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xStream完美转换XML、JSON

2018-04-24 来源:cnblogs/hoojo

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>