JAXB @XmlElements使minOccurs = 1

Question

所以我想要一個用@XmlElements注釋的列表，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;
}

我想知道是否有辦法強制列表包含至少1個元素，因為現在，xsd看起來像

<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

我建議檢查一下：

@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

假設Apple，Orange和Mango是Fruit的子類，您可能希望使用@XmlElementRef注釋entries屬性，該屬性對應於XML模式中的替換組，而不是對應於選擇概念的@XmlElements 。

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

這假定Apple，Orange和Mango類擴展了Fruit類，並使用@XmlRootElement進行了注釋。

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

欲獲得更多信息

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