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 ==>
");
        System.out.println(x.toXML(getSampleObj()));
        System.out.println("

");
    }

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

");
    }

}

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>