刚刚接触Filter求注释能加深理解,该怎么解决

刚刚接触Filter求注释能加深理解
•public class CheckLoginFilter  
• implements Filter  
•{  
• protected FilterConfig filterConfig = null;  
• private String redirectURL = null;  
• private List notCheckURLList = new ArrayList();  
• private String sessionKey = null;  
•  
• public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException  
• {  
• HttpServletRequest request = (HttpServletRequest) servletRequest;  
• HttpServletResponse response = (HttpServletResponse) servletResponse;  
•  
• HttpSession session = request.getSession();  
• if(sessionKey == null)  
• {  
• filterChain.doFilter(request, response);  
• return;  
• }  
• if((!checkRequestURIIntNotFilterList(request)) && session.getAttribute(sessionKey) == null)  
• {  
• response.sendRedirect(request.getContextPath() + redirectURL);  
• return;  
• }  
• filterChain.doFilter(servletRequest, servletResponse);  
• }  
•  
• public void destroy()  
• {  
• notCheckURLList.clear();  
• }  
•  
• private boolean checkRequestURIIntNotFilterList(HttpServletRequest request)  
• {  
• String uri = request.getServletPath() + (request.getPathInfo() == null ? "" : request.getPathInfo());  
• return notCheckURLList.contains(uri);  
• }  
•  
• public void init(FilterConfig filterConfig) throws ServletException  
• {  
• this.filterConfig = filterConfig;  
• redirectURL = filterConfig.getInitParameter("redirectURL");  
• sessionKey = filterConfig.getInitParameter("checkSessionKey");  
•  
• String notCheckURLListStr = filterConfig.getInitParameter("notCheckURLList");  
•  
• if(notCheckURLListStr != null)  
• {  
• StringTokenizer st = new StringTokenizer(notCheckURLListStr, ";");  
• notCheckURLList.clear();  
• while(st.hasMoreTokens())  
• {  
• notCheckURLList.add(st.nextToken());  
• }  
• }  
• }  
•} 
求专家帮我把这个过滤器方法中一些主要代码加下注释,IF判断条件也帮忙注释一下,在下不胜感激!

------解决方案--------------------
//这是一个检查请求安全权限的Filter，可以配置。起作用时会将不符合条件的请求重定向。
•public class CheckLoginFilter
• implements Filter //过滤器都要实现该接口
•{
• protected FilterConfig filterConfig = null; //用于保存配置信息
• private String redirectURL = null;
• private List notCheckURLList = new ArrayList(); //可以免于处理的URL清单
• private String sessionKey = null; //若null则过滤器不起作用，希望启动本过滤器的时候要设一个非null值
•
• public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException
• {
• HttpServletRequest request = (HttpServletRequest) servletRequest; //类型转换，方便后面调用getSession等方法
• HttpServletResponse response = (HttpServletResponse) servletResponse; //类型转换
•
• HttpSession session = request.getSession(); //取当前请求对应的会话
• if(sessionKey == null)
• {
• filterChain.doFilter(request, response); //放行
• return;
• }
• if((!checkRequestURIIntNotFilterList(request)) && session.getAttribute(sessionKey) == null)
• { //如果本URL必须处理，同时其会话中又没有sessionKey记号，则拦截这些请求，重定向到指定URL
• response.sendRedirect(request.getContextPath() + redirectURL);
• return;
• }
• filterChain.doFilter(servletRequest, servletResponse); //如果上面的检查通过，则放行
• }