filter过滤器,@WebFilter可用于将某个类设置为过滤器,该注解在tomcat的servlet包下,从servlet3.0版本就开始支持这个注解了。
该注解包含如下参数可以设置:
属性名 | 类型 | 说明 | 其他 |
description |
String | 对该注解的说明 | |
displayName |
String | 过滤器显示名,等同与<display-name> | |
initParams |
WebInitParam[] |
用于设置该过滤器类的一些初始化参数,等同于<init-param> |
如:initParams = {@WebInitParam(name = "ignoredUrl", value = ".css#.js#.jpg#.png#.gif#.ico") |
filterName |
String | 过滤器名,等价与<filter-name> | |
servletNames |
String[] |
String类型的数组,用于指定过滤的servlet。取值是 @WebServlet 中的 name 属性的取值,或者是 web.xml 中 <servlet-name> 的取值。 | |
value,urlPatterns | String[] | 过滤器的 URL 匹配模式。等价于 <url-pattern> 标签。 | 如: urlPatterns = {"/*"} 拦截所有,需要注意value和urlpattern只能选一个,建议urlpattern,好看些 |
dispatcherTypes | DispatcherType[] | 过滤器的转发模式。具体取值包括: ASYNC、ERROR、FORWARD、INCLUDE、REQUEST。 | 有默认值,见上图,默认为request |
asyncSupported | boolean | 过滤器是否支持异步操作模式,等价于 <async-supported> 标签。 | 默认为false |
还有就是,被@WebFilter注解的类,会在容器启动时被加载,并进行属性配置。即项目一启动容器自动加载init方法。
可以看到,项目启动后进入到filter的init方法里面了
先看一下filterconfig:
可以看到在filterDef中有我们之前提到的注解里面的所有内容。
当filter的init方法执行完毕后就注册完毕了,进入类:org.apache.catalina.core.ApplicationFilterConfig,方法:initFilter。
@WebFilter(filterName = "DabaiLoginFilter", urlPatterns = {"/*"}, initParams = {@WebInitParam(name = "ignoredUrl", value = ".css#.js#.jpg#.png#.gif#.ico"), @WebInitParam(name = "filterPath", value = "/user/login#/user/registerUser")}) public class DabaiLoginFilter implements Filter { private static final String FILTER_PATH = "filterPath"; private static final String IGNORED_PATH = "ignoredUrl"; private static final List<String> ignoredList = new ArrayList<>(); private String[] allowUrls; private String[] ignoredUrls; @Override public void init(FilterConfig filterConfig) throws ServletException { String filterPath = filterConfig.getInitParameter(FILTER_PATH); if (!StringUtils.isEmpty(filterPath)) allowUrls = filterPath.contains("#") ? filterPath.split("#") : new String[]{filterPath}; String ignoredPath = filterConfig.getInitParameter(IGNORED_PATH); if (!StringUtils.isEmpty(ignoredPath)) { ignoredUrls = ignoredPath.contains("#") ? ignoredPath.split("#") : new String[]{ignoredPath}; for (String ignoredUrl : ignoredUrls) { ignoredList.add(ignoredUrl); } } } @Override public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { HttpServletRequest servletRequest = (HttpServletRequest) request; HttpServletResponse servletResponse = (HttpServletResponse) response; String requestUrl = servletRequest.getRequestURI();/*具体,比如:处理若用户未登录,则跳转到登录页 Object userInfo = servletRequest.getSession().getAttribute("user"); if(userInfo!=null) { 如果已登录,不阻止 chain.doFilter(request, response); return; } if (requestUrl != null && (requestUrl.contains("/login.html") || requestUrl.contains("/register.html"))) */ { chain.doFilter(request, response); return; } if (verify(ignoredList, requestUrl)) { chain.doFilter(servletRequest, response); return; } if (null != allowUrls && allowUrls.length > 0) { for (String url : allowUrls) { if (requestUrl.startsWith(url)) { chain.doFilter(request, response); return; } } } servletResponse.sendRedirect("/login.html"); } private static String regexPrefix = "^.*"; private static String regexSuffix = ".*$"; private static boolean verify(List<String> ignoredList, String url) { for (String regex : ignoredList) { Pattern pattern = Pattern.compile(regexPrefix + regex + regexSuffix); Matcher matcher = pattern.matcher(url); if (matcher.matches()) { return true; } } return false; } @Override public void destroy() { } }
urlPatterns