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xStream完美转换XML、JSON

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排版不好,请看原文链接:http://www.cnblogs.com/hoojo/archive/2011/04/22/2025197.html

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:

clip_image002

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

 */

@Test
public

 void

 writeBean2XML() {
    try

 {
        fail("------------Bean->XML------------"

);
        fail(xstream.toXML(bean));
        fail("重命名后的XML"

);
        //类重命名

        //xstream.alias("account", Student.class);

        //xstream.alias("生日", Birthday.class);

        //xstream.aliasField("生日", Student.class, "birthday");

        //xstream.aliasField("生日", Birthday.class, "birthday");

        //fail(xstream.toXML(bean));

        //属性重命名

        xstream.aliasField("邮件"

, Student.class

, "email"

);
        //包重命名

        xstream.aliasPackage("hoo"

, "com.hoo.entity"

);
        fail(xstream.toXML(bean));
    } catch

 (Exception e) {
        e.printStackTrace();
    }
}

看结果中的第一份xml内容,是没有经过然后修改或重命名的文档,按照原样输出。文档中的第二份文档的package经过重命名,email属性也经过重命名以及类名也可以进行重命名的。

运行后结果如下:

------------Bean->

XML------------
<

com.hoo

.entity

.Student

>

  <

id>

1<

/id>

  <

name>

jack<

/name>

  <

email>

jack@email.com

<

/email>

  <

address

>

china<

/address

>

  <

birthday>

    <

birthday>

2010-11-22<

/birthday>

  <

/birthday>

<

/com.hoo

.entity

.Student

>

重命名后的XML
<

hoo.Student

>

  <

id>

1<

/id>

  <

name>

jack<

/name>

  <

邮件>

jack@email.com

<

/邮件>

  <

address

>

china<

/address

>

  <

birthday>

    <

birthday>

2010-11-22<

/birthday>

  <

/birthday>

<

/hoo.Student

>

2、 将List集合转换成xml文档

/**

 * <b>function:</b>将Java的List集合转换成XML对象

 * @author hoojo

 * @createDate Nov 27, 2010 12:20:07 PM

 */

@Test
public

 void

 writeList2XML() {
    try

 {
        //修改元素名称

        xstream.alias("beans"

, ListBean.class

);
        xstream.alias("student"

, Student.class

);
        fail("----------List-->XML----------"

);
        ListBean listBean = new

 ListBean();
        listBean.setName("this is a List Collection"

);
        
        List<Object> list = new

 ArrayList<Object>();
        list.add(bean);
        list.add(bean);//引用bean

        //list.add(listBean);//引用listBean,父元素

        
        bean = new

 Student();
        bean.setAddress("china"

);
        bean.setEmail("tom@125.com"

);
        bean.setId(2);
        bean.setName("tom"

);
        Birthday day = new

 Birthday("2010-11-22"

);
        bean.setBirthday(day);
        
        list.add(bean);
        listBean.setList(list);
        
        //将ListBean中的集合设置空元素,即不显示集合元素标签

        //xstream.addImplicitCollection(ListBean.class, "list");

        
        //设置reference模型

        //xstream.setMode(XStream.NO_REFERENCES);//不引用

        xstream.setMode(XStream.ID_REFERENCES);//id引用

        //xstream.setMode(XStream.XPATH_ABSOLUTE_REFERENCES);//绝对路径引用

          
        //将name设置为父类(Student)的元素的属性

        xstream.useAttributeFor(Student.class

, "name"

);
        xstream.useAttributeFor(Birthday.class

, "birthday"

);
        //修改属性的name

        xstream.aliasAttribute("姓名"

, "name"

);
        xstream.aliasField("生日"

, Birthday.class

, "birthday"

);
      
        fail(xstream.toXML(listBean));
    } catch

 (Exception e) {
        e.printStackTrace();
    }
}

上面的代码运行后,结果如下:

----------List-->

XML----------
<

beans id="1">

  <

name>

this is a List Collection<

/name>

  <

list id="2">

    <

student id="3" 姓名="jack">

      <

id>

1<

/id>

      <

email>

jack@email.com

<

/email>

      <

address

>

china<

/address

>

      <

birthday id="4" 生日="2010-11-22"/>

    <

/student>

    <

student reference="3"/>

    <

student id="5" 姓名="tom">

      <

id>

2<

/id>

      <

email>

tom@125.com

<

/email>

      <

address

>

china<

/address

>

      <

birthday id="6" 生日="2010-11-22"/>

    <

/student>

  <

/list>

<

/beans>

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

这个设置的话,会出现一个List节点包裹着Student节点元素。添加addImplicitCollection可以忽略这个list节点元素。那么上面的list节点就不存在,只会在beans元素中出现name、student这2个xml元素标签;

setMode是设置相同的对象的引用方式,如果设置XStream.NO_REFERENCES就是不引用,会输出2分相同的Student元素。如果是XStream.ID_REFERENCES会引用相同的那个对象的id属性,如果是XStream.XPATH_ABSOLUTE_REFERENCES引用,那么它将显示xpath路径。上面采用的id引用,<student reference="3"/>这个引用了id=3的那个student标签元素;

useAttributeFor是设置某个节点显示到父节点的属性中,也就是将指定class中的指定属性,在这个class元素节点的属性中显示。

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

设置好后就是这样的结果:<student name=”hoojo”></student>

aliasAttribute是修改属性名称。

3、 在JavaBean中添加Annotation注解进行重命名设置

先看看JavaBean的代码

package

 com.hoo.entity;
 
import

 java.util.Arrays;
import

 java.util.Calendar;
import

 java.util.GregorianCalendar;
import

 java.util.List;
import

 com.thoughtworks.xstream.annotations.XStreamAlias;
import

 com.thoughtworks.xstream.annotations.XStreamAsAttribute;
import

 com.thoughtworks.xstream.annotations.XStreamConverter;
import

 com.thoughtworks.xstream.annotations.XStreamImplicit;
import

 com.thoughtworks.xstream.annotations.XStreamOmitField;
 
@XStreamAlias("class"

)
public

 class

 Classes {
    
    /*

     * 设置属性显示

     */

    @XStreamAsAttribute
    @XStreamAlias("名称"

)
    private

 String name;
    
    /*

     * 忽略

     */

    @XStreamOmitField
    private

 int

 number;
    
    @XStreamImplicit(itemFieldName = "Students"

)
    private

 List<Student> students;
    
    @SuppressWarnings("unused"

)
    @XStreamConverter(SingleValueCalendarConverter.class

)
    private

 Calendar created = new

 GregorianCalendar();
 
    
    public

 Classes(){}
    public

 Classes(String name, Student... stu) {
        this

.name = name;
        this

.students = Arrays.asList(stu);
    }
    //getter、setter

}

SingleValueCalendarConverter.java这个是一个类型转换器

package

 com.hoo.entity;
 
import

 java.util.Calendar;
import

 java.util.Date;
import

 java.util.GregorianCalendar;
import

 com.thoughtworks.xstream.converters.Converter;
import

 com.thoughtworks.xstream.converters.MarshallingContext;
import

 com.thoughtworks.xstream.converters.UnmarshallingContext;
import

 com.thoughtworks.xstream.io.HierarchicalStreamReader;
import

 com.thoughtworks.xstream.io.HierarchicalStreamWriter;
 
public

 class

 SingleValueCalendarConverter implements

 Converter {
     public

 void

 marshal(Object source, HierarchicalStreamWriter writer,
                MarshallingContext context) {
            Calendar calendar = (Calendar) source;
            writer.setValue(String.valueOf(calendar.getTime().getTime()));
        }
 
        public

 Object unmarshal(HierarchicalStreamReader reader,
                UnmarshallingContext context) {
            GregorianCalendar calendar = new

 GregorianCalendar();
            calendar.setTime(new

 Date(Long.parseLong(reader.getValue())));
            return

 calendar;
        }
 
        @SuppressWarnings("unchecked"

)
        public

 boolean

 canConvert(Class type) {
            return

 type.equals(GregorianCalendar.class

);
        }
}

再看看测试用例代码

@Test
public

 void

 writeList2XML4Annotation() {
    try

 {
        failRed("---------annotation Bean --> XML---------"

);
        Student stu = new

 Student();
        stu.setName("jack"

);
        Classes c = new

 Classes("一班"

, bean, stu);
        c.setNumber(2);
        //对指定的类使用Annotation

        //xstream.processAnnotations(Classes.class);

        //启用Annotation

        //xstream.autodetectAnnotations(true);

        xstream.alias("student"

, Student.class

);
        fail(xstream.toXML(c));
    } catch

 (Exception e) {
        e.printStackTrace();
    }
}

当启用annotation或是对某个特定的类启用annotation时,上面的classes这个类才有效果。如果不启用annotation,运行后结果如下:

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

 XML---------
<

com.hoo

.entity

.Classes

>

  <

name>

一班<

/name>

  <

number>

2<

/number>

  <

students class="java.util

.Arrays

$ArrayList">

    <

a class="student-array">

      <

student>

        <

id>

1<

/id>

        <

name>

jack<

/name>

        <

email>

jack@email.com

<

/email>

        <

address

>

china<

/address

>

        <

birthday>

          <

birthday>

2010-11-22<

/birthday>

        <

/birthday>

      <

/student>

      <

student>

        <

id>

0<

/id>

        <

name>

jack<

/name>

      <

/student>

    <

/a>

  <

/students>

  <

created>

    <

time>

1303292056718<

/time>

    <

timezone>

Asia/Shanghai<

/timezone>

  <

/created>

<

/com.hoo

.entity

.Classes

>

当启用annotation后xstream.processAnnotations(Classes.class),结果如下:

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

 XML---------
<

class 名称="一班">

  <

Students>

    <

id>

1<

/id>

    <

name>

jack<

/name>

    <

email>

jack@email.com

<

/email>

    <

address

>

china<

/address

>

    <

birthday>

      <

birthday>

2010-11-22<

/birthday>

    <

/birthday>

  <

/Students>

  <

Students>

    <

id>

0<

/id>

    <

name>

jack<

/name>

  <

/Students>

  <

created>

1303292242937<

/created>

<

/class>

4、 Map集合转换xml文档

/**

 * <b>function:</b>Java Map集合转XML

 * @author hoojo

 * @createDate Nov 27, 2010 1:13:26 PM

 */

@Test
public

 void

 writeMap2XML() {
    try

 {
        failRed("---------Map --> XML---------"

);
        Map<String, Student> map = new

 HashMap<String, Student>();
        map.put("No.1"

, bean);//put

        
        bean = new

 Student();
        bean.setAddress("china"

);
        bean.setEmail("tom@125.com"

);
        bean.setId(2);
        bean.setName("tom"

);
        Birthday day = new

 Birthday("2010-11-22"

);
        bean.setBirthday(day);
        map.put("No.2"

, bean);//put

        
        bean = new

 Student();
        bean.setName("jack"

);
        map.put("No.3"

, bean);//put

        
        xstream.alias("student"

, Student.class

);
        xstream.alias("key"

, String.class

);
        xstream.useAttributeFor(Student.class

, "id"

);
        xstream.useAttributeFor("birthday"

, String.class

);
        fail(xstream.toXML(map));
    } catch

 (Exception e) {
        e.printStackTrace();
    }
}

运行后结果如下:

---------Map -->

 XML---------
<

map

>

  <

entry>

    <

key>

No.3<

/key>

    <

student id="0">

      <

name>

jack<

/name>

    <

/student>

  <

/entry>

  <

entry>

    <

key>

No.1<

/key>

    <

student id="1">

      <

name>

jack<

/name>

      <

email>

jack@email.com

<

/email>

      <

address

>

china<

/address

>

      <

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

    <

/student>

  <

/entry>

  <

entry>

    <

key>

No.2<

/key>

    <

student id="2">

      <

name>

tom<

/name>

      <

email>

tom@125.com

<

/email>

      <

address

>

china<

/address

>

      <

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

    <

/student>

  <

/entry>

<

/map

>

5、 用OutStream输出流写XML

/**

 * <b>function:</b>用OutStream输出流写XML

 * @author hoojo

 * @createDate Nov 27, 2010 1:13:48 PM

 */

@Test
public

 void

 writeXML4OutStream() {
    try

 {
        out = xstream.createObjectOutputStream(System.out);
        Student stu = new

 Student();
        stu.setName("jack"

);
        Classes c = new

 Classes("一班"

, bean, stu);
        c.setNumber(2);
        failRed("---------ObjectOutputStream # JavaObject--> XML---------"

);
        out.writeObject(stu);
        out.writeObject(new

 Birthday("2010-05-33"

));
        out.write(22);//byte

        out.writeBoolean(true);
        out.writeFloat(22.f);
        out.writeUTF("hello"

);
        
    } catch

 (Exception e) {
        e.printStackTrace();
    }
}

使用输出流后,可以通过流对象完成xml的构建,即使没有JavaBean对象,你可以用流来构建一个复杂的xml文档,运行后结果如下:

---------ObjectOutputStream # JavaObject-->

 XML---------
<

object

-stream>

  <

com.hoo

.entity

.Student

>

    <

id>

0<

/id>

    <

name>

jack<

/name>

  <

/com.hoo

.entity

.Student

>

  <

com.hoo

.entity

.Birthday

>

    <

birthday>

2010-05-33<

/birthday>

  <

/com.hoo

.entity

.Birthday

>

  <

byte>

22<

/byte>

  <

boolean>

true<

/boolean>

  <

float

>

22.0<

/float

>

  <

string>

hello<

/string>

<

/object

-stream>

三、 XML 内容转换 Java 对象

1、 用InputStream将XML文档转换成java对象

/**

 * <b>function:</b>用InputStream将XML文档转换成java对象 

 * 需要额外的jar xpp3-main.jar

 * @author hoojo

 * @createDate Nov 27, 2010 1:14:52 PM

 */

@Test
public

 void

 readXML4InputStream() {
    try

 {
        String s = "<object-stream><com.hoo.entity.Student><id>0</id><name>jack</name>"

 +
          "</com.hoo.entity.Student><com.hoo.entity.Birthday><birthday>2010-05-33</birthday>"

 +
          "</com.hoo.entity.Birthday><byte>22</byte><boolean>true</boolean><float>22.0</float>"

 +
          "<string>hello</string></object-stream>"

;
        failRed("---------ObjectInputStream## XML --> javaObject---------"

);
        StringReader reader = new

 StringReader(s);
        in = xstream.createObjectInputStream(reader);
        Student stu = (Student) in.readObject();
        Birthday b = (Birthday) in.readObject();
        byte

 i = in.readByte();
        boolean

 bo = in.readBoolean();
        float

 f = in.readFloat();
        String str = in.readUTF();
        System.out.println(stu);
        System.out.println(b);
        System.out.println(i);
        System.out.println(bo);
        System.out.println(f);
        System.out.println(str);
    } catch

 (Exception e) {
        e.printStackTrace();
    }
}

读取后,转换的Java对象,结果如下:

---------ObjectInputStream## XML --> javaObject---------
jack#0#null#null#null
2010-05-33
22
true
22.0
hello

2、 将xml文档转换成Java对象

/**

 * <b>function:</b>将XML字符串转换成Java对象

 * @author hoojo

 * @createDate Nov 27, 2010 2:39:06 PM

 */

@Test
public

 void

 readXml2Object() {
    try

 {
        failRed("-----------Xml >>> Bean--------------"

);
        Student stu = (Student) xstream.fromXML(xstream.toXML(bean));
        fail(stu.toString());
        
        List<Student> list = new

 ArrayList<Student>();
        list.add(bean);//add

        
        Map<String, Student> map = new

 HashMap<String, Student>();
        map.put("No.1"

, bean);//put

        
        bean = new

 Student();
        bean.setAddress("china"

);
        bean.setEmail("tom@125.com"

);
        bean.setId(2);
        bean.setName("tom"

);
        Birthday day = new

 Birthday("2010-11-22"

);
        bean.setBirthday(day);
        list.add(bean);//add

        map.put("No.2"

, bean);//put

        
        bean = new

 Student();
        bean.setName("jack"

);
        list.add(bean);//add

        map.put("No.3"

, bean);//put

        
        failRed("==========XML >>> List==========="

);
        List<Student> studetns = (List<Student>) xstream.fromXML(xstream.toXML(list));
        fail("size:"

 + studetns.size());//3

        for

 (Student s : studetns) {
            fail(s.toString());
        }
        
        failRed("==========XML >>> Map==========="

);
        Map<String, Student> maps = (Map<String, Student>) xstream.fromXML(xstream.toXML(map));
        fail("size:"

 + maps.size());//3

        Set<String> key = maps.keySet();
        Iterator<String> iter = key.iterator();
        while

 (iter.hasNext()) {
            String k = iter.next();
            fail(k + ":"

 + map.get(k));
        }
    } catch

 (Exception e) {
        e.printStackTrace();
    }
}

运行后结果如下:

-----------Xml >>> Bean--------------
jack#1#china#2010-11-22#jack@email.com
==========XML >>> List===========
size:3
jack#1#china#2010-11-22#jack@email.com
tom#2#china#2010-11-22#tom@125.com
jack#0#null#null#null
==========XML >>> Map===========
size:3
No.3:jack#0#null#null#null
No.1:jack#1#china#2010-11-22#jack@email.com
No.2:tom#2#china#2010-11-22#tom@125.com

怎么样,成功的完成XML到JavaBean、List、Map的转换,更多对象转换还需要大家一一尝试。用法类似~这里就不一样赘述。

四、 XStream JSON 的支持

xStream对JSON也有非常好的支持,它提供了2个模型驱动。用这2个驱动可以完成Java对象到JSON的相互转换。使用JettisonMappedXmlDriver驱动,将Java对象转换成json,需要添加jettison.jar

1、 用JettisonMappedXmlDriver完成Java对象到JSON的转换

/**

 * <b>function:</b>XStream结合JettisonMappedXmlDriver驱动,转换Java对象到JSON

 * 需要添加jettison jar

 * @author hoojo

 * @createDate Nov 27, 2010 1:23:18 PM

 */

@Test
public

 void

 writeEntity2JETTSON() {
    failRed("=======JettisonMappedXmlDriver===JavaObject >>>> JaonString========="

);
    xstream = new

 XStream(new

 JettisonMappedXmlDriver());
    xstream.setMode(XStream.NO_REFERENCES);
    xstream.alias("student"

, Student.class

);
    fail(xstream.toXML(bean));
}

运行后结果如下:

=======JettisonMappedXmlDriver===JavaObject >>>> JaonString=========
{"student"

:{"id"

:1,"name"

:"jack"

,"email"

:"jack@email.com"

,"address"

:"china"

,"birthday"

:[{},"2010-11-22"

]}}

JSON的转换和XML的转换用法一样,只是创建XStream需要传递一个参数,这个参数就是xml到JSON映射转换的驱动。这里会降到两个驱动,分别是JettisonMappedXmlDriver、JsonHierarchicalStreamDriver。

2、 JsonHierarchicalStreamDriver完成Java对象到JSON的转换

/**

 * <b>function:</b>用XStream结合JsonHierarchicalStreamDriver驱动

 * 转换java对象为JSON字符串

 * @author hoojo

 * @createDate Nov 27, 2010 1:16:46 PM

 */

@Test
public

 void

 writeEntiry2JSON() {
    failRed("======JsonHierarchicalStreamDriver====JavaObject >>>> JaonString========="

);
    xstream = new

 XStream(new

 JsonHierarchicalStreamDriver());
    //xstream.setMode(XStream.NO_REFERENCES);

    xstream.alias("student"

, Student.class

);
    failRed("-------Object >>>> JSON---------"

);
    fail(xstream.toXML(bean));
    
    //failRed("========JsonHierarchicalStreamDriver==删除根节点=========");

    //删除根节点

    xstream = new

 XStream(new

 JsonHierarchicalStreamDriver() {
        public

 HierarchicalStreamWriter createWriter(Writer out) {
            return

 new

 JsonWriter(out, JsonWriter.DROP_ROOT_MODE);
        }
    });
    //xstream.setMode(XStream.NO_REFERENCES);

    xstream.alias("student"

, Student.class

);
    fail(xstream.toXML(bean));
}

运行后结果如下:

======JsonHierarchicalStreamDriver====JavaObject >>>> JaonString=========
-------Object >>>> JSON---------
{"student"

: {
  "id"

: 1,
  "name"

: "jack"

,
  "email"

: "jack@email.com"

,
  "address"

: "china"

,
  "birthday"

: {
    "birthday"

: "2010-11-22"

  }
}}
{
  "id"

: 1,
  "name"

: "jack"

,
  "email"

: "jack@email.com"

,
  "address"

: "china"

,
  "birthday"

: {
    "birthday"

: "2010-11-22"

  }
}

使用JsonHierarchicalStreamDriver转换默认会给转换后的对象添加一个根节点,但是在构建JsonHierarchicalStreamDriver驱动的时候,你可以重写createWriter方法,删掉根节点。

看上面的结果,一个是默认带根节点的JSON对象,它只是将类名作为一个属性,将对象作为该属性的一个值。而另一个没有带根属性的JSON就是通过重写createWriter方法完成的。

3、 将List集合转换成JSON字符串

@Test
public

 void

 writeList2JSON() {
    failRed("======JsonHierarchicalStreamDriver====JavaObject >>>> JaonString========="

);
    JsonHierarchicalStreamDriver driver = new

 JsonHierarchicalStreamDriver();
    xstream = new

 XStream(driver);
    //xstream = new XStream(new JettisonMappedXmlDriver());//转换错误

    //xstream.setMode(XStream.NO_REFERENCES);

    xstream.alias("student"

, Student.class

);
    
    List<Student> list = new

 ArrayList<Student>();
    list.add(bean);//add

    
    bean = new

 Student();
    bean.setAddress("china"

);
    bean.setEmail("tom@125.com"

);
    bean.setId(2);
    bean.setName("tom"

);
    Birthday day = new

 Birthday("2010-11-22"

);
    bean.setBirthday(day);
    list.add(bean);//add

    
    bean = new

 Student();
    bean.setName("jack"

);
    list.add(bean);//add

    
    fail(xstream.toXML(list));
    
    //failRed("========JsonHierarchicalStreamDriver==删除根节点=========");

    //删除根节点

    xstream = new

 XStream(new

 JsonHierarchicalStreamDriver() {
        public

 HierarchicalStreamWriter createWriter(Writer out) {
            return

 new

 JsonWriter(out, JsonWriter.DROP_ROOT_MODE);
        }
    });
    xstream.alias("student"

, Student.class

);
    fail(xstream.toXML(list));
}

运行后结果如下

======JsonHierarchicalStreamDriver====JavaObject >>>> JaonString=========
##{"list"

: [
  {
    "id"

: 1,
    "name"

: "jack"

,
    "email"

: "jack@email.com"

,
    "address"

: "china"

,
    "birthday"

: {
      "birthday"

: "2010-11-22"

    }
  },
  {
    "id"

: 2,
    "name"

: "tom"

,
    "email"

: "tom@125.com"

,
    "address"

: "china"

,
    "birthday"

: {
      "birthday"

: "2010-11-22"

    }
  },
  {
    "id"

: 0,
    "name"

: "jack"

  }
]}
#[
  {
    "id"

: 1,
    "name"

: "jack"

,
    "email"

: "jack@email.com"

,
    "address"

: "china"

,
    "birthday"

: {
      "birthday"

: "2010-11-22"

    }
  },
  {
    "id"

: 2,
    "name"

: "tom"

,
    "email"

: "tom@125.com"

,
    "address"

: "china"

,
    "birthday"

: {
      "birthday"

: "2010-11-22"

    }
  },
  {
    "id"

: 0,
    "name"

: "jack"

  }
]

上面的list1是使用JsonHierarchicalStreamDriver 转换的,当然你也可以使用JettisonMappedXmlDriver驱动进行转换;用JettisonMappedXmlDriver转换后,你会发现格式不同而且没有根属性。

4、 Map转换json

@Test
public

 void

 writeMap2JSON() {
    failRed("======JsonHierarchicalStreamDriver==== Map >>>> JaonString========="

);
    xstream = new

 XStream(new

 JsonHierarchicalStreamDriver());
    //xstream = new XStream(new JettisonMappedXmlDriver());

    xstream.alias("student"

, Student.class

);
    
    Map<String, Student> map = new

 HashMap<String, Student>();
    map.put("No.1"

, bean);//put

    
    bean = new

 Student();
    bean.setAddress("china"

);
    bean.setEmail("tom@125.com"

);
    bean.setId(2);
    bean.setName("tom"

);
    bean.setBirthday(new

 Birthday("2010-11-21"

));
    map.put("No.2"

, bean);//put

    
    bean = new

 Student();
    bean.setName("jack"

);
    map.put("No.3"

, bean);//put

    
    fail(xstream.toXML(map));
    
    //failRed("========JsonHierarchicalStreamDriver==删除根节点=========");

    //删除根节点

    xstream = new

 XStream(new

 JsonHierarchicalStreamDriver() {
        public

 HierarchicalStreamWriter createWriter(Writer out) {
            return

 new

 JsonWriter(out, JsonWriter.DROP_ROOT_MODE);
        }
    });
    xstream.alias("student"

, Student.class

);
    fail(xstream.toXML(map));
}

运行后结果如下:

======JsonHierarchicalStreamDriver==== Map >>>> JaonString=========
{"map"

: [
  [
    "No.3"

,
    {
      "id"

: 0,
      "name"

: "jack"

    }
  ],
  [
    "No.1"

,
    {
      "id"

: 1,
      "name"

: "jack"

,
      "email"

: "jack@email.com"

,
      "address"

: "china"

,
      "birthday"

: {
        "birthday"

: "2010-11-22"

      }
    }
  ],
  [
    "No.2"

,
    {
      "id"

: 2,
      "name"

: "tom"

,
      "email"

: "tom@125.com"

,
      "address"

: "china"

,
      "birthday"

: {
        "birthday"

: "2010-11-21"

      }
    }
  ]
]}
[
  [
    "No.3"

,
    {
      "id"

: 0,
      "name"

: "jack"

    }
  ],
  [
    "No.1"

,
    {
      "id"

: 1,
      "name"

: "jack"

,
      "email"

: "jack@email.com"

,
      "address"

: "china"

,
      "birthday"

: {
        "birthday"

: "2010-11-22"

      }
    }
  ],
  [
    "No.2"

,
    {
      "id"

: 2,
      "name"

: "tom"

,
      "email"

: "tom@125.com"

,
      "address"

: "china"

,
      "birthday"

: {
        "birthday"

: "2010-11-21"

      }
    }
  ]
]

5、 将JSON转换java对象

/**

 * <b>function:</b>JsonHierarchicalStreamDriver可以将简单的json字符串转换成java对象,list、map转换不成功;

 * JsonHierarchicalStreamDriver读取JSON字符串到java对象出错

 * @author hoojo

 * @createDate Nov 27, 2010 1:22:26 PM

 * @throws JSONException

 */

@Test
public

 void

 readJSON2Object() throws

 JSONException {
    String json = "{\"student\": {"

 +
        "\"id\": 1,"

 +
        "\"name\": \"haha\","

 +
        "\"email\": \"email\","

 +
        "\"address\": \"address\","

 +
        "\"birthday\": {"

 +
            "\"birthday\": \"2010-11-22\""

 +
        "}"

 +
    "}}"

;
    //JsonHierarchicalStreamDriver读取JSON字符串到java对象出错,但JettisonMappedXmlDriver可以

    xstream = new

 XStream(new

 JettisonMappedXmlDriver());
    xstream.alias("student"

, Student.class

);
    fail(xstream.fromXML(json).toString());
    
    //JettisonMappedXmlDriver转换List集合出错,但JsonHierarchicalStreamDriver可以转换正确

    //JettisonMappedXmlDriver 转换的字符串 {"list":{"student":[{"id":1,"name":"haha","email":"email","address":"address","birthday":[{},"2010-11-22"]}]},"student":{"id":2,"name":"tom","email":"tom@125.com","address":"china","birthday":[{},"2010-11-22"]}}

    json = "{\"list\": [{"

 +
            "\"id\": 1,"

 +
            "\"name\": \"haha\","

 +
            "\"email\": \"email\","

 +
            "\"address\": \"address\","

 +
            "\"birthday\": {"

 +
              "\"birthday\": \"2010-11-22\""

 +
            "}"

 +
           "},{"

 +
            "\"id\": 2,"

 +
            "\"name\": \"tom\","

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

 +
            "\"address\": \"china\","

 +
            "\"birthday\": {"

 +
              "\"birthday\": \"2010-11-22\""

 +
            "}"

 +
          "}]}"

;
    System.out.println(json);//用js转换成功

    List list = (List) xstream.fromXML(json);
    System.out.println(list.size());//0好像转换失败

}

运行后结果如下:

haha#1#address#2010-11-22#email
{"list"

: [{"id"

: 1,"name"

: "haha"

,"email"

: "email"

,"address"

: "address"

,"birthday"

: {"birthday"

: "2010-11-22"

}},
{"id"

: 2,"name"

: "tom"

,"email"

: "tom@125.com"

,"address"

: "china"

,"birthday"

: {"birthday"

: "2010-11-22"

}}]}
0

JSON到Java的转换是fromXML方法。

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