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>