微信公众号获取access_token的方法实例分析

<!-- https://mvnrepository.com/artifact/org.apache.httpcomponents/httpclient -->
  <dependency>
   <groupId>org.apache.httpcomponents</groupId>
   <artifactId>httpclient</artifactId>
   <version>4.5.3</version>
  </dependency>
  <!-- https://mvnrepository.com/artifact/org.apache.httpcomponents/httpcore -->
  <dependency>
   <groupId>org.apache.httpcomponents</groupId>
   <artifactId>httpcore</artifactId>
   <version>4.4.6</version>
  </dependency>

public class HttpClientUtil {
  public static String doGet(String url, Map<String, String> 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<String, String> 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<NameValuePair> 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;
  }
}

public class WeChatAccessTokenTest {
  public static void main(String[] args) {
    Map<String, String> 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);
  }
}