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引入:

一提到获取用户信息，大部分人想到的都是通过session来获取用户信息，当要想获取到session，就需要获取对应的request,这样，就会增加代码的耦合性，基于以上缺陷，我们可以使用ThreadLocal来将当前的用户信息存入一个session，需要的时候，直接从全局的ThreadLocal中取出来即可

接下来我们实践操作一波:

创建一个RequestHolder类，定义相关的set和get用户信息的方法

/** * @author evan_qb * @date 2018/8/29 15:09 */public class RequestHolder {    private static final ThreadLocal
   
     userHolder = new ThreadLocal
    
     ();    private static final ThreadLocal
     
       requestHolder = new ThreadLocal<>();    public static void add(SysUser sysUser){        userHolder.set(sysUser);    }    public static void add(HttpServletRequest request){        requestHolder.set(request);    }    public static SysUser getCurrentUser(){        return userHolder.get();    }    public static HttpServletRequest getCurrentRequest(){        return requestHolder.get();    }    public static void remove(){        userHolder.remove();        requestHolder.remove();    }}
     
    
   

然后定义一个拦截器用于移除对应的ThreadLocal对象，防止内存泄漏

public class HttpInterceptor extends HandlerInterceptorAdapter {    private static final String START_TIME = "requestStartTime";    /**     * 处理前     * @param request     * @param response     * @param handler     * @return     * @throws Exception     */    @Override    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {        String url = request.getRequestURI().toString();        Map parameterMap = request.getParameterMap();        log.info("request start url:{},params:{}",url,JsonMapper.object2String(parameterMap));        long startTime = System.currentTimeMillis();        request.setAttribute(START_TIME,startTime);        return true;    }    /**     * 处理后调用（正常）     * @param request     * @param response     * @param handler     * @param modelAndView     * @throws Exception     */    @Override    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {        /*String url = request.getRequestURI().toString();        Map parameterMap = request.getParameterMap();        log.info("request finish url:{},params:{}",url,JsonMapper.object2String(parameterMap));*/    }    /**     * 处理后调用(任何情况)     * @param request     * @param response     * @param handler     * @param ex     * @throws Exception     */    @Override    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {        String url = request.getRequestURI().toString();        long start = (long) request.getAttribute(START_TIME);        long end = System.currentTimeMillis();        log.info("request exception url:{},cost:{}ms",url,end - start);        removeThreadLocalInfo();    }    /**     * 移除信息     */    public void removeThreadLocalInfo(){        RequestHolder.remove();    }}

这时，我们需要利用一个过滤器LoginFilter，将每次的请求，和每次的用户信息存入ThreadLocal中

/** * @author evan_qb * @date 2018/8/29 15:29 */public class LoginFilter implements Filter {    @Override    public void init(FilterConfig filterConfig) throws ServletException {    }    @Override    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {        HttpServletRequest req = (HttpServletRequest) request;        HttpServletResponse resp = (HttpServletResponse) response;        String path = req.getServletPath();        SysUser sysUser = (SysUser) WebUtils.getSessionAttribute(req,"user");        if (sysUser == null){            resp.sendRedirect("/signin.jsp");            return;        }        RequestHolder.add(sysUser);        RequestHolder.add(req);        chain.doFilter(request,response);        return;    }    @Override    public void destroy() {    }}

同时在web.xml中配置好LoginFilter

     
    
     loginFilter
      
    
     cn.qblank.filter.LoginFilter
    
   
     
    
     loginFilter
      
    
     /sys/*
      
    
     /admin/*
    
   

当我们需要用户的信息时，我们可以直接通过RequestHolder的方法直接获取