code: public String execute() throws IOException {
  
          if (CBStringUtil.isEmptyOrNull(this.url)) {
              return null;
          }
  
          StringBuilder netString = new StringBuilder();
          URL url = new URL(this.url);
          HttpURLConnection conn = (HttpURLConnection) url.openConnection();
  
          //设置请求方法
          conn.setRequestMethod(method.value);
  
          //设置头部
          for (Map.Entry<String, String> item : header.entrySet()) {
              conn.setRequestProperty(item.getKey(), item.getValue());
          }
  
          //保持session的把设置cookie
          if (keepSession && !CBStringUtil.isEmptyOrNull(cookie) && !header.containsKey(CBHeader.COOKIE)
                  && !pauseSessionForOnce) {
              conn.setRequestProperty(CBHeader.COOKIE, cookie);
          }
  
          pauseSessionForOnce = false;
  
          //设置超时时间
          conn.setConnectTimeout(timeout);
          conn.setReadTimeout(timeout);
  
          //设置跳转
          conn.setInstanceFollowRedirects(followRedirects);
  
          if (method == CBMethod.POST && !CBStringUtil.isEmptyOrNull(data)) {
              conn.setDoOutput(true);
              OutputStream out = conn.getOutputStream();
              out.write(data.getBytes());
              out.flush();
              out.close();
          }
          BufferedReader buff = new BufferedReader(new InputStreamReader(
                  conn.getInputStream(), charset));
          String line;
          while ((line = buff.readLine()) != null) {
              netString.append("\n");
              netString.append(line);
          }
          buff.close();
  
          //记录cookie值,用于下次传递
          String tmpCookie = conn.getHeaderField(CBHeader.SET_COOKIE);
          if (keepSession && CBStringUtil.isEmptyOrNull(cookie) && !CBStringUtil.isEmptyOrNull(tmpCookie)) {
              cookie = tmpCookie;
          }
          return netString.length() > 0 ? netString.substring(1) : netString.toString();
      }
docs: 获取网页的内容
  
  @return 网页/目标源码
  @throws IOException 异常