServletException {

HttpServletRequest request = (HttpServletRequest) req;
HttpServletResponse response  = (HttpServletResponse)res;

String page = parse(request);

String roleName = config.getProperty(page);

//忽略没有登记授权的页面
if(roleName==null){
chain.doFilter(request, response);
return;
}

//检查是否登陆用户
if(!isLogin(request)){
response.sendRedirect(config.getProperty("login.page"));
return;
}

User user = getLoninUser(request);

//验证是否有权限
if(!hasRole(user, roleName)){
response.sendRedirect(config.getProperty("access.error.page"));
return;
}

chain.doFilter(request, response);
}

private boolean hasRole(User user, String roleKeys){

boolean rv = false;
try {
ServiceFactory factory = ServiceFactory.getInstance();
UserServices services = factory.getUserService();

String[] roles = roleKeys.trim().split(",");

for (int i = 0; i < roles.length; i++) {
String roleKey = roles<i>;
boolean hasRight = services.checkRole(user,roleKey);

if(hasRight){
rv = hasRight;
break;
}
} } catch (ServicesConfigException e) {
e.printStackTrace();
} catch (ServicesInstanceExcepption e) {
e.printStackTrace();
} catch (ServiceException e) {
e.printStackTrace();
}

return rv;
} private User getLoninUser(HttpServletRequest request){

return (User) request.getSession().getAttribute(Contants.LOGIN_USER);
}

private boolean isLogin(HttpServletRequest request) {

User user = (User) request.getSession().getAttribute(Contants.LOGIN_USER);

return user!=null;
} private String parse(HttpServletRequest request) {

StringBuffer url = request.getRequestURL();

//String page = url.substring(url.indexOf())

StringBuffer page = new StringBuffer();

int count = 0;

for(int i = 0; i<url.length(); i++){
char c = url.charAt(i);

if(c=='/')
count++;

if(count>=4)
page.append(c);
}

page.deleteCharAt(0);

return page.toString();
} public void destroy() {
// TODO 自动生成方法存根 }}楼主可以参考下一上代码
楼上说的过滤器也可以也可以用判断
在页面的最上面或者 <head> 标签内调用函数或获得session
session 为空和不为来判断 ..
<%
if(session.getAttribute() == null){
    //跳转页面的代码
}
%>
不过判断的方法我用的是脚本不怎么好呢..
谢谢3楼的兄弟，Struts1里有类似的插件吗？
WEB-INF/access-config.properties
这里面的内容可以贴出来看看吗？
用这个上面那个麻烦了
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;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;public class AuthFilter implements Filter {public void destroy() {}public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse,
FilterChain filterChain) throws IOException, ServletException {
/** 1,doFilter方法的第一个参数为ServletRequest对象。此对象给过滤器提供了对进入的信息（包括
*    表单数据、cookie和HTTP请求头）的完全访问。第二个参数为ServletResponse，通常在简单的过
*    滤器中忽略此参数。最后一个参数为FilterChain，此参数用来调用servlet或JSP页。
*/HttpServletRequest request = (HttpServletRequest)servletRequest;
/** 如果处理HTTP请求，并且需要访问诸如getHeader或getCookies等在ServletRequest中
*    无法得到的方法，就要把此request对象构造成HttpServletRequest
*/
HttpServletResponse response = (HttpServletResponse)servletResponse;String currentURL = request.getRequestURI(); //取得根目录所对应的绝对路径:String targetURL = currentURL.substring(currentURL.indexOf("/", 1),
currentURL.length()); //截取到当前文件名用于比较HttpSession session = request.getSession(false);if (!"/login.jsp".equals(targetURL)) {
//判断当前页是否是重定向以后的登录页面页面，如果是就不做session的判断，防止出现死循环
if (session == null || session.getAttribute("user") == null) {
//*用户登录以后需手动添加session
System.out.println("request.getContextPath()=" + request.getContextPath());
response.sendRedirect(request.getContextPath() + "/login.jsp");
//如果session为空表示用户没有登录就重定向到login.jsp页面
return;
}
}
//加入filter链继续向下执行
filterChain.doFilter(request, response);
/**   调用FilterChain对象的doFilter方法。Filter接口的doFilter方法取一个FilterChain对象作
*     为它的一个参数。在调用此对象的doFilter方法时，激活下一个相关的过滤器。如果没有另
*     一个过滤器与servlet或JSP页面关联，则servlet或JSP页面被激活。
*/
}public void init(FilterConfig filterConfig) throws ServletException {}
} ＜filter＞
＜filter-name＞AuthFilter＜/filter-name＞
＜filter- class＞com.drp.util.filter.AuthFilter＜/filter-class＞
＜/filter＞
＜filter- mapping＞
＜filter-name＞AuthFilter＜/filter-name＞
＜url-pattern＞*.jsp＜/url- pattern＞//表示对所有jsp文件有效
＜/filter-mapping＞
跟Struts无关，那个类可以直接用，你在web.xml里配置一下就好了。