xStream框架

xStream可以轻易的将Java对象和xml文档相互转换，而且可以修改某个特定的属性和节点名称，而且也支持json的转换；
前面有介绍过json-lib这个框架，在线博文：http://www.cnblogs.com/hoojo/archive/2011/04/21/2023805.html
以及Jackson这个框架，在线博文：http://www.cnblogs.com/hoojo/archive/2011/04/22/2024628.html
它们都完美支持JSON，但是对xml的支持还不是很好。一定程度上限制了对Java对象的描述，不能让xml完全体现到对Java对象的描述。这里将会介绍xStream对JSON、XML的完美支持。xStream不仅对XML的转换非常友好，而且提供annotation注解，可以在JavaBean中完成对xml节点、属性的描述。以及对JSON也支持，只需要提供相关的JSONDriver就可以完成转换。
一、 准备工作
1、 下载jar包、及官方资源
xStream的jar下载地址：
https://nexus.codehaus.org/content/repositories/releases/com/thoughtworks/xstream/xstream-distribution/1.3.1/xstream-distribution-1.3.1-bin.zip
官方的示例很全，官方参考示例：http://xstream.codehaus.org/tutorial.html
添加xstream-1.3.1.jar文件到工程中，就可以开始下面的工作；需要的jar如下：

2、 测试用例代码
package com.hoo.test;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.StringReader;
import java.io.Writer;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import org.codehaus.jettison.json.JSONException;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import com.hoo.entity.Birthday;
import com.hoo.entity.Classes;
import com.hoo.entity.ListBean;
import com.hoo.entity.Student;
import com.thoughtworks.xstream.XStream;
import com.thoughtworks.xstream.io.HierarchicalStreamWriter;
import com.thoughtworks.xstream.io.json.JettisonMappedXmlDriver;
import com.thoughtworks.xstream.io.json.JsonHierarchicalStreamDriver;
import com.thoughtworks.xstream.io.json.JsonWriter;

/**
* <b>function:</b>Java对象和XML字符串的相互转换
* jar-lib-version: xstream-1.3.1
* @author hoojo
* @createDate Nov 27, 2010 12:15:15 PM
* @file XStreamTest.java
* @package com.hoo.test
* @project WebHttpUtils
* @blog http://blog.csdn.net/IBM_hoojo
* @email [e-mail]
* @version 1.0
*/
@SuppressWarnings("unchecked")
public class XStreamTest {

private XStream xstream = null;
private ObjectOutputStream  out = null;
private ObjectInputStream in = null;

private Student bean = null;

/**
* <b>function:</b>初始化资源准备
* @author hoojo
* @createDate Nov 27, 2010 12:16:28 PM
*/
@Before
public void init() {
try {
xstream = new XStream();
//xstream = new XStream(new DomDriver()); // 需要xpp3 jar
} catch (Exception e) {
e.printStackTrace();
}
bean = new Student();
bean.setAddress("china");
bean.setEmail("[e-mail]");
bean.setId(1);
bean.setName("jack");
Birthday day = new Birthday();
day.setBirthday("2010-11-22");
bean.setBirthday(day);
}

/**
* <b>function:</b>释放对象资源
* @author hoojo
* @createDate Nov 27, 2010 12:16:38 PM
*/
@After
public void destory() {
xstream = null;
bean = null;
try {
if (out != null) {
out.flush();
out.close();
}
if (in != null) {
in.close();
}
} catch (IOException e) {
e.printStackTrace();
}
System.gc();
}

public final void fail(String string) {
System.out.println(string);
}

public final void failRed(String string) {
System.err.println(string);
}
}
通过XStream对象的toXML方法就可以完成Java对象到XML的转换，toXML方法还有2个相同签名的方法，需要传递一个流。然后通过流来完成xml信息的输出。
3、 需要的JavaBean
package com.hoo.entity;

public class Student {
private int id;
private String name;
private String email;
private String address;
private Birthday birthday;
    //getter、setter
public String toString() {
return this.name + "#" + this.id + "#" + this.address + "#" + this.birthday + "#" + this.email;
}
}

二、 Java转换成XML
1、 JavaBean转换XM
/**
* <b>function:</b>Java对象转换成XML字符串
* @author hoojo
* @createDate Nov 27, 2010 12:19:01 PM
*/
@Test
public void writeBean2XML() {
try {
fail("------------Bean->XML------------");
fail(xstream.toXML(bean));
fail("重命名后的XML");
//类重命名
//xstream.alias("account", Student.class);
//xstream.alias("生日", Birthday.class);
//xstream.aliasField("生日", Student.class, "birthday");
//xstream.aliasField("生日", Birthday.class, "birthday");
//fail(xstream.toXML(bean));
//属性重命名
xstream.aliasField("邮件", Student.class, "email");
//包重命名
xstream.aliasPackage("hoo", "com.hoo.entity");
fail(xstream.toXML(bean));
} catch (Exception e) {
e.printStackTrace();
}
}
看结果中的第一份xml内容，是没有经过然后修改或重命名的文档，按照原样输出。文档中的第二份文档的package经过重命名，email属性也经过重命名以及类名也可以进行重命名的。
运行后结果如下：
------------Bean->XML------------
<com.hoo.entity.Student>
  <id>1</id>
  <name>jack</name>
  <email>[e-mail]</email>
  <address>china</address>
  <birthday>
    <birthday>2010-11-22</birthday>
  </birthday>
</com.hoo.entity.Student>
重命名后的XML
<hoo.Student>
  <id>1</id>
  <name>jack</name>
  <邮件>[e-mail]</邮件>
  <address>china</address>
  <birthday>
    <birthday>2010-11-22</birthday>
  </birthday>
</hoo.Student>

2、 将List集合转换成xml文档
/**
* <b>function:</b>将Java的List集合转换成XML对象
* @author hoojo
* @createDate Nov 27, 2010 12:20:07 PM
*/
@Test
public void writeList2XML() {
try {
//修改元素名称
xstream.alias("beans", ListBean.class);
xstream.alias("student", Student.class);
fail("----------List-->XML----------");
ListBean listBean = new ListBean();
listBean.setName("this is a List Collection");

List<Object> list = new ArrayList<Object>();
list.add(bean);
list.add(bean);//引用bean
//list.add(listBean);//引用listBean，父元素

bean = new Student();
bean.setAddress("china");
bean.setEmail("[e-mail]");
bean.setId(2);
bean.setName("tom");
Birthday day = new Birthday("2010-11-22");
bean.setBirthday(day);

list.add(bean);
listBean.setList(list);

//将ListBean中的集合设置空元素，即不显示集合元素标签
//xstream.addImplicitCollection(ListBean.class, "list");

//设置reference模型
//xstream.setMode(XStream.NO_REFERENCES);//不引用
xstream.setMode(XStream.ID_REFERENCES);//id引用
//xstream.setMode(XStream.XPATH_ABSOLUTE_REFERENCES);//绝对路径引用
 
//将name设置为父类（Student）的元素的属性
xstream.useAttributeFor(Student.class, "name");
xstream.useAttributeFor(Birthday.class, "birthday");
//修改属性的name
xstream.aliasAttribute("姓名", "name");
        xstream.aliasField("生日", Birthday.class, "birthday");
     
fail(xstream.toXML(listBean));
} catch (Exception e) {
e.printStackTrace();
}
}
上面的代码运行后，结果如下：
----------List-->XML----------
<beans id="1">
  <name>this is a List Collection</name>
  <list id="2">
    <student id="3" 姓名="jack">
      <id>1</id>
      <email>[e-mail]</email>
      <address>china</address>
      <birthday id="4" 生日="2010-11-22"/>
    </student>
    <student reference="3"/>
    <student id="5" 姓名="tom">
      <id>2</id>
      <email>[e-mail]</email>
      <address>china</address>
      <birthday id="6" 生日="2010-11-22"/>
    </student>
  </list>
</beans>
如果不加xstream.addImplicitCollection(ListBean.class, "list");
这个设置的话，会出现一个List节点包裹着Student节点元素。添加addImplicitCollection可以忽略这个list节点元素。那么上面的list节点就不存在，只会在beans元素中出现name、student这2个xml元素标签；
setMode是设置相同的对象的引用方式，如果设置XStream.NO_REFERENCES就是不引用，会输出2分相同的Student元素。如果是XStream.ID_REFERENCES会引用相同的那个对象的id属性，如果是XStream.XPATH_ABSOLUTE_REFERENCES引用，那么它将显示xpath路径。上面采用的id引用，<student reference="3"/>这个引用了id=3的那个student标签元素；
useAttributeFor是设置某个节点显示到父节点的属性中，也就是将指定class中的指定属性，在这个class元素节点的属性中显示。
如：<student><name>hoojo</name></student>
设置好后就是这样的结果：<student name=”hoojo”></student>
aliasAttribute是修改属性名称。
3、 在JavaBean中添加Annotation注解进行重命名设置
先看看JavaBean的代码
package com.hoo.entity;

import java.util.Arrays;
import java.util.Calendar;
import java.util.GregorianCalendar;
import java.util.List;
import com.thoughtworks.xstream.annotations.XStreamAlias;
import com.thoughtworks.xstream.annotations.XStreamAsAttribute;
import com.thoughtworks.xstream.annotations.XStreamConverter;
import com.thoughtworks.xstream.annotations.XStreamImplicit;
import com.thoughtworks.xstream.annotations.XStreamOmitField;

@XStreamAlias("class")
public class Classes {

/*
* 设置属性显示
*/
@XStreamAsAttribute
@XStreamAlias("名称")
private String name;

/*
* 忽略
*/
@XStreamOmitField
private int number;

@XStreamImplicit(itemFieldName = "Students")
private List<Student> students;

@SuppressWarnings("unused")
@XStreamConverter(SingleValueCalendarConverter.class)
private Calendar created = new GregorianCalendar();


public Classes(){}
public Classes(String name, Student... stu) {
this.name = name;
this.students = Arrays.asList(stu);
}
//getter、setter
}
SingleValueCalendarConverter.java这个是一个类型转换器
package com.hoo.entity;

import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import com.thoughtworks.xstream.converters.Converter;
import com.thoughtworks.xstream.converters.MarshallingContext;
import com.thoughtworks.xstream.converters.UnmarshallingContext;
import com.thoughtworks.xstream.io.HierarchicalStreamReader;
import com.thoughtworks.xstream.io.HierarchicalStreamWriter;

public class SingleValueCalendarConverter implements Converter {
public void marshal(Object source, HierarchicalStreamWriter writer,
            MarshallingContext context) {
        Calendar calendar = (Calendar) source;
        writer.setValue(String.valueOf(calendar.getTime().getTime()));
    }

    public Object unmarshal(HierarchicalStreamReader reader,
            UnmarshallingContext context) {
        GregorianCalendar calendar = new GregorianCalendar();
        calendar.setTime(new Date(Long.parseLong(reader.getValue())));
        return calendar;
    }

    @SuppressWarnings("unchecked")
public boolean canConvert(Class type) {
        return type.equals(GregorianCalendar.class);
    }
}
再看看测试用例代码
@Test
public void writeList2XML4Annotation() {
try {
failRed("---------annotation Bean --> XML---------");
Student stu = new Student();
stu.setName("jack");
Classes c = new Classes("一班", bean, stu);
c.setNumber(2);
//对指定的类使用Annotation
//xstream.processAnnotations(Classes.class);
//启用Annotation
//xstream.autodetectAnnotations(true);
xstream.alias("student", Student.class);
fail(xstream.toXML(c));
} catch (Exception e) {
e.printStackTrace();
}
}
当启用annotation或是对某个特定的类启用annotation时，上面的classes这个类才有效果。如果不启用annotation，运行后结果如下：
---------annotation Bean --> XML---------
<com.hoo.entity.Classes>
  <name>一班</name>
  <number>2</number>
  <students class="java.util.Arrays$ArrayList">
    <a class="student-array">
      <student>
        <id>1</id>
        <name>jack</name>
        <email>[e-mail]</email>
        <address>china</address>
        <birthday>
          <birthday>2010-11-22</birthday>
        </birthday>
      </student>
      <student>
        <id>0</id>
        <name>jack</name>
      </student>
    </a>
  </students>
  <created>
    <time>1303292056718</time>
    <timezone>Asia/Shanghai</timezone>
  </created>
</com.hoo.entity.Classes>
当启用annotation后xstream.processAnnotations(Classes.class)，结果如下：
---------annotation Bean --> XML---------
<class 名称="一班">
  <Students>
    <id>1</id>
    <name>jack</name>
    <email>[e-mail]</email>
    <address>china</address>
    <birthday>
      <birthday>2010-11-22</birthday>
    </birthday>
  </Students>
  <Students>
    <id>0</id>
    <name>jack</name>
  </Students>
  <created>1303292242937</created>
</class>

4、 Map集合转换xml文档
/**
* <b>function:</b>Java Map集合转XML
* @author hoojo
* @createDate Nov 27, 2010 1:13:26 PM
*/
@Test
public void writeMap2XML() {
try {
failRed("---------Map --> XML---------");
Map<String, Student> map = new HashMap<String, Student>();
map.put("No.1", bean);//put

bean = new Student();
bean.setAddress("china");
bean.setEmail("[e-mail]");
bean.setId(2);
bean.setName("tom");
Birthday day = new Birthday("2010-11-22");
bean.setBirthday(day);
map.put("No.2", bean);//put

bean = new Student();
bean.setName("jack");
map.put("No.3", bean);//put

xstream.alias("student", Student.class);
xstream.alias("key", String.class);
xstream.useAttributeFor(Student.class, "id");
xstream.useAttributeFor("birthday", String.class);
fail(xstream.toXML(map));
} catch (Exception e) {
e.printStackTrace();
}
}
运行后结果如下：
---------Map --> XML---------
<map>
  <entry>
    <key>No.3</key>
    <student id="0">
      <name>jack</name>
    </student>
  </entry>
  <entry>
    <key>No.1</key>
    <student id="1">
      <name>jack</name>
      <email>[e-mail]</email>
      <address>china</address>
      <birthday birthday="2010-11-22"/>
    </student>
  </entry>
  <entry>
    <key>No.2</key>
    <student id="2">
      <name>tom</name>
      <email>[e-mail]</email>
      <address>china</address>
      <birthday birthday="2010-11-22"/>
    </student>
  </entry>
</map>

5、 用OutStream输出流写XML
/**
* <b>function:</b>用OutStream输出流写XML
* @author hoojo
* @createDate Nov 27, 2010 1:13:48 PM
*/
@Test
public void writeXML4OutStream() {
try {
out = xstream.createObjectOutputStream(System.out);
Student stu = new Student();
stu.setName("jack");
Classes c = new Classes("一班", bean, stu);
c.setNumber(2);
failRed("---------ObjectOutputStream # JavaObject--> XML---------");
out.writeObject(stu);
out.writeObject(new Birthday("2010-05-33"));
out.write(22);//byte
out.writeBoolean(true);
out.writeFloat(22.f);
out.writeUTF("hello");

} catch (Exception e) {
e.printStackTrace();
}
}
使用输出流后，可以通过流对象完成xml的构建，即使没有JavaBean对象，你可以用流来构建一个复杂的xml文档，运行后结果如下：
---------ObjectOutputStream # JavaObject--> XML---------
<object-stream>
  <com.hoo.entity.Student>
    <id>0</id>
    <name>jack</name>
  </com.hoo.entity.Student>
  <com.hoo.entity.Birthday>
    <birthday>2010-05-33</birthday>
  </com.hoo.entity.Birthday>
  <byte>22</byte>
  <boolean>true</boolean>
  <float>22.0</float>
  <string>hello</string>
</object-stream>

三、 XML内容转换Java对象
1、 用InputStream将XML文档转换成java对象
/**
* <b>function:</b>用InputStream将XML文档转换成java对象
* 需要额外的jar xpp3-main.jar
* @author hoojo
* @createDate Nov 27, 2010 1:14:52 PM
*/
@Test
public void readXML4InputStream() {
try {
String s = "<object-stream><com.hoo.entity.Student><id>0</id><name>jack</name>" +
  "</com.hoo.entity.Student><com.hoo.entity.Birthday><birthday>2010-05-33</birthday>" +
  "</com.hoo.entity.Birthday><byte>22</byte><boolean>true</boolean><float>22.0</float>" +
  "<string>hello</string></object-stream>";
failRed("---------ObjectInputStream## XML --> javaObject---------");
StringReader reader = new StringReader(s);
in = xstream.createObjectInputStream(reader);
Student stu = (Student) in.readObject();
Birthday b = (Birthday) in.readObject();
byte i = in.readByte();
boolean bo = in.readBoolean();
float f = in.readFloat();
String str = in.readUTF();
System.out.println(stu);
System.out.println(b);
System.out.println(i);
System.out.println(bo);
System.out.println(f);
System.out.println(str);
} catch (Exception e) {
e.printStackTrace();
}
}
读取后，转换的Java对象，结果如下：
---------ObjectInputStream## XML --> javaObject---------
jack#0#null#null#null
2010-05-33
22
true
22.0
hello

2、 将xml文档转换成Java对象
/**
* <b>function:</b>将XML字符串转换成Java对象
* @author hoojo
* @createDate Nov 27, 2010 2:39:06 PM
*/
@Test
public void readXml2Object() {
try {
failRed("-----------Xml >>> Bean--------------");
Student stu = (Student) xstream.fromXML(xstream.toXML(bean));
fail(stu.toString());

List<Student> list = new ArrayList<Student>();
        list.add(bean);//add
       
        Map<String, Student> map = new HashMap<String, Student>();
map.put("No.1", bean);//put
       
        bean = new Student();
bean.setAddress("china");
bean.setEmail("[e-mail]");
bean.setId(2);
bean.setName("tom");
Birthday day = new Birthday("2010-11-22");
bean.setBirthday(day);
        list.add(bean);//add
        map.put("No.2", bean);//put
       
        bean = new Student();
bean.setName("jack");
list.add(bean);//add
map.put("No.3", bean);//put

failRed("==========XML >>> List===========");
List<Student> studetns = (List<Student>) xstream.fromXML(xstream.toXML(list));
fail("size:" + studetns.size());//3
for (Student s : studetns) {
fail(s.toString());
}

failRed("==========XML >>> Map===========");
Map<String, Student> maps = (Map<String, Student>) xstream.fromXML(xstream.toXML(map));
fail("size:" + maps.size());//3
Set<String> key = maps.keySet();
Iterator<String> iter = key.iterator();
while (iter.hasNext()) {
String k = iter.next();
fail(k + ":" + map.get(k));
}
} catch (Exception e) {
e.printStackTrace();
}
}
运行后结果如下：
-----------Xml >>> Bean--------------
jack#1#china#2010-11-22#[e-mail]
==========XML >>> List===========
size:3
jack#1#china#2010-11-22#[e-mail]
tom#2#china#2010-11-22#[e-mail]
jack#0#null#null#null
==========XML >>> Map===========
size:3
No.3:jack#0#null#null#null
No.1:jack#1#china#2010-11-22#[e-mail]
No.2:tom#2#china#2010-11-22#[e-mail]
怎么样，成功的完成XML到JavaBean、List、Map的转换，更多对象转换还需要大家一一尝试。用法类似~这里就不一样赘述。

四、 XStream对JSON的支持
xStream对JSON也有非常好的支持，它提供了2个模型驱动。用这2个驱动可以完成Java对象到JSON的相互转换。使用JettisonMappedXmlDriver驱动，将Java对象转换成json，需要添加jettison.jar
1、 用JettisonMappedXmlDriver完成Java对象到JSON的转换
/**
* <b>function:</b>XStream结合JettisonMappedXmlDriver驱动，转换Java对象到JSON
* 需要添加jettison jar
* @author hoojo
* @createDate Nov 27, 2010 1:23:18 PM
*/
@Test
public void writeEntity2JETTSON() {
failRed("=======JettisonMappedXmlDriver===JavaObject >>>> JaonString=========");
xstream = new XStream(new JettisonMappedXmlDriver());
    xstream.setMode(XStream.NO_REFERENCES);
    xstream.alias("student", Student.class);
    fail(xstream.toXML(bean));
}
运行后结果如下：
=======JettisonMappedXmlDriver===JavaObject >>>> JaonString=========
{"student":{"id":1,"name":"jack","email":"[e-mail]","address":"china","birthday":[{},"2010-11-22"]}}
JSON的转换和XML的转换用法一样，只是创建XStream需要传递一个参数，这个参数就是xml到JSON映射转换的驱动。这里会降到两个驱动，分别是JettisonMappedXmlDriver、JsonHierarchicalStreamDriver。
2、 JsonHierarchicalStreamDriver完成Java对象到JSON的转换
/**
* <b>function:</b>用XStream结合JsonHierarchicalStreamDriver驱动
* 转换java对象为JSON字符串
* @author hoojo
* @createDate Nov 27, 2010 1:16:46 PM
*/
@Test
public void writeEntiry2JSON() {
failRed("======JsonHierarchicalStreamDriver====JavaObject >>>> JaonString=========");
xstream = new XStream(new JsonHierarchicalStreamDriver());
    //xstream.setMode(XStream.NO_REFERENCES);
    xstream.alias("student", Student.class);
    failRed("-------Object >>>> JSON---------");
    fail(xstream.toXML(bean));
   
    //failRed("========JsonHierarchicalStreamDriver==删除根节点=========");
    //删除根节点
    xstream = new XStream(new JsonHierarchicalStreamDriver() {
public HierarchicalStreamWriter createWriter(Writer out) {
return new JsonWriter(out, JsonWriter.DROP_ROOT_MODE);
}
    });
    //xstream.setMode(XStream.NO_REFERENCES);
    xstream.alias("student", Student.class);
    fail(xstream.toXML(bean));
}
运行后结果如下：
======JsonHierarchicalStreamDriver====JavaObject >>>> JaonString=========
-------Object >>>> JSON---------
{"student": {
  "id": 1,
  "name": "jack",
  "email": "[e-mail]",
  "address": "china",
  "birthday": {
    "birthday": "2010-11-22"
  }
}}
{
  "id": 1,
  "name": "jack",
  "email": "[e-mail]",
  "address": "china",
  "birthday": {
    "birthday": "2010-11-22"
  }
}
使用JsonHierarchicalStreamDriver转换默认会给转换后的对象添加一个根节点，但是在构建JsonHierarchicalStreamDriver驱动的时候，你可以重写createWriter方法，删掉根节点。
看上面的结果，一个是默认带根节点的JSON对象，它只是将类名作为一个属性，将对象作为该属性的一个值。而另一个没有带根属性的JSON就是通过重写createWriter方法完成的。
3、 将List集合转换成JSON字符串
@Test
public void writeList2JSON() {
failRed("======JsonHierarchicalStreamDriver====JavaObject >>>> JaonString=========");
JsonHierarchicalStreamDriver driver = new JsonHierarchicalStreamDriver();
xstream = new XStream(driver);
//xstream = new XStream(new JettisonMappedXmlDriver());//转换错误
    //xstream.setMode(XStream.NO_REFERENCES);
    xstream.alias("student", Student.class);
   
    List<Student> list = new ArrayList<Student>();
    list.add(bean);//add
   
    bean = new Student();
bean.setAddress("china");
bean.setEmail("[e-mail]");
bean.setId(2);
bean.setName("tom");
Birthday day = new Birthday("2010-11-22");
bean.setBirthday(day);
    list.add(bean);//add
   
    bean = new Student();
bean.setName("jack");
list.add(bean);//add
   
    fail(xstream.toXML(list));
   
    //failRed("========JsonHierarchicalStreamDriver==删除根节点=========");
    //删除根节点
    xstream = new XStream(new JsonHierarchicalStreamDriver() {
public HierarchicalStreamWriter createWriter(Writer out) {
return new JsonWriter(out, JsonWriter.DROP_ROOT_MODE);
}
    });
    xstream.alias("student", Student.class);
    fail(xstream.toXML(list));
}
运行后结果如下
======JsonHierarchicalStreamDriver====JavaObject >>>> JaonString=========
##{"list": [
  {
    "id": 1,
    "name": "jack",
    "email": "[e-mail]",
    "address": "china",
    "birthday": {
      "birthday": "2010-11-22"
    }
  },
  {
    "id": 2,
    "name": "tom",
    "email": "[e-mail]",
    "address": "china",
    "birthday": {
      "birthday": "2010-11-22"
    }
  },
  {
    "id": 0,
    "name": "jack"
  }
]}
#[
  {
    "id": 1,
    "name": "jack",
    "email": "[e-mail]",
    "address": "china",
    "birthday": {
      "birthday": "2010-11-22"
    }
  },
  {
    "id": 2,
    "name": "tom",
    "email": "[e-mail]",
    "address": "china",
    "birthday": {
      "birthday": "2010-11-22"
    }
  },
  {
    "id": 0,
    "name": "jack"
  }
]
上面的list1是使用JsonHierarchicalStreamDriver 转换的，当然你也可以使用JettisonMappedXmlDriver驱动进行转换；用JettisonMappedXmlDriver转换后，你会发现格式不同而且没有根属性。

4、 Map转换json
@Test
public void writeMap2JSON() {
failRed("======JsonHierarchicalStreamDriver==== Map >>>> JaonString=========");
xstream = new XStream(new JsonHierarchicalStreamDriver());
//xstream = new XStream(new JettisonMappedXmlDriver());
    xstream.alias("student", Student.class);
   
    Map<String, Student> map = new HashMap<String, Student>();
map.put("No.1", bean);//put

bean = new Student();
bean.setAddress("china");
bean.setEmail("[e-mail]");
bean.setId(2);
bean.setName("tom");
bean.setBirthday(new Birthday("2010-11-21"));
map.put("No.2", bean);//put

bean = new Student();
bean.setName("jack");
map.put("No.3", bean);//put
   
    fail(xstream.toXML(map));
   
    //failRed("========JsonHierarchicalStreamDriver==删除根节点=========");
    //删除根节点
    xstream = new XStream(new JsonHierarchicalStreamDriver() {
public HierarchicalStreamWriter createWriter(Writer out) {
return new JsonWriter(out, JsonWriter.DROP_ROOT_MODE);
}
    });
    xstream.alias("student", Student.class);
    fail(xstream.toXML(map));
}
运行后结果如下：
======JsonHierarchicalStreamDriver==== Map >>>> JaonString=========
{"map": [
  [
    "No.3",
    {
      "id": 0,
      "name": "jack"
    }
  ],
  [
    "No.1",
    {
      "id": 1,
      "name": "jack",
      "email": "[e-mail]",
      "address": "china",
      "birthday": {
        "birthday": "2010-11-22"
      }
    }
  ],
  [
    "No.2",
    {
      "id": 2,
      "name": "tom",
      "email": "[e-mail]",
      "address": "china",
      "birthday": {
        "birthday": "2010-11-21"
      }
    }
  ]
]}
[
  [
    "No.3",
    {
      "id": 0,
      "name": "jack"
    }
  ],
  [
    "No.1",
    {
      "id": 1,
      "name": "jack",
      "email": "[e-mail]",
      "address": "china",
      "birthday": {
        "birthday": "2010-11-22"
      }
    }
  ],
  [
    "No.2",
    {
      "id": 2,
      "name": "tom",
      "email": "[e-mail]",
      "address": "china",
      "birthday": {
        "birthday": "2010-11-21"
      }
    }
  ]
]

5、 将JSON转换java对象
/**
* <b>function:</b>JsonHierarchicalStreamDriver可以将简单的json字符串转换成java对象，list、map转换不成功；
* JsonHierarchicalStreamDriver读取JSON字符串到java对象出错
* @author hoojo
* @createDate Nov 27, 2010 1:22:26 PM
* @throws JSONException
*/
@Test
public void readJSON2Object() throws JSONException {
String json = "{\"student\": {" +
"\"id\": 1," +
"\"name\": \"haha\"," +
"\"email\": \"email\"," +
"\"address\": \"address\"," +
"\"birthday\": {" +
    "\"birthday\": \"2010-11-22\"" +
"}" +
"}}";
//JsonHierarchicalStreamDriver读取JSON字符串到java对象出错，但JettisonMappedXmlDriver可以
xstream = new XStream(new JettisonMappedXmlDriver());
    xstream.alias("student", Student.class);
    fail(xstream.fromXML(json).toString());
   
    //JettisonMappedXmlDriver转换List集合出错，但JsonHierarchicalStreamDriver可以转换正确
    //JettisonMappedXmlDriver 转换的字符串 {"list":{"student":[{"id":1,"name":"haha","email":"email","address":"address","birthday":[{},"2010-11-22"]}]},"student":{"id":2,"name":"tom","email":"[e-mail]","address":"china","birthday":[{},"2010-11-22"]}}
    json = "{\"list\": [{" +
        "\"id\": 1," +
        "\"name\": \"haha\"," +
        "\"email\": \"email\"," +
        "\"address\": \"address\"," +
        "\"birthday\": {" +
          "\"birthday\": \"2010-11-22\"" +
        "}" +
       "},{" +
        "\"id\": 2," +
        "\"name\": \"tom\"," +
        "\"email\": \"[e-mail]\"," +
        "\"address\": \"china\"," +
        "\"birthday\": {" +
          "\"birthday\": \"2010-11-22\"" +
        "}" +
      "}]}";
    System.out.println(json);//用js转换成功
    List list = (List) xstream.fromXML(json);
    System.out.println(list.size());//0好像转换失败
}
运行后结果如下：
haha#1#address#2010-11-22#email
{"list": [{"id": 1,"name": "haha","email": "email","address": "address","birthday": {"birthday": "2010-11-22"}},{"id": 2,"name": "tom","email": "[e-mail]","address": "china","birthday": {"birthday": "2010-11-22"}}]}
0
JSON到Java的转换是fromXML方法。