使用jaxb从一个对象模型中产生xml文档

// instantiates tag objectstag tag1 = new tag("working hours");tag tag2 = new tag("week-ends");tag tag3 = new tag("mind the dog");// instantiates an individual object with home addresscalendar.set(1940, 7, 7, 0, 0, 0);individual individual = new individual(1l, "ringo", "starr", "+187445", 
      "ringo@star.co.uk", calendar.gettime());individual.sethomeaddress(new address(2l, "abbey road", "london", "sw14", "uk"));// instantiates a first delivery addressaddress deliveryaddress1 = new address(3l, "findsbury avenue", "london", "ce451", "uk");deliveryaddress1.addtag(tag1);deliveryaddress1.addtag(tag3);individual.adddeliveryaddress(deliveryaddress1);// instantiates a second delivery addressaddress deliveryaddress2 = new address(4l, "camden street", "brighton", "nw487", "uk");deliveryaddress2.addtag(tag1);deliveryaddress2.addtag(tag2);individual.adddeliveryaddress(deliveryaddress2);// generates xml representation of an individualstringwriter writer = new stringwriter();jaxbcontext context = jaxbcontext.newinstance(customer.class);marshaller m = context.createmarshaller();m.marshal(individual, writer);system.out.println(writer);

<?xml version="1.0" encoding="utf-8" standalone="yes"?><customer>    <deliveryaddresses>        <city>london</city>        <country>uk</country>        <id>3</id>        <street>findsbury avenue</street>        <tags>            <name>working hours</name>        </tags>        <tags>            <name>mind the dog</name>        </tags>        <zipcode>ce451</zipcode>    </deliveryaddresses>    <deliveryaddresses>        <city>brighton</city>        <country>uk</country>        <id>4</id>        <street>camden street</street>        <tags>            <name>working hours</name>        </tags>        <tags>            <name>week-ends</name>        </tags>        <zipcode>nw487</zipcode>    </deliveryaddresses>    <email>ringo@star.co.uk</email>    <homeaddress>        <city>london</city>        <country>uk</country>        <id>2</id>        <street>abbey road</street>        <zipcode>sw14</zipcode>    </homeaddress>    <id>1</id>    <telephone>+187445</telephone></customer>

    通过一个注释@xmlrootelemen，一个marshaller对象和异常产生的代码，可以很容易的得到对象图形的xml表示。根元素<customer>代表customer对象，它包括所有的属性（一个家庭地址，两个发货地址，一个id，一个电话号码等）。

    定制xml文档

    音乐公司和他的商业伙伴对上面给出的xml文档（listing 2）并不完全满意，他们可能抛弃某些信息（地址标识符号，tags）出生日期的格式，订单的某些属性等。由于有了javax.xml.bind.annotation包的注释，jaxb提供了一种方式来定制和控制xml的结构。

    首先，如果你想抛弃<customer>元素而使用<individual>或者<company>来替代根元素。如果让jaxb不使用抽象customer类，可以放弃使用@xmlrootelement而使用@xmltransient来产生临时类。

@xmltransientpublic abstract class customer ...{ @xmlattribute protected long id; protected string telephone; protected string email; protected address homeaddress; @xmlelementwrapper(name = "delivery") @xmlelement(name = "address") protected list<address> deliveryaddresses = new arraylist<address>(); // constructors, getters, setters}

@xmltype(proporder = ...{"street", "zipcode", "city", "country"})@xmlaccessortype(xmlaccesstype.field)public class address ...{ @xmltransient private long id; private string street; private string city; @xmlelement(name = "zip") private string zipcode; private string country; @xmltransient private list<tag> tags = new arraylist<tag>(); // constructors, getters, setters}

public class dateadapter extends xmladapter<string, date> ...{ dateformat df = new simpledateformat("dd/mm/yyyy"); public date unmarshal(string date) throws exception ...{ return df.parse(date); } public string marshal(date date) throws exception ...{ return df.format(date); }}

// xmlstring contains the xml document of an individualstringreader reader = new stringreader(xmlstring);jaxbcontext context = jaxbcontext.newinstance(individual.class);unmarshaller u = context.createunmarshaller();individual individual = (individual) u.unmarshal(reader);system.out.println(individual.getfirstname());

<?xml version="1.0" encoding="utf-8" standalone="yes"?><xs:schema version="1.0" xmlns:xs="http://www.w3.org/2001/xmlschema">  <xs:complextype name="address">    <xs:sequence>      <xs:element name="street" type="xs:string" minoccurs="0"/>      <xs:element name="zip" type="xs:string" minoccurs="0"/>      <xs:element name="city" type="xs:string" minoccurs="0"/>      <xs:element name="country" type="xs:string" minoccurs="0"/>    </xs:sequence>  </xs:complextype>  <xs:complextype name="company">    <xs:sequence>      <xs:element name="contactname" type="xs:string" minoccurs="0"/>      <xs:element name="telephone" type="xs:string" minoccurs="0"/>      <xs:element name="email" type="xs:string" minoccurs="0"/>      <xs:element name="numberofemployees" type="xs:int" minoccurs="0"/>      <xs:element name="homeaddress" type="address" minoccurs="0"/>      <xs:element name="delivery" minoccurs="0">        <xs:complextype>          <xs:sequence>           <xs:element name="address" type="address" minoccurs="0" maxoccurs="unbounded"/>          </xs:sequence>        </xs:complextype>      </xs:element>    </xs:sequence>    <xs:attribute name="id" type="xs:long"/>    <xs:attribute name="name" type="xs:string"/>  </xs:complextype>  <xs:complextype name="individual">    <xs:sequence>      <xs:element name="firstname" type="xs:string" minoccurs="0"/>      <xs:element name="dateofbirth" type="xs:string" minoccurs="0"/>      <xs:element name="telephone" type="xs:string" minoccurs="0"/>      <xs:element name="email" type="xs:string" minoccurs="0"/>      <xs:element name="homeaddress" type="address" minoccurs="0"/>      <xs:element name="delivery" minoccurs="0">        <xs:complextype>          <xs:sequence>            <xs:element name="address" type="address" minoccurs="0" 
                 maxoccurs="unbounded"/>          </xs:sequence>        </xs:complextype>      </xs:element>    </xs:sequence>    <xs:attribute name="id" type="xs:long"/>    <xs:attribute name="lastname" type="xs:string"/>  </xs:complextype>  <xs:complextype name="tag">    <xs:sequence>      <xs:element name="addresses" type="address" nillable="true" 
         minoccurs="0" maxoccurs="unbounded"/>      <xs:element name="name" type="xs:string" minoccurs="0"/>    </xs:sequence>  </xs:complextype>  <xs:complextype name="dateadapter">    <xs:complexcontent>      <xs:extension base="xmladapter">        <xs:sequence/>      </xs:extension>    </xs:complexcontent>  </xs:complextype>  <xs:complextype name="xmladapter" abstract="true">    <xs:sequence/>  </xs:complextype></xs:schema>

@entity@table(name = "t_address")@xmltype(proporder = ...{"street", "zipcode", "city", "country"})@xmlaccessortype(xmlaccesstype.field)public class address ...{  @xmltransient  @id @generatedvalue  private long id;  private string street;  @column(length = 100)  private string city;  @column(name = "zip_code", length = 10)  @xmlelement(name = "zip")  private string zipcode;  @column(length = 50)  private string country;  @xmltransient  @manytomany(cascade = cascadetype.persist)  @jointable(name = "t_address_tag",    joincolumns = ...{@joincolumn(name = "address_fk")},    inversejoincolumns = ...{@joincolumn(name = "tag_fk")})  private list<tag> tags = new arraylist<tag>();  // constructors, getters, setters}