将对象映射到多个XML模式

我已经在EclipseLink JAXB（MOXy）的@XmlPath和外部绑定文件扩展中撰写了以前的文章。在本文中，我将通过将单个对象模型映射到两个不同的XML模式来演示这些扩展的功能。

为了使示例更加“真实”，XML数据将来自提供天气信息的两种不同服务：Google和Yahoo。

Java模型

以下域模型将用于此帖子：

天气预报

package blog.weather;import java.util.List;public class WeatherReport {private String location;private int currentTemperature;private String currentCondition;private List forecast;}

预测

package blog.weather;public class Forecast {private String dayOfTheWeek;private int low;private int high;private String condition;}

Google Weather API

首先，我们将利用Google的Weather API。以下URL将用于访问加拿大渥太华的天气数据：

http://www.google.com/ig/api?weather=渥太华

以下是在我撰写本文时执行上述查询的结果。我已经突出显示了我们将映射到XML文档的部分：

<xml_api_reply version="1"><weather module_id="0" tab_id="0" mobile_row="0" mobile_zipped="1"row="0" section="0"><forecast_information><city data="Ottawa, ON" /><postal_code data="Ottawa" /><latitude_e6 data="" /><longitude_e6 data="" /><forecast_date data="2011-09-08" /><current_date_time data="2011-09-08 14:00:00 +0000" /><unit_system data="US" /></forecast_information><current_conditions><condition data="Mostly Cloudy" /><temp_f data="66" /><temp_c data="19" /><humidity data="Humidity: 73%" /><icon data="/ig/images/weather/mostly_cloudy.gif" /><wind_condition data="Wind: NE at 13 mph" /></current_conditions><forecast_conditions><day_of_week data="Thu" /><low data="55" /><high data="75" /><icon data="/ig/images/weather/cloudy.gif" /><condition data="Cloudy" /></forecast_conditions><forecast_conditions><day_of_week data="Fri" /><low data="46" /><high data="77" /><icon data="/ig/images/weather/mostly_sunny.gif" /><condition data="Partly Sunny" /></forecast_conditions><forecast_conditions><day_of_week data="Sat" /><low data="43" /><high data="68" /><icon data="/ig/images/weather/sunny.gif" /><condition data="Clear" /></forecast_conditions><forecast_conditions><day_of_week data="Sun" /><low data="55" /><high data="75" /><icon data="/ig/images/weather/sunny.gif" /><condition data="Clear" /></forecast_conditions></weather>
</xml_api_reply>

Java模型-通过注释映射到Google的XML模式

我们将通过标准JAXB和MOXy扩展注释的组合来映射Google weather API的结果。

天气预报

package blog.weather;import java.util.List;import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;import org.eclipse.persistence.oxm.annotations.XmlPath;@XmlRootElement(name="xml_api_reply")
@XmlType(propOrder={"location", "currentCondition", "currentTemperature", "forecast"})
@XmlAccessorType(XmlAccessType.FIELD)
public class WeatherReport {@XmlPath("weather/forecast_information/city/@data")private String location;@XmlPath("weather/current_conditions/temp_f/@data")private int currentTemperature;@XmlPath("weather/current_conditions/condition/@data")private String currentCondition;@XmlPath("weather/forecast_conditions")private List<Forecast> forecast;}

预测

package blog.weather;import org.eclipse.persistence.oxm.annotations.XmlPath;public class Forecast {@XmlPath("day_of_week/@data")private String dayOfTheWeek;@XmlPath("low/@data")private int low;@XmlPath("high/@data")private int high;@XmlPath("condition/@data")private String condition;}

演示版

以下演示代码将读取Google气象服务的XML数据，并将对象编组回XML：

package blog.weather;import java.net.URL;
import javax.xml.bind.*;public class GoogleDemo {public static void main(String[] args) throws Exception {JAXBContext jc = JAXBContext.newInstance(WeatherReport.class);Unmarshaller unmarshaller = jc.createUnmarshaller();URL url = new URL("http://www.google.com/ig/api?weather=Ottawa");WeatherReport weatherReport = (WeatherReport) unmarshaller.unmarshal(url);Marshaller marshaller = jc.createMarshaller();marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);marshaller.marshal(weatherReport, System.out);}}

输出量

以下是运行演示代码的结果。输出代表我们映射到的XML文档的一部分：

<?xml version="1.0" encoding="UTF-8"?>
<xml_api_reply><weather><forecast_information><city data="Ottawa, ON"/></forecast_information><current_conditions><condition data="Mostly Cloudy"/><temp_f data="68"/></current_conditions><forecast_conditions><day_of_week data="Thu"/><low data="55"/><high data="75"/><condition data="Cloudy"/></forecast_conditions><forecast_conditions><day_of_week data="Fri"/><low data="46"/><high data="77"/><condition data="Partly Sunny"/></forecast_conditions><forecast_conditions><day_of_week data="Sat"/><low data="43"/><high data="68"/><condition data="Clear"/></forecast_conditions><forecast_conditions><day_of_week data="Sun"/><low data="55"/><high data="75"/><condition data="Clear"/></forecast_conditions></weather>
</xml_api_reply>

雅虎天气API

以下URL将用于使用Yahoo Weather API（3369是渥太华的WOEID）访问渥太华的天气数据：

http://weather.yahooapis.com/forecastrss?w=3369

以下是在我撰写本文时执行上述查询的结果：

<?xml version="1.0" encoding="UTF-8"?>
<rss version="2.0" xmlns:yweather="http://xml.weather.yahoo.com/ns/rss/1.0"xmlns:geo="http://www.w3.org/2003/01/geo/wgs84_pos#"><channel><title>Yahoo! Weather - Ottawa, CA</title><link>http://us.rd.yahoo.com/dailynews/rss/weather/Ottawa__CA/*http://weather.yahoo.com/forecast/CAXX0343_f.html</link><description>Yahoo! Weather for Ottawa, CA</description><language>en-us</language><lastBuildDate>Thu, 08 Sep 2011 10:58 am EDT</lastBuildDate><ttl>60</ttl><yweather:location city="Ottawa" region="ON"country="Canada" /><yweather:units temperature="F" distance="mi" pressure="in"speed="mph" /><yweather:wind chill="66" direction="40" speed="12" /><yweather:atmosphere humidity="73" visibility=""pressure="30.14" rising="0" /><yweather:astronomy sunrise="6:31 am" sunset="7:25 pm" /><image><title>Yahoo! Weather</title><width>142</width><height>18</height><link>http://weather.yahoo.com</link><url>http://l.yimg.com/a/i/brand/purplelogo//uh/us/news-wea.gif</url></image><item><title>Conditions for Ottawa, CA at 10:58 am EDT</title><geo:lat>45.42</geo:lat><geo:long>-75.69</geo:long><link>http://us.rd.yahoo.com/dailynews/rss/weather/Ottawa__CA/*http://weather.yahoo.com/forecast/CAXX0343_f.html</link><pubDate>Thu, 08 Sep 2011 10:58 am EDT</pubDate><yweather:condition text="Mostly Cloudy" code="28"temp="66" date="Thu, 08 Sep 2011 10:58 am EDT" /><description><![CDATA[
<img src="http://l.yimg.com/a/i/us/we/52/28.gif"/><b>Current Conditions:</b>Mostly Cloudy, 66 F<b>Forecast:</b>Thu - Partly Cloudy. High: 75 Low: 57Fri - Partly Cloudy. High: 79 Low: 53<a href="http://us.rd.yahoo.com/dailynews/rss/weather/Ottawa__CA/*http://weather.yahoo.com/forecast/CAXX0343_f.html">Full Forecast at Yahoo! Weather</a>(provided by <a href="http://www.weather.com" >The Weather Channel</a>)]]></description><yweather:forecast day="Thu" date="8 Sep 2011" low="57"high="75" text="Partly Cloudy" code="30" /><yweather:forecast day="Fri" date="9 Sep 2011" low="53"high="79" text="Partly Cloudy" code="30" /><guid isPermaLink="false">CAXX0343_2011_09_09_7_00_EDT</guid></item></channel>
</rss><!-- api4.weather.sp2.yahoo.com uncompressed/chunked Thu Sep 8 08:32:54PDT 2011 -->

Java模型–通过XML元数据映射到Yahoo的XML模式

由于我们无法通过注释提供到对象模型的第二套映射，因此我们必须利用MOXy的XML元数据提供后续的映射。默认情况下，MOXy的映射文档用于补充模型上指定的所有注释。但是，如果设置了xml-mapping-metadata-complete标志，则XML元数据将完全替换注释提供的元数据（用于Google映射的注释将保留在POJO上，但是xml-mapping-metadata-complete标志告诉MOXy忽略它们）。

<?xml version="1.0"?>
<xml-bindingsxmlns="http://www.eclipse.org/eclipselink/xsds/persistence/oxm"package-name="blog.weather"xml-mapping-metadata-complete="true"><xml-schema element-form-default="QUALIFIED"><xml-ns prefix="yweather" namespace-uri="http://xml.weather.yahoo.com/ns/rss/1.0"/></xml-schema><java-types><java-type name="WeatherReport" xml-accessor-type="FIELD"><xml-root-element name="rss"/><xml-type prop-order="location currentTemperature currentCondition forecast"/><java-attributes><xml-attribute java-attribute="location" xml-path="channel/yweather:location/@city"/><xml-attribute java-attribute="currentTemperature" name="channel/item/yweather:condition/@temp"/><xml-attribute java-attribute="currentCondition" name="channel/item/yweather:condition/@text"/><xml-element java-attribute="forecast" name="channel/item/yweather:forecast"/></java-attributes></java-type><java-type name="Forecast" xml-accessor-type="FIELD"><java-attributes><xml-attribute java-attribute="dayOfTheWeek" name="day"/><xml-attribute java-attribute="low"/><xml-attribute java-attribute="high"/><xml-attribute java-attribute="condition" name="text"/></java-attributes></java-type></java-types>
</xml-bindings>

演示版

以下演示代码将读取Yahoo气象服务的XML数据，并将对象编组回XML。由于与未映射的CDATA部分有关的MOXy错误（https://bugs.eclipse.org/357145），使用了经过过滤的XMLStreamReader将其从XML输入中删除：

package blog.weather;import java.util.HashMap;
import java.util.Map;import javax.xml.bind.JAXBContext;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;
import javax.xml.stream.StreamFilter;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamReader;
import javax.xml.transform.stream.StreamSource;import org.eclipse.persistence.jaxb.JAXBContextFactory;public class YahooDemo {public static void main(String[] args) throws Exception {Map<String, Object> properties = new HashMap<String, Object>(1);properties.put(JAXBContextFactory.ECLIPSELINK_OXM_XML_KEY, "blog/weather/yahoo-binding.xml");JAXBContext jc = JAXBContext.newInstance(new Class[] {WeatherReport.class}, properties);XMLInputFactory xif = XMLInputFactory.newFactory();StreamSource xml = new StreamSource("http://weather.yahooapis.com/forecastrss?w=3369");XMLStreamReader xsr = xif.createXMLStreamReader(xml);xsr = xif.createFilteredReader(xsr, new CDATAFilter());Unmarshaller unmarshaller = jc.createUnmarshaller();WeatherReport weatherReport = (WeatherReport) unmarshaller.unmarshal(xsr);Marshaller marshaller = jc.createMarshaller();marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);marshaller.marshal(weatherReport, System.out);}private static class CDATAFilter implements StreamFilter {public boolean accept(XMLStreamReader xsr) {return XMLStreamReader.CDATA != xsr.getEventType();}}}

输出量

以下是运行演示代码的结果。输出代表我们映射到的XML文档的一部分：

<?xml version="1.0" encoding="UTF-8"?>
<rss xmlns:yweather="http://xml.weather.yahoo.com/ns/rss/1.0"><channel><yweather:location city="Ottawa"/><item><yweather:forecast day="Thu" low="57" high="74" text="Partly Cloudy"/><yweather:forecast day="Fri" low="53" high="79" text="Partly Cloudy"/></item></channel>
</rss>

参考： Java XML和JSON绑定博客上的 JCG合作伙伴 Blaise Doughan的参考：将 对象映射到多个XML模式-天气示例。

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