access_token是公众号的全局唯一接口调用凭据，我们和微信服务器进行交互，服务器通过access_token判断我们是谁(哪个公众号服务的请求)。所以 我们在开发过程中服务端拿到的access_token是一定不能显式暴露给外部，否则将导致数据安全问题。别人拿到你的accessToken操作你的公众号。access_token的有效期目前为2个小时，过期需要再次获取。

下面是一种获取access_token方式

1.项目添加httpclient相关依赖，示例使用httpclient请求微信服务器，获取微信返回结果。

    org.apache.httpcomponents   httpclient   4.5.3         org.apache.httpcomponents   httpcore   4.4.6  

2.httpClientUtil类，网上随手找的 试了一下本例的doget方法 没有问题，其他的 暂不考虑

public class HttpClientUtil {  public static String doGet(String url, Map param) {    // 创建Httpclient对象    CloseableHttpClient httpclient = HttpClients.createDefault();    String resultString = "";    CloseableHttpResponse response = null;    try {      // 创建uri      URIBuilder builder = new URIBuilder(url);      if (param != null) {        for (String key : param.keySet()) {          builder.addParameter(key, param.get(key));        }      }      URI uri = builder.build();      // 创建http GET请求      HttpGet httpGet = new HttpGet(uri);      // 执行请求      response = httpclient.execute(httpGet);      // 判断返回状态是否为200      if (response.getStatusLine().getStatusCode() == 200) {        resultString = EntityUtils.toString(response.getEntity(), "UTF-8");      }    } catch (Exception e) {      e.printStackTrace();    } finally {      try {        if (response != null) {          response.close();        }        httpclient.close();      } catch (IOException e) {        e.printStackTrace();      }    }    return resultString;  }  public static String doGet(String url) {    return doGet(url, null);  }  public static String doPost(String url, Map param) {    // 创建Httpclient对象    CloseableHttpClient httpClient = HttpClients.createDefault();    CloseableHttpResponse response = null;    String resultString = "";    try {      // 创建Http Post请求      HttpPost httpPost = new HttpPost(url);      // 创建参数列表      if (param != null) {        List paramList = new ArrayList<>();        for (String key : param.keySet()) {          paramList.add(new BasicNameValuePair(key, param.get(key)));        }        // 模拟表单        UrlEncodedFormEntity entity = new UrlEncodedFormEntity(paramList,"utf-8");        httpPost.setEntity(entity);      }      // 执行http请求      response = httpClient.execute(httpPost);      resultString = EntityUtils.toString(response.getEntity(), "utf-8");    } catch (Exception e) {      e.printStackTrace();    } finally {      try {        response.close();      } catch (IOException e) {        // TODO Auto-generated catch block        e.printStackTrace();      }    }    return resultString;  }  public static String doPost(String url) {    return doPost(url, null);  }  public static String doPostJson(String url, String json) {    // 创建Httpclient对象    CloseableHttpClient httpClient = HttpClients.createDefault();    CloseableHttpResponse response = null;    String resultString = "";    try {      // 创建Http Post请求      HttpPost httpPost = new HttpPost(url);      // 创建请求内容      StringEntity entity = new StringEntity(json, ContentType.APPLICATION_JSON);      httpPost.setEntity(entity);      // 执行http请求      response = httpClient.execute(httpPost);      resultString = EntityUtils.toString(response.getEntity(), "utf-8");    } catch (Exception e) {      e.printStackTrace();    } finally {      try {        response.close();      } catch (IOException e) {        // TODO Auto-generated catch block        e.printStackTrace();      }    }    return resultString;  }}

3.第三步就是简单的测试代码了

public class WeChatAccessTokenTest {  public static void main(String[] args) {    Map params = new HashMap<>();    // TODO: 2018/11/16 *号改成真实appid    params.put("appid", "******");    // TODO: 2018/11/16 *号改成真实secret    params.put("secret", "******");    params.put("grant_type", "client_credential");    String response = HttpClientUtil.doGet("https://api.weixin.qq.com/cgi-bin/token", params);    JSONObject accessTokenObject = JSONObject.parseObject(response);    String accessToken = accessTokenObject.getString("access_token");    Long expire = accessTokenObject.getLong("expires_in");    System.out.println(accessToken);  }}