java后台代码（MD5加密+token验证）：

import com.smart.ssai.admin.domain.User;
import com.smart.ssai.admin.service.UserService;
import com.smart.ssai.VO.Response;
import com.smart.ssai.common.utils.ResultVOUtil;
import com.smart.ssai.common.utils.ToolUtils;
import com.smart.ssai.constant.TokenConstant;
import io.jsonwebtoken.JwtBuilder;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.SignatureAlgorithm;
import org.springframework.beans.BeanUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import java.util.Date;
import java.util.HashMap;
import java.util.Map;


@RestController
@RequestMapping("/api")
public class LoginController {

    @Autowired
    private UserService userService;

    /**
     * 用户登录
     * @param username 用户名
     * @param password 密码
     * @return
     */
    @PostMapping("/login")
    public ResponseEntity<Response> login(@RequestParam(value = "username") String username
            , @RequestParam(value = "password") String password){
        User user = userService.getUserByUsername(username);
        //判断用户是否存在
        if(null == user){
            return ResultVOUtil.show(0,"用户不存在，请重新输入",null);
        }
        //判断密码是否正确
        String password1 = ToolUtils.md5Hex(password,String.valueOf(user.getCode()));
        if(!user.getPassword().equals(password1)){
            return ResultVOUtil.show(0,"用户密码错误",null);
        }
        //登录成功，生成token，并更新数据库token和过期时间
        Date date = new Date();
        Integer nowTime = (int)(date.getTime()/1000);//当前时间戳
        String token = createToken(user,date);//token
        User model = new User();
        BeanUtils.copyProperties(user,model);
//        model.setId(user.getId());
        model.setTimeout(nowTime);
        model.setToken(token);
        userService.insert(model);
        //跳转到指定页面，这里不跳转，返回token信息给前端
        Map<String,Object> map = new HashMap<>();
        map.put("token",token);
        return ResultVOUtil.show(1,"登录成功",map);
    }

    /**
     * 生成token,根据有效的用户信息
     * @param user 用户实例
     * @param date 当前日期
     * @return
     */
    private String createToken(User user, Date date){
        SignatureAlgorithm signatureAlgorithm = SignatureAlgorithm.HS256;
        JwtBuilder builder = Jwts.builder().setHeaderParam("typ", "JWT")//设置header
                .setHeaderParam("alg", "HS256").setIssuedAt(date)//设置签发时间
                .setExpiration(new Date(date.getTime() + TokenConstant.EXPIRE))//设置过期时间，30天，超出int，要加L
                .claim("userid",String.valueOf(user.getId()))//设置内容
                .setIssuer(TokenConstant.ISSUER)//设置签发人
                .signWith(signatureAlgorithm, TokenConstant.SECRETKEY);//签名，需要算法和key
        String jwt = builder.compact();
        return jwt;
    }
}