springboot如何通过controller层实现页面切换

//return "dashboard";//这是由模板引擎解析，然后拼串
//return "forward:/dashboard.html";//这是转发
return "redirect:/main.html";//这是重定向

package com.zr.gktjweb.controller.login;
 
import com.zr.gktjweb.common.HttpClientUtil;
import com.zr.gktjweb.common.ResponseBean;
import com.zr.gktjweb.constant.SysCode;
import com.zr.gktjweb.model.SysUser;
import com.zr.gktjweb.util.JSONUtils;
import com.zr.gktjweb.util.UserUtil;
import io.swagger.annotations.Api;
import io.swagger.annotations.ApiImplicitParam;
import io.swagger.annotations.ApiImplicitParams;
import io.swagger.annotations.ApiOperation;
import net.sf.json.JSONObject;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;
 
import javax.servlet.http.HttpServletRequest;
import java.util.HashMap;
import java.util.Map;
 
@Api(tags = "登录")
@Controller
public class LoginController {
    @Value("${baseurl}")
    private String baseurl;
    @Value("${login_url}")
    private String loginUrl;
    @Value("${logout_url}")
    private String logoutUrl;
    private static final Logger LOGGER = LoggerFactory.getLogger(LoginController.class);
 
    @ApiOperation(value = "登录", notes = "登录验证")
    @ApiImplicitParams({@ApiImplicitParam(name = "username", value = "姓名", required = true, dataType = "String"),
            @ApiImplicitParam(name = "password", value = "密码", required = true, dataType = "String")
    })
    @RequestMapping(value = "/login.do", method = RequestMethod.POST)
    @ResponseBody
    public ResponseBean login(String username, String password) {
        String url = baseurl + loginUrl;
        Map<String, String> map = new HashMap<>();
        map.put("username", username);
        map.put("password", password);
        String result = "";
        //请求服务失败
        try {
            result = HttpClientUtil.doPost(url, map);
        } catch (Exception e) {
            e.printStackTrace();
            LOGGER.error("用户登录", e);
            return new ResponseBean(SysCode.errCode, "系统异常，请联系管理员", "");
        }
        JSONObject json = JSONObject.fromObject(result);
        //登录验证未通过
        if (!json.getString("code").equals(SysCode.successCode + "")) {
            ResponseBean responseBean = JSONUtils.jsonToObject(ResponseBean.class, result);
            return responseBean;
        }
        //验证通过，在session中设置token
        JSONObject dataJson = (JSONObject) json.get("data");
        String userJson = dataJson.getString("user");
        SysUser sysUser = JSONUtils.jsonToObject(SysUser.class, userJson);
        JSONObject tokenJson = (JSONObject) dataJson.get("token");
        String token = tokenJson.getString("token");
        UserUtil.setToken(token);
        UserUtil.setUserSession(sysUser);
//        session.setAttribute("token", token);
//        session.setAttribute("user", sysUser);
        String url1 = "/index.html";
        Map<String, Object> resMap = new HashMap<>();
        resMap.put("url", url1);
        return new ResponseBean(SysCode.successCode, "登录成功", resMap);
    }
 
    /**
     * 注销登录
     *
     * @param request
     * @return
     */
    @RequestMapping("/loginout.do")
    public String loginOut(HttpServletRequest request) {
        request.getSession().invalidate();
        String url=baseurl+logoutUrl;
        HttpClientUtil.doGet(url);
        return "redirect:/";
    }
}