Question

我正在根据节点的元素解析rss feed并将其设置为bean对象。后来，我需要将它存储在bean的ArrayList中。看起来我在设置bean值时做错了，并且还将它添加到了Bean的ArrayList中。这是我的代码：

public static void main(String arg[]) {
  ArrayList<RssBean> list = new ArrayList<RssBean>(); 
  RssBean bean = new RssBean(null, null, null); 

 String xmlRecords =
  "<rss>" +"<channel>"+
  " <item>" +
  "   <title>John</title>" + 
  "   <description> Desc1 </description>"+
  " </item>" +
  " <item>" +
  "   <title>Sara</title>" + 
  "   <description> Desc2 </description>"+
  " </item>" + "</channel>"+
  "</rss>";

try {
    DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
    DocumentBuilder db = dbf.newDocumentBuilder();
    InputSource is = new InputSource();
    is.setCharacterStream(new StringReader(xmlRecords));

    Document doc = db.parse(is);
    NodeList nodes = doc.getElementsByTagName("item");

    // iterate the  items
    for (int i = 0; i < nodes.getLength(); i++) {
       Element element = (Element) nodes.item(i);

       NodeList title = element.getElementsByTagName("title");
       Element line = (Element) title.item(0);  
       bean.setTitle(getCharacterDataFromElement(line));

       NodeList description = element.getElementsByTagName("description");
       line = (Element) description.item(0); 
       bean.setDescription(getCharacterDataFromElement(line));

       list.add(bean);           
    } 

    //print list values
    ListIterator<RssBean> iter = list.listIterator() ;
    while(iter.hasNext()) 
    {
        RssBean result = (RssBean)iter.next();
        System.out.println(result);
    }

}
catch (Exception e) {
    e.printStackTrace();
} 
}

public static String getCharacterDataFromElement(Element e) {
Node child = e.getFirstChild();
if (child instanceof CharacterData) {
   CharacterData cd = (CharacterData) child;
   return cd.getData();
}
return "?";
}

当我打印出列表值时，我得到 - 列出值======＆gt; [RssBean @ 450cceb3，RssBean @ 450cceb3]这是不期望的。我需要将实际值存储在bean的数组列表中。 ArrayList显示对象而不是存储的实际值。你能纠正我的代码吗？

Answer 1

ArrayList不复制存储值，它只存储对添加对象的引用。因此，在您的代码中，您将一个bean实例放置三次。

如果问题仅在于复制打印项目中的值，则应更改代码以在每次循环迭代时创建新的bean实例

for (int i = 0; i < nodes.getLength(); i++) {
  RssBean bean = new RssBean(null, null, null);
  Element element = (Element) nodes.item(i);
  // ...
  list.add(bean)
}

但是如果你在打印bean字段时遇到问题，你应该在RssBean类中重写toString（）方法

@Override
public String toString() {
    return "Bean Values ======>" + getTitle + "&&" + getDesc();
}

Answer 2

您正在列表中添加对象，这就是打印对象“RssBean @ 450cceb3”的原因。

值存储在Objects中，您可以通过覆盖RssBean类中的toString（）方法来打印它。

更新您的RssBean，如：

public class RssBean {

    String title;
    String description;
    String value;

    public RssBean(String title, String description, String value) {
        this.title = title;
        this.description = description;
        this.value = value;
    }

    @Override
    public String toString() {
        StringBuilder result = new StringBuilder();

        result.append("Title: " + title);
        result.append("Description: " + description);
        result.append("Value: " + value);


        return result.toString();
    }
}

如何将nodevalues设置为Bean并添加到Bean的ArrayList

2 个答案: