vue-axios与Servlet前后端连接，进行数据交互

在vue文件中引入axios，也可以在main.js中引入

import axios from "axios";

发送网络请求的代码

axios({
        method: 'POST',    //提交方法
        url: 'http://localhost:8080/PPFM/userLogin',    //后端的servlet登录接口
        data: {
          userName: this.ruleForm.username,    //传输的用户名
          password: this.ruleForm.password,    //传输的密码
        },
      }).then(res => {
        console.log(res);     //对后端servlet接口返回的数据进行输出
        //获取返回数据中的信息
        console.log(res.data.msg);   
        console.log(res.data.data.userName);
      })

后端servlet登录接口代码

package servlet;

import com.alibaba.fastjson.JSONObject;
import com.google.gson.Gson;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import dao.userInfo.UserInfoMapper;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import pojo.UserInfo;
import utils.MybatisUtils;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.HashMap;
import java.util.List;

@WebServlet("/userLogin")
public class UserLogin extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        //设置传值的编码
        resp.setContentType("text/html;charset=UTF-8");
        req.setCharacterEncoding("utf-8");

        //数据流获取信息
        StringBuilder sb = new StringBuilder();
        BufferedReader reader = req.getReader();
        char[] buf = new char[1024];
        int len;
        while ((len = reader.read(buf)) != -1){
            sb.append(buf,0,len);
        }

        //转json
        String str = sb.toString();
        JSONObject jsonObject = JSONObject.parseObject(str);

        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserInfoMapper mapper = sqlSession.getMapper(UserInfoMapper.class);

        HashMap map = new HashMap<>();
        
        //获取前端传入数据中的用户名和密码，到数据库中进行查询
        map.put("name",jsonObject.getString("userName"));
        map.put("password",jsonObject.getString("password"));
        List userInfos = mapper.queryUserInfo(map);

        for (UserInfo userInfo : userInfos) {
            System.out.println(userInfo);
        }


        //用Google的Gson把list对象转化为json数据格式
        Gson gson = new Gson();
        JsonElement jsonElement = gson.toJsonTree(userInfos);
        JsonObject jsonObject1 = new JsonObject();
        jsonObject1.add("data",jsonElement);

        if (userInfos.size() != 0) {
            //查询成功返回0
            jsonObject1.addProperty("msg","0");
        } else {
            //查询失败返回1
            jsonObject1.addProperty("msg","1");
        }

        String s = gson.toJson(jsonObject1);

        //将json数据进行一个输出打印
        PrintWriter writer = resp.getWriter();
        writer.write( s );
        writer.flush();
        writer.close();

        sqlSession.close();

    }
}