一、什么是access_token
微信公众平台技术文档中对access_token的解释：
access_token是公众号的全局唯一接口调用凭据，公众号调用各接口时都需使用access_token。开发者需要进行妥善保存。access_token的存储至少要保留512个字符空间。access_token的有效期目前为2个小时，需定时刷新，重复获取将导致上次获取的access_token失效。
技术文档中建议
1.使用中控服务器统一获取刷新access_token，避免不同的业务逻辑各自刷新容易引起冲突；
2.access_token中有expire_in，目前是7200秒之内的值可以根据该值控制刷新access_token，刷新过程中中控服务器可以继续对外输出老的access_token，公众平台后台会保证在5分钟内新老access_token可以继续使用；
二、调用access_token请求说明
使用https请求：GET
https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=APPID&secret=APPSECRET
请求成功后返回JSON数据包
{"access_token":"ACCESS_TOKEN","expires_in":7200}
错误时会返回错误原因
{"errcode":40013,"errmsg":"invalid appid"}
三、实现思路
通过HttpURLConnection实现https请求，获取到返回数据包后根据ACCESS_TOKEN保存到文本文件中供业务逻辑调用，expires_in中的时间控制刷新。
三、实现代码
公用类HttpsUtil用来调用http连接
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor. */package priv.liu.weichat.util;import java.io.BufferedReader;import java.io.InputStream;import java.io.InputStreamReader;import java.io.OutputStream;import java.net.URL;import java.net.HttpURLConnection;import javax.net.ssl.HttpsURLConnection;import net.sf.json.JSONObject;/**
*
* @author liu */public class HttpsUtil {
/**
* HttpsUtil方法https请求结果返回蔚json类型
* @param Url http请求地址
* @param Method http请求类型支持POST GET
* @param Output
* @return InputStream转换成JSONObject后返回
* @throws Exception
*/
public JSONObject HttpsUtil(String Url,String Method,String Output) throws Exception{
JSONObject jsonObject = null;
URL conn_url = new URL(Url);
HttpURLConnection conn = (HttpsURLConnection)conn_url.openConnection();
conn.setRequestMethod(Method);
conn.setReadTimeout(5000);
conn.setConnectTimeout(5000);
conn.connect(); //output获取access_token是不会用到
if(Output != null){
OutputStream outputstream =conn.getOutputStream(); //字符集，防止出现中文乱码
outputstream.write(Output.getBytes("UTF-8"));
outputstream.close();
} //正常返回代码为200
if(conn.getResponseCode()==200){
InputStream stream = conn.getInputStream();
InputStreamReader inputStreamReader = new InputStreamReader(stream, "utf-8");
BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
String str = null;
StringBuffer buffer = new StringBuffer(); while ((str = bufferedReader.readLine()) != null) {
buffer.append(str);
}
bufferedReader.close();
inputStreamReader.close();
stream.close();
conn.disconnect();
jsonObject = JSONObject.fromObject(buffer.toString());
}
System.out.println(conn.getResponseCode()); return jsonObject;
}
}循环获取accesst_token代码
/*
* To change this license header, choose License Headers in Project Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor. */package priv.liu.weichat.token;import static java.lang.Thread.sleep;import net.sf.json.JSONObject;import priv.liu.weichat.util.HttpsUtil;/**
*
* @author liu */public class GetToken { /**
* @param args the command line arguments
* @throws java.lang.Exception */
public static void main(String[] args) throws Exception { // TODO code application logic here //访问地址
String TOKEN_URL = "https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=APPID&secret=APPSECRET"; //appid
String APPID = "wxf62ff5631358ef2e"; //appsecret
String APPSECRET = "2af33a0092006148a5000ff06e9151bb";
String request_url = TOKEN_URL.replace("APPID", APPID).replace("APPSECRET", APPSECRET);
HttpsUtil httpsUtil = new HttpsUtil();
System.out.println(request_url); int i = 0; while(true){
JSONObject jsonObject = httpsUtil.HttpsUtil(request_url,"GET",null); if(null != jsonObject){
String access_tocken = jsonObject.getString("access_token");
String expires_in = jsonObject.getString("expires_in"); //获取到的access_tocken值可以写入到文本文件中供其他业务逻辑调用，实例中只打印了没有保存到文件
System.out.println("获取成功"+"access_tocken="+access_tocken+"||expires_in="+expires_in);
i=Integer.parseInt(expires_in);
} //休眠1小时57分钟，提前三分钟获取新的access_token
sleep((7200-180)*1000);
}
}
}
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