XStream、JAXB 日期(Date)、数字(Number)格式化输出xml

XStream、Jaxb是java中用于对象xml序列化/反序列化 的经典开源项目，利用它们将对象转换成xml时，经常会遇到日期(Date)、数字按指定格式输出的需求，下面是使用示例：

一、日期字段格式化输出

1.1 xStream

 XStream x = new XStream();
 x.registerConverter(new DateConverter("yyyy-MM-dd HH:mm:ss", null,TimeZone.getTimeZone("GMT+8")));

xStream默认使用UTC时间格式输出，上面的代码演示了如何按北京时间输出 yyyy-MM-dd HH:mm:ss 格式

1.2 jaxb

jaxb处理这个要麻烦一点，先要创建一个Adapter，下面是示例

 package com.cnblogs.yjmyzz.test;

 import java.text.DateFormat;
 import java.text.SimpleDateFormat;
 import java.util.Date;

 import javax.xml.bind.annotation.adapters.XmlAdapter;

 public class JaxbDateAdapter extends XmlAdapter<String, Date> {
     static final String STANDARM_DATE_FORMAT = "yyyy-MM-dd HH:mm:ss";

     @Override
     public Date unmarshal(String v) throws Exception {
         if (v == null) {
             return null;
         }

         DateFormat format = new SimpleDateFormat(STANDARM_DATE_FORMAT);
         return format.parse(v);
     }

     @Override
     public String marshal(Date v) throws Exception {
         DateFormat format = new SimpleDateFormat(STANDARM_DATE_FORMAT);
         return format.format(v);
     }
 }

然后要处理的dto类，相应的Date字段的get方法上使用刚才这个Adapter

    @XmlJavaTypeAdapter(JaxbDateAdapter.class)
    public Date getCreateDate() {
        return createDate;
    }

注：不要在private上使用，最好将注解打在get方法上，否则有可能报错。

这里，再给一个List<T>类型的常见用法：

@XmlElementWrapper(name="details")
@XmlElement(name="detail")
public List<FSUDetail> getDetails() {
    return details;
}

如果没有这二个注解，xml的结果类似：

<root>
...
    <details>...</details>
    <details>...</details>
...
</root>
加上这二个注释后，xml的结果类似：
<root>
...
    <details>
        <detail>...</detail>
        <detail>...</detail>
    </details>    
...
</root>

二、数字格式化

假设我们要将一个Double型的成员，按中国货币的格式输出

2.1 xStream

默认的DoubleConverter满足不了要求，得从它派生一个子类来重写toString(Object obj)方法

 package com.cnblogs.yjmyzz.test;

 import java.text.NumberFormat;
 import java.util.Locale;

 import com.thoughtworks.xstream.converters.basic.DoubleConverter;

 public class DoubleToCurrencyStringConverter extends DoubleConverter {

     NumberFormat format;

     public DoubleToCurrencyStringConverter(Locale local) {
         format = NumberFormat.getCurrencyInstance(local);
     }

     public String toString(Object obj) {
         return format.format(obj);
     }

 }

然后这样使用：

         XStream x = new XStream();
         x.registerConverter(new DoubleToCurrencyStringConverter(Locale.CHINA));

2.2 Jaxb

仍然是按Adapter的老路，定义一个专用的Adapter

 package com.cnblogs.yjmyzz.test;

 import java.text.NumberFormat;
 import java.util.Locale;

 import javax.xml.bind.annotation.adapters.XmlAdapter;

 public class JaxbNumberAdapter extends XmlAdapter<String, Number> {

     @Override
     public Number unmarshal(String v) throws Exception {
         if (v == null) {
             return null;
         }
         NumberFormat format = NumberFormat.getCurrencyInstance(Locale.CHINA);
         return format.parse(v);
     }

     @Override
     public String marshal(Number v) throws Exception {
         NumberFormat format = NumberFormat.getCurrencyInstance(Locale.CHINA);
         return format.format(v);
     }
 }

然后在相关的Double字段的get方法上，用注解使用这个Adapter

     @XmlJavaTypeAdapter(JaxbNumberAdapter.class)
     public Double getAmount() {
         return amount;
     }

最后附一个完整的示例：

为演示效果，先定义一个Dto类：

 package com.cnblogs.yjmyzz.test;

 import java.io.Serializable;
 import java.util.Date;

 import javax.xml.bind.annotation.XmlRootElement;
 import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
 import com.thoughtworks.xstream.annotations.XStreamAlias;

 @XmlRootElement(name = "sample")
 @XStreamAlias("sample")
 public class Sample implements Serializable{    

     private static final long serialVersionUID = -6271703229325404123L;

     private Double amount;

     private Date createDate;

     @XmlJavaTypeAdapter(JaxbNumberAdapter.class)
     public Double getAmount() {
         return amount;
     }

     public void setAmount(Double amount) {
         this.amount = amount;
     }

     @XmlJavaTypeAdapter(JaxbDateAdapter.class)
     public Date getCreateDate() {
         return createDate;
     }

     public void setCreateDate(Date createDate) {
         this.createDate = createDate;
     }

 }

同时为了使用jaxb更方便，定义一个JaxbUtil辅助类

 package com.cnblogs.yjmyzz.util;

 import java.io.StringReader;
 import java.io.StringWriter;

 import javax.xml.bind.JAXBContext;
 import javax.xml.bind.Marshaller;
 import javax.xml.bind.Unmarshaller;

 public class JaxbUtil {

     public static String toXml(Object obj) {
         return toXml(obj, "UTF-8", false);
     }

     public static String toXml(Object obj, String encoding,
             boolean isFormatOutput) {
         String result = null;
         try {
             JAXBContext context = JAXBContext.newInstance(obj.getClass());
             Marshaller marshaller = context.createMarshaller();
             marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT,
                     isFormatOutput);
             marshaller.setProperty(Marshaller.JAXB_ENCODING, encoding);

             StringWriter writer = new StringWriter();
             marshaller.marshal(obj, writer);
             result = writer.toString();
         } catch (Exception e) {
             e.printStackTrace();
         }

         return result;
     }

     @SuppressWarnings("unchecked")
     public static <T> T toObject(String xml, Class<T> c) {
         T t = null;
         try {
             JAXBContext context = JAXBContext.newInstance(c);
             Unmarshaller unmarshaller = context.createUnmarshaller();
             t = (T) unmarshaller.unmarshal(new StringReader(xml));
         } catch (Exception e) {
             e.printStackTrace();
         }

         return t;
     }
 }

完整的单元测试如下：

 package com.cnblogs.yjmyzz.test;

 import java.util.Calendar;
 import java.util.Locale;
 import java.util.TimeZone;
 import org.junit.Test;
 import com.cnblogs.yjmyzz.util.JaxbUtil;
 import com.thoughtworks.xstream.converters.basic.DateConverter;
 import com.thoughtworks.xstream.XStream;

 public class XStreamAndJaxbTest {

     private Sample getSampleObj() {
         Calendar c = Calendar.getInstance(Locale.CHINA);
         c.set(2014, 9, 31, 0, 0, 0);
         Sample obj = new Sample();
         obj.setCreateDate(c.getTime());
         obj.setAmount(1234.5678);
         return obj;
     }

     @Test
     public void testXStream() {
         XStream x = new XStream();
         x.alias("sample", Sample.class);
         x.registerConverter(new DateConverter("yyyy-MM-dd HH:mm:ss", null,
                 TimeZone.getTimeZone("GMT+8")));
         x.registerConverter(new DoubleToCurrencyStringConverter(Locale.CHINA));
         System.out.println("==> xstream ==>\n");
         System.out.println(x.toXML(getSampleObj()));
         System.out.println("\n\n");
     }

     @Test
     public void testJaxb() {
         System.out.println("==> jaxb ==>\n");
         System.out.println(JaxbUtil.toXml(getSampleObj(),"UTF-8",true));
         System.out.println("\n\n");
     }

 }

测试结果如下：

==> jaxb ==>

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<sample>
<amount>￥1,234.57</amount>
<createDate>2014-10-31 00:00:00</createDate>
</sample>

 

==> xstream ==>

<sample>
<amount>￥1,234.57</amount>
<createDate>2014-10-31 00:00:00</createDate>
</sample>