我正在尝试建立一个网站,允许用户创建自己的页面 - 作为该网站的子域,因此我当前正在尝试做的是有一个查看子域的过滤器,如果子域未使用或已保留,则用户将被转发到他们选择子域名的页面。
我遇到的问题是,当我在 ServletRequest 对象上设置属性,然后使用 RequestDispatcher 转发时,过滤器会再次被调用 - 但它看不到我设置的属性。
我已经调试并观察它的工作(或不工作!),并且正在设置属性,但是在转发之后,该属性不存在。
有人可以帮忙解释一下发生了什么事,以及我如何解决这个问题吗?
我可能还应该提到我正在为 Java Google App Engine 进行开发。
这是我的过滤器代码。
import java.io.IOException;
import java.util.Enumeration;
import java.util.logging.Logger;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
public class SubdomainFilter implements Filter{
private static Logger log = Logger.getLogger(SubdomainFilter.class.getName());
private static final String[] RESERVED_SUBDOMAINS = {"admin", "home", "www"};
private static final String registerPage = "/register_a_page";
@Override
public void destroy() {
// TODO Auto-generated method stub
}
@Override
public void doFilter(ServletRequest arg0, ServletResponse arg1,
FilterChain arg2) throws IOException, ServletException {
//if we've been forwarded, it must have been because of an invalid subdomain
if(arg0.getAttribute("subdomain") != null) {
arg2.doFilter(arg0, arg1);
} else { //otherwise, look at the subdomain and determine what to do
boolean invalidSubdomain = false;
try {
String requestURLInfo = ((HttpServletRequest)arg0).getRequestURL().toString();
String subdomain = URLUtils.getLowestSubdomainFromURL(requestURLInfo);
arg0.setAttribute("subdomain", subdomain);
if(subdomainReserved(subdomain) || subdomainInUse(subdomain)) {
invalidSubdomain = true;
}//Otherwise the subdomain must be valid
} catch(Exception ex) {
log.severe("Filter could not get subdomain:\n" + ex.toString());
} finally {
if(invalidSubdomain) {
RequestDispatcher dispatcher = arg0.getRequestDispatcher(registerPage);
dispatcher.forward(arg0, arg1);
} else {
arg2.doFilter(arg0, arg1);
}
}
}
}
private boolean subdomainReserved(String subdomain) {
boolean subdomainReserved = false;
for(String reservedSubdomain : RESERVED_SUBDOMAINS) {
if(reservedSubdomain.equals(subdomain)) {
subdomainReserved = true;
break;
}
}
return subdomainReserved;
}
private boolean subdomainInUse(String subdomain) {
boolean subdomainInUse = false;
//TODO: implement
return subdomainInUse;
}
@Override
public void init(FilterConfig arg0) throws ServletException {
// TODO Auto-generated method stub
}
}
最佳答案
我认为问题是我没有在 web.xml 中声明以下内容:
<filter-mapping>
<filter-name>SubdomainFilter</filter-name>
<servlet-name>*</servlet-name>
<dispatcher>REQUEST</dispatcher>
<dispatcher>FORWARD</dispatcher>
</filter-mapping>
关于java - Servlet 过滤器 - 传递不适用于 RequestDispatcher#forward 的属性,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/3166220/