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 patterns = new ArrayList();

  @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;
  }

}

实际开发中往往有很多请求要直接请求进来，不需要鉴权登陆的，所以代码中过滤掉这种请求的代码，装进list就好了。

  
  @Bean
  public FilterRegistrationBean someFilterRegistration() {
    FilterRegistrationBean registration = new FilterRegistrationBean();
    registration.setFilter(sessionFilter());
    registration.addUrlPatterns("
  @Bean(name = "sessionFilter")
  public Filter sessionFilter() {
    return new SessionFilter();
  }

经过上面这俩步的配置，过滤器基本上就可以了。

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