项目不可少之一过滤器（Filter）

什么是Filter？

Filter实际上就是对web资源进行拦截，做一些处理后再交给下一个过滤器或servlet处理

应用场景 1、权限验证 2、使用Filter进行重写init 可以在项目的启动的时候进行初始化一些资源 3、是否登录拦截

配置及使用Filter

基于ssm及xml形式 创建一个类并实现Filter中三个方法

public class LoginFilter implements Filter { public void destroy() { /*销毁时调用*/ } public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException { /*过滤方法 主要是对request和response进行一些处理，然后交给下一个过滤器或Servlet处理*/ chain.doFilter(req, resp);//交给下一个过滤器或servlet处理 } public void init(FilterConfig config) throws ServletException { /*初始化方法 接收一个FilterConfig类型的参数 该参数是对Filter的一些配置*/ } }

配置web.xml

<filter> <filter-name>loginFilter</filter-name> <filter-class>com.ivs.filter.LoginFilter</filter-class> </filter> <filter-mapping> <filter-name>loginFilter</filter-name> <!--拦截的url--> <url-pattern>/sys/*</url-pattern> <url-pattern>/admin/*</url-pattern> </filter-mapping>

实战使用Filter进行验证是否登录

package com.mmall.filter; import com.mmall.common.RequestHolder; import com.mmall.model.SysUser; import lombok.extern.slf4j.Slf4j; 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; import java.io.IOException; @Slf4j public class LoginFilter implements Filter { public void init(FilterConfig filterConfig) throws ServletException { } public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { HttpServletRequest req = (HttpServletRequest) servletRequest; HttpServletResponse resp = (HttpServletResponse) servletResponse; SysUser sysUser = (SysUser)req.getSession().getAttribute("user"); if (sysUser == null) { String path = "/signin.jsp"; resp.sendRedirect(path); return; } RequestHolder.add(sysUser); RequestHolder.add(req); filterChain.doFilter(servletRequest, servletResponse); return; } public void destroy() { } }

web.xml配置

<filter> <filter-name>loginFilter</filter-name> <filter-class>com.mmall.filter.LoginFilter</filter-class> </filter> <filter-mapping> <filter-name>loginFilter</filter-name> <url-pattern>/sys/*</url-pattern> <url-pattern>/admin/*</url-pattern> </filter-mapping>

实战使用Filter进行权限验证

package com.mmall.filter; import com.google.common.base.Splitter; import com.google.common.collect.Sets; import com.mmall.common.ApplicationContextHelper; import com.mmall.common.JsonData; import com.mmall.common.RequestHolder; import com.mmall.model.SysUser; import com.mmall.service.SysCoreService; import com.mmall.utils.JsonMapper; import lombok.extern.slf4j.Slf4j; import javax.servlet.*; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; import java.util.List; import java.util.Map; import java.util.Set; @Slf4j public class AclControlFilter implements Filter { private static Set<String> exclusionUrlSet = Sets.newConcurrentHashSet(); private final static String noAuthUrl = "/sys/user/noAuth.page"; @Override public void init(FilterConfig filterConfig) throws ServletException { String exclusionUrls = filterConfig.getInitParameter("exclusionUrls"); List<String> exclusionUrlList = Splitter.on(",").trimResults().omitEmptyStrings().splitToList(exclusionUrls); exclusionUrlSet = Sets.newConcurrentHashSet(exclusionUrlList); exclusionUrlSet.add(noAuthUrl); } @Override public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { HttpServletRequest request = (HttpServletRequest) servletRequest; HttpServletResponse response = (HttpServletResponse) servletResponse; String servletPath = request.getServletPath(); Map requestMap = request.getParameterMap(); if (exclusionUrlSet.contains(servletPath)) { filterChain.doFilter(servletRequest, servletResponse); return; } SysUser sysUser = RequestHolder.getCurrentUser(); if (sysUser == null) { log.info("someone visit {}, but no login, parameter:{}", servletPath, JsonMapper.obj2String(requestMap)); noAuth(request, response); return; } SysCoreService sysCoreService = ApplicationContextHelper.popBean(SysCoreService.class); if (!sysCoreService.hasUrlAcl(servletPath)) { log.info("{} visit {}, but no login, parameter:{}", JsonMapper.obj2String(sysUser), servletPath, JsonMapper.obj2String(requestMap)); noAuth(request, response); return; } filterChain.doFilter(servletRequest, servletResponse); return; } private void noAuth(HttpServletRequest request, HttpServletResponse response) throws IOException { String servletPath = request.getServletPath(); if (servletPath.endsWith(".json")) { JsonData jsonData = JsonData.fail("没有访问权限，如需要访问，请联系管理员"); response.setHeader("Content-Type", "application/json"); response.getWriter().print(JsonMapper.obj2String(jsonData)); return; } else { clientRedirect(noAuthUrl, response); return; } } private void clientRedirect(String url, HttpServletResponse response) throws IOException{ response.setHeader("Content-Type", "text/html"); response.getWriter().print("<!DOCTYPE html PUBLIC \"-//W3C//DTD XHTML 1.0 Strict//EN\" \"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd\">\n" + "<html xmlns=\"http://www.w3.org/1999/xhtml\">\n" + "<head>\n" + "<meta http-equiv=\"content-type\" content=\"text/html; charset=UTF-8\"/>\n" + "<title>跳转中...</title>\n" + "</head>\n" + "<body>\n" + "跳转中，请稍候...\n" + "<script type=\"text/javascript\">//<![CDATA[\n" + "window.location.href='" + url + "?ret='+encodeURIComponent(window.location.href);\n" + "//]]></script>\n" + "</body>\n" + "</html>\n"); } @Override public void destroy() { } }

web.xml配置

<filter> <filter-name>aclControlFilter</filter-name> <filter-class>com.mmall.filter.AclControlFilter</filter-class> <init-param> <param-name>targetFilterLifecycle</param-name> <param-value>true</param-value> </init-param> //初始化时设置的参数，filterConfig.getInitParameter("exclusionUrls");可以获取 <init-param> <param-name>exclusionUrls</param-name> <param-value>/sys/user/noAuth.page,/login.page</param-value> </init-param> </filter> <filter-mapping> <filter-name>aclControlFilter</filter-name> <url-pattern>/sys/*</url-pattern> <url-pattern>/admin/*</url-pattern> </filter-mapping>