private static final long MAX_TIME = 7200 * 1000;// 微信允許最長Access_token有效時間（ms）
private static final String TAG = "WeixinApiTest";// TAG
private static final String APPID = "wx889b****b3666b0b8";// APPID
private static final String SECERT = "6da7676***f0a9f15fbf06027856bb";// 秘鑰

/*
 * 該測試用例演示了如何獲取access_token。
 * access_token是公眾號的全局唯一票據(jù)，公眾號調(diào)用各接口時都需使用access_token。
 */
@Test
public void getAccess_token() throws IOException {
  // 拼接api要求的httpsurl鏈接
  String urlString = "https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid="
      + APPID + "&secret=" + SECERT;
  // 創(chuàng)建一個url
  URL reqURL = new URL(urlString);
  // 拿取鏈接
  HttpsURLConnection httpsConn = (HttpsURLConnection) reqURL
      .openConnection();
  // 取得該連接的輸入流，以讀取響應內(nèi)容
  InputStreamReader isr = new InputStreamReader(
      httpsConn.getInputStream());
  // 讀取服務器的響應內(nèi)容并顯示
  char[] chars = new char[1024];
  String reslut = "";
  int len;
  while ((len = isr.read(chars)) != -1) {
    reslut += new String(chars, 0, len);
  }
  isr.close();
  /*
   * 轉(zhuǎn)化json成javabean。引入了第三方jar:GSON
   */
  Gson gson = new Gson();// 將獲取的json轉(zhuǎn)化為java中的bean
  // 注意：Access_token access_token是一個自己創(chuàng)建的javabean
  Access_token access_token = gson.fromJson(reslut,
      new Access_token().getClass());
  if (access_token.getAccess_token() != null) {
    System.out.println("獲取的access_token是："
        + access_token.getAccess_token());
    System.out.println("該access_token的有效時間是："
        + access_token.getExpires_in() + "s");
  } else {
    System.out.println(TAG + "獲取access_token失敗，請檢查");

  }

}

  /*
   * 該方法實現(xiàn)獲取Access_token、保存并且只保存2小時Access_token。如果超過兩個小時重新獲??；如果沒有超過兩個小時，直接獲取。該方法依賴
   * ：public static String getAccessToken()；
   * 
   * 思路:將獲取到的Access_token和當前時間存儲到file里，
   * 取出時判斷當前時間和存儲里面的記錄的時間的時間差，如果大于MAX_TIME,重新獲取，并且將獲取到的存儲到file替換原來的內(nèi)容
   * ，如果小于MAX_TIME，直接獲取。
   */
  @Test
  public void getSavedAccess_token() throws IOException {
    Gson gson = new Gson();
    String mAccess_token = null;// 需要獲取的Access_token；
    File file = new File("temp_access_token.temp");// Access_token保存的位置
    // 如果文件不存在，創(chuàng)建
    if (!file.exists())
      file.createNewFile();
    // 如果文件大小等于0，說明第一次使用，存入Access_token
    if (file.length() == 0) {
      mAccess_token = getAccessToken();
      FileOutputStream fos = new FileOutputStream(file, false);// 不允許追加
      Access_token at = new Access_token();
      at.setAccess_token(mAccess_token);
      at.setExpires_in(System.currentTimeMillis() + "");
      String json = gson.toJson(at);
      fos.write((json).getBytes());
      fos.close();
    } else {
      // 讀取文件內(nèi)容
      FileInputStream fis = new FileInputStream(file);
      byte[] b = new byte[2048];
      int len = fis.read(b);
      String mJsonAccess_token = new String(b, 0, len);// 讀取到的文件內(nèi)容
      Access_token access_token = gson.fromJson(mJsonAccess_token,
          new Access_token().getClass());
      if (access_token.getExpires_in() != null) {
        long saveTime = Long.parseLong(access_token.getExpires_in());
        long nowTime = System.currentTimeMillis();
        long remianTime = nowTime - saveTime;
        // System.out.println(TAG + "時間差：" + remianTime);
        if (remianTime < MAX_TIME) {
          Access_token at = gson.fromJson(mJsonAccess_token,
              new Access_token().getClass());
          mAccess_token = at.getAccess_token();
        } else {
          mAccess_token = getAccessToken();
          FileOutputStream fos = new FileOutputStream(file, false);// 不允許追加
          Access_token at = new Access_token();
          at.setAccess_token(mAccess_token);
          at.setExpires_in(System.currentTimeMillis() + "");
          String json = gson.toJson(at);
          fos.write((json).getBytes());
          fos.close();
        }

      }
    }

    System.out.println("獲取到的Access_token是：" + mAccess_token);
  }

  /*
   * 獲取微信服務器AccessToken。該部分和getAccess_token() 一致，不再加注釋
   */
  public static String getAccessToken() {
    String urlString = "https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid="
        + APPID + "&secret=" + SECERT;
    String reslut = null;
    try {
      URL reqURL = new URL(urlString);
      HttpsURLConnection httpsConn = (HttpsURLConnection) reqURL
          .openConnection();
      InputStreamReader isr = new InputStreamReader(
          httpsConn.getInputStream());
      char[] chars = new char[1024];
      reslut = "";
      int len;
      while ((len = isr.read(chars)) != -1) {
        reslut += new String(chars, 0, len);
      }
      isr.close();
    } catch (IOException e) {

      e.printStackTrace();
    }
    Gson gson = new Gson();
    Access_token access_token = gson.fromJson(reslut,
        new Access_token().getClass());
    if (access_token.getAccess_token() != null) {
      return access_token.getAccess_token();
    } else {
      return null;
    }
  }