JAXB XJC解析机制

原創

2020-02-21 08:20

大家都知道使用JAXB的xjc工具可以把schema自动生成对应的java类，这仔细对比了一下不同schema的结构生成的java类，有一些不明白的地方

如果schema定义如下

  <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类结果如下
[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结构


  <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类却如下所示，可以忽略@XMLElementRef(s)的注释暂时不用管
[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]
我就不明白为什么不是生成以下这样的类结构呢？
[quote]
public class PartnerBusinessIdentification {
protected ProprietaryBusinessIdentifier proprietaryBusinessIdentifier;
protected ProprietaryDomainIdentifier proprietaryDomainIdentifier;
protected ProprietaryIdentifierAuthority proprietaryIdentifierAuthority;
}
[/quote]

后来比较多个类似结构的schema发现，问题应该是在<xs:sequence>上，[b]如果它加上了maxOccurs="unbounded"属性的话，就只会在此元素对应的java类中生成一个List<?>类型的元素，而不管里面<xs:sequence>究竟有一个还是多个子元素[/b]，这样一来生成的java类就非常难处理了。我正在想对策中