(转)xStream圆满转换XML、JSON

2012-09-20

(转)xStream完美转换XML、JSONxStream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

(转)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：[url]http://www.cnblogs.com/hoojo/archive/2011/04/21/2023805.html [/url]

以及Jackson这个框架，在线博文：[url]http://www.cnblogs.com/hoojo/archive/2011/04/22/2024628.html [/url]

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：

[url]https://nexus.codehaus.org/content/repositories/releases/com/thoughtworks/xstream/xstream-distribution/1.3.1/xstream-distribution-1.3.1-bin.zip [/url]

官方的示例很全，官方参考示例：[url]http://xstream.codehaus.org/tutorial.html [/url]

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 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 */@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------------

<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>

可以用

XStream xstream = new XStream(new DomDriver());Annotations.configureAliases(xstream, WorkOrderNewRsp.class);

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 */@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<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 @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---------

<com.hoo.entity.Classes>  <name>一班</name>  <number>2</number>  <students name="code"><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 */@Testpublic 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 */@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---------

<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 */@Testpublic 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 */@Testpublic 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 */@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

/** * <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 */@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<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

@Testpublic 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 */@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。

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