使用XStream來映射xml中列表元素到java對象

[size=medium]網上很多講述使用XStream來映射xml文件到java對象的文章，但是幾乎沒有一篇文章講述，如何使用XStream來映射xml中的同級的列表元素到java對象的文章。本文示例中將使用XStream 1.3.1。請去XStream的官方站點上下載相應的包。[/size]

[size=medium]在Eclipse中新建一個Java Project，然後引入XStream的包：xstream－1.3.1.jar和xpp3-min-1.1.4c.jar。在這裏使用xpp的xml解析技術來解析xml，而不是傳統的DOM或者sax來進行xml的解析。[/size]

[size=medium]在src下新建sample.xml文件。代碼如下：[/size]

<?xml version="1.0" encoding="UTF-8"?>
<person id="1" name="sample">
	<wife name="wife_name" age="25"></wife>
	<house name="house1" address="address1"></house> 
	<house name="house1" address="address1"></house> 
	<house name="house1" address="address1"></house> 
	<house name="house1" address="address1"></house> 
</person>

[size=medium]新建House類來映射house元素，House類的源代碼如下：
[/size]

public class House {
	private String name = "";
	private String address = "";
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getAddress() {
		return address;
	}
	public void setAddress(String address) {
		this.address = address;
	}


}

[size=medium]新建Wife類來映射wife標籤，源代碼如下：
[/size]

public class Wife {
	private String name = "";
	private int age;
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}


}

新建Person類來映射person元素，源代碼如下：

import java.util.List;


public class Person {
	private int id;
	private String name;
	private Wife wife;
	private List<House> houseList;

	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public Wife getWife() {
		return wife;
	}
	public void setWife(Wife wife) {
		this.wife = wife;
	}
	public List<House> getHouseList() {
		return houseList;
	}
	public void setHouseList(List<House> houseList) {
		this.houseList = houseList;
	}
}

[size=medium]新建TestMain方法，包含main方法。首先，構建XStream的實例：
[/size]

	XStream xstream = new XStream();

[size=medium]然後，就是配置xml文件和java對象之間的映射，源代碼如下：[/size]

		xstream.alias("person", Person.class);
		xstream.aliasAttribute(Person.class, "id", "id");
		xstream.aliasAttribute(Person.class, "name", "name");

		xstream.alias("wife", Wife.class);
		xstream.aliasAttribute(Wife.class, "name", "name");

		xstream.addImplicitCollection(Person.class, "houseList");
		xstream.alias("house", House.class);
		xstream.aliasAttribute(House.class,"name", "name");
		xstream.aliasAttribute(House.class, "address", "address");

注意代碼中的這句“xstream.addImplicitCollection(Person.class, "houseList");”，如果不加，xml配置文件的house元素將作爲houselist的子元素。將變成

<houseList>
<house name="house1" address="address1"></house> 
	<house name="house1" address="address1"></house> 
	<house name="house1" address="address1"></house> 
	<house name="house1" address="address1"></house> 
</houseList>

。
[size=medium]最後，使用XStream.fromXML來將對應的xml轉化成java對象。代碼如下：[/size]

Person person = (Person)xstream.fromXML(TestMain.class.getClassLoader()
.getResourceAsStream("sample.xml"));

[size=medium]由於sample.xml文件位於classpath下，所以使用了ClassLoader來加載sample.xml。[/size]

[size=medium]測試代碼如下：[/size]

        System.out.println("[person.name=" + person.getName() + "]");
	System.out.println("[wife.name=" + person.getWife().getName() + ", wife.age=" + person.getWife().getAge() + "]");
	System.out.println("[person.houseList.size=" + person.getHouseList().size() + "]");
	System.out.println("[person.houseList.house1.name=" +                person.getHouseList().get(0).getName() + ",address=" + person.getHouseList().get(0).getAddress() +"]");

[size=medium]測試結果如下：[/size]
[person.name=sample]
[wife.name=wife_name, wife.age=0]
[person.houseList.size=4]
person.houseList.house1.name=house1,address=address1]