java 对接微信公众号(一)获取token

1.登录微信公众平台，在基本配置里获取AppId和AppSecret

2.获取token（token获取到存本地，后续API都要带token访问）

需要在基本配置里配置ip白名单才能获取到token

    /** TokenURL */
    private final static String GET_TOKEN_URL = "https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid={0}&secret={1}";

    /** APP_ID */
    private final static String APP_ID = "wx1234567891011121";

    /** APP_SECRET */
    private final static String APP_SECRET = "123qgs4vg5yt67vsf8r9bri1011j1i2b";


    /**
     * 获取token，默认7200秒过期，所以存redis7200秒取一次
     *
     * @return 获取用户详情
     */
    public String getToken() {
        String redisKey = "Tencent:AccessToken";
        String token  = (String)redisUtils.get(redisKey);
        if(ObjectUtils.isEmpty(token)){
            token = tencentService.getToken();
            //设置缓存 2小时
            redisUtils.setEx(redisKey,token, 7200, TimeUnit.SECONDS);
        }
        return token;
    }


    //tencentService.getToken();
    @Override
    public String  getToken(){
        try {
            HttpClient client = HttpClients.createDefault();
            String tokenUrl = MessageFormat.format(GET_TOKEN_URL, APP_ID, APP_SECRET);
            HttpGet request = new HttpGet(tokenUrl);
            HttpResponse response = client.execute(request);
            JSONObject object = getResponseJson(response);
            if (object == null) {
                return null;
            }
            return ObjectUtils.isEmpty(object) ? null : object.getString("access_token");
        }catch (Exception e){ log.info(e.getMessage()); }
        return null;
    }

    //getResponseJson();
    private static JSONObject getResponseJson(HttpResponse response) throws IOException {
        JSONObject json = null;
        HttpEntity entity = response.getEntity();
        if(entity!=null){
            String result = EntityUtils.toString(entity,"UTF-8");
            json = JSONObject.parseObject(result);
        }
        if(ObjectUtils.isEmpty(json)){
            return null;
        }
        return json;
    }

//可能用到的包
import com.alibaba.fastjson.JSONArray;
import com.alibaba.fastjson.JSONObject;
import com.baomidou.mybatisplus.core.toolkit.ObjectUtils;
import com.baomidou.mybatisplus.core.toolkit.StringUtils;
import lombok.extern.slf4j.Slf4j;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import javax.annotation.Resource;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.text.MessageFormat;
import java.util.Date;
import java.util.Map;