http切換https後redirect跳轉過濾

全站HTTPS並不是配置證書CA，改改路徑URL那麼簡單！ 

SSL卸載（SSL Offloading）:把SSL配置在負載均衡器上，然後通過其處理握手之後將decode的https數據轉發給後臺的Web服務器。 
如下構成： 

            | 
            |(https) 
            | 
         Load Balancer 
      /        |        \ 
     /         |         \ 
    /(http)   |(http)    \(http) 
WebServer1  WebServer2  WebServer3 

HTTPS的加密傳輸將只限於客戶端發起請求到負載均衡器之間的公網階段，內網的通訊扔使用非加密的HTTP傳輸。每個Web服務器中所有的處理請求都認爲是來自http，所有相對路徑的 sendredirect 將都會被轉發到http！ 

比如在Filter或Interceptor裏的sendRedirect： 

response.sendRedirect(request.getContextPath() + "/admin/welcome.do?flag=timeout");

或者Spring的Controller裏的“redirect:”： 

return "redirect:/admin/welcome.do";

通過HttpServletResponseWrapper可以通過Filter攔截SendRedirect請求並固定跳轉到HTTPS。 

web.xml 

<filter>
<filter-name>AbsoluteSendRedirectFilter</filter-name>
<filter-class>com.rensanning.core.filter.AbsoluteSendRedirectFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>AbsoluteSendRedirectFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

AbsoluteSendRedirectFilter.java 

public class AbsoluteSendRedirectFilter extends OncePerRequestFilter {

@Override
protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
RedirectResponseWrapper redirectResponseWrapper = new RedirectResponseWrapper(request, response);
filterChain.doFilter(request, redirectResponseWrapper);
}

}

RedirectResponseWrapper.java 

public class RedirectResponseWrapper extends HttpServletResponseWrapper {

private final HttpServletRequest request;

public RedirectResponseWrapper(final HttpServletRequest inRequest, final HttpServletResponse response) {
super(response);
this.request = inRequest;
}

@Override
public void sendRedirect(final String pLocation) throws IOException {

if (StringUtils.isBlank(pLocation)) {
super.sendRedirect(pLocation);
return;
}

try {
final URI uri = new URI(pLocation);
if (uri.getScheme() != null) {
super.sendRedirect(pLocation);
return;
}
} catch (URISyntaxException ex) {
super.sendRedirect(pLocation);
}

// !!! FIX Scheme !!!
String finalurl = "https://" + this.request.getServerName();
if (request.getServerPort() != 80 && request.getServerPort() != 443) {
finalurl += ":" + request.getServerPort();
}
finalurl += pLocation;

super.sendRedirect(finalurl);
}

}