• 導讀
• 別名配置的三種情況
• 官方Demo
  • 問題
  • Model
  • A Simple Test
  • Class aliasing
  • Field aliasing
  • Implicit Collections
  • Attribute aliasing
• Package aliasing
• 示例源碼

導讀

在Spring OXM-XStream快速入門 的案例中，我們看到生成的xml報文如下：

<com.xgj.oxm.xstream.quickDemo.domain.User><id>1</id><userName>Artisan</userName><password>artisan</password><credits>1000</credits><lastVisit>2017-12-05 07:30:46.772 UTC</lastVisit><logs><com.xgj.oxm.xstream.quickDemo.domain.LoginLog><loginLogId>99</loginLogId><userId>1</userId><ip>127.0.0.1</ip><loginDate>2017-12-05 07:30:46.772 UTC</loginDate></com.xgj.oxm.xstream.quickDemo.domain.LoginLog></logs> </com.xgj.oxm.xstream.quickDemo.domain.User>

在默認情況下，Java對象到XML的映射是Java對象屬性名對應XML的元素名，Java類的全名對應XML根元素的名字。

事實上，在實際應用中,如果XML和Java類都已經存在相應的名稱，那么在進行轉換時，需要設置別名進行映射。

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別名配置的三種情況

• 類別名： 使用alias(String name,Class type)

• 類成員別名：使用aliasField（String alias, Class definedIn, String fieldName）

• 類成員作為xml屬性別名：使用aliasAttribute(Class definedIn, String attributeName, String alias)方法。 并且需要通過 useAttributeFor(Class definedIn, String fieldName) 應用到某個類上。

從上面的實例中我們看到XML元素結構不是很友好，接下來我們通過XStream提供的別名機制來修飾生成的XML元素的結構。

package com.xgj.oxm.xstream.quickDemo.aliasDemo;import java.text.ParseException; import java.util.Date;import com.thoughtworks.xstream.XStream; import com.xgj.oxm.xstream.quickDemo.domain.LoginLog; import com.xgj.oxm.xstream.quickDemo.domain.User;public class XStreamAliasDemo {private static XStream xstream;static {// 創建一個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的父節點，即忽略xml中的<logs></logs>標記xstream.addImplicitCollection(User.class, "logs");}/*** * * @Title: getUser* * @Description: 初始化轉換對象* * @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對象轉換成XML* * @throws Exception* * @return: void*/public static void objectToXml() throws Exception {// 獲取轉換的User對象實例User user = getUser();// 輸出內容到控制臺,查看一下System.out.println(xstream.toXML(user));System.out.println("objectToXml successfully");}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>2017-12-05 13:39:32.698 UTC</lastVisit><loginLog id="1"><loginLogId>99</loginLogId><ip>127.0.0.1</ip><loginDate>2017-12-05 13:39:32.698 UTC</loginDate></loginLog><loginLog id="2"><loginLogId>22</loginLogId><ip>192.168.1.1</ip><loginDate>2017-12-05 13:39:32.698 UTC</loginDate></loginLog> </user>

說明：

在（1）處，通過XStream的alias方法來設置類別名。

在（2）處，通過XStream的aliasField方法將User類的id屬性設置為userId

在（3）處，通過XStream的aliasAttribute和useAttributeFor方法將LoginLog類的userId屬性設置為id，并設置為LoginLog元素的屬性。 默認為LoginLog元素的子元素。

在（4）處，通過XStream的addImplicitCollection方法刪除集合節點logs,即忽略XML中的<logs></logs>標記。

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官方Demo

問題

假設我們有如下的XML，我們如何使用XStream去讀寫呢？

<blog author="Guilherme Silveira"><entry><title>first</title><description>My first blog entry.</description></entry><entry><title>tutorial</title><description>Today we have developed a nice alias tutorial. Tell your friends! NOW!</description></entry> </blog>

結合XStream中的方法，我們來分析一下

• blog 節點有個 author 屬性 ,可以使用aliasAttribute 和 useAttributeFor方法應用到Blog類上，也可以使用XStream的轉換器，這里我們使用轉換器的方式。 因為要使用轉換器，所以需要一個Author類以及對應的一個name屬性用于存儲name的值

• 子節點是多個entry，可以使用List來存儲

• entry節點有title 和 description 屬性 ，所以需要一個Entry類以及2個屬性

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Model

接下來我們來看下我們創建的幾個model類

package com.xgj.oxm.xstream.quickDemo.aliasDemo.officeDemo;import java.util.ArrayList; import java.util.List;public class Blog {// Authorprivate Author writer;// Entry集合private List<Entry> entries = new ArrayList<Entry>();/*** * * @Title:Blog* * @Description:構造函數* * @param writer*/public Blog(Author writer) {this.writer = writer;}/*** * * @Title: add* * @Description: 添加Entry* * @param entry* * @return: void*/public void add(Entry entry) {entries.add(entry);}/*** * * @Title: getContent* * @Description: 獲取Entry List集合* * @return* * @return: List<Entry>*/public List<Entry> getContent() {return entries;} } package com.xgj.oxm.xstream.quickDemo.aliasDemo.officeDemo;public class Author {private String name;public Author(String name) {this.name = name;}public String getName() {return name;} } package com.xgj.oxm.xstream.quickDemo.aliasDemo.officeDemo;public class Entry {private String title, description;public Entry(String title, String description) {this.title = title;this.description = description;} }

我們沒有創建set/get方法，可根據需要創建。

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A Simple Test

接下來，我們來測試一下

public static void main(String[] args) {Blog teamBlog = new Blog(new Author("Guilherme Silveira"));teamBlog.add(new Entry("first","My first blog entry."));teamBlog.add(new Entry("tutorial","Today we have developed a nice alias tutorial. Tell your friends! NOW!"));XStream xstream = new XStream();System.out.println(xstream.toXML(teamBlog));}

輸出如下

<com.xgj.oxm.xstream.quickDemo.aliasDemo.officeDemo.Blog><writer><name>Guilherme Silveira</name></writer><entries><com.xgj.oxm.xstream.quickDemo.aliasDemo.officeDemo.Entry><title>first</title><description>My first blog entry.</description></com.xgj.oxm.xstream.quickDemo.aliasDemo.officeDemo.Entry><com.xgj.oxm.xstream.quickDemo.aliasDemo.officeDemo.Entry><title>tutorial</title><description>Today we have developed a nice alias tutorial. Tell your friends! NOW!</description></com.xgj.oxm.xstream.quickDemo.aliasDemo.officeDemo.Entry></entries> </com.xgj.oxm.xstream.quickDemo.aliasDemo.officeDemo.Blog>

Class aliasing

我們需要把com.xgj.oxm.xstream.quickDemo.aliasDemo.officeDemo.Blog 和 com.xgj.oxm.xstream.quickDemo.aliasDemo.officeDemo.Entry 轉換成 blog 和 entry.

通過

xstream.alias("blog", Blog.class);xstream.alias("entry", Entry.class); Blog teamBlog = new Blog(new Author("Guilherme Silveira"));teamBlog.add(new Entry("first", "My first blog entry."));teamBlog.add(new Entry("tutorial","Today we have developed a nice alias tutorial. Tell your friends! NOW!"));XStream xstream = new XStream();// alias Classxstream.alias("blog", Blog.class);xstream.alias("entry", Entry.class);System.out.println(xstream.toXML(teamBlog));

輸出結果如下

<blog><writer><name>Guilherme Silveira</name></writer><entries><entry><title>first</title><description>My first blog entry.</description></entry><entry><title>tutorial</title><description>Today we have developed a nice alias tutorial. Tell your friends! NOW!</description></entry></entries> </blog>

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Field aliasing

下面把wirter轉換為 author .通過

xstream.aliasField("author", Blog.class, "writer");

輸出如下

<blog><author><name>Guilherme Silveira</name></author><entries><entry><title>first</title><description>My first blog entry.</description></entry><entry><title>tutorial</title><description>Today we have developed a nice alias tutorial. Tell your friends! NOW!</description></entry></entries> </blog>

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Implicit Collections

去掉entries節點，通過

xstream.addImplicitCollection(Blog.class, "entries");

輸出如下

<blog><author><name>Guilherme Silveira</name></author><entry><title>first</title><description>My first blog entry.</description></entry><entry><title>tutorial</title><description>Today we have developed a nice alias tutorial. Tell your friends! NOW!</description></entry> </blog>

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Attribute aliasing

下一步是將writer成員變量轉換為xml的屬性 ， 為了做到這一點，我們需要告訴XStream將Blog#writer字段同義為author

問題 ： how does XStream converts an Author in a String so it can be written as a XML tag attribute?

Attributes cannot be written for types that are handled by Converter implementations, we have to use a SingleValueConverter and implement our own converter for the Author:

package com.xgj.oxm.xstream.quickDemo.aliasDemo.officeDemo;import com.thoughtworks.xstream.converters.SingleValueConverter;public class AuthorConverter implements SingleValueConverter {/*** tells XStream which types it can deal with*/public boolean canConvert(Class type) {return type.equals(Author.class);}/*** extract a String from an Author*/public String toString(Object obj) {return ((Author) obj).getName();}/*** takes a String and returns an Author*/public Object fromString(String name) {return new Author(name);} }

然后注冊轉換器

xstream.useAttributeFor(Blog.class, "writer"); xstream.registerConverter(new AuthorConverter());

完整的代碼如下

package com.xgj.oxm.xstream.quickDemo.aliasDemo.officeDemo;import com.thoughtworks.xstream.XStream;public class AliasTest {public static void main(String[] args) {Blog teamBlog = new Blog(new Author("Guilherme Silveira"));teamBlog.add(new Entry("first", "My first blog entry."));teamBlog.add(new Entry("tutorial","Today we have developed a nice alias tutorial. Tell your friends! NOW!"));XStream xstream = new XStream();xstream.alias("blog", Blog.class);xstream.alias("entry", Entry.class);xstream.aliasField("author", Blog.class, "writer");xstream.addImplicitCollection(Blog.class, "entries");xstream.useAttributeFor(Blog.class, "writer");xstream.registerConverter(new AuthorConverter());System.out.println(xstream.toXML(teamBlog));} }

輸出

<blog author="Guilherme Silveira"><entry><title>first</title><description>My first blog entry.</description></entry><entry><title>tutorial</title><description>Today we have developed a nice alias tutorial. Tell your friends! NOW!</description></entry> </blog>

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Package aliasing

xstream.aliasPackage("my.company", "org.thoughtworks");

比如

package com.xgj.oxm.xstream.quickDemo.aliasDemo.officeDemo;import com.thoughtworks.xstream.XStream;public class AliasPackage {public static void main(String[] args) {Blog teamBlog = new Blog(new Author("Guilherme Silveira"));teamBlog.add(new Entry("first", "My first blog entry."));teamBlog.add(new Entry("tutorial","Today we have developed a nice alias tutorial. Tell your friends! NOW!"));XStream xstream = new XStream();xstream.aliasPackage( "com.artisan","com.xgj.oxm.xstream.quickDemo.aliasDemo.officeDemo");System.out.println(xstream.toXML(teamBlog));}}

輸出

<com.artisan.Blog><writer><name>Guilherme Silveira</name></writer><entries><com.artisan.Entry><title>first</title><description>My first blog entry.</description></com.artisan.Entry><com.artisan.Entry><title>tutorial</title><description>Today we have developed a nice alias tutorial. Tell your friends! NOW!</description></com.artisan.Entry></entries> </com.artisan.Blog>

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示例源碼

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

總結

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