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

 * @email [email protected]

 * @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("[email protected]");

        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("[email protected]");

        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("[email protected]");

        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("[email protected]");

        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#[email protected]

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

size:3

jack#1#china#2010-11-22#[email protected]

tom#2#china#2010-11-22#[email protected]

jack#0#null#null#null

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

size:3

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

No.1:jack#1#china#2010-11-22#[email protected]

No.2:tom#2#china#2010-11-22#[email protected]

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":"[email protected]","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": "[email protected]",

  "address": "china",

  "birthday": {

    "birthday": "2010-11-22"

  }

}}

{

  "id": 1,

  "name": "jack",

  "email": "[email protected]",

  "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("[email protected]");

    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": "[email protected]",

    "address": "china",

    "birthday": {

      "birthday": "2010-11-22"

    }

  },

  {

    "id": 2,

    "name": "tom",

    "email": "[email protected]",

    "address": "china",

    "birthday": {

      "birthday": "2010-11-22"

    }

  },

  {

    "id": 0,

    "name": "jack"

  }

]}

#[

  {

    "id": 1,

    "name": "jack",

    "email": "[email protected]",

    "address": "china",

    "birthday": {

      "birthday": "2010-11-22"

    }

  },

  {

    "id": 2,

    "name": "tom",

    "email": "[email protected]",

    "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("[email protected]");

    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": "[email protected]",

      "address": "china",

      "birthday": {

        "birthday": "2010-11-22"

      }

    }

  ],

  [

    "No.2",

    {

      "id": 2,

      "name": "tom",

      "email": "[email protected]",

      "address": "china",

      "birthday": {

        "birthday": "2010-11-21"

      }

    }

  ]

]}

[

  [

    "No.3",

    {

      "id": 0,

      "name": "jack"

    }

  ],

  [

    "No.1",

    {

      "id": 1,

      "name": "jack",

      "email": "[email protected]",

      "address": "china",

      "birthday": {

        "birthday": "2010-11-22"

      }

    }

  ],

  [

    "No.2",

    {

      "id": 2,

      "name": "tom",

      "email": "[email protected]",

      "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":"[email protected]","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\": \"[email protected]\"," +

            "\"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": "[email protected]","address": "china","birthday": {"birthday": "2010-11-22"}}]}

0

JSON到Java的转换是fromXML方法。

原文地址：http://www.cnblogs.com/hoojo/archive/2011/04/22/2025197.html