xStream完美转换XML、JSON

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[/code] 
* @email hoojo_@126.com


* @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("jack@email.com");


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>jack@email.com</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>jack@email.com</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("tom@125.com");


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>jack@email.com</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>tom@125.com</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>jack@email.com</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>jack@email.com</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("tom@125.com");


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>jack@email.com</email>


<address>china</address>


  <birthday birthday="2010-11-22"/>


</student>


</entry>


<entry>


<key>No.2</key>


<student id="2">


  <name>tom</name>


  <email>tom@125.com</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("tom@125.com");


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#jack@email.com


==========XML >>> List===========


size:3


jack#1#china#2010-11-22#jack@email.com


tom#2#china#2010-11-22#tom@125.com


jack#0#null#null#null


==========XML >>> Map===========


size:3


No.3:jack#0#null#null#null


No.1:jack#1#china#2010-11-22#jack@email.com


No.2:tom#2#china#2010-11-22#tom@125.com


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":"jack@email.com","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": "jack@email.com",


"address": "china",


"birthday": {


"birthday": "2010-11-22"


}


}}


{


"id": 1,


"name": "jack",


"email": "jack@email.com",


"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("tom@125.com");


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": "jack@email.com",


"address": "china",


"birthday": {


  "birthday": "2010-11-22"


}


},


{


"id": 2,


"name": "tom",


"email": "tom@125.com",


"address": "china",


"birthday": {


  "birthday": "2010-11-22"


}


},


{


"id": 0,


"name": "jack"


}


]}


#[


{


"id": 1,


"name": "jack",


"email": "jack@email.com",


"address": "china",


"birthday": {


  "birthday": "2010-11-22"


}


},


{


"id": 2,


"name": "tom",


"email": "tom@125.com",


"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("tom@125.com");


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": "jack@email.com",


"address": "china",


"birthday": {


"birthday": "2010-11-22"


}


}


],


[


"No.2",


{


  "id": 2,


  "name": "tom",


  "email": "tom@125.com",


"address": "china",


"birthday": {


"birthday": "2010-11-21"


}


}


]


]}


[


[


"No.3",


{


  "id": 0,


  "name": "jack"


}


],


[


"No.1",


{


"id": 1,


"name": "jack",


"email": "jack@email.com",


"address": "china",


"birthday": {


"birthday": "2010-11-22"


}


}


],


[


"No.2",


{


  "id": 2,


  "name": "tom",


  "email": "tom@125.com",


"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":"tom@125.com","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/": /"tom@125.com/"," +


"/"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": "tom@125.com","address": "china","birthday": {"birthday": "2010-11-22"}}]}


0


JSON到Java的转换是fromXML方法。