原文出处：
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：
以及Jackson这个框架，在线博文：
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：
官方的示例很全，官方参考示例：
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; /** * function: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 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; /** * function: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); } /** * function: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
/** * function:Java对象转换成XML字符串 * @author hoojo * @createDate Nov 27, 2010 12:19:01 PM */@Testpublic 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------------
1 jack jack@email.com china2010-11-22
重命名后的XML
1 jack <邮件> jack@email.com china2010-11-22
2、 将List集合转换成xml文档
/** * function:将Java的List集合转换成XML对象 * @author hoojo * @createDate Nov 27, 2010 12:20:07 PM */@Testpublic 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 上面的代码运行后，结果如下：
----------List-->XML----------
this is a List Collection
1 jack@email.com china2 tom@125.com china
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 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
@Testpublic 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---------
一班 2 1 jack jack@email.com china2010-11-22 0 jack Asia/Shanghai
当启用annotation后xstream.processAnnotations(Classes.class)，结果如下：
---------annotation Bean --> XML---------
1 jack jack@email.com china2010-11-22 0 jack 1303292242937
4、 Map集合转换xml文档
/** * function:Java Map集合转XML * @author hoojo * @createDate Nov 27, 2010 1:13:26 PM */@Testpublic void writeMap2XML() { try { failRed("---------Map --> XML---------"); Map map = new HashMap (); 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---------
5、 用OutStream输出流写XML
/** * function:用OutStream输出流写XML * @author hoojo * @createDate Nov 27, 2010 1:13:48 PM */@Testpublic 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---------
0 jack 2010-05-33 22 true 22.0 hello
三、XML内容转换Java对象
1、 用InputStream将XML文档转换成java对象
/** * function: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 */@Testpublic void readXML4InputStream() { try { String s = " 0 jack " + " 2010-05-33 " + " 22 true 22.0 " + " hello "; 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#null2010-05-3322true22.0hello
2、 将xml文档转换成Java对象
/** * function:将XML字符串转换成Java对象 * @author hoojo * @createDate Nov 27, 2010 2:39:06 PM */@Testpublic void readXml2Object() { try { failRed("-----------Xml >>> Bean--------------"); Student stu = (Student) xstream.fromXML(xstream.toXML(bean)); fail(stu.toString()); List list = new ArrayList (); list.add(bean);//add Map map = new HashMap (); 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 studetns = (List ) xstream.fromXML(xstream.toXML(list)); fail("size:" + studetns.size());//3 for (Student s : studetns) { fail(s.toString()); } failRed("==========XML >>> Map==========="); Map maps = (Map ) xstream.fromXML(xstream.toXML(map)); fail("size:" + maps.size());//3 Set key = maps.keySet(); Iterator 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:3jack#1#china#2010-11-22#jack@email.comtom#2#china#2010-11-22#tom@125.comjack#0#null#null#null==========XML >>> Map===========size:3No.3:jack#0#null#null#nullNo.1:jack#1#china#2010-11-22#jack@email.comNo.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
/** * function: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 */@Testpublic 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
/** * function: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 */@Testpublic 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
@Testpublic 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 list = new ArrayList (); 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
@Testpublic void writeMap2JSON() { failRed("======JsonHierarchicalStreamDriver==== Map >>>> JaonString========="); xstream = new XStream(new JsonHierarchicalStreamDriver()); //xstream = new XStream(new JettisonMappedXmlDriver()); xstream.alias("student", Student.class); Map map = new HashMap (); 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
/** * function: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 */@Testpublic 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。