@RequestMapping("forelogout")
    public String logout( HttpSession session) {
        session.removeAttribute("user");
        return "redirect:forehome";
    }
}

package com.how2java.tmall.controller;

import com.how2java.tmall.pojo.Category;
import com.how2java.tmall.pojo.User;
import com.how2java.tmall.service.*;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.util.HtmlUtils;

import javax.servlet.http.HttpSession;
import java.util.List;

@Controller
@RequestMapping("")
public class ForeController {
    @Autowired
    CategoryService categoryService;
    @Autowired
    ProductService productService;
    @Autowired
    UserService userService;
    @Autowired
    ProductImageService productImageService;
    @Autowired
    PropertyValueService propertyValueService;
    @Autowired
    OrderService orderService;
    @Autowired
    OrderItemService orderItemService;
    @RequestMapping("forehome")
    public String home(Model model) {
        List<Category> cs= categoryService.list();
        productService.fill(cs);
        productService.fillByRow(cs);
         model.addAttribute("cs", cs);
        return "fore/home";
    }

    @RequestMapping("foreregister")
    public String register(Model model,User user) {
        String name =  user.getName();
        name = HtmlUtils.htmlEscape(name);
        user.setName(name);
        boolean exist = userService.isExist(name);
        
        if(exist){
            String m ="用户名已经被使用,不能使用";
            model.addAttribute("msg", m);

            return "fore/register";
        }
        userService.add(user);

        return "redirect:registerSuccessPage";
    }
    @RequestMapping("forelogin")
    public String login(@RequestParam("name") String name, @RequestParam("password") String password, Model model, HttpSession session) {
        name = HtmlUtils.htmlEscape(name);
        User user = userService.get(name,password);

        if(null==user){
            model.addAttribute("msg", "账号密码错误");
            return "fore/login";
        }
        session.setAttribute("user", user);
        return "redirect:forehome";
    }
    @RequestMapping("forelogout")
    public String logout( HttpSession session) {
        session.removeAttribute("user");
        return "redirect:forehome";
    }
}