在当前进程下取得当前登陆用户

这个也是一个工具类

场景：比如说我们需要在controller或者service或者dao层用到当前登陆人的信息。我们之前的做法，肯定是从session中取出来。然后哪里需要传哪里。这样很麻烦。这时候我们需要造一个工具类。目的是在任何地方都能获取到当前登陆人的信息。

在这里我们要用到一个对象  ThreadLocal  这个对象 这个类相当于一个map，但是这个类的key是当前的进程。所以说，一个这样类只能放一个对象。这里要注意一下。

为什么要用这样的一个类呢？因为这个类的特性，每个进程的是完全隔离的，避免高并发情况下发生一些错误（我也不知道啥错误，反正就是防止高并发，这个坑回来再填！！！ToDo~~）

1.RequestHolder.java

package com.mmall.common;

import com.mmall.model.SysUser;

import javax.servlet.http.HttpServletRequest;

public class RequestHolder {

    private static final ThreadLocal<SysUser> userHolder = new ThreadLocal<SysUser>();

    private static final ThreadLocal<HttpServletRequest> requestHolder = new ThreadLocal<HttpServletRequest>();

    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();
    }
}

说明：这里new了两个这样的类，一个放当前对象，一个放当前request，然后自定义add方法，还有一个remove方法，因为在每次请求完之后，要把ThreadLocal 里面的数据移除掉

 2. 然后写一个filter过滤器。拦截所有的请求。没有登录直接返回登录页面，登录了就从session中获取当前对象，然后add进去

LoginFilter.java

package com.mmall.filter;

import com.mmall.common.RequestHolder;
import com.mmall.model.SysUser;
import lombok.extern.slf4j.Slf4j;

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * Created by 敲代码的卡卡罗特
 * on 2018/3/28 23:49.
 */
@Slf4j
public class LoginFilter implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    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;
    }

    @Override
    public void destroy() {

    }
}

3.每次请求结束清除当前数据   如何知道每次当前请求结束 请看我这一篇博客

HttpInterceptor.java

package com.mmall.common;

import com.mmall.util.JsonMapper;
import lombok.extern.slf4j.Slf4j;
import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.Map;

@Slf4j
public class HttpInterceptor extends HandlerInterceptorAdapter {

    private static final String START_TIME = "requestStartTime";

    @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.obj2String(parameterMap));
        long start = System.currentTimeMillis();
        request.setAttribute(START_TIME, start);
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        String url = request.getRequestURI().toString();
        long start = (Long) request.getAttribute(START_TIME);
        long end = System.currentTimeMillis();
        log.info("request finished. url:{}, cost:{}", url, end - start);
    }

    @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 completed. url:{}, cost:{}", url, end - start);
        removeThreadLocalInfo();
    }

    public void removeThreadLocalInfo() {
        RequestHolder.remove();;
    }

}

4.在web.xml中配置过滤器

<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>