检查某些元素是否有文本，然后只选择一个

Question

我正在尝试使用JSoup从Amazon中提取价格，但有两个不同的元素可以提取它。我可以从元素中的aria-tag属性中获取它，也可以从元素中的文本中获取它。最好，我总是想从aria-tag属性中获取它，但有时它不存在，所以我需要从第二个span类中提取它。我的问题是，如何创建一个if语句来检查属性是否有任何文本，然后如果没有，尝试从第二个span类中提取文本？

另外，我试图从名称相同的类中获取几个价格，但是当我编写 doc.select（“span.sx-price.sx-price.sx-价格-大”）.get（0）.text（） 时，没有任何弹出。

以下是我要从中提取项目的一个项目的 HTML 代码：

<a class="a-size-small a-link-normal a-text-normal" href="https://rads.stackoverflow.com/amzn/click/B01MZYYWUH">1</a></div>
<div class="a-row a-spacing-mini"><span class="a-size-small a-color-secondary a-text-bold">Product Description</span><br><span class="a-size-small a-color-secondary">... Cards Radeon&trade; <em>RX</em> 460 Graphics Cards Radeon&trade; R9 <em>390</em> Graphics Cards ...</span></div>
</div></div></div></div></div></div></li>
<li id="result_2" data-asin="B00IAAU6SS" class="s-result-item celwidget ">
   <div class="s-item-container">
   <div class="a-fixed-left-grid">
   <div class="a-fixed-left-grid-inner" style="padding-left:218px">
   <div class="a-fixed-left-grid-col a-col-left" style="width:218px;margin-left:-218px;_margin-left:-109px;float:left;">
      <div class="a-row">
         <div aria-hidden="true" class="a-column a-span12 a-text-center">
            <a class="a-link-normal a-text-normal" href="https://rads.stackoverflow.com/amzn/click/B00IAAU6SS"><img src="https://images-na.ssl-images-amazon.com/images/I/419c5Ci-UqL._AC_US218_.jpg" srcset="https://images-na.ssl-images-amazon.com/images/I/419c5Ci-UqL._AC_US218_.jpg 1x, https://images-na.ssl-images-amazon.com/images/I/419c5Ci-UqL._AC_US327_FMwebp_QL65_.jpg 1.5x, https://images-na.ssl-images-amazon.com/images/I/419c5Ci-UqL._AC_US436_FMwebp_QL65_.jpg 2x, https://images-na.ssl-images-amazon.com/images/I/419c5Ci-UqL._AC_US500_FMwebp_QL65_.jpg 2.2935x" width="218" height="218" alt="Product Details" class="s-access-image cfMarker" data-search-image-load></a>
            <div class="a-section a-spacing-none a-text-center"></div>
         </div>
      </div>
   </div>
   <div class="a-fixed-left-grid-col a-col-right" style="padding-left:2%;*width:97.6%;float:left;">
   <div class="a-row a-spacing-small">
      <div class="a-row a-spacing-none scx-truncate-medium sx-line-clamp-3 s-list-title-long">
         <a class="a-link-normal s-access-detail-page  s-color-twister-title-link a-text-normal" title="Arctic Accelero Xtreme IV 280(X) - High-End Graphics Card Cooler with Backside Cooler for Efficient RAM and VR-Cooling - DCACO-V930001-GBA01" href="https://rads.stackoverflow.com/amzn/click/B00IAAU6SS">
            <h2 data-attribute="Arctic Accelero Xtreme IV 280(X) - High-End Graphics Card Cooler with Backside Cooler for Efficient RAM and VR-Cooling - DCACO-V930001-GBA01" data-max-rows="3" class="a-size-medium s-inline  s-access-title  a-text-normal">Arctic Accelero Xtreme IV 280(X) - High-End Graphics Card Cooler with Backside Cooler for Efficient RAM and VR-Cooling - DCACO-V930001-GBA01</h2>
         </a>
      </div>
      <div class="a-row a-spacing-none"><span class="a-size-small a-color-secondary">by </span><span class="a-size-small a-color-secondary">ARCTIC</span></div>
   </div>
   <div class="a-row">
   <div class="a-column a-span7">
   <div class="a-row a-spacing-none"><a class="a-link-normal a-text-normal" href="https://rads.stackoverflow.com/amzn/click/B00IAAU6SS"><span aria-label="$85.99" class="a-color-base sx-zero-spacing"><span class="sx-price sx-price-large">
      <sup class="sx-price-currency">$</sup>
      <span class="sx-price-whole">85</span>
      <sup class="sx-price-fractional">99</sup>
      </span>
      </span></a><span class="a-letter-space"></span><i class="a-icon a-icon-prime a-icon-small s-align-text-bottom" aria-label="Prime"><span class="a-icon-alt">Prime</span></i>
   </div>
   <div class="a-row a-spacing-mini">
      <div class="a-row a-spacing-none"><span class="a-size-small a-color-secondary">FREE Shipping on eligible orders</span></div>
      <div class="a-row a-spacing-none"><span class="a-size-small a-color-price">Only 8 left in stock - order soon.</span></div>
   </div>
   <div class="a-row a-spacing-mini">
   <div class="a-row a-spacing-none">
      <div class="a-row a-spacing-mini"></div>
      <span class="a-size-small a-color-secondary">More Buying Choices</span>
   </div>
   <div class="a-row a-spacing-none">
   <a class="a-size-small a-link-normal a-text-normal" href="https://rads.stackoverflow.com/amzn/click/B00IAAU6SS"><span class="a-color-secondary a-text-strike"></span><span class="a-size-base a-color-base">$85.99</span>

Answer 1

根据您的示例，我们选择< code>span。之后，检查“selected”元素是否为< code>NULL，如果不是< code>NULL，则从子span的。

试试这个（它还没有被我测试过-只是由内存编写的（当然你需要先获取一个文档，我想你已经有了））：

try{
 Element span = doc.select("span.a-color-base.sx-zero-spacing").first();

 if(span != null) {
  System.out.println(span.attr("aria-label"));
 } else {
   Element beforeSep = doc.select("span.sx-price-whole").first();
   Element afterSep = doc.select("sup.sx-price-fractional").first();

   System.out.println(beforeSep.text() + "." + afterSep.text());
 }
} catch (Exception ex){
  // exception handler
}

Answer 2

我建议选择带有class. sx-price的元素，因为它的名称表明它包含价格。然后您可以选择需要aria-tag属性的父元素，使用简单的正则表达式检查它是否包含价格-如果为真，则直接从此属性中获取价格，否则从嵌套的子跨度中收集数据。

下面你可以找到一个我玩过的代码，工作得很好。

final Document doc = Jsoup.parse(html);

final Elements prices = doc.select(".sx-price");

final Pattern pattern = Pattern.compile("^\\$?([0-9]+)\\.([0-9]{2})$");

for (Element el : prices) {
    String price = "";
    if (el.parent().hasAttr("aria-label") && pattern.matcher(el.parent().attr("aria-label")).find()) {
        System.out.println("Extracting price from aria-label...");
        price = el.parent().attr("aria-label");

    } else {
        System.out.println("Extracting price from span body...");
        String currency = el.select(".sx-price-currency").text();
        String whole = el.select(".sx-price-whole").text();
        String fractional = el.select(".sx-price-fractional").text();

        price = String.format("%s%s.%s", currency, !whole.isEmpty() ? whole : "00", !fractional.isEmpty() ? fractional : "00");
    }

    System.out.println(price);
}

我希望有帮助。