JAXB @XmlElements使minOccurs = 1

Question

所以我想要一个用@XmlElements注释的列表,如下所示

@XmlElements(
        {
            @XmlElement(name = "Apple", type = Apple.class),
            @XmlElement(name = "Orange", type = Orange.class),
            @XmlElement(name = "Mango", type = Mango.class)
        }
)
public List<Fruit> getEntries() {
        return fruitList;
}

我想知道是否有办法强制列表包含至少1个元素,因为现在,xsd看起来像

<xs:complexType name="fruitList">
    <xs:sequence>
      <xs:choice minOccurs="0" maxOccurs="unbounded">
        <xs:element name="Apple" type="tns:apple"/>
        <xs:element name="Orange" type="tns:orange"/>
        <xs:element name="Mango" type="tns:mango"/>
      </xs:choice>
    </xs:sequence>
  </xs:complexType>

Answer 1

我建议检查一下:

@XmlElements(
    {
        @XmlElement(name = "Apple", type = Apple.class, required = true),
        @XmlElement(name = "Orange", type = Orange.class, required = true),
        @XmlElement(name = "Mango", type = Mango.class, required = true)
    }
)

Answer 2

假设 Apple、Orange 和 Mango 是 Fruit 的子类，您可能需要注释对应于 XML 模式中的替换组的entries属性@XmlElementRef，而不是@XmlElements对应于选择概念的属性。

@XmlElementRef
public List<Fruit> getEntries() {
        return fruitList;
}

假设 Apple、Orange 和 Mango 类扩展了 Fruit 类，并注释为@XmlRootElement

@XmlRootElement
public class Apple extends Fruit {
   ...
}

了解更多信息

• http://bdoughan.blogspot.com/2010/11/jaxb-and-inheritance-using-substitution.html
• http://bdoughan.blogspot.com/2010/10/jaxb-and-xsd-choice-xmlelements.html