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XStream入坑指南

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1.Xstream介绍

(1)Xstream介绍
    Xstream是一种OXMapping 技术,是用来处理XML文件序列化的框架,在将JavaBean序列化,或将XML文件反序列化的时候,不需要其它辅助类和映射文件,使得XML序列化不再繁索。Xstream也可以将JavaBean序列化成Json或反序列化,使用非常方便。
(2)Xstream的简单例子
class Person//JavaBean实体类
{
	private String name;
	private int age;
	public Person(String name,int age)
	{
		this.name=name;
		this.age=age;
	}
	@Override
	public String toString()
	{
		return "Person [name=" + name + ", age=" + age + "]";
	}
}
public class Test
{
	public static void main(String[] args)
	{
		Person bean=new Person("张三",19);
		XStream xstream = new XStream();
		//XML序列化
		String xml = xstream.toXML(bean);
		System.out.println(xml);
		//XML反序列化
		bean=(Person)xstream.fromXML(xml);
		System.out.println(bean);
		
		xstream = new XStream(new JettisonMappedXmlDriver());
		xstream.setMode(XStream.NO_REFERENCES);
		//Json序列化
		String json=xstream.toXML(bean);
		System.out.println(json);
		//Json反序列
		bean=(Person)xstream.fromXML(json);
		System.out.println(bean);
	}
}
    程序运行结果:
<test.Person>
  <name>张三</name>
  <age>19</age>
</test.Person>
Person [name=张三, age=19]
{"test.Person":{"name":"张三","age":19}}
Person [name=张三, age=19
    注意:Xstream序列化XML时需要引用的jar包:xstream-[version].jar、xpp3-[version].jar、xmlpull-[version].jar。Xstream序列化Json需要引用的jar包:jettison-[version].jar。
    使用Xstream序列化时,对JavaBean没有任何限制。JavaBean的字段可以是私有的,也可以没有getter或setter方法,还可以没有默认的构造函数。

2.Xstream的基本使用

(1)Xstream序列化XML
    Xstream序列化XML时可以允许用户使用不同的XML解析器,用户可以使用一个标准的JAXP DOM解析器或自Java6集成StAX解析器。这样用户就不需要依赖xpp3-[version].jar。
    Xstream序列化XML时,也可以对XML节点重命名。
public class Test
{
	public static void main(String[] args)
	{
		Person bean=new Person("张三",19);
		//XStream xstream = new XStream();//需要XPP3库
		//XStream xstream = new XStream(new DomDriver());//不需要XPP3库
		XStream xstream = new XStream(new StaxDriver());//不需要XPP3库开始使用Java6 
		xstream.alias("人",Person.class);//为类名节点重命名
		//XML序列化
		String xml = xstream.toXML(bean);
		System.out.println(xml);
		//XML反序列化
		bean=(Person)xstream.fromXML(xml);
		System.out.println(bean);
	}
}
    程序运行结果:
<?xml version="1.0" ?><人><name>张三</name><age>19</age></人>
Person [name=张三, age=19]
(2)Xstream序列化Json
    Xstream序列化Json与序列化XML类似,例如:
public class Test
{
	public static void main(String[] args)
	{
		Person bean=new Person("张三",19);
		XStream xstream = new XStream(new JettisonMappedXmlDriver());//设置Json解析器
        xstream.setMode(XStream.NO_REFERENCES);//设置reference模型,不引用
		xstream.alias("人",Person.class);//为类名节点重命名
		//Json序列化
		String xml = xstream.toXML(bean);
		System.out.println(xml);
		//Json反序列化
		bean=(Person)xstream.fromXML(xml);
		System.out.println(bean);
	}
}
    程序运行结果:
{"人":{"name":"张三","age":19}}
Person [name=张三, age=19]

3.Xstream序列化重命名

(1)为包重命名:Xstream.aliasPackage()方法
public class Test
{
	public static void main(String[] args)
	{
		Person bean=new Person("张三",19);
		XStream xstream = new XStream();
		xstream.aliasPackage("com.lzw", "test");//为包名称重命名
		//序列化
		String xml = xstream.toXML(bean);
		System.out.println(xml);
		//反序列化
		bean=(Person)xstream.fromXML(xml);
		System.out.println(bean);
	}
}
    程序运行结果:
<com.lzw.Person>
  <name>张三</name>
  <age>19</age>
</com.lzw.Person>
Person [name=张三, age=19]
(2)为类重命名:Xstream.alias()方法
public class Test
{
	public static void main(String[] args)
	{
		Person bean=new Person("张三",19);
		XStream xstream = new XStream();
		xstream.alias("人", Person.class);//为类名节点重命名
		//序列化
		String xml = xstream.toXML(bean);
		System.out.println(xml);
		//反序列化
		bean=(Person)xstream.fromXML(xml);
		System.out.println(bean);
	}
}
    程序运行结果:
<人>
  <name>张三</name>
  <age>19</age>
</人>
Person [name=张三, age=19]
(3)为字段重命名:Xstream.aliasField()方法
public class Test
{
	public static void main(String[] args)
	{
		Person bean=new Person("张三",19);
		XStream xstream = new XStream();
		xstream.aliasField("姓名", Person.class,"name");//为类的字段节点重命名
		xstream.aliasField("年龄", Person.class,"age");//为类的字段节点重命名
		//序列化
		String xml = xstream.toXML(bean);
		System.out.println(xml);
		//反序列化
		bean=(Person)xstream.fromXML(xml);
		System.out.println(bean);
	}
}
    程序运行结果:
<test.Person>
  <姓名>张三</姓名>
  <年龄>19</年龄>
</test.Person>
Person [name=张三, age=19]
(4)省略集合根节点:Xstream.addImplicitCollection()方法
class Person
{
	private String name;
	private int age;
	private List friends;
	public Person(String name, int age, String... friends)
	{
		this.name = name;
		this.age = age;
		this.friends = Arrays.asList(friends);
	}
	@Override
	public String toString()
	{
		return "Person [name=" + name + ", age=" + age + ", friends=" + friends + "]";
	}
}
public class Test
{
	public static void main(String[] args)
	{
		Person bean =new Person("张三",19,"李四","王五","赵六");
		XStream xstream = new XStream();
		xstream.addImplicitCollection(Person.class, "friends");//省略集合根节点
		//序列化
		String xml = xstream.toXML(bean);
		System.out.println(xml);
		//反序列化
		bean=(Person)xstream.fromXML(xml);
		System.out.println(bean);
	}
}
    程序运行结果:
<test.Person>
  <name>张三</name>
  <age>19</age>
  <string>李四</string>
  <string>王五</string>
  <string>赵六</string>
</test.Person>
Person [name=张三, age=19, friends=[李四, 王五, 赵六]]
(5)把字段节点设置成属性:Xstream.useAttributeFor()方法
public class Test
{
	public static void main(String[] args)
	{
		Person bean =new Person("张三",19,"李四","王五","赵六");
		XStream xstream = new XStream();
		xstream.useAttributeFor(Person.class, "name");//把字段节点设置成属性
		//序列化
		String xml = xstream.toXML(bean);
		System.out.println(xml);
		//反序列化
		bean=(Person)xstream.fromXML(xml);
		System.out.println(bean);
	}
}
    程序运行结果:
<test.Person name="张三">
  <age>19</age>
  <friends class="java.util.Arrays$ArrayList">
    <a class="string-array">
      <string>李四</string>
      <string>王五</string>
      <string>赵六</string>
    </a>
  </friends>
</test.Person>
Person [name=张三, age=19, friends=[李四, 王五, 赵六]]
(6)隐藏字段:xstream.omitField()方法
public class Test
{
	public static void main(String[] args)
	{
		Person bean =new Person("张三",19,"李四","王五","赵六");
		XStream xstream = new XStream();
		xstream.omitField(Person.class, "friends");//把字段节点隐藏
		//序列化
		String xml = xstream.toXML(bean);
		System.out.println(xml);
		//反序列化
		bean=(Person)xstream.fromXML(xml);
		System.out.println(bean);
	}
}
    程序运行结果:
<test.Person>
  <name>张三</name>
  <age>19</age>
</test.Person>
Person [name=张三, age=19, friends=null]

4.Xstream注解的使用

(1)设置Xstream应用注解
    使用Xstream注解前需要对Xstream进行配置,可以使用两种方式:应用某个JavaBean类的注解或自动使用JavaBean类的注解。代码如下:
XStream xstream = new XStream();
xstream.processAnnotations(Person.class);//应用Person类的注解
xstream.autodetectAnnotations(true);//自动检测注解
(2)重命名注解:@XStreamAlias()
@XStreamAlias("人")
class Person
{
	@XStreamAlias("姓名")
	private String name;
	@XStreamAlias("年龄")
	private int age;
	@XStreamAlias("朋友")
	private List friends;
	public Person(String name, int age, String... friends)
	{
		this.name = name;
		this.age = age;
		this.friends = Arrays.asList(friends);
	}
	@Override
	public String toString()
	{
		return "Person [name=" + name + ", age=" + age + ", friends=" + friends + "]";
	}
}
    程序运行结果:
<人>
  <姓名>张三</姓名>
  <年龄>19</年龄>
  <朋友 class="java.util.Arrays$ArrayList">
    <a class="string-array">
      <string>李四</string>
      <string>王五</string>
      <string>赵六</string>
    </a>
  </朋友>
</人>
Person [name=张三, age=19, friends=[李四, 王五, 赵六]]
(3)省略集合根节点:@XStreamImplicit
class Person
{
	private String name;
	private int age;
	//@XStreamImplicit//只隐藏集合根节点
	@XStreamImplicit(itemFieldName="朋友")//设置重复的节点名,可能会导致无法反序列化
	private List<String> friends;
	public Person(String name, int age, String... friends)
	{
		this.name = name;
		this.age = age;
		this.friends = Arrays.asList(friends);
	}
	@Override
	public String toString()
	{
		return "Person [name=" + name + ", age=" + age + ", friends=" + friends + "]";
	}
}
    程序运行结果:
<test.Person>
  <name>张三</name>
  <age>19</age>
  <朋友>李四</朋友>
  <朋友>王五</朋友>
  <朋友>赵六</朋友>
</test.Person>
Person [name=张三, age=19, friends=[李四, 王五, 赵六]]
(4)把字段节点设置成属性:@XStreamAsAttribute
class Person
{
	@XStreamAsAttribute
	private String name;
	@XStreamAsAttribute
	private int age;
	private List<String> friends;
	public Person(String name, int age, String... friends)
	{
		this.name = name;
		this.age = age;
		this.friends = Arrays.asList(friends);
	}
	@Override
	public String toString()
	{
		return "Person [name=" + name + ", age=" + age + ", friends=" + friends + "]";
	}
}
    程序运行结果:
<test.Person name="张三" age="19">
  <friends class="java.util.Arrays$ArrayList">
    <a class="string-array">
      <string>李四</string>
      <string>王五</string>
      <string>赵六</string>
    </a>
  </friends>
</test.Person>
Person [name=张三, age=19, friends=[李四, 王五, 赵六]]
(5)隐藏字段:@XStreamOmitField
class Person
{
	private String name;
	private int age;
	@XStreamOmitField
	private List<String> friends;
	public Person(String name, int age, String... friends)
	{
		this.name = name;
		this.age = age;
		this.friends = Arrays.asList(friends);
	}
	@Override
	public String toString()
	{
		return "Person [name=" + name + ", age=" + age + ", friends=" + friends + "]";
	}
}
    程序运行结果:
<test.Person>
  <name>张三</name>
  <age>19</age>
</test.Person>
Person [name=张三, age=19, friends=null]
(6)设置转换器:@XStreamConverter()
class Person
{
	private String name;
	private int age;
        @XStreamConverter(value=BooleanConverter.class,booleans={false},strings={"男","女"})
	private boolean sex;
	public Person(String name, int age, boolean sex)
	{
		this.name = name;
		this.age = age;
		this.sex=sex;
	}
	@Override
	public String toString()
	{
		return "Person [name=" + name + ", age=" + age + ", sex=" + sex + "]";
	}
}
    程序运行结果:
<test.Person>
  <name>张三</name>
  <age>19</age>
  <sex></sex>
</test.Person>
Person [name=张三, age=19, sex=true]

5.Xstream自定义的转换器

(1)Xstream自带的转换器
    Xstream内部有许多转换器,用于JavaBean对象到XML或Json之间的转换。这些转换器的详细信息网址:http://xstream.codehaus.org/converters.html
(2)使用自定义的转换器
class Person
{
	private String name;
	private int age;
	public Person(String name, int age)
	{
		this.name = name;
		this.age = 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;
	}
	@Override
	public String toString()
	{
		return "Person [name=" + name + ", age=" + age + "]";
	}
}
public class PersonConverter implements Converter 
{
	@Override//定义转换器能转换的JavaBean类型
	public boolean canConvert(Class type)
	{
		return type.equals(Person.class);
	}
	@Override//把对象序列化成XML或Json
	public void marshal(Object value, HierarchicalStreamWriter writer, 
MarshallingContext context)
	{
		Person person = (Person) value;
        writer.startNode("姓名");
        writer.setValue(person.getName());
        writer.endNode();
        writer.startNode("年龄");
        writer.setValue(person.getAge()+"");
        writer.endNode();
        writer.startNode("转换器");
        writer.setValue("自定义的转换器");
        writer.endNode();
	}
	@Override//把XML或Json反序列化成对象
	public Object unmarshal(HierarchicalStreamReader reader, 
UnmarshallingContext context)
	{
		   Person person = new Person("",-1);
           reader.moveDown();
           person.setName(reader.getValue());
           reader.moveUp();
           reader.moveDown();
           person.setAge(Integer.parseInt(reader.getValue()));
           reader.moveUp();
           return person;
	}
}
public class Test
{
	public static void main(String[] args)
	{
		Person bean =new Person("张三",19);
		XStream xstream = new XStream();
		xstream.registerConverter(new PersonConverter());//注册转换器
		//序列化
		String xml = xstream.toXML(bean);
		System.out.println(xml);
		//反序列化
		bean=(Person)xstream.fromXML(xml);
		System.out.println(bean);
	}
}
    程序运行结果:
<test.Person>
  <姓名>张三</姓名>
  <年龄>19</年龄>
  <转换器>自定义的转换器</转换器>
</test.Person>
Person [name=张三, age=19]
(3)常用的转换器接口与抽象类
    SingleValueConverter:单值转换接口
    AbstractSingleValueConverter:单值转换抽象类
    Converter:常规转换器接口

6.Xstream对象流的使用

(1)Xstream对象输出流
class Person
{
	private String name;
	private int age;
	public Person(String name, int age)
	{
		this.name = name;
		this.age = age;
	}
}
public class Test
{
	public static void main(String[] args) throws IOException
	{		
		XStream xstream = new XStream();
		ObjectOutputStream out = xstream.createObjectOutputStream(System.out);
		out.writeObject(new Person("张三",12));
		out.writeObject(new Person("李四",19));
		out.writeObject("Hello");
		out.writeInt(12345);
		out.close();
	}
}
    程序运行结果:
<object-stream>
  <test.Person>
    <name>张三</name>
    <age>12</age>
  </test.Person>
  <test.Person>
    <name>李四</name>
    <age>19</age>
  </test.Person>
  <string>Hello</string>
  <int>12345</int>
</object-stream>
    注意:XStream对象流是通过标准java.io.ObjectOutputStream和java.io.ObjectInputStream对象。因为XML文档只能有一个根节点,必须包装在一个序列化的所有元素 额外的根节点。 这个根节点默认 < object-stream > 上面的例子所示。
(2)Xstream对象输出流
class Person
{
	private String name;
	private int age;
	public Person(String name, int age)
	{
		this.name = name;
		this.age = age;
	}
	@Override
	public String toString()
	{
		return "Person [name=" + name + ", age=" + age + "]";
	}
}
public class Test
{
	public static void main(String[] args) throws IOException, ClassNotFoundException
	{
		String s="<object-stream><test.Person><name>张三</name><age>12</age></test.Person><int>12345</int></object-stream>";
		StringReader reader = new StringReader(s);
		XStream xstream = new XStream();
		ObjectInputStream in = xstream.createObjectInputStream(reader);
		System.out.println((Person) in.readObject());
		System.out.println(in.readInt());
	}
}
    程序运行结果:
Person [name=张三, age=12]
12345

7.Xstream持久化API

(1)保存JavaBean对象
class Person
{
	private String name;
	private int age;
	public Person(String name, int age)
	{
		this.name = name;
		this.age = age;
	}
	@Override
	public String toString()
	{
		return "Person [name=" + name + ", age=" + age + "]";
	}
}
public class Test
{
	public static void main(String[] args) throws IOException, ClassNotFoundException
	{
		PersistenceStrategy strategy = new FilePersistenceStrategy(new File("D:\\tmp"));
		List list = new XmlArrayList(strategy);
		list.add(new Person("张三",13));//保存数据
		list.add(new Person("李四",21));
		list.add(new Person("王五",17));
	}
}
    程序运行结果:如果我们检查D:\tmp目录,有三个文件:int@0.xml、int@1.xml、int@2.xml;每个对象都被序列化到XML文件里。
(2)读取并删除JavaBean对象
public class Test
{
	public static void main(String[] args) throws IOException, ClassNotFoundException
	{
		PersistenceStrategy strategy = new FilePersistenceStrategy(new File("D:\\tmp"));
		List list = new XmlArrayList(strategy);
		for (Iterator it = list.iterator(); it.hasNext();)
		{
			System.out.println((Person) it.next());
			it.remove();//删除对象序列化文件
		}
	}
}
    程序运行结果:
Person [name=张三, age=13]
Person [name=李四, age=21]
Person [name=王五, age=17]

8.Xstream操作Json

(1)Xstream序列化Json的重命名
@XStreamAlias("人")
class Person
{
	@XStreamAlias("姓名")
	private String name;
	@XStreamAlias("年龄")
	private int age;
	public Person(String name, int age)
	{
		this.name = name;
		this.age = age;
	}
	@Override
	public String toString()
	{
		return "Person [name=" + name + ", age=" + age + "]";
	}
}
public class Test
{
	public static void main(String[] args)
	{
		Person bean=new Person("张三",19);
		XStream xstream = new XStream(new JettisonMappedXmlDriver());//设置Json解析器
		xstream.autodetectAnnotations(true);
		//Json序列化
		String xml = xstream.toXML(bean);
		System.out.println(xml);
		//Json反序列化
		bean=(Person)xstream.fromXML(xml);
		System.out.println(bean);
	}
}
    程序运行结果:
{"人":{"姓名":"张三","年龄":19}}
Person [name=张三, age=19]
    注意:Xstream序列化Json的重命名的方式与其序列化成XML的方式一样!
(2)去掉序列化Json的根节点
class Person
{
	private String name;
	private int age;
	public Person(String name, int age)
	{
		this.name = name;
		this.age = age;
	}
	@Override
	public String toString()
	{
		return "Person [name=" + name + ", age=" + age + "]";
	}
}
public class Test00
{
	public static void main(String[] args)
	{
		Person bean=new Person("张三",19);
		XStream xstream = new XStream(new JsonHierarchicalStreamDriver()
		{
			public HierarchicalStreamWriter createWriter(Writer writer)
			{
				return new JsonWriter(writer, JsonWriter.DROP_ROOT_MODE);
			}
		});
		//Json序列化
		String xml = xstream.toXML(bean);
		System.out.println(xml);
	}
}
    程序运行结果:
  1. { "name": "张三", "age": 19 }
    注意:去掉根节点后的Json串是不能反序列化的,因为XStream 不知道它的类型。
(3)Json的解析器区别
    前面两个例子使用了不同的Json解析器,这里说明他们的不同之处:
    1. JettisonMappedXmlDriver:是支持序列化和反序列化Json的。
    2. JsonHierarchicalStreamDriver:只支持序列化,不支持反序列化。
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