使用XStream將java物件轉換成xml資料格式

簡介

之前介紹過Apache Commons Digester套件，可以將以xml格式表示的資料轉換成Java的model物件(請參考該網誌)。若要進行相反的動作，即將Java的model物件轉換成xml格式，可以使用XStream(http://xstream.codehaus.org/)套件。

XStream的使用方式如下：

XStream xstream = new XStream();

xstream.alias("addressBook", AddressBook.class);

xstream.alias("person", Person.class);

xstream.alias("address", Address.class);

xstream.addImplicitCollection(AddressBook.class, "personList"); // to avoid <personList> tag

xstream.addImplicitCollection(Person.class, "addressList"); // to avoid <addressList> tag

String xml = xstream.toXML(addressBook1);

logger.info("addressBook.toXML(use xstream) = " + xml);

執行結果：

[2014/09/01 11:27:54]  INFO tw.blogspot.saminjava.demo.xstream.AddressBook:171 - addressBook.toXML(use xstream) = <addressBook>
  <personList>
    <person>
      <id>1</id>
      <name>Gonzo</name>
      <emailMap>
        <entry>
          <string>business</string>
          <string>gonzo@muppets.com</string>
        </entry>
      </emailMap>
      <addressList>
        <address>
          <type>home</type>
          <street>123 Maine Ave.</street>
          <city>Las Vegas</city>
          <state>NV</state>
          <zip>01234</zip>
          <country>USA</country>
        </address>
        <address>
          <type>business</type>
          <street>234 Maple Dr.</street>
          <city>Los Angeles</city>
          <state>CA</state>
          <zip>98765</zip>
          <country>USA</country>
        </address>
      </addressList>
    </person>
    <person>
      <id>2</id>
      <name>Kermit</name>
      <emailMap>
        <entry>
          <string>home</string>
          <string>kermie@acme.com</string>
        </entry>
        <entry>
          <string>business</string>
          <string>kermit@muppets.com</string>
        </entry>
      </emailMap>
      <addressList>
        <address>
          <type>business</type>
          <street>987 Brown Rd</street>
          <city>Las Cruces</city>
          <state>NM</state>
          <zip>75321</zip>
          <country>USA</country>
        </address>
      </addressList>
    </person>
  </personList>
</addressBook>

若是使用XStream產出XML格式，要反轉回Java物件，其使用方式如下：

AddressBook addressBook2 = (AddressBook)xstream.fromXML(xml);

logger.info("addressBook2.toString(use xstream) = " + addressBook2.toString());

執行結果：

[2014/09/01 11:44:03]  INFO tw.blogspot.saminjava.demo.xstream.AddressBook:175 - addressBook2.toString(use xstream) = tw.blogspot.saminjava.demo.xstream.AddressBook@11f2ee1[personList=[tw.blogspot.saminjava.demo.xstream.Person@3ecfff[id=1,name=Gonzo,emailMap={business=gonzo@muppets.com},addressList=[tw.blogspot.saminjava.demo.xstream.Address@1c99159[type=home,street=123 Maine Ave.,city=Las Vegas,state=NV,zip=01234,country=USA], tw.blogspot.saminjava.demo.xstream.Address@65a77f[type=business,street=234 Maple Dr.,city=Los Angeles,state=CA,zip=98765,country=USA]]], tw.blogspot.saminjava.demo.xstream.Person@1d7ad1c[id=2,name=Kermit,emailMap={home=kermie@acme.com, business=kermit@muppets.com},addressList=[tw.blogspot.saminjava.demo.xstream.Address@a61164[type=business,street=987 Brown Rd,city=Las Cruces,state=NM,zip=75321,country=USA]]]]]

XStream除了XML格式外，還可以另產出JSON格式，其使用方式如下：

xstream = new XStream(new JettisonMappedXmlDriver());

xstream.setMode(XStream.NO_REFERENCES);

xstream.alias("addressBook", AddressBook.class);

xstream.alias("person", Person.class);

xstream.alias("address", Address.class);

xstream.addImplicitCollection(AddressBook.class, "personList"); // to avoid <personList> tag

xstream.addImplicitCollection(Person.class, "addressList"); // to avoid <addressList> tag

String json = xstream.toXML(addressBook1);

logger.info("addressBook.toJSON(use xstream) = " + json);

執行結果：

[2014/09/01 11:50:04]  INFO tw.blogspot.saminjava.demo.xstream.AddressBook:195 - addressBook.toJSON(use xstream) = {"addressBook":{"person":[{"id":1,"name":"Gonzo","emailMap":[{"entry":{"string":["business","gonzo@muppets.com"]}}],"address":[{"type":"home","street":"123 Maine Ave.","city":"Las Vegas","state":"NV","zip":"01234","country":"USA"},{"type":"business","street":"234 Maple Dr.","city":"Los Angeles","state":"CA","zip":98765,"country":"USA"}]},{"id":2,"name":"Kermit","emailMap":[{"entry":[{"string":["home","kermie@acme.com"]},{"string":["business","kermit@muppets.com"]}]}],"address":{"type":"business","street":"987 Brown Rd","city":"Las Cruces","state":"NM","zip":75321,"country":"USA"}}]}}