• 概述
• 示例
• 示例源碼

概述

我們在開發(fā)的過程中，有的時候需要轉(zhuǎn)換一些自定義類型，此時默認的映射方式可能無法滿足需要。

XStream為我們提供了豐富的擴展，用戶可以實現(xiàn)自己的轉(zhuǎn)換器，然后調(diào)用registerConverter方法注冊自定義的轉(zhuǎn)換器。

實現(xiàn)自定義的轉(zhuǎn)換器很簡單，只需要實現(xiàn)XStream提供的Converter接口并實現(xiàn)其方法即可。

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示例

我們在上個案例中的代碼

package com.xgj.oxm.xstream.quickDemo.convert;import java.text.ParseException; import java.util.Date; import java.util.Locale;import com.thoughtworks.xstream.XStream; import com.xgj.oxm.xstream.quickDemo.domain.LoginLog; import com.xgj.oxm.xstream.quickDemo.domain.User;public class XStreamConverterDemo {private static XStream xstream;static {// 創(chuàng)建一個Xstream實例，使用默認的XPP解析器xstream = new XStream();// (1)設置類別名，修改默認的全限定名的名稱xstream.alias("user", User.class);xstream.alias("loginLog", LoginLog.class);// (2)設置類成員別名 <id>1</id> 改為<userId>1</userId>xstream.aliasField("userId", User.class, "id");// (3)把LoginLog的userId屬性視為xml屬性，默認為xml的元素xstream.aliasAttribute(LoginLog.class, "userId", "id");xstream.useAttributeFor(LoginLog.class, "userId");// (4)去掉集合類型生成XML的父節(jié)點，即忽略xml中的<logs></logs>標記xstream.addImplicitCollection(User.class, "logs");}/*** * * @Title: getUser* * @Description: 初始化轉(zhuǎn)換對象* * @return* * @return: User* @throws ParseException*/public static User getUser() throws ParseException {LoginLog log = new LoginLog();log.setIp("127.0.0.1");log.setLoginLogId(99);log.setUserId(1);log.setLoginDate(new Date());LoginLog log2 = new LoginLog();log2.setIp("192.168.1.1");log2.setLoginLogId(22);log2.setUserId(2);log2.setLoginDate(new Date());User user = new User();user.setId(1);user.setUserName("Artisan");user.setPassword("artisan");user.setCredits(1000);user.setLastVisit(new Date());user.addLoginLog(log);user.addLoginLog(log2);return user;}/*** * * @Title: objectToXml* * @Description: Java對象轉(zhuǎn)換成XML* * @throws Exception* * @return: void*/public static void objectToXml() throws Exception {// 獲取轉(zhuǎn)換的User對象實例User user = getUser();// 輸出內(nèi)容到控制臺,查看一下System.out.println(xstream.toXML(user));}public static void main(String[] args) throws Exception {objectToXml();} }

輸出如下

<user><userId>1</userId><userName>Artisan</userName><password>artisan</password><credits>1000</credits><lastVisit>2017-12-06 12:32:06.504 UTC</lastVisit><loginLog id="1"><loginLogId>99</loginLogId><ip>127.0.0.1</ip><loginDate>2017-12-06 12:32:06.504 UTC</loginDate></loginLog><loginLog id="2"><loginLogId>22</loginLogId><ip>192.168.1.1</ip><loginDate>2017-12-06 12:32:06.504 UTC</loginDate></loginLog> </user>

可以看到時間格式如下：

2017-12-06 12:32:06.504 UTC

UTC與格林尼治平均時(GMT, Greenwich Mean Time)一樣，都與英國倫敦的本地時相同，UTC + 時區(qū)差＝本地時間

如果我們希望顯示北京時間呢？

就需要用到轉(zhuǎn)換器了

package com.xgj.oxm.xstream.quickDemo.convert;import java.text.SimpleDateFormat; import java.util.Date; import java.util.GregorianCalendar; import java.util.Locale;import com.thoughtworks.xstream.converters.ConversionException; import com.thoughtworks.xstream.converters.Converter; import com.thoughtworks.xstream.converters.MarshallingContext; import com.thoughtworks.xstream.converters.UnmarshallingContext; import com.thoughtworks.xstream.io.HierarchicalStreamReader; import com.thoughtworks.xstream.io.HierarchicalStreamWriter;public class DateConverter implements Converter {private Locale locale;public DateConverter(Locale locale) {super();this.locale = locale;}/*** 重寫該方法，判斷需要轉(zhuǎn)換的類型*/@Overridepublic boolean canConvert(Class type) {return Date.class.isAssignableFrom(type);}/*** 重寫該方法，編寫Java 到 XML 的轉(zhuǎn)換邏輯*/@Overridepublic void marshal(Object source, HierarchicalStreamWriter writer,MarshallingContext context) {// DateFormat format = DateFormat.getDateInstance(DateFormat.DATE_FIELD,// this.locale);SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss", this.locale);writer.setValue(format.format(source));}/*** 重寫該方法，編寫XML 到 Java 的轉(zhuǎn)換邏輯*/@Overridepublic Object unmarshal(HierarchicalStreamReader reader,UnmarshallingContext context) {GregorianCalendar calendar = new GregorianCalendar();// DateFormat format = DateFormat.getDateInstance(DateFormat.DATE_FIELD,// this.locale);SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss",this.locale);try {calendar.setTime(format.parse(reader.getValue()));} catch (Exception e) {throw new ConversionException(e.getMessage(), e);}return calendar.getGregorianChange();}}

解析

• 通過 canConvert 方法來判斷轉(zhuǎn)換邏輯

• 通過marshal方法，完成對象編組（對象轉(zhuǎn)XML）操作的處理邏輯

• 通過unmarshal方法，完成對象f反編組（XML轉(zhuǎn)對象）操作的處理邏輯

• 最后調(diào)用registerConverter方法注冊自定義的轉(zhuǎn)換器

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修改生成xml的代碼注冊轉(zhuǎn)換器，完整代碼如下

package com.xgj.oxm.xstream.quickDemo.convert;import java.text.ParseException; import java.util.Date; import java.util.Locale;import com.thoughtworks.xstream.XStream; import com.xgj.oxm.xstream.quickDemo.domain.LoginLog; import com.xgj.oxm.xstream.quickDemo.domain.User;public class XStreamConverterDemo {private static XStream xstream;static {// 創(chuàng)建一個Xstream實例，使用默認的XPP解析器xstream = new XStream();// (1)設置類別名，修改默認的全限定名的名稱xstream.alias("user", User.class);xstream.alias("loginLog", LoginLog.class);// (2)設置類成員別名 <id>1</id> 改為<userId>1</userId>xstream.aliasField("userId", User.class, "id");// (3)把LoginLog的userId屬性視為xml屬性，默認為xml的元素xstream.aliasAttribute(LoginLog.class, "userId", "id");xstream.useAttributeFor(LoginLog.class, "userId");// (4)去掉集合類型生成XML的父節(jié)點，即忽略xml中的<logs></logs>標記xstream.addImplicitCollection(User.class, "logs");// 注冊轉(zhuǎn)換器xstream.registerConverter(new DateConverter(Locale.CHINESE));}/*** * * @Title: getUser* * @Description: 初始化轉(zhuǎn)換對象* * @return* * @return: User* @throws ParseException*/public static User getUser() throws ParseException {LoginLog log = new LoginLog();log.setIp("127.0.0.1");log.setLoginLogId(99);log.setUserId(1);log.setLoginDate(new Date());LoginLog log2 = new LoginLog();log2.setIp("192.168.1.1");log2.setLoginLogId(22);log2.setUserId(2);log2.setLoginDate(new Date());User user = new User();user.setId(1);user.setUserName("Artisan");user.setPassword("artisan");user.setCredits(1000);user.setLastVisit(new Date());user.addLoginLog(log);user.addLoginLog(log2);return user;}/*** * * @Title: objectToXml* * @Description: Java對象轉(zhuǎn)換成XML* * @throws Exception* * @return: void*/public static void objectToXml() throws Exception {// 獲取轉(zhuǎn)換的User對象實例User user = getUser();// 輸出內(nèi)容到控制臺,查看一下System.out.println(xstream.toXML(user));}public static void main(String[] args) throws Exception {objectToXml();} }

輸出

<user><userId>1</userId><userName>Artisan</userName><password>artisan</password><credits>1000</credits><lastVisit>2017-12-06 20:34:42</lastVisit><loginLog id="1"><loginLogId>99</loginLogId><ip>127.0.0.1</ip><loginDate>2017-12-06 20:34:42</loginDate></loginLog><loginLog id="2"><loginLogId>22</loginLogId><ip>192.168.1.1</ip><loginDate>2017-12-06 20:34:42</loginDate></loginLog> </user>

可以看到時間已經(jīng)是 2017-12-06 20:34:42 北京時間了。 轉(zhuǎn)換器起作用了。

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示例源碼

代碼已托管到Github—> https://github.com/yangshangwei/SpringMaster

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