import java.io.IOException;
import java.util.regex.Pattern;

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;

public class HeaderFilter implements Filter {

    /**
     * 忽略的URL的正则表达式.
     */
    private static final String IGNORE = "^.+\\.(jsp|png|gif|jpg|js|css|jspx|jpeg|swf|ico)$";

    /**
     * 忽略的URL的正则对象.
     */
    private Pattern ignorePtn;

    @Override
    public void destroy() {
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {

        // 解决IE下，IFRAME引起的内部cookie丢失
        HttpServletResponse res = (HttpServletResponse) response;
        res.setHeader("P3P", "CP=CAO PSA OUR");

        // 判断URL是否跳过后续的Filter
        HttpServletRequest req = (HttpServletRequest) request;

        // URI是“/UserManage/special/pic/201308.jpg”，要把/UserManage去掉。
        String path = req.getRequestURI().substring(
                req.getContextPath().length());
        if (ignorePtn.matcher(path).find()) {
            request.getRequestDispatcher(path).forward(request, response);
        } else if (chain != null) {
            chain.doFilter(request, response);
        }
    }

    @Override
    public void init(FilterConfig conf) throws ServletException {

        // 取得参数
        String ignore = conf.getInitParameter("ignore");
        if (ignore == null || ignore.trim().length() == 0) {
            ignore = IGNORE;
        } else {
            ignore = ignore.trim();
        }

        // 创建正则对象
        ignorePtn = Pattern.compile(ignore, Pattern.CASE_INSENSITIVE);
    }

}