DOM介绍
DOM(Document Object Model)解析是官方提供的XML解析方式之一，使用时无需引入第三方包，代码编写简单，方便修改树结构，但是由于DOM解析时是将整个XML文件加载到内存中进行解析，因此当XML文件较大时，使用DOM解析效率会降低，而且可能造成内存溢出。
XML生成
代码如下：
public static void write() {
//文档构建工厂
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
try {
//文档构建器
DocumentBuilder builder = dbf.newDocumentBuilder();
//文档
Document doc = builder.newDocument();
//设置xml文件是否独立
doc.setXmlStandalone(true);
//设置xml文件版本,默认1.0
doc.setXmlVersion("1.1");
//创建根目录节点
Element root = doc.createElement("conpany");
//设置节点属性
root.setAttribute("name", "hd");
//添加根节点
doc.appendChild(root);
Element department = doc.createElement("department");
department.setAttribute("name", "test");
//设置节点文本
department.setTextContent("123456");
//添加到根节点
root.appendChild(department);
// 工厂类，用来获取转换对象
TransformerFactory transFactory = TransformerFactory.newInstance();
//转化对象
Transformer transFormer = transFactory.newTransformer();
// 设置文档自动换行
transFormer.setOutputProperty(OutputKeys.INDENT, "yes");
//设置编码方式，默认UTF-8
//transFormer.setOutputProperty(OutputKeys.ENCODING, "GB2312");
//文件源
DOMSource domSource = new DOMSource(doc);
File file = new File("src/doc-write.xml");
if (file.exists()) {
file.delete();
}
file.createNewFile();
//输出文件流
FileOutputStream out = new FileOutputStream(file);
//结果流
StreamResult xmlResult = new StreamResult(out);
//转化
transFormer.transform(domSource, xmlResult);
System.out.println("创建生成文件位置===========" + file.getAbsolutePath());
} catch (Exception e) {
e.printStackTrace();
}
}
输出：创建生成文件位置===========D:\workspace\test-xml\src\doc-write.xml
doc-write.xml的内容：
XML解析
需要在src目录中，先存放一个test.xml文件
<?xml version="1.0" encoding="UTF-8"?>
<conpany name="hd">
<department name="department1">
<employee name="employee1" id="1">123</employee>
</department>
<department name="department2">
<employee name="employee2" id="2">321</employee>
<employee name="employee3" id="3"></employee>
</department>
<department name="department3">
</department>
</conpany>
新建一个TestDom的java类，里面写一个read方法，代码如下：
public static void read() {
DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
try {
DocumentBuilder builder = builderFactory.newDocumentBuilder();
//输入流
InputStream is = TestDom.class.getClassLoader().getResourceAsStream("test.xml");
//文档构建器解析，得到文档
Document doc = builder.parse(is);
//获取根目录，元素
Element root = doc.getDocumentElement();
if (root == null) return;
//获取元素名字
System.out.print(root.getNodeName());
//获取元素属性name的值
System.out.println("\t" + root.getAttribute("name"));
//获取根元素下的子节点，此方法获取节点（节点包括：标签间的文本，和空白部分）
NodeList departmentNodes = root.getChildNodes();
if (departmentNodes == null) return;
//遍历节点
for (int i = 0; i < departmentNodes.getLength(); i++) {
Node department = departmentNodes.item(i);
if (department != null && department.getNodeType() == Node.ELEMENT_NODE) {//非空白文本标签
//获取节点名字
System.out.print("\t" + department.getNodeName());
//先获取节点属性集，再获取属性name的值
System.out.println("\t" + department.getAttributes().getNamedItem("name").getNodeValue());
//获取节点下面的所有子节点
NodeList employees = department.getChildNodes();
if (employees == null) continue;
for (int j = 0; j < employees.getLength(); j++) {
Node employee = employees.item(j);
if (employee != null && employee.getNodeType() == Node.ELEMENT_NODE) {
System.out.print("\t" + "\t" + employee.getNodeName());
System.out.print("\t" + employee.getAttributes().getNamedItem("id").getNodeValue());
System.out.print("\t" + employee.getAttributes().getNamedItem("name").getNodeValue());
System.out.println("\t" + employee.getTextContent().trim());
}
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
XML修改
新建一个TestDom的java类，里面写一个update方法，代码如下：
public static void update() {
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
try {
DocumentBuilder builder = dbf.newDocumentBuilder();
InputStream is = TestDom.class.getClassLoader().getResourceAsStream("test.xml");
Document doc = builder.parse(is);
Element root = doc.getDocumentElement();
if (root == null) return;
// 修改属性
root.setAttribute("name", "hd2");
NodeList departmentNodes = root.getChildNodes();
if (departmentNodes != null) {
for (int i = 0; i < departmentNodes.getLength() - 1; i++) {
Node department = departmentNodes.item(i);
if (department.getNodeType() == Node.ELEMENT_NODE) {
String departmentName = department.getAttributes().getNamedItem("name").getNodeValue();
if ("department3".equals(departmentName)) {
// 删除节点
root.removeChild(department);
} else if ("department2".equals(departmentName)) {
//新增节点
Element newChild = doc.createElement("employee");
newChild.setAttribute("name", "employee4");
newChild.setTextContent("44444");
department.appendChild(newChild);
}
}
}
}
TransformerFactory transFactory = TransformerFactory.newInstance();
Transformer transFormer = transFactory.newTransformer();
transFormer.setOutputProperty(OutputKeys.INDENT, "yes");
DOMSource domSource = new DOMSource(doc);
File file = new File("src/dom-test.xml");
if (file.exists()) {
file.delete();
}
file.createNewFile();
FileOutputStream out = new FileOutputStream(file);
StreamResult xmlResult = new StreamResult(out);
transFormer.transform(domSource, xmlResult);
System.out.println("修改生成文件位置===========" + file.getAbsolutePath());
} catch (Exception e) {
e.printStackTrace();
}
}
}
输出：修改生成文件位置===========D:\workspace\test-xml\src\dom-test.xml
doc-test.xml的内容：