J2EE—— 第 6 章 Document Object Model (DO

M)

文档与数据 DOM, JDOM, dom4j 区别

存在于层次结构中的节点的种类 “ 混和内容”的能力

混和内容模型<sentence>This is an <bold>important</bold> idea.</sentence>ELEMENT: sentence

+ TEXT: This is an + ELEMENT: bold

+ TEXT: important + TEXT: idea

第一个节点： nodeName()=sentence nodeValue()=null第二个节点： nodeName()=#text nodeValue()=This is an

更简单的模型 DOM(org.w3c.dom.Element)element.getChildNodes().item(0).getNodeValue(); JDOM, dom4j(org.jdom.Element, org.dom4j.Elemen

t)element.getText();

<addressbook><entry>Fred

<email>fred@home</email></entry>...

</addressbook>

增加复杂性<sentence>

The &projectName; <![CDATA[<i>project</i>]]> is <?editor: red?><bold>important</bold><?editor: normal?>.

</sentence> + ELEMENT: sentence + TEXT: The + ENTITY REF: projectName + COMMENT: The latest name we're using + TEXT: Eagle + CDATA: <i>project</i> + TEXT: is + PI: editor: red + ELEMENT: bold + TEXT: important + PI: editor: normal

健壮的 DOM 程序的必要任务 在搜索元素时

忽略注释、属性和处理指令 允许子元素不以预期的顺序出现 跳过哪些包含可忽略的空格的 TEXT 节点

在为节点提取文本时 从 CDATA 节点提取文本，就像从文本节点提取文

本一样 在收集文本时，忽略注释、属性和处理指令 如果碰到了实体引用节点或其他元素节点，则进行

递归（即，将文本提取过程施加于所有子节点）

选择模型 DOM

成熟的文档 复杂的应用程序 使用 Schema 同时处理文档和数据

JDOM, dom4j 简单的数据类型

将 XML 读到 DOM 中import javax.xml.parsers.DocumentBuilder;import javax.xml.parsers.DocumentBuilderFactory;import javax.xml.parsers.FactoryConfigurationError;import javax.xml.parsers.ParserConfigurationException;import org.xml.sax.SAXException;import org.xml.sax.SAXParseException;import java.io.File;import java.io.IOException;import org.w3c.dom.Document;import org.w3c.dom.DOMException;DocumentBuilderFactory factory =

DocumentBuilderFactory.newInstance();DocumentBuilder builder = factory.newDocumentBuilder();document = builder.parse( new File(argv[0]) );

其它信息factory.setValidating(true); factory.setNamespaceAware(true);builder.setErrorHandler( new org.xml.sax.ErrorHandler() {

// ignore fatal errors (an exception is guaranteed) public void fatalError(SAXParseException exception) throws SAXException { } // treat validation errors as fatalpublic void error(SAXParseException e) throws SAXParseException {

throw e;}

} );

创建适配器显示 JTree 中的 DOM

public class AdapterNode {

org.w3c.dom.Node domNode;public AdapterNode(org.w3c.dom.Node node) { domNode = node; } public String toString() {

String s = typeName[domNode.getNodeType()]; String nodeName = domNode.getNodeName();if (! nodeName.startsWith("#")) { s += ": " + nodeName; } if (domNode.getNodeValue() != null) {

if (s.startsWith("ProcInstr")) s += ", "; else s += ": "; String t = domNode.getNodeValue().trim();int x = t.indexOf("\n");if (x >= 0) t = t.substring(0, x);s += t;

}return s;

}}

检查 DOM 的结构

DOCTYPE 节点

处理指令节点

实体引用

factory.setExpandEntityReference(false)

CDATA 节点

词汇控制 setCoalescing(): 将 CDATA 段转换为 Text 节

点，并追加到一个相邻的 Text 节点 setExpandEntityReference(): 扩展实体引用

节点 setIgnoringComments(): 忽略注释 setIgnoringElementContentWhiteSpace():

忽略并非元素内容的重要组成部分的那些空格

创建 DOMDocumentBuilderFactory factory =

DocumentBuilderFactory.newInstance();DocumentBuilder builder = factory.newDocumentBuilder();document = builder.newDocument(); Element root = (Element) document.createElement("rootEleme

nt");document.appendChild(root); root.appendChild(document.createTextNode("Some") );root.appendChild(document.createTextNode(" ") );root.appendChild(document.createTextNode("text") );document.getDocumentElement().normalize();

遍历节点 getFirstChild getLastChild getNextSibling getPreviousSibling getParentNode

搜索节点public Node findSubNode(String name, Node node) {

if (node.getNodeType() != Node.ELEMENT_NODE) {System.err.println("Error: Search node not of element type");System.exit(22);

}if (! node.hasChildNodes()) return null; NodeList list = node.getChildNodes(); for (int i=0; i < list.getLength(); i++) {

Node subnode = list.item(i); if (subnode.getNodeType() == Node.ELEMENT_NODE) {

if (subnode.getNodeName().equals(name)) return subnode;

} } return null;

}

获取节点内容public String getText(Node node) {

StringBuffer result = new StringBuffer();if (! node.hasChildNodes()) return "";NodeList list = node.getChildNodes(); for (int i=0; i < list.getLength(); i++) {

Node subnode = list.item(i); if (subnode.getNodeType() == Node.TEXT_NODE) {

result.append(subnode.getNodeValue()); } else if (subnode.getNodeType() == Node.CDATA_SECTION_NODE) {

result.append(subnode.getNodeValue()); } else if (subnode.getNodeType() == Node.ENTITY_REFERENCE_NODE) {

result.append(getText(subnode)); }

} return result.toString();

}

其它操作 创建属性： setAttribute 删除节点： removeChild 修改节点： replaceChild, setNodeValu

e

用 XML Schema 验证static final String JAXP_SCHEMA_LANGUAGE = "http://java.sun.

com/xml/jaxp/properties/schemaLanguage"; static final String W3C_XML_SCHEMA ="http://www.w3.org/2001/XMLSchema";factory.setNamespaceAware(true);factory.setValidating(true);try {

factory.setAttribute(JAXP_SCHEMA_LANGUAGE, W3C_XML_SCHEMA);

} catch (IllegalArgumentException x) { }

将文档与 Schema 关联起来<documentRoot xmlns:xsi="http://www.w3.org/2001/XMLSchema-insta

nce" xsi:noNamespaceSchemaLocation=‘YourSchemaDefinition.xsd'> static final String schemaSource = "YourSchemaDefinition.xsd"; static final String JAXP_SCHEMA_SOURCE =

"http://java.sun.com/xml/jaxp/properties/schemaSource";DocumentBuilderFactory factory = DocumentBuilderFactory.newInstanc

e()factory.setAttribute(JAXP_SCHEMA_SOURCE, new File(schemaSource));

用多个名称空间验证<documentRoot xmlns:xsi="http://www.w3.org/2001/XMLSchema-instanc

e" xsi:noNamespaceSchemaLocation="employeeDatabase.xsd" xsi:schemaLocation= "http://www.irs.gov/ fullpath/w2TaxForm.xsd http://www.ourcompany.com/ relpath/hiringForm.xsd" xmlns:tax="http://www.irs.gov/" xmlns:hiring="http://www.ourcompany.com/">

static final String employeeSchema = "employeeDatabase.xsd";static final String taxSchema = "w2TaxForm.xsd";static final String hiringSchema = "hiringForm.xsd";static final String[] schemas = { employeeSchema, taxSchema, hiringSchem

a,}; static final String JAXP_SCHEMA_SOURCE ="http://java.sun.com/xml/jaxp/properties/schemaSource";DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance() factory.setAttribute(JAXP_SCHEMA_SOURCE, schemas);