标签案例-开发防盗链标签

package cn.itcast.web.tag;

import java.io.IOException;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.SkipPageException;
import javax.servlet.jsp.tagext.SimpleTagSupport;

public class RefererTag extends SimpleTagSupport {

    private String site;
    private String page;

    public void setSite(String site) {
        this.site = site;
    }

    public void setPage(String page) {
        this.page = page;
    }

    @Override
    public void doTag() throws JspException, IOException {
    
        PageContext pageContext = (PageContext) this.getJspContext();
        HttpServletRequest request = (HttpServletRequest) pageContext.getRequest();
        HttpServletResponse response = (HttpServletResponse) pageContext.getResponse();
        
        //1.得到来访者referer
        String referer = request.getHeader("referer");
        if(referer==null||!referer.startsWith(site)){
            if(page.startsWith(request.getContextPath())){
                response.sendRedirect(page);
            }else if(page.startsWith("/")){
                response.sendRedirect(request.getContextPath()+page);
            }else{
                response.sendRedirect(request.getContextPath()+"/"+page);
            }
            
            throw new SkipPageException();
        }
        
    }
    
    

}

<e:referer site="http://localhost" page="index.jsp"></e:referer>