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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
1 XStream x = new XStream();
2 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
1 package com.cnblogs.yjmyzz.test;
3 import java.text.DateFormat;
4 import java.text.SimpleDateFormat;
5 import java.util.Date;
7 import javax.xml.bind.annotation.adapters.XmlAdapter;
9 public class JaxbDateAdapter extends XmlAdapter<String, Date> {
10 static final String STANDARM_DATE_FORMAT = "yyyy-MM-dd HH:mm:ss";
12 @Override
13 public Date unmarshal(String v) throws Exception {
14 if (v == null) {
15 return null;
16 }
18 DateFormat format = new SimpleDateFormat(STANDARM_DATE_FORMAT);
19 return format.parse(v);
20 }
22 @Override
23 public String marshal(Date v) throws Exception {
24 DateFormat format = new SimpleDateFormat(STANDARM_DATE_FORMAT);
25 return format.format(v);
26 }
27 }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： <details>...</details> <details>...</details> </root> 加上这二个注释后，xml的结果类似： <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
1 package com.cnblogs.yjmyzz.test;
3 import java.text.NumberFormat;
4 import java.util.Locale;
6 import com.thoughtworks.xstream.converters.basic.DoubleConverter;
8 public class DoubleToCurrencyStringConverter extends DoubleConverter {
10 NumberFormat format;
12 public DoubleToCurrencyStringConverter(Locale local) {
13 format = NumberFormat.getCurrencyInstance(local);
14 }
16 public String toString(Object obj) {
17 return format.format(obj);
18 }
20 }然后这样使用：
1 XStream x = new XStream();
2 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
1 package com.cnblogs.yjmyzz.test;
3 import java.text.NumberFormat;
4 import java.util.Locale;
6 import javax.xml.bind.annotation.adapters.XmlAdapter;
8 public class JaxbNumberAdapter extends XmlAdapter<String, Number> {
10 @Override
11 public Number unmarshal(String v) throws Exception {
12 if (v == null) {
13 return null;
14 }
15 NumberFormat format = NumberFormat.getCurrencyInstance(Locale.CHINA);
16 return format.parse(v);
17 }
19 @Override
20 public String marshal(Number v) throws Exception {
21 NumberFormat format = NumberFormat.getCurrencyInstance(Locale.CHINA);
22 return format.format(v);
23 }
24 }然后在相关的Double字段的get方法上，用注解使用这个Adapter
1 @XmlJavaTypeAdapter(JaxbNumberAdapter.class)
2 public Double getAmount() {
3 return amount;
4 }最后附一个完整的示例：
为演示效果，先定义一个Dto类：
1 package com.cnblogs.yjmyzz.test;
3 import java.io.Serializable;
4 import java.util.Date;
6 import javax.xml.bind.annotation.XmlRootElement;
7 import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
8 import com.thoughtworks.xstream.annotations.XStreamAlias;
10 @XmlRootElement(name = "sample")
11 @XStreamAlias("sample")
12 public class Sample implements Serializable{
14 private static final long serialVersionUID = -6271703229325404123L;
16 private Double amount;
19 private Date createDate;
21 @XmlJavaTypeAdapter(JaxbNumberAdapter.class)
22 public Double getAmount() {
23 return amount;
24 }
26 public void setAmount(Double amount) {
27 this.amount = amount;
28 }
30 @XmlJavaTypeAdapter(JaxbDateAdapter.class)
31 public Date getCreateDate() {
32 return createDate;
33 }
35 public void setCreateDate(Date createDate) {
36 this.createDate = createDate;
37 }
39 }同时为了使用jaxb更方便，定义一个JaxbUtil辅助类
1 package com.cnblogs.yjmyzz.util;
3 import java.io.StringReader;
4 import java.io.StringWriter;
6 import javax.xml.bind.JAXBContext;
7 import javax.xml.bind.Marshaller;
8 import javax.xml.bind.Unmarshaller;
10 public class JaxbUtil {
12 public static String toXml(Object obj) {
13 return toXml(obj, "UTF-8", false);
14 }
16 public static String toXml(Object obj, String encoding,
17 boolean isFormatOutput) {
18 String result = null;
19 try {
20 JAXBContext context = JAXBContext.newInstance(obj.getClass());
21 Marshaller marshaller = context.createMarshaller();
22 marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT,
23 isFormatOutput);
24 marshaller.setProperty(Marshaller.JAXB_ENCODING, encoding);
26 StringWriter writer = new StringWriter();
27 marshaller.marshal(obj, writer);
28 result = writer.toString();
29 } catch (Exception e) {
30 e.printStackTrace();
31 }
33 return result;
34 }
36 @SuppressWarnings("unchecked")
37 public static <T> T toObject(String xml, Class<T> c) {
38 T t = null;
39 try {
40 JAXBContext context = JAXBContext.newInstance(c);
41 Unmarshaller unmarshaller = context.createUnmarshaller();
42 t = (T) unmarshaller.unmarshal(new StringReader(xml));
43 } catch (Exception e) {
44 e.printStackTrace();
45 }
47 return t;
48 }
49 }完整的单元测试如下：
1 package com.cnblogs.yjmyzz.test;
3 import java.util.Calendar;
4 import java.util.Locale;
5 import java.util.TimeZone;
6 import org.junit.Test;
7 import com.cnblogs.yjmyzz.util.JaxbUtil;
8 import com.thoughtworks.xstream.converters.basic.DateConverter;
9 import com.thoughtworks.xstream.XStream;
11 public class XStreamAndJaxbTest {
13 private Sample getSampleObj() {
14 Calendar c = Calendar.getInstance(Locale.CHINA);
15 c.set(2014, 9, 31, 0, 0, 0);
16 Sample obj = new Sample();
17 obj.setCreateDate(c.getTime());
18 obj.setAmount(1234.5678);
19 return obj;
20 }
22 @Test
23 public void testXStream() {
24 XStream x = new XStream();
25 x.alias("sample", Sample.class);
26 x.registerConverter(new DateConverter("yyyy-MM-dd HH:mm:ss", null,
27 TimeZone.getTimeZone("GMT+8")));
28 x.registerConverter(new DoubleToCurrencyStringConverter(Locale.CHINA));
29 System.out.println("==> xstream ==>\n");
30 System.out.println(x.toXML(getSampleObj()));
31 System.out.println("\n\n");
32 }
34 @Test
35 public void testJaxb() {
36 System.out.println("==> jaxb ==>\n");
37 System.out.println(JaxbUtil.toXml(getSampleObj(),"UTF-8",true));
38 System.out.println("\n\n");
39 }
41 }测试结果如下：
==> jaxb ==>
<?xml version="1.0" encoding="UTF-8" standalone="yes"?> <sample> <amount>￥1,234.57</amount>