spring boot 配置Filter过滤器的方法

Filter 过滤器是web开发中很重要的一个组件，下面以一个session登陆的例子介绍下Spring Boot中如何使用Filter

首先要准备一个实现了Filter的接口的类 SessionFilter：

import org.slf4j.LoggerFactory;import javax.servlet.*;import javax.servlet.Http.httpservletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;import java.io.IOException;import java.util.ArrayList;import java.util.List;import java.util.regex.Matcher;import java.util.regex.Pattern;public class SessionFilter implements Filter {  private static final org.slf4j.Logger logger = LoggerFactory.getLogger(SessionFilter.class);    protected static List<Pattern> patterns = new ArrayList<Pattern>();  @Override  public void init(FilterConfig filterConfig) throws ServletException {  }  @Override  public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain chain) throws IOException, ServletException {    HttpServletRequest httpRequest = (HttpServletRequest) servletRequest;    HttpServletResponse httpResponse = (HttpServletResponse) servletResponse;    logger.info("aaaaaaaaaa");    String url = httpRequest.getRequestURI().substring(httpRequest.getContextPath().length());    if (url.startsWith("/") && url.length() > 1) {      url = url.substring(1);    }    if (isInclude(url)){      chain.doFilter(httpRequest, httpResponse);      return;    } else {      HttpSession session = httpRequest.getSession();      if (session.getAttribute("") != null){        // session存在        chain.doFilter(httpRequest, httpResponse);        return;      } else {        // session不存在 准备跳转失败                chain.doFilter(httpRequest, httpResponse);        return;      }    }  }  @Override  public void destroy() {  }    private boolean isInclude(String url) {    for (Pattern pattern : patterns) {      Matcher matcher = pattern.matcher(url);      if (matcher.matches()) {        return true;      }    }    return false;  }}