JAVA解析XML的四種方法

XML現在已經成爲一種通用的數據交換格式,它的平臺無關性,語言無關性,系統無關性,給數據集成與交互帶來了極大的方便。對於XML本身的語法知識與技 術細節,需要閱讀相關的技術文獻,這裏麪包括的內容有DOM(Document Object Model),DTD(Document Type Definition),SAX(Simple API for XML),XSD(Xml Schema Definition),XSLT(Extensible Stylesheet Language Transformations),具體可參閱w3c官方網站文檔http://www.w3.org獲取更多信息。
XML在不同的語言裏解析方式都是一樣的,只不過實現的語法不同而已。基本的解析方式有兩種,一種叫SAX，另一種叫DOM。SAX是基於事件流的解析,DOM是基於XML文檔樹結構的解析。假設我們XML的內容和結構如下:

<?xml version="1.0" encoding="UTF-8"?>
<employees>
<employee>
    <name>ddviplinux</name>
    <sex>m</sex>
    <age>30</age>
</employee>
</employees>


本文使用JAVA語言來實現DOM與SAX的XML文檔生成與解析。
首先定義一個操作XML文檔的接口XmlDocument 它定義了XML文檔的建立與解析的接口。

package com.alisoft.facepay.framework.bean;
/**
*
* @author hongliang.dinghl
* 定義XML文檔建立與解析的接口
*/
public interface XmlDocument {
/**
* 建立XML文檔
* @param fileName 文件全路徑名稱
*/
public void createXml(String fileName);
/**
* 解析XML文檔
* @param fileName 文件全路徑名稱
*/
public void parserXml(String fileName);
}


1.DOM生成和解析XML文檔
爲 XML 文檔的已解析版本定義了一組接口。解析器讀入整個文檔，然後構建一個駐留內存的樹結構，然後代碼就可以使用 DOM 接口來操作這個樹結構。優點：整個文檔樹在內存中，便於操作；支持刪除、修改、重新排列等多種功能；缺點：將整個文檔調入內存（包括無用的節點），浪費時 間和空間；使用場合：一旦解析了文檔還需多次訪問這些數據；硬件資源充足（內存、CPU）。
package com.alisoft.facepay.framework.bean;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;
/**
*
* @author hongliang.dinghl
* DOM生成與解析XML文檔
*/
public class DomDemo implements XmlDocument {

private Document document;

private String fileName;

public void init() {
try {
DocumentBuilderFactory factory = DocumentBuilderFactory
.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
this.document = builder.newDocument();
} catch (ParserConfigurationException e) {
System.out.println(e.getMessage());
}
}

public void createXml(String fileName) {

Element root = this.document.createElement("employees");
this.document.appendChild(root);
Element employee = this.document.createElement("employee");
Element name = this.document.createElement("name");
name.appendChild(this.document.createTextNode("丁宏亮"));
employee.appendChild(name);
Element sex = this.document.createElement("sex");
sex.appendChild(this.document.createTextNode("m"));
employee.appendChild(sex);
Element age = this.document.createElement("age");
age.appendChild(this.document.createTextNode("30"));
employee.appendChild(age);
root.appendChild(employee);

TransformerFactory tf = TransformerFactory.newInstance();
try {
Transformer transformer = tf.newTransformer();
DOMSource source = new DOMSource(document);
transformer.setOutputProperty(OutputKeys.ENCODING, "gb2312");
transformer.setOutputProperty(OutputKeys.INDENT, "yes");
PrintWriter pw = new PrintWriter(new FileOutputStream(fileName));
StreamResult result = new StreamResult(pw);
transformer.transform(source, result);
System.out.println("生成XML文件成功!");
} catch (TransformerConfigurationException e) {

System.out.println(e.getMessage());
} catch (IllegalArgumentException e) {

System.out.println(e.getMessage());
} catch (FileNotFoundException e) {

System.out.println(e.getMessage());
} catch (TransformerException e) {

System.out.println(e.getMessage());
}

}

public void parserXml(String fileName) {
try {
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
Document document = db.parse(fileName);
NodeList employees = document.getChildNodes();
for (int i = 0; i < employees.getLength(); i++) {
Node employee = employees.item(i);
NodeList employeeInfo = employee.getChildNodes();
for (int j = 0; j < employeeInfo.getLength(); j++) {
Node node = employeeInfo.item(j);
NodeList employeeMeta = node.getChildNodes();
for (int k = 0; k < employeeMeta.getLength(); k++) {
System.out.println(employeeMeta.item(k).getNodeName()
+ ":" + employeeMeta.item(k).getTextContent());
}
}
}
System.out.println("解析完畢");
} catch (FileNotFoundException e) {
System.out.println(e.getMessage());
} catch (ParserConfigurationException e) {
System.out.println(e.getMessage());
} catch (SAXException e) {
System.out.println(e.getMessage());
} catch (IOException e) {
System.out.println(e.getMessage());
}

}


}

2.SAX生成和解析XML文檔
爲解決DOM的問題，出現了SAX。SAX ，事件驅動。當解析器發現元素開始、元素結束、文本、文檔的開始或結束等時，發送事件，程序員編寫響應這些事件的代碼，保存數據。優點：不用事先調入整個 文檔，佔用資源少；SAX解析器代碼比DOM解析器代碼小，適於Applet，下載。缺點：不是持久的；事件過後，若沒保存數據，那麼數據就丟了；無狀態 性；從事件中只能得到文本，但不知該文本屬於哪個元素；使用場合：Applet;只需XML文檔的少量內容，很少回頭訪問；機器內存少；

 

package
 com.alisoft.facepay.framework.bean;

import
 java.io.FileInputStream;
import
 java.io.FileNotFoundException;
import
 java.io.IOException;
import
 java.io.InputStream;

import
 javax.xml.parsers.ParserConfigurationException;
import
 javax.xml.parsers.SAXParser;
import
 javax.xml.parsers.SAXParserFactory;

import
 org.xml.sax.Attributes;
import
 org.xml.sax.SAXException;
import
 org.xml.sax.helpers.DefaultHandler;
/**
 *
 * @author hongliang.dinghl
 * SAX文檔解析
 */
public
 
class
 SaxDemo 
implements
 XmlDocument {

    public
 
void
 createXml(String fileName) {
         System.out.println("<<"
+filename+
">>"
);
     }

    public
 
void
 parserXml(String fileName) {
         SAXParserFactory saxfac = SAXParserFactory.newInstance();

        try
 {

             SAXParser saxparser = saxfac.newSAXParser();

             InputStream is = new
 FileInputStream(fileName);

             saxparser.parse(is, new
 MySAXHandler());

         } catch
 (ParserConfigurationException e) {

             e.printStackTrace();

         } catch
 (SAXException e) {

             e.printStackTrace();

         } catch
 (FileNotFoundException e) {

             e.printStackTrace();

         } catch
 (IOException e) {

             e.printStackTrace();

         }

     }

}

class
 MySAXHandler 
extends
 DefaultHandler {

    boolean
 hasAttribute = 
false
;

     Attributes attributes = null
;

    public
 
void
 startDocument() 
throws
 SAXException {

         System.out.println("文檔開始打印了"
);

     }

    public
 
void
 endDocument() 
throws
 SAXException {

         System.out.println("文檔打印結束了"
);

     }

    public
 
void
 startElement(String uri, String localName, String qName,

     Attributes attributes) throws
 SAXException {

        if
 (qName.equals(
"employees"
)) {

            return
;

         }

        if
 (qName.equals(
"employee"
)) {

             System.out.println(qName);

         }

        if
 (attributes.getLength() > 
0
) {

            this
.attributes = attributes;

            this
.hasAttribute = 
true
;

         }

     }

    public
 
void
 endElement(String uri, String localName, String qName)

    throws
 SAXException {

        if
 (hasAttribute && (attributes != 
null
)) {

            for
 (
int
 i = 
0
; i < attributes.getLength(); i++) {

                 System.out.println(attributes.getQName(0
)
                         + attributes.getValue(0
));

             }

         }

     }

    public
 
void
 characters(
char
[] ch, 
int
 start, 
int
 length)

    throws
 SAXException {

         System.out.println(new
 String(ch, start, length));

     }

}