blocks|key|785950|text|下面是一个快速的DOM示例，它展示了如何使用其dtd读写一个简单的xml文件：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|785951|<?xml+version="1.0"+encoding="UTF-8"+standalone="no"?>
<!DOCTYPE+roles+SYSTEM+"roles.dtd">
<roles>
++++<role1>User</role1>
++++<role2>Author</role2>
++++<role3>Admin</role3>
++++<role4/>
</roles>|code-block|syntax|javascript|785952|和dtd：|785953|<?xml+version="1.0"+encoding="UTF-8"?>
<!ELEMENT+roles+(role1,role2,role3,role4)>
<!ELEMENT+role1+(#PCDATA)>
<!ELEMENT+role2+(#PCDATA)>
<!ELEMENT+role3+(#PCDATA)>
<!ELEMENT+role4+(#PCDATA)>|785954|首先导入以下内容：|785955|import+javax.xml.parsers.*;
import+javax.xml.transform.*;
import+javax.xml.transform.dom.*;
import+javax.xml.transform.stream.*;
import+org.xml.sax.*;
import+org.w3c.dom.*;|785956|以下是您需要的几个变量：|785957|private+String+role1+=+null;
private+String+role2+=+null;
private+String+role3+=+null;
private+String+role4+=+null;
private+ArrayList<String>+rolev;|785958|下面是一个阅读器(字符串xml是您的xml文件的名称)：|785959|public+boolean+readXML(String+xml)+{
++++++++rolev+=+new+ArrayList<String>();
++++++++Document+dom;
++++++++//+Make+an++instance+of+the+DocumentBuilderFactory
++++++++DocumentBuilderFactory+dbf+=+DocumentBuilderFactory.newInstance();
++++++++try+{
++++++++++++//+use+the+factory+to+take+an+instance+of+the+document+builder
++++++++++++DocumentBuilder+db+=+dbf.newDocumentBuilder();
++++++++++++//+parse+using+the+builder+to+get+the+DOM+mapping+of+the++++
++++++++++++//+XML+file
++++++++++++dom+=+db.parse(xml);

++++++++++++Element+doc+=+dom.getDocumentElement();

++++++++++++role1+=+getTextValue(role1,+doc,+"role1");
++++++++++++if+(role1+!=+null)+{
++++++++++++++++if+(!role1.isEmpty())
++++++++++++++++++++rolev.add(role1);
++++++++++++}
++++++++++++role2+=+getTextValue(role2,+doc,+"role2");
++++++++++++if+(role2+!=+null)+{
++++++++++++++++if+(!role2.isEmpty())
++++++++++++++++++++rolev.add(role2);
++++++++++++}
++++++++++++role3+=+getTextValue(role3,+doc,+"role3");
++++++++++++if+(role3+!=+null)+{
++++++++++++++++if+(!role3.isEmpty())
++++++++++++++++++++rolev.add(role3);
++++++++++++}
++++++++++++role4+=+getTextValue(role4,+doc,+"role4");
++++++++++++if+(+role4+!=+null)+{
++++++++++++++++if+(!role4.isEmpty())
++++++++++++++++++++rolev.add(role4);
++++++++++++}
++++++++++++return+true;

++++++++}+catch+(ParserConfigurationException+pce)+{
++++++++++++System.out.println(pce.getMessage());
++++++++}+catch+(SAXException+se)+{
++++++++++++System.out.println(se.getMessage());
++++++++}+catch+(IOException+ioe)+{
++++++++++++System.err.println(ioe.getMessage());
++++++++}

++++++++return+false;
++++}|785960|下面是一位作家：|785961|public+void+saveToXML(String+xml)+{
++++Document+dom;
++++Element+e+=+null;

++++//+instance+of+a+DocumentBuilderFactory
++++DocumentBuilderFactory+dbf+=+DocumentBuilderFactory.newInstance();
++++try+{
++++++++//+use+factory+to+get+an+instance+of+document+builder
++++++++DocumentBuilder+db+=+dbf.newDocumentBuilder();
++++++++//+create+instance+of+DOM
++++++++dom+=+db.newDocument();

++++++++//+create+the+root+element
++++++++Element+rootEle+=+dom.createElement("roles");

++++++++//+create+data+elements+and+place+them+under+root
++++++++e+=+dom.createElement("role1");
++++++++e.appendChild(dom.createTextNode(role1));
++++++++rootEle.appendChild(e);

++++++++e+=+dom.createElement("role2");
++++++++e.appendChild(dom.createTextNode(role2));
++++++++rootEle.appendChild(e);

++++++++e+=+dom.createElement("role3");
++++++++e.appendChild(dom.createTextNode(role3));
++++++++rootEle.appendChild(e);

++++++++e+=+dom.createElement("role4");
++++++++e.appendChild(dom.createTextNode(role4));
++++++++rootEle.appendChild(e);

++++++++dom.appendChild(rootEle);

++++++++try+{
++++++++++++Transformer+tr+=+TransformerFactory.newInstance().newTransformer();
++++++++++++tr.setOutputProperty(OutputKeys.INDENT,+"yes");
++++++++++++tr.setOutputProperty(OutputKeys.METHOD,+"xml");
++++++++++++tr.setOutputProperty(OutputKeys.ENCODING,+"UTF-8");
++++++++++++tr.setOutputProperty(OutputKeys.DOCTYPE_SYSTEM,+"roles.dtd");
++++++++++++tr.setOutputProperty("{http://xml.apache.org/xslt}indent-amount",+"4");

++++++++++++//+send+DOM+to+file
++++++++++++tr.transform(new+DOMSource(dom),+
+++++++++++++++++++++++++++++++++new+StreamResult(new+FileOutputStream(xml)));

++++++++}+catch+(TransformerException+te)+{
++++++++++++System.out.println(te.getMessage());
++++++++}+catch+(IOException+ioe)+{
++++++++++++System.out.println(ioe.getMessage());
++++++++}
++++}+catch+(ParserConfigurationException+pce)+{
++++++++System.out.println("UsersXML:+Error+trying+to+instantiate+DocumentBuilder+"+%2B+pce);
++++}
}|785962|getTextValue在这里：|785963|private+String+getTextValue(String+def,+Element+doc,+String+tag)+{
++++String+value+=+def;
++++NodeList+nl;
++++nl+=+doc.getElementsByTagName(tag);
++++if+(nl.getLength()+>+0+&&+nl.item(0).hasChildNodes())+{
++++++++value+=+nl.item(0).getFirstChild().getNodeValue();
++++}
++++return+value;
}|785964|添加几个访问器和修改器，您就完成了！|785965|entityMap^0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|18|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|19|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|1A|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|1B|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|1C|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|1D|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|1E|8|@]|9|@]|A|$]]|$1|Q|3|R|5|D|7|1F|8|@]|9|@]|A|$E|F]]|$1|S|3|T|5|6|7|1G|8|@]|9|@]|A|$]]|$1|U|3|V|5|D|7|1H|8|@]|9|@]|A|$E|F]]|$1|W|3|X|5|6|7|1I|8|@]|9|@]|A|$]]|$1|Y|3|Z|5|D|7|1J|8|@]|9|@]|A|$E|F]]|$1|10|3|11|5|6|7|1K|8|@]|9|@]|A|$]]|$1|12|3|13|5|D|7|1L|8|@]|9|@]|A|$E|F]]|$1|14|3|15|5|6|7|1M|8|@]|9|@]|A|$]]|$1|16|3|-4|5|6|7|1N|8|@]|9|@]|A|$]]]|17|$]]

Here is a quick DOM example that shows how to read and write a simple xml file with its dtd:

<pre><code>&lt;?xml version="1.0" encoding="UTF-8" standalone="no"?&gt;
&lt;!DOCTYPE roles SYSTEM "roles.dtd"&gt;
&lt;roles&gt;
 &lt;role1&gt;User&lt;/role1&gt;
 &lt;role2&gt;Author&lt;/role2&gt;
 &lt;role3&gt;Admin&lt;/role3&gt;
 &lt;role4/&gt;
&lt;/roles&gt;
</code></pre>

and the dtd:

<pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;!ELEMENT roles (role1,role2,role3,role4)&gt;
&lt;!ELEMENT role1 (#PCDATA)&gt;
&lt;!ELEMENT role2 (#PCDATA)&gt;
&lt;!ELEMENT role3 (#PCDATA)&gt;
&lt;!ELEMENT role4 (#PCDATA)&gt;
</code></pre>

First import these:

<pre><code>import javax.xml.parsers.*;
import javax.xml.transform.*;
import javax.xml.transform.dom.*;
import javax.xml.transform.stream.*;
import org.xml.sax.*;
import org.w3c.dom.*;
</code></pre>

Here are a few variables you will need:

<pre><code>private String role1 = null;
private String role2 = null;
private String role3 = null;
private String role4 = null;
private ArrayList&lt;String&gt; rolev;
</code></pre>

Here is a reader (String xml is the name of your xml file):

<pre><code>public boolean readXML(String xml) {
 rolev = new ArrayList&lt;String&gt;();
 Document dom;
 // Make an instance of the DocumentBuilderFactory
 DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
 try {
 // use the factory to take an instance of the document builder
 DocumentBuilder db = dbf.newDocumentBuilder();
 // parse using the builder to get the DOM mapping of the 
 // XML file
 dom = db.parse(xml);

 Element doc = dom.getDocumentElement();

 role1 = getTextValue(role1, doc, "role1");
 if (role1 != null) {
 if (!role1.isEmpty())
 rolev.add(role1);
 }
 role2 = getTextValue(role2, doc, "role2");
 if (role2 != null) {
 if (!role2.isEmpty())
 rolev.add(role2);
 }
 role3 = getTextValue(role3, doc, "role3");
 if (role3 != null) {
 if (!role3.isEmpty())
 rolev.add(role3);
 }
 role4 = getTextValue(role4, doc, "role4");
 if ( role4 != null) {
 if (!role4.isEmpty())
 rolev.add(role4);
 }
 return true;

 } catch (ParserConfigurationException pce) {
 System.out.println(pce.getMessage());
 } catch (SAXException se) {
 System.out.println(se.getMessage());
 } catch (IOException ioe) {
 System.err.println(ioe.getMessage());
 }

 return false;
 }
</code></pre>

And here a writer:

<pre><code>public void saveToXML(String xml) {
 Document dom;
 Element e = null;

 // instance of a DocumentBuilderFactory
 DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
 try {
 // use factory to get an instance of document builder
 DocumentBuilder db = dbf.newDocumentBuilder();
 // create instance of DOM
 dom = db.newDocument();

 // create the root element
 Element rootEle = dom.createElement("roles");

 // create data elements and place them under root
 e = dom.createElement("role1");
 e.appendChild(dom.createTextNode(role1));
 rootEle.appendChild(e);

 e = dom.createElement("role2");
 e.appendChild(dom.createTextNode(role2));
 rootEle.appendChild(e);

 e = dom.createElement("role3");
 e.appendChild(dom.createTextNode(role3));
 rootEle.appendChild(e);

 e = dom.createElement("role4");
 e.appendChild(dom.createTextNode(role4));
 rootEle.appendChild(e);

 dom.appendChild(rootEle);

 try {
 Transformer tr = TransformerFactory.newInstance().newTransformer();
 tr.setOutputProperty(OutputKeys.INDENT, "yes");
 tr.setOutputProperty(OutputKeys.METHOD, "xml");
 tr.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
 tr.setOutputProperty(OutputKeys.DOCTYPE_SYSTEM, "roles.dtd");
 tr.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "4");

 // send DOM to file
 tr.transform(new DOMSource(dom), 
 new StreamResult(new FileOutputStream(xml)));

 } catch (TransformerException te) {
 System.out.println(te.getMessage());
 } catch (IOException ioe) {
 System.out.println(ioe.getMessage());
 }
 } catch (ParserConfigurationException pce) {
 System.out.println("UsersXML: Error trying to instantiate DocumentBuilder " + pce);
 }
}
</code></pre>

getTextValue is here:

<pre><code>private String getTextValue(String def, Element doc, String tag) {
 String value = def;
 NodeList nl;
 nl = doc.getElementsByTagName(tag);
 if (nl.getLength() &gt; 0 &amp;&amp; nl.item(0).hasChildNodes()) {
 value = nl.item(0).getFirstChild().getNodeValue();
 }
 return value;
}
</code></pre>

Add a few accessors and mutators and you are done!

blocks|key|569958|text|上面的答案只涉及DOM解析器(它通常读取内存中的整个文件并对其进行解析，对于大文件来说是个问题)，您可以使用使用较少内存且速度更快的SAX解析器(无论如何，这取决于您的代码)。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|569959|当SAX解析器找到元素的开头、元素的结尾、属性、元素之间的文本等时，它会回调一些函数，这样它就可以解析文档，同时您也可以获得所需的内容。|569960|一些示例代码：|569961|http://www.mkyong.com/java/how-to-read-xml-file-in-java-sax-parser/|offset|length|569962|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|0|0|1V|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|R|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|S|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|T|8|@]|9|@$H|U|I|V|1|W]]|A|$]]|$1|J|3|-4|5|6|7|X|8|@]|9|@]|A|$]]]|K|$L|$5|M|N|O|A|$P|G]]]]

The above answer only deal with DOM parser (that normally reads the entire file in memory and parse it, what for a big file is a problem), you could use a SAX parser that uses less memory and is faster (anyway that depends on your code).

SAX parser callback some functions when it find a start of element, end of element, attribute, text between elements, etc, so it can parse the document and at the same time you
get what you need.

Some example code:

<a href="http://www.mkyong.com/java/how-to-read-xml-file-in-java-sax-parser/">http://www.mkyong.com/java/how-to-read-xml-file-in-java-sax-parser/</a>

blocks|key|786117|text|使用JAXB+(用于XML绑定的Java体系结构)编写XML：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|786118|http://www.mkyong.com/java/jaxb-hello-world-example/|offset|length|786119|package+com.mkyong.core;

import+javax.xml.bind.annotation.XmlAttribute;
import+javax.xml.bind.annotation.XmlElement;
import+javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public+class+Customer+{

++++String+name;
++++int+age;
++++int+id;

++++public+String+getName()+{
++++++++return+name;
++++}

++++@XmlElement
++++public+void+setName(String+name)+{
++++++++this.name+=+name;
++++}

++++public+int+getAge()+{
++++++++return+age;
++++}

++++@XmlElement
++++public+void+setAge(int+age)+{
++++++++this.age+=+age;
++++}

++++public+int+getId()+{
++++++++return+id;
++++}

++++@XmlAttribute
++++public+void+setId(int+id)+{
++++++++this.id+=+id;
++++}

}+

package+com.mkyong.core;

import+java.io.File;
import+javax.xml.bind.JAXBContext;
import+javax.xml.bind.JAXBException;
import+javax.xml.bind.Marshaller;

public+class+JAXBExample+{
++++public+static+void+main(String[]+args)+{

++++++Customer+customer+=+new+Customer();
++++++customer.setId(100);
++++++customer.setName("mkyong");
++++++customer.setAge(29);

++++++try+{

++++++++File+file+=+new+File("C:\\file.xml");
++++++++JAXBContext+jaxbContext+=+JAXBContext.newInstance(Customer.class);
++++++++Marshaller+jaxbMarshaller+=+jaxbContext.createMarshaller();

++++++++//+output+pretty+printed
++++++++jaxbMarshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT,+true);

++++++++jaxbMarshaller.marshal(customer,+file);
++++++++jaxbMarshaller.marshal(customer,+System.out);

++++++++++}+catch+(JAXBException+e)+{
++++++++e.printStackTrace();
++++++++++}

++++}
}|code-block|syntax|javascript|786120|entityMap|0|LINK|mutability|MUTABLE|url^0|0|0|1G|0|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|S|8|@]|9|@$D|T|E|U|1|V]]|A|$]]|$1|F|3|G|5|H|7|W|8|@]|9|@]|A|$I|J]]|$1|K|3|-4|5|6|7|X|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|C]]]]

Writing XML using JAXB (Java Architecture for XML Binding):

<a href="http://www.mkyong.com/java/jaxb-hello-world-example/" rel="noreferrer">http://www.mkyong.com/java/jaxb-hello-world-example/</a>

<pre><code>package com.mkyong.core;

import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class Customer {

 String name;
 int age;
 int id;

 public String getName() {
 return name;
 }

 @XmlElement
 public void setName(String name) {
 this.name = name;
 }

 public int getAge() {
 return age;
 }

 @XmlElement
 public void setAge(int age) {
 this.age = age;
 }

 public int getId() {
 return id;
 }

 @XmlAttribute
 public void setId(int id) {
 this.id = id;
 }

} 

package com.mkyong.core;

import java.io.File;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;

public class JAXBExample {
 public static void main(String[] args) {

 Customer customer = new Customer();
 customer.setId(100);
 customer.setName("mkyong");
 customer.setAge(29);

 try {

 File file = new File("C:\\file.xml");
 JAXBContext jaxbContext = JAXBContext.newInstance(Customer.class);
 Marshaller jaxbMarshaller = jaxbContext.createMarshaller();

 // output pretty printed
 jaxbMarshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);

 jaxbMarshaller.marshal(customer, file);
 jaxbMarshaller.marshal(customer, System.out);

 } catch (JAXBException e) {
 e.printStackTrace();
 }

 }
}
</code></pre>

blocks|key|786197|text|答案只涉及DOM+/+SAX和一个JAXB示例的复制粘贴实现。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|786198|但是，在使用XML时缺少一个很大的方面。在许多项目/程序中，需要存储/检索一些基本的数据结构。您的程序已经为您漂亮而闪亮的业务对象/数据结构提供了一个类，您只需要一种舒适的方式将这些数据转换为XML结构，这样您就可以对其进行更多的操作(使用XSLT进行存储、加载、发送和操作)。|786199|这就是XStream的闪亮之处。您只需注释保存数据的类，或者如果您不想更改这些类，则可以为编组(对象->+xml)或解组(xml+->对象)配置一个XStream实例。|786200|在内部，XStream使用反射，即标准Java对象序列化的readObject和readResolve方法。|786201|你会得到一个又好又快的教程here：|offset|length|786202|为了简要介绍它的工作原理，我还提供了一些用于编组和解组数据结构的示例代码。编组/解组都发生在main方法中，其余的只是生成一些测试对象并向其中填充一些数据的代码。配置xStream实例非常简单，编组/解组只需要一行代码就可以完成。|style|CODE|786203|import+java.math.BigDecimal;
import+java.util.ArrayList;
import+java.util.List;

import+com.thoughtworks.xstream.XStream;

public+class+XStreamIsGreat+{

++public+static+void+main(String[]+args)+{
++++XStream+xStream+=+new+XStream();
++++xStream.alias("good",+Good.class);
++++xStream.alias("pRoDuCeR",+Producer.class);
++++xStream.alias("customer",+Customer.class);

++++Producer+a+=+new+Producer("Apple");
++++Producer+s+=+new+Producer("Samsung");
++++Customer+c+=+new+Customer("Someone").add(new+Good("S4",+10,+new+BigDecimal(600),+s))
++++++++.add(new+Good("S4+mini",+5,+new+BigDecimal(450),+s)).add(new+Good("I5S",+3,+new+BigDecimal(875),+a));
++++String+xml+=+xStream.toXML(c);+//+objects+->+xml
++++System.out.println("Marshalled:\n"+%2B+xml);
++++Customer+unmarshalledCustomer+=+(Customer)xStream.fromXML(xml);+//+xml+->+objects
++}

++static+class+Good+{
++++Producer+producer;

++++String+name;

++++int+quantity;

++++BigDecimal+price;

++++Good(String+name,+int+quantity,+BigDecimal+price,+Producer+p)+{
++++++this.producer+=+p;
++++++this.name+=+name;
++++++this.quantity+=+quantity;
++++++this.price+=+price;
++++}

++}

++static+class+Producer+{
++++String+name;

++++public+Producer(String+name)+{
++++++this.name+=+name;
++++}
++}

++static+class+Customer+{
++++String+name;

++++public+Customer(String+name)+{
++++++this.name+=+name;
++++}

++++List<Good>+stock+=+new+ArrayList<Good>();

++++Customer+add(Good+g)+{
++++++stock.add(g);
++++++return+this;
++++}
++}
}|code-block|syntax|javascript|786204|entityMap|0|LINK|mutability|MUTABLE|url|http://xstream.codehaus.org/tutorial.html^0|0|0|0|0|D|4|0|0|1A|4|2B|7|0|0^^$0|@$1|2|3|4|5|6|7|12|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|13|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|14|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|15|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|16|8|@]|9|@$J|17|K|18|1|19]]|A|$]]|$1|L|3|M|5|6|7|1A|8|@$J|1B|K|1C|N|O]|$J|1D|K|1E|N|O]]|9|@]|A|$]]|$1|P|3|Q|5|R|7|1F|8|@]|9|@]|A|$S|T]]|$1|U|3|-4|5|6|7|1G|8|@]|9|@]|A|$]]]|V|$W|$5|X|Y|Z|A|$10|11]]]]

The answers only cover DOM / SAX and a copy paste implementation of a JAXB example.

However, one big area of when you are using XML is missing. In many projects / programs there is a need to store / retrieve some basic data structures. Your program has already a classes for your nice and shiny business objects / data structures, you just want a comfortable way to convert this data to a XML structure so you can do more magic on it (store, load, send, manipulate with XSLT).

This is where XStream shines. You simply annotate the classes holding your data, or if you do not want to change those classes, you configure a XStream instance for marshalling (objects -> xml) or unmarshalling (xml -> objects).

Internally XStream uses reflection, the readObject and readResolve methods of standard Java object serialization.

You get a good and speedy tutorial <a href="http://xstream.codehaus.org/tutorial.html" rel="nofollow">here</a>: 

To give a short overview of how it works, I also provide some sample code which marshalls and unmarshalls a data structure.
The marshalling / unmarshalling happens all in the <code>main</code> method, the rest is just code to generate some test objects and populate some data to them.
It is super simple to configure the <code>xStream</code> instance and marshalling / unmarshalling is done with one line of code each.

<pre><code>import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.List;

import com.thoughtworks.xstream.XStream;

public class XStreamIsGreat {

 public static void main(String[] args) {
 XStream xStream = new XStream();
 xStream.alias("good", Good.class);
 xStream.alias("pRoDuCeR", Producer.class);
 xStream.alias("customer", Customer.class);

 Producer a = new Producer("Apple");
 Producer s = new Producer("Samsung");
 Customer c = new Customer("Someone").add(new Good("S4", 10, new BigDecimal(600), s))
 .add(new Good("S4 mini", 5, new BigDecimal(450), s)).add(new Good("I5S", 3, new BigDecimal(875), a));
 String xml = xStream.toXML(c); // objects -&gt; xml
 System.out.println("Marshalled:\n" + xml);
 Customer unmarshalledCustomer = (Customer)xStream.fromXML(xml); // xml -&gt; objects
 }

 static class Good {
 Producer producer;

 String name;

 int quantity;

 BigDecimal price;

 Good(String name, int quantity, BigDecimal price, Producer p) {
 this.producer = p;
 this.name = name;
 this.quantity = quantity;
 this.price = price;
 }

 }

 static class Producer {
 String name;

 public Producer(String name) {
 this.name = name;
 }
 }

 static class Customer {
 String name;

 public Customer(String name) {
 this.name = name;
 }

 List&lt;Good&gt; stock = new ArrayList&lt;Good&gt;();

 Customer add(Good g) {
 stock.add(g);
 return this;
 }
 }
}
</code></pre>

blocks|key|570198|text|好了，已经有了DOM、JaxB和XStream，还有一种完全不同的读写方法：Data+projection你可以通过使用一个库来解耦XML结构和XStream结构，这个库提供了对Data+projection数据的读写视图。从tutorials|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|570199|给定一些真实的XML：|570200|<weatherdata>
++<weather
++++...+
++++degreetype="F"
++++lat="50.5520210266113"+lon="6.24060010910034"+
++++searchlocation="Monschau,+Stadt+Aachen,+NW,+Germany"+
++++++++++++...+>
++++<current+...+skytext="Clear"+temperature="46"/>
++</weather>
</weatherdata>|code-block|syntax|javascript|570201|使用数据投影，您可以定义一个投影接口：|570202|public+interface+WeatherData+{

@XBRead("/weatherdata/weather/@searchlocation")+++
String+getLocation();

@XBRead("/weatherdata/weather/current/@temperature")
int+getTemperature();

@XBRead("/weatherdata/weather/@degreetype")
String+getDegreeType();

@XBRead("/weatherdata/weather/current/@skytext")
String+getSkytext();

/**
+*+This+would+be+our+"sub+projection".+A+structure+grouping+two+attribute
+*+values+in+one+object.
+*/
interface+Coordinates+{
++++@XBRead("@lon")
++++double+getLongitude();

++++@XBRead("@lat")
++++double+getLatitude();
}

@XBRead("/weatherdata/weather")
Coordinates+getCoordinates();
}|570203|并像POJO一样使用此接口的实例：|570204|private+void+printWeatherData(String+location)+throws+IOException+{

final+String+BaseURL+=+"http://weather.service.msn.com/find.aspx?outputview=search&weasearchstr=";

//+We+let+the+projector+fetch+the+data+for+us
WeatherData+weatherData+=+new+XBProjector().io().url(BaseURL+%2B+location).read(WeatherData.class);

//+Print+some+values
System.out.println("The+weather+in+"+%2B+weatherData.getLocation()+%2B+":");
System.out.println(weatherData.getSkytext());
System.out.println("Temperature:+"+%2B+weatherData.getTemperature()+%2B+"°"
+++++++++++++++++++++++++++++++++++%2B+weatherData.getDegreeType());

//+Access+our+sub+projection
Coordinates+coordinates+=+weatherData.getCoordinates();
System.out.println("The+place+is+located+at+"+%2B+coordinates.getLatitude()+%2B+","
++++++++++++++++++++++++++++++++++++++++++++++%2B+coordinates.getLongitude());
}|570205|这甚至适用于创建XML，XPath表达式可以是可写的。|570206|entityMap|0|LINK|mutability|MUTABLE|url|http://xmlbeam.org/|1|2|http://xmlbeam.org/t01.html#E01:_Printing_some_weather_data^0|12|F|0|2H|F|1|35|9|2|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|15|8|@]|9|@$A|16|B|17|1|18]|$A|19|B|1A|1|1B]|$A|1C|B|1D|1|1E]]|C|$]]|$1|D|3|E|5|6|7|1F|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|1G|8|@]|9|@]|C|$I|J]]|$1|K|3|L|5|6|7|1H|8|@]|9|@]|C|$]]|$1|M|3|N|5|H|7|1I|8|@]|9|@]|C|$I|J]]|$1|O|3|P|5|6|7|1J|8|@]|9|@]|C|$]]|$1|Q|3|R|5|H|7|1K|8|@]|9|@]|C|$I|J]]|$1|S|3|T|5|6|7|1L|8|@]|9|@]|C|$]]|$1|U|3|-4|5|6|7|1M|8|@]|9|@]|C|$]]]|V|$W|$5|X|Y|Z|C|$10|11]]|12|$5|X|Y|Z|C|$10|11]]|13|$5|X|Y|Z|C|$10|14]]]]

Ok, already having DOM, JaxB and XStream in the list of answers, there is still a complete different way to read and write XML: <a href="http://xmlbeam.org" rel="nofollow">Data projection</a> You can decouple the XML structure and the Java structure by using a library that provides read and writeable views to the XML Data as Java interfaces. From the <a href="http://xmlbeam.org/t01.html#E01:_Printing_some_weather_data" rel="nofollow">tutorials</a>:

Given some real world XML:

<pre><code>&lt;weatherdata&gt;
 &lt;weather
 ... 
 degreetype="F"
 lat="50.5520210266113" lon="6.24060010910034" 
 searchlocation="Monschau, Stadt Aachen, NW, Germany" 
 ... &gt;
 &lt;current ... skytext="Clear" temperature="46"/&gt;
 &lt;/weather&gt;
&lt;/weatherdata&gt;
</code></pre>

With data projection you can define a projection interface:

<pre><code>public interface WeatherData {

@XBRead("/weatherdata/weather/@searchlocation") 
String getLocation();

@XBRead("/weatherdata/weather/current/@temperature")
int getTemperature();

@XBRead("/weatherdata/weather/@degreetype")
String getDegreeType();

@XBRead("/weatherdata/weather/current/@skytext")
String getSkytext();

/**
 * This would be our "sub projection". A structure grouping two attribute
 * values in one object.
 */
interface Coordinates {
 @XBRead("@lon")
 double getLongitude();

 @XBRead("@lat")
 double getLatitude();
}

@XBRead("/weatherdata/weather")
Coordinates getCoordinates();
}
</code></pre>

And use instances of this interface just like POJOs:

<pre><code>private void printWeatherData(String location) throws IOException {

final String BaseURL = "http://weather.service.msn.com/find.aspx?outputview=search&amp;weasearchstr=";

// We let the projector fetch the data for us
WeatherData weatherData = new XBProjector().io().url(BaseURL + location).read(WeatherData.class);

// Print some values
System.out.println("The weather in " + weatherData.getLocation() + ":");
System.out.println(weatherData.getSkytext());
System.out.println("Temperature: " + weatherData.getTemperature() + "°"
 + weatherData.getDegreeType());

// Access our sub projection
Coordinates coordinates = weatherData.getCoordinates();
System.out.println("The place is located at " + coordinates.getLatitude() + ","
 + coordinates.getLongitude());
}
</code></pre>

This works even for creating XML, the XPath expressions can be writable.

I have to read and write to and from an <a href="http://en.wikipedia.org/wiki/XML">XML</a> file. What is the easiest way to read and write XML files using Java?

How to read and write XML files?

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