小编Win*_*dle的帖子

我想循环遍历每个XML打印的所有元素.我的问题是我在staff1标签后不断获得空指针异常,即john 465456433 gmail1 area1 city1

这是我的Java代码,用于打印xml文件中的所有元素:

File fXmlFile = new File("file.xml");
DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
Document doc = dBuilder.parse(fXmlFile);

doc.getDocumentElement().normalize();

System.out.println("Root element :" + doc.getDocumentElement().getNodeName());

NodeList nList = doc.getElementsByTagName("*");

System.out.println("----------------------------");

Node n=null;
Element eElement=null;

for (int i = 0; i < nList.getLength(); i++) {           
  System.out.println(nList.getLength());     
  n= nList.item(i);                            
  System.out.println("\nCurrent Element :" + n.getNodeName());


  if (n.getNodeType() == Node.ELEMENT_NODE) {
    eElement = (Element) n.getChildNodes();
    System.out.println("\nCurrent Element :" + n.getNodeName());
    name = eElement.getElementsByTagName("name").item(i).getTextContent(); //here throws null pointer …

我有一个servlet,传递给查询参数,从DAO获取对象列表,将列表转换为JSON,并将其发送回响应中.每个列表都由具有方法的对象组成:

public String getAsJson(){...}

servlet有一堆看似简单的方法:

private String getUserListAsJson() {
    List<User> userList = this.dao.getUsers();
    StringBuilder builder = new StringBuilder();
    builder.append('[');
    // loops over the list appending the value of each objects getAsJson()
    builder.append(']');
    return builder.toString();
}

问题是我有大约6种方法(并且还在增长),除了不同的DAO查询外,它们看起来完全一样.我的想法是创建一个只有getAsJson()方法定义的接口,让每个bean实现它,然后在servlet中有另一个方法来接受实现该接口的对象.结束看起来像这样:

public Interface JsonEnabled {
    public String getAsJson();
}

public class User implements JsonEnabled {
    ....
    @Override
    public String getAsJson() {...}
}

public class TheServlet {
    ...
    private String getUserListAsJson() {
        List<User> userList = this.dao.getUsers();
        return this.getListAsJson(userList);
    }
    private String getListAsJson(List<? implements JsonEnabled> list) { …

我正在尝试将列表框1中的选定项目移动到列表框2,反之亦然.我有两个按钮,>>和<<.当我在listbox1中选择项目然后单击>>项目应该从listbox1移动到listbox2.

private void MoveListBoxItems(ListBox source, ListBox destination)
{
    ListBox.SelectedObjectCollection sourceItems = source.SelectedItems;
    foreach (var item in sourceItems)
    {
        destination.Items.Add(item);
    }
    while (source.SelectedItems.Count > 0)
    {
        source.Items.Remove(source.SelectedItems[0]);
    }
}

private void button2_Click_1(object sender, EventArgs e)
{
    MoveListBoxItems(listbox , lstActivity);
}

这是标题DIV的CSS:

#header { 
  display: block;
  float: left;
  min-width: 100%;
  min-height: 170px;
  height: auto; 
  background-color: #030309; 
  background-color: #191718; 
  position:fixed; 
  margin-top: -210px; 
  z-index: 999999; 
  opacity:.76;
  -webkit-transition: opacity 1s ease-in-out;
  -moz-transition: opacity 1s ease-in-out;
  -o-transition: opacity 1s ease-in-out;
  -ms-transition: opacity 1s ease-in-out;
  transition: opacity 1s ease-in-out;
  top: 0;
}

这是为了悬停状态:

#header:hover { 
  display:block; 
  opacity:1;
  -webkit-transition: opacity 1s ease-in-out;
  -moz-transition: opacity 1s ease-in-out;
  -o-transition: opacity 1s ease-in-out;
  -ms-transition: opacity 1s ease-in-out;   
  transition: opacity 1s ease-in-out;
}

我想做什么,所以标题默认隐藏,并在它悬停时出现.我试着添加display: none上#header和display:block;上 …