JAXB XJC解析機制

大家都知道使用JAXB的xjc工具可以把schema自動生成對應的java類，這仔細對比了一下不同schema的結構生成的java類，有一些不明白的地方

如果schema定義如下

  <xs:element name="PhysicalAddress">
    <xs:complexType>
      <xs:sequence minOccurs="0" maxOccurs="1">
        <xs:element minOccurs="0" maxOccurs="1" ref="addressLine1" />
        <xs:element minOccurs="0" maxOccurs="1" ref="addressLine2" />
        <xs:element minOccurs="0" maxOccurs="1" ref="addressLine3" />
        <xs:element minOccurs="0" maxOccurs="1" ref="cityName" />
        <xs:element minOccurs="0" maxOccurs="1" ref="GlobalCountryCode" />
        <xs:element minOccurs="0" maxOccurs="1" ref="GlobalLocationIdentifier" />
        <xs:element minOccurs="0" maxOccurs="1" ref="NationalPostalCode" />
        <xs:element minOccurs="0" maxOccurs="1" ref="postOfficeBoxIdentifier" />
        <xs:element minOccurs="0" maxOccurs="1" ref="regionName" />
      </xs:sequence>
    </xs:complexType>
  </xs:element>

生成的java類結果如下
[quote]
public class PhysicalAddress {

protected AddressLine1 addressLine1;
protected AddressLine2 addressLine2;
protected AddressLine3 addressLine3;
protected CityName cityName;
protected String globalCountryCode;
protected String globalLocationIdentifier;
protected String nationalPostalCode;
protected PostOfficeBoxIdentifier postOfficeBoxIdentifier;
protected RegionName regionName;
}
[/quote]

但是，如下的schema結構

  <xs:element name="PartnerBusinessIdentification">
    <xs:complexType>
      <xs:sequence minOccurs="0" maxOccurs="unbounded">
        <xs:element ref="ProprietaryBusinessIdentifier" />
        <xs:element ref="ProprietaryDomainIdentifier" />
        <xs:element minOccurs="0" maxOccurs="1" ref="ProprietaryIdentifierAuthority" />
      </xs:sequence>
    </xs:complexType>
  </xs:element>

生成的java類卻如下所示，可以忽略@XMLElementRef(s)的註釋暫時不用管
[quote]
public class PartnerBusinessIdentification {

@XmlElementRefs({
@XmlElementRef(name = "ProprietaryBusinessIdentifier", type = JAXBElement.class),
@XmlElementRef(name = "ProprietaryDomainIdentifier", type = JAXBElement.class),
@XmlElementRef(name = "ProprietaryIdentifierAuthority", type = JAXBElement.class)
})

protected List<JAXBElement<String>> proprietaryBusinessIdentifierAndProprietaryDomainIdentifierAndProprietaryIdentifierAuthority;
}
[/quote]
我就不明白爲什麼不是生成以下這樣的類結構呢？
[quote]
public class PartnerBusinessIdentification {
protected ProprietaryBusinessIdentifier proprietaryBusinessIdentifier;
protected ProprietaryDomainIdentifier proprietaryDomainIdentifier;
protected ProprietaryIdentifierAuthority proprietaryIdentifierAuthority;
}
[/quote]

後來比較多個類似結構的schema發現，問題應該是在<xs:sequence>上，[b]如果它加上了maxOccurs="unbounded"屬性的話，就只會在此元素對應的java類中生成一個List<?>類型的元素，而不管裏面<xs:sequence>究竟有一個還是多個子元素[/b]，這樣一來生成的java類就非常難處理了。我正在想對策中