android 中XML和對象轉換利器Xstream的使用

XStream框架:

雖說pull dom dom4j等優秀的xml解析工具使用非常廣泛,但對於複雜龐大的數據交互來說,使用它們無疑讓你倍加痛苦,你可能大部分精力都放在無聊繁瑣的解析和拼裝上,如果接口稍微改動,更令你有股辭職不相干的衝動,或許你更傾向選擇JSON,但有時候你還是不得不面對JSON,XML,對象之間的轉化的煩惱,如何用最簡單的辦法一統混亂的局面,讓你全心全意做設計寫業務?現在有了XStream,一切將變得美好,永遠告別原始手工作坊,讓你輕鬆的享受coding帶來的快樂

XStream可以輕易的將Java對象和xml文檔相互轉換，而且可以修改某個特定的屬性和節點名稱，而且也支持json的轉換；

 json-lib這個框架 ,Jackson這個框架， 它們都完美支持JSON，但是對xml的支持還不是很好。一定程度上限制了對Java對象的描述，不能讓xml完全體現到對Java對象的描述。這裏將會介紹XStream對JSON、XML的完美支持。XStream不僅對XML的轉換非常友好，而且提供annotation註解，可以在JavaBean中完成對xml節點、屬性的描述。以及對JSON也支持，只需要提供相關的JSONDriver就可以完成轉換。  

準備環境

首先去 Xstream官方網址 下載最新的jar包,此jar包可以再java和Android環境下都適用

測試用例代碼

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對象和XML字符串的相互轉換
 * 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>初始化資源準備
     * @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>釋放對象資源
     * @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);
    }
}

通過XStream對象的toXML方法就可以完成Java對象到XML的轉換，toXML方法還有2個相同簽名的方法，需要傳遞一個流。然後通過流來完成xml信息的輸出。

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;
    }
}

一、Java轉換成XML

1、 JavaBean轉換XM

/**
 * <b>function:</b>Java對象轉換成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("重命名後的XML");
        //類重命名
        //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));
        //屬性重命名
        xstream.aliasField("郵件", Student.class, "email");
        //包重命名
        xstream.aliasPackage("hoo", "com.hoo.entity");
        fail(xstream.toXML(bean));
    } catch (Exception e) {
        e.printStackTrace();
    }
}

看結果中的第一份xml內容，是沒有經過然後修改或重命名的文檔，按照原樣輸出。文檔中的第二份文檔的package經過重命名，email屬性也經過重命名以及類名也可以進行重命名的。

運行後結果如下： 

------------Bean->XML------------

<com.hoo.entity.Student>
  <id>1</id>
  <name>jack</name>
  <email>[email protected]</email>
  <address>china</address>
  <birthday>
    <birthday>2010-11-22</birthday>
  </birthday>
</com.hoo.entity.Student>
重命名後的XML
<hoo.Student>
  <id>1</id>
  <name>jack</name>
  <郵件>[email protected]</郵件>
  <address>china</address>
  <birthday>
    <birthday>2010-11-22</birthday>
  </birthday>
</hoo.Student>

2、 將List集合轉換成xml文檔

/**
 * <b>function:</b>將Java的List集合轉換成XML對象
 * @author hoojo
 * @createDate Nov 27, 2010 12:20:07 PM
 */
@Test
public void writeList2XML() {
    try {
        //修改元素名稱
        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);

        //將ListBean中的集合設置空元素，即不顯示集合元素標籤
        //xstream.addImplicitCollection(ListBean.class, "list");

        //設置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);//絕對路徑引用

        //將name設置爲父類（Student）的元素的屬性
        xstream.useAttributeFor(Student.class, "name");
        xstream.useAttributeFor(Birthday.class, "birthday");
        //修改屬性的name
        xstream.aliasAttribute("姓名", "name");
        xstream.aliasField("生日", Birthday.class, "birthday");

        fail(xstream.toXML(listBean));
    } catch (Exception e) {
        e.printStackTrace();
    }
}

上面的代碼運行後，結果如下： 

----------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>[email protected]</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>[email protected]</email>
      <address>china</address>
      <birthday id="6" 生日="2010-11-22"/>
    </student>
  </list>
</beans>

如果不加xstream.addImplicitCollection(ListBean.class, "list");

這個設置的話，會出現一個List節點包裹着Student節點元素。添加addImplicitCollection可以忽略這個list節點元素。那麼上面的list節點就不存在，只會在beans元素中出現name、student這2個xml元素標籤；

setMode是設置相同的對象的引用方式，如果設置XStream.NO_REFERENCES就是不引用，會輸出2分相同的Student元素。如果是XStream.ID_REFERENCES會引用相同的那個對象的id屬性，如果是XStream.XPATH_ABSOLUTE_REFERENCES引用，那麼它將顯示xpath路徑。上面採用的id引用，<student reference="3"/>這個引用了id=3的那個student標籤元素；

useAttributeFor是設置某個節點顯示到父節點的屬性中，也就是將指定class中的指定屬性，在這個class元素節點的屬性中顯示。

如：<student><name>hoojo</name></student>

設置好後就是這樣的結果：<student name=”hoojo”></student>

aliasAttribute是修改屬性名稱。

3、 在JavaBean中添加Annotation註解進行重命名設置

先看看JavaBean的代碼 

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 {

    /*
     * 設置屬性顯示
     */
    @XStreamAsAttribute
    @XStreamAlias("名稱")
    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這個是一個類型轉換器

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);
        }
}
再看看測試用例代碼
@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);
        //對指定的類使用Annotation
        //xstream.processAnnotations(Classes.class);
        //啓用Annotation
        //xstream.autodetectAnnotations(true);
        xstream.alias("student", Student.class);
        fail(xstream.toXML(c));
    } catch (Exception e) {
        e.printStackTrace();
    }
}

當啓用annotation或是對某個特定的類啓用annotation時，上面的classes這個類纔有效果。如果不啓用annotation，運行後結果如下：

---------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>[email protected]</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>

當啓用annotation後xstream.processAnnotations(Classes.class)，結果如下：

---------annotation Bean --> XML---------

<class 名稱="一班">
  <Students>
    <id>1</id>
    <name>jack</name>
    <email>[email protected]</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集合轉換xml文檔 

/**
 * <b>function:</b>Java Map集合轉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();
    }
}

運行後結果如下： 

---------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>[email protected]</email>
      <address>china</address>
      <birthday birthday="2010-11-22"/>
    </student>
  </entry>
  <entry>
    <key>No.2</key>
    <student id="2">
      <name>tom</name>
      <email>[email protected]</email>
      <address>china</address>
      <birthday birthday="2010-11-22"/>
    </student>
  </entry>
</map>

5、 用OutStream輸出流寫XML

/**
 * <b>function:</b>用OutStream輸出流寫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();
    }
}

使用輸出流後，可以通過流對象完成xml的構建，即使沒有JavaBean對象，你可以用流來構建一個複雜的xml文檔，運行後結果如下：

---------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>

二、XML內容轉換Java對象

1、 用InputStream將XML文檔轉換成java對象

/**
 * <b>function:</b>用InputStream將XML文檔轉換成java對象
 * 需要額外的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();
    }
}

讀取後，轉換的Java對象，結果如下： 

---------ObjectInputStream## XML --> javaObject---------

jack#0#null#null#null
2010-05-33
22
true
22.0
hello

2、 將xml文檔轉換成Java對象 

/**
 * <b>function:</b>將XML字符串轉換成Java對象
 * @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();
    }
}

運行後結果如下： 

-----------Xml >>> Bean--------------

jack#1#china#2010-11-22#[e-mail]
==========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]

怎麼樣，成功的完成XML到JavaBean、List、Map的轉換，更多對象轉換還需要大家一一嘗試。用法類似~這裏就不一樣贅述。

三、XStream對JSON的支持

xStream對JSON也有非常好的支持，它提供了2個模型驅動。用這2個驅動可以完成Java對象到JSON的相互轉換。使用JettisonMappedXmlDriver驅動，將Java對象轉換成json，需要添加jettison.jar

1、 用JettisonMappedXmlDriver完成Java對象到JSON的轉換

/**
 * <b>function:</b>XStream結合JettisonMappedXmlDriver驅動，轉換Java對象到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));
}

運行後結果如下： 

=======JettisonMappedXmlDriver===JavaObject >>>> JaonString=========

{"student":{"id":1,"name":"jack","email":"[email protected]","address":"china","birthday":[{},"2010-11-22"]}}

JSON的轉換和XML的轉換用法一樣，只是創建XStream需要傳遞一個參數，這個參數就是xml到JSON映射轉換的驅動。這裏會降到兩個驅動，分別是JettisonMappedXmlDriver、JsonHierarchicalStreamDriver。

2、 JsonHierarchicalStreamDriver完成Java對象到JSON的轉換

/**
 * <b>function:</b>用XStream結合JsonHierarchicalStreamDriver驅動
 * 轉換java對象爲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==刪除根節點=========");
    //刪除根節點
    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));
}

運行後結果如下： 

======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轉換默認會給轉換後的對象添加一個根節點，但是在構建JsonHierarchicalStreamDriver驅動的時候，你可以重寫createWriter方法，刪掉根節點。

看上面的結果，一個是默認帶根節點的JSON對象，它只是將類名作爲一個屬性，將對象作爲該屬性的一個值。而另一個沒有帶根屬性的JSON就是通過重寫createWriter方法完成的。

3、 將List集合轉換成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());//轉換錯誤
    //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==刪除根節點=========");
    //刪除根節點
    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));
}

運行後結果如下 

======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 轉換的，當然你也可以使用JettisonMappedXmlDriver驅動進行轉換；用JettisonMappedXmlDriver轉換後，你會發現格式不同而且沒有根屬性。

4、 Map轉換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==刪除根節點=========");
    //刪除根節點
    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));
}

運行後結果如下： 

======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、 將JSON轉換java對象

/**
 * <b>function:</b>JsonHierarchicalStreamDriver可以將簡單的json字符串轉換成java對象，list、map轉換不成功；
 * JsonHierarchicalStreamDriver讀取JSON字符串到java對象出錯
 * @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讀取JSON字符串到java對象出錯，但JettisonMappedXmlDriver可以
    xstream = new XStream(new JettisonMappedXmlDriver());
    xstream.alias("student", Student.class);
    fail(xstream.fromXML(json).toString());

    //JettisonMappedXmlDriver轉換List集合出錯，但JsonHierarchicalStreamDriver可以轉換正確
    //JettisonMappedXmlDriver 轉換的字符串 {"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轉換成功
    List list = (List) xstream.fromXML(json);
    System.out.println(list.size());//0好像轉換失敗
}

運行後結果如下： 

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的轉換是fromXML方法。

四.android源碼實例

上面的代碼是不是還不夠過癮?Xstream原則上只要是符合XML和JSON語法規範的都能可以轉換成對象形式.

AndroidXstream示例下載 逐個手敲測試傾情奉上