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简析Java开发中的XML编程


IT168技术文档】 
    之后写XML的测试类,笔者把这个类命名为XMLTest,为了读写XML文件,需要导入如下JAVA包,"//"后为注释说明,笔者的环境是JDK 1.3.1_04,在JDK 1.4.0中测试也通过,XML解释器用Apache的Crimson,可以到Apache主页去上载。 
import java.io.*; //Java基础包,包含各种IO操作  import java.util.*; //Java基础包,包含各种标准数据结构操作  import javax.xml.parsers.*; //XML解析器接口  import org.w3c.dom.*; //XML的DOM实现  import org.apache.crimson.tree.XmlDocument;//写XML文件要用到 
    为了保存多个学生信息,还得借助一个集合类(并不是单纯意义上的集合,JAVA中的集合是集合框架的概念,包含向量、列表、哈希表等),这里采用Vector向量类。定义在XMLTest测试类中,命名为student_Vector。然后定义两个方法readXMLFile和writeXMLFile,实现读写操作。代码如下: 
private void readXMLFile(String inFile) throws Exception {   //为解析XML作准备,创建DocumentBuilderFactory实例,指定DocumentBuilder   DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();   DocumentBuilder db = null;   try {    db = dbf.newDocumentBuilder();   }catch (ParserConfigurationException pce) {    System.err.println(pce); //出异常时输出异常信息,然后退出,下同    System.exit(1);   }   Document doc = null;   try {    doc = db.parse(inFile);   } catch (DOMException dom) {    System.err.println(dom.getMessage());    System.exit(1);   } catch (IOException ioe) {    System.err.println(ioe);    System.exit(1);   }   //下面是解析XML的全过程,比较简单,先取根元素"学生花名册"   Element root = doc.getDocumentElement();   //取"学生"元素列表   NodeList students = root.getElementsByTagName("学生");   for (int i = 0; i < students.getLength(); i++) {    //依次取每个"学生"元素    Element student = (Element) students.item(i);    //创建一个学生的Bean实例    StudentBean studentBean = new StudentBean();    //取学生的性别属性    studentBean.setSex(student.getAttribute("性别"));    //取"姓名"元素,下面类同    NodeList names = student.getElementsByTagName("姓名");    if (names.getLength() == 1) {     Element e = (Element) names.item(0);     Text t = (Text) e.getFirstChild();     studentBean.setName(t.getNodeValue());    }    NodeList ages = student.getElementsByTagName("年龄");    if (ages.getLength() == 1) {     Element e = (Element) ages.item(0);     Text t = (Text) e.getFirstChild();     studentBean.setAge(Integer.parseInt(t.getNodeValue()));    }    NodeList phones = student.getElementsByTagName("电话");    if (phones.getLength() == 1) {     Element e = (Element) phones.item(0);     Text t = (Text) e.getFirstChild();     studentBean.setPhone(t.getNodeValue());    }    student_Vector.add(studentBean);   }  } 
private void writeXMLFile(String outFile) throws Exception {   //为解析XML作准备,创建DocumentBuilderFactory实例,指定DocumentBuilder   DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();   DocumentBuilder db = null;   try {    db = dbf.newDocumentBuilder();   } catch (ParserConfigurationException pce) {    System.err.println(pce);    System.exit(1);   }   Document doc = null;   doc = db.newDocument();   //下面是建立XML文档内容的过程,先建立根元素"学生花名册"   Element root = doc.createElement("学生花名册");   //根元素添加上文档   doc.appendChild(root);   //取学生信息的Bean列表   for (int i = 0; i < student_Vector.size(); i++) {    //依次取每个学生的信息    StudentBean studentBean = (StudentBean) student_Vector.get(i);    //建立"学生"元素,添加到根元素    Element student = doc.createElement("学生");    student.setAttribute("性别", studentBean.getSex());    root.appendChild(student);    //建立"姓名"元素,添加到学生下面,下同    Element name = doc.createElement("姓名");    student.appendChild(name);    Text tName = doc.createTextNode(studentBean.getName());    name.appendChild(tName);    Element age = doc.createElement("年龄");    student.appendChild(age);    Text tAge = doc.createTextNode(String.valueOf(studentBean.getAge()));    age.appendChild(tAge);    Element phone = doc.createElement("电话");    student.appendChild(phone);    Text tPhone = doc.createTextNode(studentBean.getPhone());     phone.appendChild(tPhone);   }   //把XML文档输出到指定的文件   FileOutputStream outStream = new FileOutputStream(outFile);   OutputStreamWriter outWriter = new OutputStreamWriter(outStream);   ((XmlDocument) doc).write(outWriter, "GB2312");   outWriter.close();   outStream.close();   } 

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