Nodejs implements Android login

In mobile application development, user login is one of the essential functions. In Android clients, login verification by requesting the server interface is a common implementation method. On the server side, a simple login verification interface service can be quickly built using Node.js. This article will help readers understand how to use Node.js to implement the Android login function by introducing the relevant knowledge and sample code of Node.js.

1. Introduction to Node.js

Node.js is an open source, cross-platform JavaScript runtime environment. It is based on the event-driven, asynchronous I/O event model and can quickly build high-performance Performance, scalable web applications. Node.js is based on the V8 engine and implements an efficient event loop mechanism by encapsulating the asynchronous I/O API provided by the libuv library, making Node.js perform well in handling a large number of concurrent connections and high-load workloads. At the same time, Node.js also provides a wealth of standard libraries and third-party modules to facilitate developers to quickly build various web applications, server applications, command line tools and other applications.

2. Android login process

Before introducing the specific implementation details of Node.js to implement Android login, let us first sort out the basic process of Android login:

1. The user opens the Android client, clicks the login button, enters the username and password, and submits the login request.
2. The client sends login information such as user name and password to the server through an HTTP request.
3. After the server receives the login request, it verifies the user name and password entered by the user. If successful, it returns a token indicating successful login, otherwise it returns a login failure message.
4. After the client receives the token for successful login, it saves it locally for subsequent requests.
5. The client requests the API interface that requires login verification by carrying the token. The server determines whether the login is valid by verifying the token. If it is valid, the corresponding data information will be returned. Otherwise, an error indicating that the login is invalid or not logged in will be returned. information.

According to the above process, the main functions we need to implement on the server side are: receiving login requests, verifying user information, generating and returning tokens, verifying whether the token is valid, etc.

3. Example of Android login using Node.js

The following is a sample code for using Node.js to implement Android login:

1. Login request interface (login.js )

const express = require('express');
const bodyParser = require('body-parser');
const jwt = require('jsonwebtoken');
const secretKey = 'mySecretKey'; //Token加密密钥
const app = express();
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: true }));

//处理登录请求
app.post('/api/login', (req, res) => {
  const { username, password } = req.body;
  //TODO: 用户信息验证
  if (username === 'test' && password === '123456') {
    //生成AccessToken
    const payload = { username };
    const accessToken = jwt.sign(payload, secretKey, { expiresIn: '1h' });
    res.json({ code: 200, msg: '登录成功', accessToken });
  } else {
    res.json({ code: 401, msg: '用户名或密码错误' });
  }
});

const server = app.listen(3000, () => {
  console.log(`Server listening at http://${server.address().address}:${server.address().port}`);
});

2. Token verification middleware (auth.js)

const jwt = require('jsonwebtoken');
const secretKey = 'mySecretKey'; //Token加密密钥

//Token验证中间件
module.exports = (req, res, next) => {
  const authHeader = req.headers['authorization'];
  const token = authHeader && authHeader.split(' ')[1];
  if (token == null) {
    return res.status(401).json({ code: 401, msg: '未登录或Token已过期' });
  }
  jwt.verify(token, secretKey, (err, user) => {
    if (err) {
      return res.status(403).json({ code: 403, msg: 'Token验证失败' });
    }
    req.user = user;
    next();
  });
};

3. Login verification interface (user.js)

const express = require('express');
const auth = require('./auth.js');
const app = express();

app.get('/api/user', auth, (req, res) => {
  const { username } = req.user;
  //TODO: 获取用户信息并返回
  res.json({ code: 200, msg: '获取用户信息成功', data: { username } });
});

const server = app.listen(3000, () => {
  console.log(`Server listening at http://${server.address().address}:${server.address().port}`);
});

Note:

• In login.js, we use the Express framework to process HTTP requests, receive login requests through the POST method, and verify user information. After successfully verifying the user information, use the jsonwebtoken library to generate an AccessToken and return it to the client as JSON data.
• In auth.js, we define a Token verification middleware, which is used to check whether the token in the request header is valid when processing API interface requests that require login verification. If the token has expired or an error occurs in token decryption, the corresponding error message will be returned.
• In user.js, we define an API interface that requires login verification, which uses the Token verification middleware defined above. If the login verification is successful, you can obtain the information of the logged in user through req.user, then obtain the relevant user information through the TODO section, and return it to the client as JSON data.

4. How to implement the login request in the Android client

In the Android client, you can use the HTTP request library to make HTTP requests to the login interface. After receiving the token for successful login, save it in SharedPreferences for use by other interfaces that require login verification. The following is a simple sample code for using the OkHttp3 library to make a login request:

private void login(String username, String password) {
  OkHttpClient client = new OkHttpClient();
  MediaType JSON = MediaType.parse("application/json; charset=utf-8");
  JSONObject requestBody = new JSONObject();
  try {
    requestBody.put("username", username).put("password", password);
  } catch (JSONException e) {
    e.printStackTrace();
  }
  RequestBody body = RequestBody.create(JSON, requestBody.toString());
  Request request = new Request.Builder()
    .url("http://your-server-host/api/login")
    .post(body)
    .build();
  client.newCall(request).enqueue(new Callback() {
    @Override
    public void onFailure(Call call, IOException e) {
      e.printStackTrace();
      //TODO: 处理请求失败
    }

    @Override
    public void onResponse(Call call, Response response) throws IOException {
      try (ResponseBody responseBody = response.body()) {
        String responseStr = responseBody.string();
        JSONObject jsonObject = new JSONObject(responseStr);
        int code = jsonObject.getInt("code");
        if (code == 200) {
          String accessToken = jsonObject.getString("accessToken");
          //将accessToken保存在SharedPreferences中
        } else {
          String msg = jsonObject.getString("msg");
          //TODO: 处理登录失败
        }
      } catch (JSONException e) {
        e.printStackTrace();
      }
    }
  });
}

Instructions:

• First, you need to introduce the OkHttp3 library into the Android project and define related Interface request method, such as the above login() method.
• In the login() method, we use the OkHttpClient object to create a POST request and send login information such as user name and password to the server in JSON data format. After receiving the response from the server, parse the JSON data of the response and save the accessToken locally for subsequent use.

5. Summary

This article introduces how to use Node.js to implement the Android login verification interface, and demonstrates its basic implementation process through sample code. In actual projects, in order to ensure login security, issues such as data transmission encryption, password encrypted storage, and multi-terminal login also need to be considered. Through continuous improvement and optimization, a more complete, secure and efficient login verification system can be built.

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