spring boot 配置Filter过滤器

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

filter功能，它使用户可以改变一个 request和修改一个response. Filter 不是一个servlet,它不能产生一个response,它能够在一个request到达servlet之前预处理request,也可以在离开 servlet时处理response.换种说法,filter其实是一个”servlet chaining”(servlet 链).

一个Filter包括：
1）、在servlet被调用之前截获;
2）、在servlet被调用之前检查servlet request;
3）、根据需要修改request头和request数据;
4）、根据需要修改response头和response数据;
5）、在servlet被调用之后截获.

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;

/**
 * Created by mazhenhua on 2016/12/27.
 *
 * 过滤器
 */
public class SessionFilter implements Filter {
    private static final org.slf4j.Logger logger = LoggerFactory.getLogger(SessionFilter.class);


    /**
     * 封装，不需要过滤的list列表
     */
    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
                /* RequestDispatcher dispatcher = request.getRequestDispatcher(path);
                    dispatcher.forward(request, response);*/
                chain.doFilter(httpRequest, httpResponse);
                return;
            }
        }


    }

    @Override
    public void destroy() {

    }


    /**
     * 是否需要过滤
     * @param url
     * @return
     */
    private boolean isInclude(String url) {
        for (Pattern pattern : patterns) {
            Matcher matcher = pattern.matcher(url);
            if (matcher.matches()) {
                return true;
            }
        }
        return false;
    }

}
 
 
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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。

    /**
     * 配置过滤器
     * @return
     */
    @Bean
    public FilterRegistrationBean someFilterRegistration() {
        FilterRegistrationBean registration = new FilterRegistrationBean();
        registration.setFilter(sessionFilter());
        registration.addUrlPatterns("/*");
        registration.addInitParameter("paramName", "paramValue");
        registration.setName("sessionFilter");
        return registration;
    }

    /**
     * 创建一个bean
     * @return
     */
    @Bean(name = "sessionFilter")
    public Filter sessionFilter() {
        return new SessionFilter();
    }
 
 
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经过上面这俩步的配置，过滤器基本上就可以了。