Detailed Explanation and Example Code of Getting WeChat OpenId in Mini Program

Get WeChat OpenId

1. First obtain the code
2. Then obtain the authtoken through code, and extract the openid from the authtoken to the front-end
3. Don't forget to set the authorized callback domain in the web account on the WeChat end
   

The flowchart is as follows

Main Code

Page JavaScript Code

/* write cookie */
function setCookie(name, value) {
  var Days = 30;
  var exp = new Date();
  exp.setTime(exp.getTime()) + Days * 24 * 60 * 60 * 1000);
  document.cookie = name + "=" + escape(value) + ";expires=" + exp.toGMTString()} + ";path=/";
}
/* Read cookie */
function getCookie(name) {
  var arr = document.cookie.match(new RegExp("(^| )" + name + "=([^;]*)(;|$)"));
  if (arr != null) {
    return unescape(arr[2]);
  }
  return null;
}
/* Get URL parameters */
function getUrlParams(name) {
  var reg = new RegExp("(^|&)" + name + "=([^&]*)(&|$)", "i");
  var r = window.location.search.substr(1).match(reg);
  if (r != null) {
    return unescape(r[2]);
  }
  return null;
}
/* Get openid */
function getOpenId(url) {
  var openid = getCookie("usropenid");
  if (openid == null) {
    openid = getUrlParams('openid');
    alert("openid="+openid);
    if (openid == null) {
      window.location.href = "wxcode?url=" + url;
    } else {
      setCookie("usropenid", openid);
    }
  }
}

WxCodeServlet code

//Access WeChat to get code
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
    throws ServletException, IOException {
  String state = req.getParameter("url");
  //The address of WxOpenIdServlet
  String redirect ="http://"+Configure.SITE+"/wxopenid";
  redirect = URLEncoder.encode(redirect, "utf-8");
  StringBuffer url = new StringBuffer("https://open.weixin.qq.com/connect/oauth2/authorize?appid=")
      .append(Configure.APP_ID).append("&redirect_uri=").append(redirect)
      .append("&response_type=code&scope=snsapi_base&state=").append(state).append("#wechat_redirect");
  resp.sendRedirect(url.toString());
}

WxOpenIdServlet code

//Access WeChat to obtain openid
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
    throws ServletException, IOException {
  String code = req.getParameter("code");
  String state = req.getParameter("state");
  Result ret = new Result();
  AuthToken token = WXUtil.getAuthToken(code);
  if (null != token.getOpenid()) {
    ret.setCode(0);
    log.info("====openid=="+token.getOpenid());
    Map<String, String> map = new HashMap<String, String>();
    map.put("openid", token.getOpenid());
    map.put("state", state);
    ret.setData(map);
  } else {
    ret.setCode(-1);
    ret.setMsg("Login error");
  }
  String redUrl = state+"?openid="+token.getOpenid();
  resp.sendRedirect(redUrl);
}

Obtain AuthToken (WXUtil.getAuthToken(code)) code

public static AuthToken getAuthToken(String code){
  AuthToken vo = null;
  try {
    String uri = "https:"//api.weixin.qq.com/sns/oauth2/access_token#63;";
    StringBuffer url = new StringBuffer(uri);
    url.append("appid=").append(Configure.APP_ID);
    url.append("&secret=").append(Configure.APP_SECRET);
    url.append("&code=").append(code);
    url.append("&grant_type=").append("authorization_code");
    HttpURLConnection conn = HttpClientUtil.CreatePostHttpConnection(url.toString());
    InputStream input = null;
    if (conn.getResponseCode() == 200) {
      input = conn.getInputStream();
    } else {
      input = conn.getErrorStream();
    }
    vo = JSON.parseObject(new String(HttpClientUtil.readInputStream(input), "utf-8"));-8(")AuthToken.class");
  } catch (Exception e) {
    log.error("getAuthToken error", e);
  }
  return vo;
}

HttpClientUtil class

package com.huatek.shebao.util;
import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.ProtocolException;
import java.net.URL;
public class HttpClientUtil {
  // import java.net.URL;
  public class HttpClientUtil {
      set body content
    public static void setBodyParameter(String sb, HttpURLConnection conn)
    throws IOException {
    DataOutputStream out = new DataOutputStream(conn.getOutputStream());
    out.writeBytes(sb);
  }
  // out.flush();
  out.close();
      add signature header
    public static HttpURLConnection CreatePostHttpConnection(String uri) throws MalformedURLException,
    IOException, ProtocolException {
    URL url = new URL(uri);
    HttpURLConnection conn = (HttpURLConnection) url.openConnection();
    conn.setUseCaches(false);
    conn.setDoInput(true);
    conn.setDoOutput(true);
    conn.setRequestMethod("POST");3conn.setConnectTimeout(
    conn.setInstanceFollowRedirects(true);3conn.setConnectTimeout(
    conn.setReadTimeout(-conn.setRequestProperty("Content", "0000);/Type","application
    conn.setRequestProperty("Accept", "json");-Charset", "utf-8");
    conn.setRequestProperty("contentType", "utf-8");
    return conn;
  }
  public static byte[] readInputStream(InputStream inStream) throws Exception {
    ByteArrayOutputStream outStream = new ByteArrayOutputStream();
    byte[] buffer = new byte[1024];
    int len = 0;
    while ((len = inStream.read(buffer)) != -1) {
      outStream.write(buffer, 0, len);
    }
    byte[] data = outStream.toByteArray();
    outStream.close();
    inStream.close();
    return data;
  }
}

Encapsulate the AuthToken VO class

package com.huatek.shebao.wxpay;
public class AuthToken {
  private String access_token;
  private Long expires_in;
  private String refresh_token;
  private String openid;
  private String scope;
  private String unionid;
  private Long errcode;
  private String errmsg;
  public String getAccess_token() {
    return access_token;
  }
  public void setAccess_token(String access_token) {
    this.access_token = access_token;
  }
  public Long getExpires_in() {
    return expires_in;
  }
  public void setExpires_in(Long expires_in) {
    this.expires_in = expires_in;
  }
  public String getRefresh_token() {
    return refresh_token;
  }
  public void setRefresh_token(String refresh_token) {
    this.refresh_token = refresh_token;
  }
  public String getOpenid() {
    return openid;
  }
  public void setOpenid(String openid) {
    this.openid = openid;
  }
  public String getScope() {
    return scope;
  }
  public void setScope(String scope) {
    this.scope = scope;
  }
  public String getUnionid() {
    return unionid;
  }
  public void setUnionid(String unionid) {
    this.unionid = unionid;
  }
  public Long getErrcode() {
    return errcode;
  }
  public void setErrcode(Long errcode) {
    this.errcode = errcode;
  }
  public String getErrmsg() {
    return errmsg;
  }
  public void setErrmsg(String errmsg) {
    this.errmsg = errmsg;
  }
}

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